Hacker News new | past | comments | ask | show | jobs | submit login
Cooling a house without air conditioning (bbc.com)
296 points by lots2learn 57 days ago | hide | past | web | favorite | 278 comments

A lot of the need for AC (and having lights on) is just really, really bad modern house design. I recently finished building a house (my first one) and everyone acted like I was crazy for not building in central air conditioning. (This is in New Hampshire)

I built in an older style, with windows on every side, with a mind towards ventilation and light. Inexplicably most houses in the area, even $500k+ houses do not have these two things. My mom's condo has central air but the system is so feeble and the venting upstairs so poor that two bedrooms in the house remain stuffy anyways. It seems like light and natural ventilation are not even afterthoughts, but non-thoughts, and the designs all rely on electric light and forced air. Its amazing being in an expensive home where you need a light on in the kitchen at 8am. How do they decide what to build?

I built 9 foot ceilings on the first floor and 8.5 on the second. Then I placed the attic (3rd story) door centrally in the upstairs hallway. The result of the design is that airflow moves on the first floor in all directions, and upward, and on the second floor can move at least east-west (bathroom and hallway windows), and also north-south if bedroom doors are open. Finally, air flows upwards to the attic, which has windows north-south. So winds should suck air higher, and out.

If I close windows in the morning and open around 7pm, the result is that the house stays very cool, about(? only tested with temp gun a few times) 74 downstairs and 76 upstairs during these 90 degree days, and then gets cooler at night as I open windows again. So far, I've only bought one fan, though things might work better with more. Note I'm not an expert or an architect, I just included some design features that should be obvious to anyone who's lived in an old house for a summer.

This takes some manual control, but there are far fewer parts to maintain (this was a general design goal beyond AC), and summer electric bills are $50-60/month. With this design, there have been 3 icky-hot days so far this year, when there was no wind and the night did not get very cool.

My house has windows on every side for similar reasons, but it's back firing big time. I have to keep them closed at all time because of noise, and they let the sun in, requiring even more A/C. We have blackout/insulating shades, but it's still not as good as straight up walls.

So millage will vary.

Similarly with light, in winter by the time I get home its pitch black either way, so it wouldn't change a whole lot. And in summer the light from the windows doesn't play well with TV/monitors/etc.

Cats like the windows a lot though.

Depending on the style of house it may look out of place but can you put awnings on the exterior above your windows? This usually has the effect of blocking sun when it's high in the sky and the hottest while still allowing the sun to hit the window when it's lower and cooler (morning, evening, winter months).

Not surprised - solar gain from having lots of big windows is one of the big reasons why some homes get far too hot here in the UK. They effectively turn the house into a big greenhouse. Supposedly the problem can be reduced a bit by having the windows aligned north-south so they avoid getting so much direct sunshine into the rooms over summer, though that's going to be very latitude dependent.

I am suffering that at the moment in Oxfordshire. Just a bit of morning sun heats my bedroom up to 28 C. Totally insane.

Leaving the windows open barely helps.

My grandmas flat, in Southern spain, did not have AC. But thanks to big walls and external blinds you could live comfortably even during 40+ C Summer days.

External blinds are a killer feature both for heat and cold insulation.

This is what eaves are for. Since the sun is lower in the sky in the winter, properly sized eaves will shade the windows in summer and expose them to sunlight in the winter.

>A lot of the need for AC (and having lights on) is just really, really bad modern house design.

Agreed, but people also seem uninterested in simple techniques to work with what they've got. I live in MA, in an old house that doesn't have much in the way of modern energy efficiency but we get by without AC on all but the hottest days of the year by doing really simple things. Open windows at night. Close them in the morning. Pull the blinds down on windows that have sun exposure. You get the idea. The only serious retrofit we've done so far is have a contractor add cellulose insulation to the attic. On 90+ degree days the second floor will reach 80+ by the evening so then we turn on the AC if a window fan is unable to bring the temperature back down to something comfortable. In our climate AC should be the backup plan, not the primary cooling system.

+1 on this, I live in an apartment without balconies and without external blinds, so one cannot survive without full AC in summer. At least the glass windows can be opened when it is not raining, some commercial buildings have fixed windows. My parents' house has Venetian blinds and we survived without AC, now they have AC but just for sleep time.

> If I close windows in the morning and open around 7pm,

I have explained the same things to my friends who come over to visit me. Some of them think I am crazy, others get it.

I have the benefit of a giant open loft, 2 story ceilings coming off the living room right into the master bedroom, with a giant ceiling fan sucking air in from outside and a large window open upstairs so the air has someplace to go.

If it gets to 90 it can be a bit uncomfortable, but the mid 80s is fine, it only gets a bit hot around 5pm or so.

I have friends who keep all their doors / windows open and use a fan throughout the entire day. Great job sucking the hot air into the house!

Although for older houses with lower ceiling that is pretty much the only way.

Have you looked at installing a attic fan to pull air from the lower floors upwards into the attic for venting? I recall This Old House doing a segment on this some time ago and a cooling option.

(edit) added link to youtube video


This is an easy upgrade for any home and can be done by a relatively competent DIYer or an HVAC contractor. The main point is that your attic is much hotter than anywhere in the house, so if you can get the attic close to outside ambient, it will help. I personally have my attic fans (one at either end of the house) set up on a separate thermostat from the rest of the house, where any time the attic temp exceeds 90F, the fans kick on.

Doing this will even make your AC system work better if you have one, since you won’t have the extremely hot air in your attic heating your ceilings

This is much less of a good idea than you think:


A whole house fan is a very different story, but it’s only really useful in some climates.

Yeah I read through that posting and I’m still not convinced that the original poster there is on to much. To add to all of the disagreements in the comments there, I also noticed that my AC works much less hard on hotter days, and noticed a slight reduction in costs monthly electrical costs year of year. There are a lot of variables in play to go into an electrical bill however.

It seems plausible to me that if you have decent air sealing in your house and wildly inadequate ceiling insulation then an attic fan could help. Or if you have poor air sealing but you have enough space for outside air to enter your attic.

In a well-built house, the roof and ceiling shouldn’t be a major source of summer heat gain.

My parents have one and you can feel it all over the house. Works great if a little loud.

Do you have any renders by chance (assuming you used CAD to design it)? I want to build a house optimized for natural light as well (not sure about ventilation since the place it would be built is cold most of the year).

Yeah, it's not too hard to deal with 90F without AC, but we often get 99F (37C) during the day and 86F (30C) at night, so no amount of ventilation will save you from feeling overheated day and night.

What we really need is solar-powered AC. Ideally DC-driven air conditioning.

there are two common mistakes in many modern implementations of central air.

the first is the hardest to get done as most hvac companies resist, having the exhaust not be at the exact end of the the pipe. the pipe should end just beyond it.

the second is not having a return or sufficient returns in each room. if you are stuck with a central return then make sure doors are open if the room has no pass through vent to the hall with the central return; at most the master bedroom will have pass through vents to a hall so the door can remain closed.

the only omission from my current home is an attic fan but building codes precluded it at the time but I hear I can do it now if I want.

still I find even with central air a lot of comfort can be found by having a dehumidifier. down in the south it is not uncommon to wake to humidity higher than the temperature which makes it feel sticky and uncomfortable.

with regards to cooling needs and such, we simply have changed what we want and want we are willing to tolerate. its not a bad thing, we just have to find efficient ways to have it.

Building very tight house with good insulation is the key. Then of course you need an ERV to keep the air good and a separate dehumidifier is also great.

If you have cool nights and your heatwaves don't last too long large thermal mass is also very good and can be enough.

A dehumidifier is an air conditioner, but packaged in a way that doesn't allow it to work as one. (The upside is the easy installation.) Suggesting a dehumidifier to avoid AC is ridiculous.

how much power do you actually save with a dehumidifier compared to an efficient ac installation? afaik, most dehumidifiers need to cool the air anyway to lower the humidity. seems like any savings would be marginal.

Having lived where it cools off nicely at night, and then where it doesn't - this is just not a generally applicable solution.

When it only gets down into the upper 80s (thats around 31C for those afflicted with metric) at night with humidity at 90% or higher, AC is mandatory.

When its up around 98 (37C) with high humidity during the day, not having AC can be a killer.

> everyone acted like I was crazy for not building in central air conditioning. (This is in New Hampshire)

Really? In NH? How many days a year it even reaches 90?

I’m sure it’s nothing like the south east, but it gets pretty hot, mostly in July and August. Living in a hotter but drier climate now (which is on the whole more comfortable than back in NH), I realize that the humidity played an important part in it feeling hot and uncomfortable. Mid 80s in dry heat is many times more bearable than mid 80s in humid weather, and the same thing goes for the cold too.

Yeah I was going to say the same. I live in MA to the SOUTH, and almost no one here has central air except richer and/or older people.

Most American houses are barely fit for purpose. It's time for a major re-think of construction methods, styles, materials, and priorities.

Somewhere, the ghost of Bucky Fuller is sighing, and looking at one of his wrist watches...


Did you put an awning around the outside of the house? At least on the first floor? This is a common feature in Australian houses to keep the actual house shaded and cool.

Another interesting feature are houses that are built on brick pillars raised off the ground without a concrete slab. It’s amazing how even on a hot day they remain quite cool underneath and seem to cool off quicker at night. Many older wooden houses seem to be built this way.

I like to mentally toy with the idea of high rises or large apartment blocks having some kind of large retractable awnings on the sunny side of the buildings, or some kind of fake outside wall which can diffuse some of the suns light / heat.

Are there any resources where I can educate myself on this? I bought an apartment in a 28 storey building recently and I was struck with the lack of interest and thought on my questions on natural ventilation and natural lighting. I'm a long way from designing a house but I'd definitely want to educate myself on topics like how do you guess the air flow direction, what direction is the sunlight going to be during what months, what about rain fall, what are good insulators you can use, etc. you get what I'm getting at.

You can read more about the design and construction techniques used in zero-energy buildings.[0] They consider natural ventilation, sunlight, insulation, etc. in ways that conventional construction ignores.

[0] https://en.wikipedia.org/wiki/Zero-energy_building

Well, the easiest way to see what the air flow direction is at any time in any space, is to light a stick of incense, and then watch which way the smoke goes if you hold it quite still.

This works, as you say, until the air during the night is much colder than during the day. In one summer there were weeks when the air during the night was 27C and it obviously did not cool down.

Another downside is that when you do not have mechanical ventilation with heat recovery and your rooms are relatively well built (i.e. air tight) then you are left with bad air quality inside.

I think that best is to combine night cooling with mechanical ventilation with heat recovery.

> With this design, there have been 3 icky-hot days so far this year, when there was no wind and the night did not get very cool.

As you noted, this used to be a fairly standard design for homes in some areas.

Perhaps a "whole house attic fan" could help on those marginal days?

The same thing happens here in Arizona; the proper way they should be building houses here would probably be a monolithic dome with most of the home set below grade - although caliche would make that difficult in some areas (and it would be expensive regardless). The next best thing would probably be rammed earth with 2-3 foot thick walls.

Modern insulation is really good - much better than you get with rammed earth. Rammed earth isn't a particularly good insulator, it just has really high thermal mass, so once it heats up (and out here, it will heat up), it will continue leaking heat into the interior of your structure for quite a long time. Thermal mass doesn't prevent heat transmission, it just delays it.

The biggest heat transmission problem in most construction isn't the walls, it's the windows. The amount of heat transmission you get via glass - even high-performance triple-pane glass - is significantly higher than heat transmission through the rest of the structure. Your walls are going to be R20+, your attic insulation will be R35+. Your best windows are going to be equivalent to R6 or so, with the median windows being significantly lower.

Main energy gain happens because of the radiation.

I think that the best combination is high thermal mass structure followed by the insulation inside. This way the heat is not easily transmitted to the inside and the thermal mass can cool off to the outside during the night.

Of course when the heat finally does get inside then it is trapped because the house will act like a thermos and only way of cooling would be the by circulation of cold air.

Problem of windows can be solved by outside blinds (or shutters but blinds are better) and IR reflective coating.

There's newer double/triple pane windows that have blinds built in which are nice

Are you aware of anyone using eutectic salts in the walls in the desert? I remember reading an article from the 70s about it and it seemed well suited for desert environments where there's a large temperature swing from day to night. They would absorb heat in the day keeping the house cool and release it at night keeping it warm. If I remember correctly, the difficulty was finding salts that worked on the right temp range

I'm not sure why you're getting downvoted? I was in Tucson in the summer in a rammed earth house (about 2-3 feet thick as you mention) and it was comfortably cool inside. The whole house had very large eaves, as well [1]

[1] I don't recall the other design details that made it so cool in temperature, but it was all analog/natural (i.e. no AC)

"I built in an older style, with windows on every side, with a mind towards ventilation and light. Inexplicably most houses in the area, even $500k+ houses do not have these two things."

Many people do not have exterior walls on all sides. You must be generally aware, because your next sentence mentions a condo (in my case I have a townhouse).

>A lot of the need for AC (and having lights on) is just really, really bad modern house design.

You can design a house however you want, but without AC it's going to be hot and miserable here in Indiana when it's in the 80's or 90's with 80%+ humidity unless you have AC.

Major function of AC is humidity control. If you have humid summers, AC will help your house to stay dryer and prevent mold and other damage. There are climates in which AC is essential and even the most advanced thermal and airflow design can not replace conditioning.

I was told many times to go with a slightly undersized AC, precisely for this reason - they're better dehumidifiers because they run for longer periods of time.

No, you're just forcing your expensive AC to run longer and run less efficiently. On the flip side, if you get a unit that's too big it'll cycle on and off too frequently - shortening the lifespan. You should get a correct sized unit for your house and space. The AC unit will last longer and use the least amount of energy.

If you live somewhere that humidity is an issue - in some places that's in the winter (when you wouldn't use cooling AC) - get a whole house dehumidifier system. Ex: https://www.sylvane.com/whole-house-dehumidifiers.html -- Those will run and maintain the correct humidity regardless of AC.

Use the right tool for the right and you'll get the most efficient results.

If you can afford to pay more, just get a two-stage or variable-speed air conditioner. This is the exact problem they're meant to solve.

They have compressors which can adjust speed, not just turn off/on like a single-stage AC compressor does. So there's a lot less worry about whether it's sized right because it basically "resizes" itself as necessary.

The two-stage type has off/low/high, so it can get a lot closer to the right size. The variable-speed type is essentially continuously adjustable, so it's like always having the perfectly-sized AC unit for whatever the weather happens to be like today.

Today that might be a bad idea.

Generally most modern forced air systems are designed to run more often (for heat and cool) / longer periods of time now.

On top of that you can get multi stage AC units. Mine will run at a lower setting for a longer period of time when the less efficient "full blast" stage is too much, but AC is still needed.

Why would an undersized air conditioner be more effective? What’s the size got to do with the efficacy?

Less effective at cooling, more effective at dehumidifying (it seems there is a presumption that dehumidification is roughly linear with operating time.)

AC units also last longer if they run continually vs frequent starts and stops.

Why not just buy a dehumidifier made specifically for this with collection bucket and all?

That would be less energy-efficient.

Both air conditioners and dehumidifiers are built on heat pumps. They both dehumidify in the same way: water condenses on a coil and drains away. But an AC unit pumps the extracted heat outside, and a dehumidifier pumps it back inside. When it's hot and humid, it wouldn't make sense to forgo the opportunity to pump heat outside.

A better solution is to get some variation of a two-stage air conditioner. Instead of a compressor that's either off or on, these have a compressor that can run at two speeds. Most of the time, it runs at the lower speed and behaves like an AC that is undersized, runs longer, and dehumidifies well. But when it gets really hot, it goes up to full speed so it can the temperature down. Compared to a single-stage AC, it costs more, but it's more energy-efficient and quieter and more comfortable because of smaller temperature swings.

These days they also variable-speed air conditioners that can adjust in tiny increments and run the compressor at almost any speed, so they are kind of the next generation beyond two-stage. They more or less run continuously, adjusting their power level instead of having an on/off duty cycle. It costs more than a two-stage, but it is even more efficient, quieter, and comfortable.

Most folks will need an AC unit regardless, and there is already a condensate drain line from the air handler. You could get an additional dehumidifier if your use case calls for it (dehumidification without a need to cool) but the cost is non-insignificant.

I have explored a dehumidifier for my Florida home, and after looking at the numbers, it just made more sense to tighten up the envelope and set the AC to 74. I have solar on the roof though, so the energy costs aren’t terribly high (vs possible mold remediation) for this approach. YMMV.

A dehumidifier is an air conditioner. It's the same device.

It operates a compressor that condenses a fluid with a boiling point below room temperature. As it condenses to a liquid, it generates a lot of heat. This heat is removed from the liquid. The liquid is then allowed to boil, which pulls heat from the environment.

In an air conditioner, the heat is radiated outside, and the cool air is vented inside. In a dehumidifier, the air is sucked in, blown over the cool radiator, which creates condensation which is collected, then blown over the hot radiator, and then blown back into the house.

So you might as well just use an AC and be more comfortable. There aren't any upsides to using a dehumidifier.

That bucket can fill in a day and click off the machine sometimes.

Some (all? most?) dehumidifiers can accept a hose connection in place to the collection bucket, my parents have one on a raised shelf in their basement and have the hose drain in the laundry sink -- no need to empty the bucket.

Are you sure? Despite starting and stopping the compressor during their operation?

Starting the compressor is the hardest operation on it.

Isn't running the AC constantly means the thermostat is stopping the compressor every time the temperature gets too low and starting it again when it becomes too high? If so, why is it better to run it constantly?

If other variables are constant, the dehumidification is proportional to air changes/air flow.

However, some of those other variables are not consistent across different designs. For example, they may use a different refrigerant that requires a different compressor. Centrifugal devices like fans and compressors use power in a non-linear fashion. Look up pychrometric chart and/or fan affinity laws for more detail

It runs for a longer time; the dehumidifying function of an air conditioner (the original use, thus the name) is a function of airflow x time, and airflow doesn't change much.

Does this mean that you could dehumidify a room very quickly by just vent-ducting a blower fan to your dehumidifier? Or is there a point of diminishing returns where the air must linger for a certain time within the dehumidifier to actually have any humidity extracted?

(Yes, I'm aware that such a set-up would be impractically noisy; it's just a thought experiment.)

A dehumidifier already has its heat pump capacity minimized for its design airflow.

An air conditioner has its heat pump capacity sized to cool a house, far in excess of what is needed merely to remove the humidity.

Mold and other damage again is symptomatic of modern building techniques. Humans for centuries had figured out how to live without AC sustainably on most regions for earth.

As the other poster said - ability to do it doesn't mean it works really well.

From my 96 year old grandfather: We planned to replace every piece of plaster in the wall in 10 years, and we kept hardwood floors because we could throw the rugs away and sand the floors down when the mold started to get bad.

That's wasteful and time intensive. No thanks.

Yes, but often they did that by simply living with some mold and rebuilding every few years. Just because they could live with it didn’t make it ideal.

Yeah, they lived in moldy damaged houses in constant disrepair.

That's not entirely true. In Bulgaria, even during the hottest summer days, you go into a traditional stonewall building and it is cool inside with no mold as walls are whitewashed. In some newer traditional houses, the first floor is dug half in the ground, which also keeps the first floor cooler in the summer and warmer during the winter, and it's where the living room typically is.

AC's were invented to do humidity control mainly actually, I think the cooling was a side-effect

For paper, or all things.

can actual dehumidifier be used as a more environmentally friendly solution?

If you rely on ventilation for cooling you're just constantly pulling in high humidity air from outside and the dehumidifier will do nothing.

> There are climates in which AC is essential and even the most advanced thermal and airflow design can not replace conditioning.

Essential? You mean these climates were completely uninhabited before the invention of AC?

The charitable interpretation is "essential to keeping the home dry and free of mold" not "essential to live there".

Not everyone has the time and energy to build their entire house, but I found that one relatively easy thing that helps a lot is attic insulation and a bit of DYI. It turns out that contractors often do really shoddy work when it comes to insulation because it's exceptionally easy to skimp on materials to save money: they buy the cheap fiberglass stuff and they use too little of it.

You can buy 15-20 bags of cellulose insulation and rent the blower machine from home depot, and you can do the whole attic in a few hours yourself. Including a rental van, that cost me around $600.

This alone made a noticeable difference in my house in Toronto (where it can easily get to 32°C/90°F in sun in the summer)

I’d asking recommend people try to air seal as well as they possibly can from the attic side too. And install fire proof covers over all recessed cans.

Halogen light and others that create heat are so very bad. I’ve found scorched and charred timber several times and they have appeared to be installed correctly. LEDs are just so much better.

My mom paid to re-insulate her attic a few years ago. I think she paid $3,000 (in a rural area), but says it's dropped the temperature in her house by 10F, and when I've visited in the summer I've noticed. It's a remarkable win.

Also in hotter areas good to have ridge vents installed. Its basically make small slot in the peak of the roof with a cap above it. This allows hot air to circulate out of the attic.

This is next up on my todo list.

Any particular advice/pain points for re-insulating an attic with cellulose?

Wear a respirator and goggles and do it during the coolest period of the year; even so, bring some water with you. Put down as much as you can afford to (as thick as possible, but evenly thick). When my contractor did mine, he put in 1-2 feet thick.

Also, because I live in Phoenix, we installed some ventilators on the roof to help exhaust hot air in the summer (in addition to the peak eave "vents" at the ends of the house). We wanted to do an exhaust fan, but there wasn't any way to get one into the attic. So far, the ventilators have worked fine.

It's actually surprisingly simple to do.

If you've never done it or seen it done before, my only real advice is break up the cellulose into fluff before you put it into the blower machine, and put little bits gradually and slowly rather than stuffing it to the top. My wife thought she could shove a whole bag inside and have the mixing blade break it up, but it clogged the machine instead, and I had to waste a couple of hours unclogging the tube.

In terms of applying the insulation, you just want it to be thick, fluffy and somewhat even.

Other than that, just captain obvious stuff:

- you need two people (one in the attic and one feeding the blower machine)

- start from the edges towards the manhole

- use a respirator mask

- stay hydrated and take breaks if you need to (the attic is surprisingly hot)

The worst mistake I've ever made in an attic was doing cable runs (TV to the bedrooms) on a summer day in Texas. Sure, we started when it was cool at 7am... but we finished around noon.

So, to add to that: do it on a nice day in spring or fall.

Thanks for taking the time to respond.

Did you remove the old stuff first? Or do you just layer over it?

Just layer it on top. The rule of thumb is: the more you have, the better, regardless of which material you use.

This is a bad rule of thumb in some climates. Your technique of piling on insulation might create a dew point at a place that isn't ventilated, and thus cause a buildup of mold.

AFAIK, cellulose insulation is chemically treated to be mold-resistant and fire-resistant. Also, remember a rule of thumb is just that: by definition it can't cover 100% of edge cases. If you have a water leak in your roof, you obviously have bigger problems to address first...

It doesn't matter much if your insulation is mold-resistant. Presumably it's resting against wooden beams or other things that would be friendly to mold, or the water can drip down once it condenses to something that's friendlier to mold.

You wouldn't get water from a leak, you'd get it from thin air via condensation. Ever had fog on your car window? That's water on the inside of your window, and not because the roof of your car has a hole in it that's letting water through. Water condenses out of the air.

Making sure condensation happens in the right places is one of the main jobs of well designed insulation. What you saw as shoddy work from a contractor may have been a standard insulation design that's intentionally skimpy on the internal insulation, because the condensation should happen in an outside layer.

By piling on insulation you may have moved that dew point to the inside of the house or past a layer of insulation meant to deal with it.

The rule of thumb is that you can't just add more to one layer of your overall insulation (which is everything from your outside weather layer to the paint on your inside wall) without considering the system as a whole.

Search for "hygrothermal analysis" or "dew point" in relation to outer wall insulation. You'll find resources like [1] and [2]. The former has an example where more interior without corresponding changes to the exterior makes things worse.

I'm no expert on insulation, just a fellow home DIY-er. I've had enough experience with it to be very paranoid if I were in your shoes. It's worth bringing in a professional to evaluate this home improvement job of yours,

You may have created conditions for mold to thrive in your attic, or for water to seep into structural layers of your roof. By the time you notice those sorts of problems without having to open up a wall it's often too late.

1. https://www.jlconline.com/how-to/insulation/avoiding-wet-wal...

2. http://www.superhomes.org.uk/resources/interstitial-condensa...

I did have a mold issue in the bathroom shortly after buying my house (a few years before adding insulation). Had to redo the ceiling paint job, which was annoying to be sure, but that was about the extent of the damage, and we never got a mold problem again afterwards.

I also did have someone come over to quote me on insulation work when I was planning it (since the mold thing was a concern). They said my setup was fine as far as mold risk was concerned, and that it was clear that the two layers that were there were insufficient.

If in doubt, you can always ask for a professional opinion before attempting any DYI.

This article isn't so much "cooling a house without air conditioning" - it's more "here's some designs for houses that can be cooled without air conditioning".

This has very little to no help for existing homes unless you have a large budget to demo your existing home/yard/surrounding-infrastructure. For a perpetual renter such as myself (bay area lifestyle), this is useless information.

Where I live in the bay area - we live in a greenhouse of an in-law unit. Only solution to cool it without AC would be to tear it down and build something different. I can't even keep the top room below 80F on quite a few days with a window unit I installed. That unit is rated to do over 2x the size of the room too but it can't keep up. On days we know it'll be 95+, we leave the AC on all day. Otherwise, the heat soaks into the walls so much that we can't cool the house down after we get home and it'll still be 85+ in our bedroom past midnight. Opening windows has no effect since we can't get an effective cross-breeze.

I feel bad about it but I don't have much of an option if I want to be somewhat content. I get quite unbearable to be around if I am suffering in the heat.

As a renter you can look for a more energy efficient space.

If your in-law unit was built without permits (which seems likely since it's apparently below-standard for insulation), you can probably get out of your lease early if you wanted to.

Putting in more insulation doesn't require a full teardown, but it's not cheap if you had to, say, build false walls to add insulation.

More energy efficient space -> remodeled recently -> $$$$$.

I'm not able to afford such a thing. Most apartments/in-laws in my price range (<$2500/month) were remodeled no later than 1970.

Putting in insulation means you have to take down the dry wall (if it is even drywall - might not be). That's pretty extensive for most people.

In most European countries building energy efficiency is required by law and anything under a certain rating cannot be rented forcing owners to renovate with energy efficiency in mind

Depending on what's inside the walls, it may be possible to spray in foam insulation by drilling holes behind the baseboard.

I feel like the climate is so mild or hot & dry in the bay that houses can get away with being badly made and old here way more than other places of the world.

The funny thing about solar panels is that just having panels above your ceiling cool your house a ton.

It makes me wonder if people in hot climates that can't afford solar shouldn't just put white glossy panels a foot above their roof.

There are a lot of other obvious, non-exotic things we can do, like require a certain amount of tree coverage and reduce the spread of concrete surfaces. We could also use shade sails a ton more than we do (which are nice because they can be removed in the winter).

Even white glossy paint gets the job done. My parents recently had the roof of their house painted white and the indoor temperature has dropped by what feels like at least 5 degrees Celsius. This is in super hot North Indian summer.

One thing that was found with solar panels is that because they are dark colored, they heat up in the sun, and on an angled roof, the gap between the panel and the roof has a "chimney" effect that draws the air up and out the top edge of the panels, which helps to cool the roof.

Buckminster Fuller would be proud http://www.stuartmcmillen.com/comic/chilling-domes/

Solar panels became cheap just in time.

Painting roofs white, or using light-colored shingles, keeps buildings cooler. It sounds like white paint is easiest for flat commercial roofs.


Honestly, when we re-roof our home when the shingles go, we're putting on a white roof. I'm sure it will tank the resale value because it will be the only white roofed home in my county or even region, but the cost savings on cooling has to make up for that, to me.

You can get light grey shingles. Might look fine if it works with the paint color of the walls.

I'm thinking about the non-visible wavelength ranges. Changing the IR properties might be very helpful as well.

Is there a particular brand you are considering? I'm planning to change our own roof in a year or so.

It would be nice if there were a cheap way to have a white roof in the summer and a black roof in the winter. Perhaps some kind of temperature sensitive paint that darkens when it drops below 60F or something.

In the usvi every house has a white gloss roof

There is something termed cool roofs. Basically the roofing material reflects a little more light.

I was in Phoenix last summer in what (to my poor Canadian body) was the hottest day ever, anywhere. I think it was like 111F / 44C. While my friends and I were over at an outdoor mall looking for dinner, we entered a spot that was more than 10C lower than the ambient temperature. Just instantly colder. I honestly stopped in my tracks.

Above us, a mister was spraying water. None of the water was coming within 10 feet of the ground as it all instantly evaporated- Phoenix is a desert- but in doing so, the air was chilled. The cold air dropped, cooling this small area.

I cannot believe just how effective this means was. Now, granted, to do this they had to waste clean fresh water in the middle of a desert, which isn't great. But it does go to show the potential of some of these tricks. May not work in 99% humidity, mind you, but there are other tricks up the sleeve of the clever engineer.

It's called evaporative cooling, and until recently the principle was the way the vast majority of Arizonans cooled their houses. (They are called swamp coolers down there.)

It only works in dry climates, but it makes such a difference.

Yeah, I'm from FL. Swamp coolers don't work most days. Just makes ya wetter. I was in Az a couple months ago and it was pretty neat figuring out that sweat truly does work.

Also - it only works for part of the summer; we're in our so-called "monsoon season" right now, and humidity is highly variable, but is generally above what most evap coolers will help with.

However, if there is some evaporation that can takes place (that is, the evap gradient is large enough to let it happen, but directly using that cooler air would make it uncomfortably humid), you can instead do what is called "evaporative chilling" (or something like that), where you run the water over a radiator, and the water evaporates, cooling the radiator (actually, removing the heat), and inside the radiator, you run coolant/water mix - that's your outdoor side. Inside you have another radiator, with a fan circulating air over it. It's something like an A/C system, with water/coolant as the "working fluid" and no compressor, just a pump. Think of it like a "dry evaporative cooler".

This kind of system does work - it's actually used for industrial A/C systems as some kind of "pre-chiller" or something, but it isn't something you can buy for a home that I know of - but you can build it. But like all evap systems, once the humidity gets too high, it stops working.

Another kind of system that can be used here in Arizona, but few do because it is ugly, big, and works only so well - are something called "solar chimneys".

The simplest is just a large 2-3 story structure painted mostly white at the bottom and mostly black toward the top; the idea is that the sun warms it, sucking air thru it and out the top - the bottom end is connected to the house, to make a "forced draft" through the house.

The better way is to make a similar "chimney" on the opposite side of the house and add cooling pads and a fan at the top (basically a large diy swamp cooler). Misting can also be used. So you evap cool the air, which falls, enters the house, then is sucked up and out the other side by the "hot" chimney.

Another "hot climate" design for cooling is something that used to be found all over the middle east:


Sometimes used in combination with:


As you can see, this is basically the ancient form of "solar chimneys" - if we instead used these in Arizona, coupled with either monolithic dome construction and/or rammed earth, and below-grade construction (to take advantage of earth insulation and cooling) - it'd be so much better for energy use here in Arizona.

Oh, this irritated me so much growing up in Tucson. I would read about something like passive water heating, or all of the ways we could reduce our need for AC (even back growing up where climate change was more theoretical) and saw that people didn't care.

> I think it was like 111F / 44C.

HA! That's like a cool summer day - stay a while here in Phoenix, and you can easily experience 120+F days at times.

Nothing like it being 2am and 100+F degrees outside...

On the flipside - shorts at Christmas-time!

I was living in Riverside county in 2016. In late June, I remember one day in particular the thermometer on the back porch read 119F in partial shade. I had to drive to Phoenix later that day to help a family member (one of my wifes aunts, her daughter had recently and unexpectedly passed and she was elderly, alone, was having issues with her AC and couldn't get things sorted out on her own). I left Murrieta around 10PM and while passing through the desert around midnight, close to the AZ/CA border, I had to stop and take a picture of the temperature gauge on my car. Midnight and 102F. It blew my mind. I knew that it was going to stay hot but I'd have never thought that it'd be > 100F at midnight. It gave me a renewed respect for this desert that we live near (and that you live in...).

My question is, why did somewhere so inhospitiable grow so large? There is no stand out industry like las vegas.

In Southern California the dry air often gives me breathing problems so this may offer another benefit besides cooling .

I only use air conditioning once or twice a year (in DC). This article was very interesting, but if you can't rebuild your home you have fewer options. Here's how I deal with it to make it not miserable.

1. You don't need to cool "a house" - just the room you're in. If I do run the air conditioning for 20 minutes before bed, I'll block under my door to keep that cold air in.

2. If there's no reason for you to be in a hot house, then don't be. If I'm teleworking, I end up not just being cooler, but also happier, if I find a nice quiet spot somewhere else. I'm lucky enough that I have a free museum not far from me that has an indoor courtyard I can work at.

3. Air circulation and window fans that expel heat from the room can do a lot. Fan quality and fan placement is tremendously important for circulation.

4. At least the last two minutes of your shower should be cold.

5. Blinds should be closed during the day.

6. Drink lots of water, of course.

I think there's more I can probably do. For example, I've been meaning to research reflective blinds to see if they do more than normal blinds at keeping out heat. (Shutters aren't an option for my building.) Dehumidifiers are also something I want to look into.

I haven't personally found that bed sheets make much of a difference, outside the way too obvious things like I don't use my winter (flannel) sheets. But this might reflect that I only buy nice ones.

Come to Atlanta and try it. My upstairs will get 80 degrees in the morning easily. My wife and my offices are upstairs. Luckily I have 2 units so I can balance it. Even if I didn’t use AC I would have mold problems due to humidity. Dehumidifiers also warm up the room they are in. The only plus is I have lots of tree cover in the afternoon.

I'm in Atlanta. We live in a house built in the 20s just south of I-20. Thick brick walls on all sides, windows laid out so you can create a relatively strong breeze by opening the front and the back windows.

Most days we can leave the AC off. Temps will climb to about 75-76 by mid-afternoon, but rarely get too far above that.

The only part of the house that absolutely needs the AC is the upstairs converted attic. It was renovated in the 80s with no thought to air flow, and no way to get a cross breeze from the windows. So we have a mini-split we can run for that floor.

The house is going to feel warm if you're used to running AC 24/7, but 2 weeks in and 76 with a breeze feels fine.

I understand where you're coming from, the last place we lived was a more modern ranch house near Morningside, with bad layout for airflow and it was MISERABLE in the summer (routinely 90+ by 11am if the AC was off).

I'm just saying design matters a lot here, and makes a big difference. There's nothing special about Atlanta that makes that any less true.

Ranch has better cooling but I actually pay less in my new house compared to the ranch I was in. The ranch I was renting had roof issues. My new place is a 2 story house with half basement and garage underneath. 3 sided brick. Bought a place in Roswell to be closer to work and family.

My wife is almost 9 months pregnant and AC is mandatory!

Why would I try it in Atlanta? I'm not arguing nobody should be allowed A/C. My point is that there's a lot that I do to lessen the amount that I use here in DC.

> I only use air conditioning once or twice a year (in DC).

I'm honestly shocked that's possible after living in the northern Virginia area for a summer. It was miserably hot/humid for the majority of the ~9 weeks I spent in the area.

I do the same living just down the highway in Richmond.

It's easy because I live in an old 1920s apartment with thick brick walls, covered porches, and ceiling fans. The walls insulate most of the heat, the shade over the front and rear windows makes light less extreme, and the fans keep air moving which helps with humidity.

Buildings should be designed to fit their environment. My electricity bill would be much higher if I lived in a modern prefabricated cube with thin plywood walls and nothing hanging over the windows.

I don't think I'll be able to do it when I'm older. Heat stroke is a serious thing and if I ever had a sense that my body wasn't good I'd 100% use A/C more.

(Also I don't have kids.)

I do the same things (at age 60) in the Philly suburbs. I fire up the AC in my bedroom at night only about 5 days per year, and I have none elsewhere in the house.

No, it isn't ideal, but I'm cheap and I don't mind using fans. And frankly, I don't like AC. I hate walking through a blast of 20 degree colder air whenever I pass a register.

I've found that having a big shade tree that blocks direct sunlight from the house helps a lot. (I know this since my shade tree died and was removed a year ago.) My house is natural brick and retains heat from sunlight for at least 8 hours, so any shade helps cool it a surprising amount.

It's the noise of window air conditioners that bothers me more than anything else. My hearing is average, but for some reason I get annoyed by noise more than others. This is true when it comes to everything from restaurants to commuting (walking, subway/metro, etc). I also don't get why people like earbuds over headphones when you can block out so much noise!

I have earplugs, but prefer just not using the A/C.

There's always minisplits - the noisy part stays outside the window. Though it can get annoying when you're outside and multiple neighbours are blasting their ACs.

> For example, I've been meaning to research reflective blinds to see if they do more than normal blinds at keeping out heat.

I can confirm they work. It's much cooler in my small flat when they are closed for day, even though they are inside and a little warm. On a sunny day, my outer wall heats up to 60°C. Inside temperature can be 50°C with blinds open or 35°C with blinds closed. This was with outside temp 30°C and wall directly exposed to sun.

The point about remote work is one interesting downside that I haven't seen discussed before. But it's very real in my experience as well.

Even just from running fans, my electric bill in summer is much higher in months when I'm working from home frequently.

I wouldn't be surprised if I consume more energy cooling my house during a work-at-home day than I do commuting round-trip on the subway.

My MO is to schedule the work-from-office days to coincide with the hottest forecasts :) Wouldn't work well if everyone did the same, of course.

>5. Blinds should be closed during the day.

No, then the plants die, the occupants die a little by being in a prison.

Before AC buildings used to have awnings. They still should. New buildings should have functional overhangs. Often new buildings have an ornamental overhang that does nothing. Also window film can reflect heat so thats an option too

I'm generally not home during the day. Keeping them closed means I come home to a cooler house. But yes, I agree with your broader point being made generally-speaking. When I'm home, I'm using fans, including my window fan to expel heat from inside -- so windows are open.

>I'll block under my door to keep that cold air in.

Wasnt there concern that sleeping with a closed door raised CO2 levels?

And there's a real concern that sleeping with a door open will kill you if your house catches fire.


houses are just too dangerous, time to sleep outside.

Interesting, I hadn't heard that. That certainly makes sense. Might have to stop that one. This was just the one or two times I use the A/C, because otherwise my bedroom windows are both open (one of which with a window fan). But yeah, I hadn't considered that!

Reflective blinds aren't a bad idea, but at that point the sunlight is already on the wrong side of the glass. Much better to cover the outside of your sunny windows, whether that's with fancy powered shades, uv-blocking film, or simpler roman shades, bamboo screens, and awnings.

Or build an arbor above the window with grapes or other leaves that will block the sun in the summer, and let sunlight through in the winter.

I saw a neighbour covering the windows with reflective oven foil on the inside. Should work to reflect the heat back out.

> I only use air conditioning once or twice a year (in DC). This article was very interesting, but if you can't rebuild your home you have fewer options. Here's how I deal with it to make it not miserable.

Note that even if you can't rebuild the house, there are still steps which can be taken like interior wall insulation, replacing windows, …

If you live in a dry climate (I'm in Colorado), consider a swamp cooler. It's an amazingly simple and efficient machine: just a water pump and a fan, and peanuts in electrical costs compared to a full air conditioner. As long as you can establish airflow throughout the home, it feels just like A/C on days below 95F; you won't feel chilly on 95F+ days, but it's still quite livable.

Swamp coolers are ubiquitous in New Mexico too, but they're falling out of fashion for new construction. Partially because they require a lot of maintenance, but mostly because water is no longer being seen as free and unlimited here in the high desert.

The maintenance issue could be remedied with better engineering. But the water issue will require lifestyle changes that include getting serious about recycling gray water and harvesting rainwater, both of which are basically illegal now in many parts of the West.

I have a swamp cooler in Reno NV, and on 95+ days if I leave it on all day on max the house will be 60-70 degrees. It works so well I rarely run it on max settings as it just gets too cold. Of course there are some draw backs like swelling due to the humidity, and if there is smoke in the air I can't run it.

>draw backs like swelling

swelling of what, my I ask? (My guess would be the drywall or plaster of the home being cooled.)

curious why can't you run it if there's smoke?

It pulls in air from outside. So if their is smoke in the air from a wild fire then it will just fill your whole house with smoke. So you can run it, just highly ill advised.

What about dust storms? Seems like some areas in the American Southwest (AZ, NM, West Texas) are dry enough for swamp coolers, but they also can have these insane dust storms that are so intense you can't see to drive on the highway.

They are cheap, but they are also frequent causes of rotting out the structural members around the cooler. Beware leaks!

Yeah and to add to this, adding too much humidity inside of your home can cause mold and other rot issues, not just around the wet swamp cooler itself. AC is definitely most convenient, maintenance, and hassle free for most people, but swamp coolers can be good if you are attentive and diligent about maintenance and noticing problems before they get big

Good to know.

I lived in a house with a swamp cooler, it was miserable. Instead of hot and dry, I ended up hot and wet.

The Earthship[1] were designed to solve this problem (among others).


Fun factoid: Joey Hess (Debian developer & creator of git-annex) lives/lived in one: https://joeyh.name/blog/entry/hackerholler/

His blog has occasional experiments with off-grid and low-power living.

My next house will be an Earthship. My current house has an amazing permaculture footprint, but I want to demolish it and rebuild. Can't though, so I'm looking for land instead ..

Persians know for millenia how to store ice in scorching desert [1] and have in places like Yazd 'windcatchers' [2]

I've seen through Islamic world and India buildings at least 500 years old that were constructed around constant air flow through buildings, having patterned stone mesh windows. It can be done with low tech approach.

[1] https://en.wikipedia.org/wiki/Yakhch%C4%81l [2] https://en.wikipedia.org/wiki/Windcatcher

My question: Is it healthy or safe to live in a house or apartment that has no working AC in areas like the southeastern US. I know AC is a modern luxury and that people survived for years without it, but I wonder if the design and construction of later houses or apartments affects anything. My AC ritualistically dies every summer and while I wait for maintenance to drag its feet, I often find myself waking up in pools of sweat

When really bad heat waves hit Europe where home AC is rare, they can kill thousands (mostly elderly).

The 2003 heatwave killed upwards of 70,000 people (in France, 8 consecutive days of 40°C [104 °F], in the Netherlands it reached 37.8°C) https://en.wikipedia.org/wiki/2003_European_heat_wave

This is what really scares me about cities like Phoenix, that can get so hot, have a high elderly population, and are increasingly vulnerable to blackouts. What is going to happen if the city loses power on a 110 degree day?

Some of them will die.

It's that brutal. It's also something people used to do a lot of, especially if they were working outdoors.

I've seen house designs for the South which have an open central corridor. It catches and channels any wind and helps cools the rooms on either side.

I'm sure there are other tricks, but builders don't seem to know them any more, and architects build more with a view to looks than practicality.

Modern architecture - whether it's McMansion design, concrete box design, glass tower design, or suburban vernacular design - can be almost criminally stupid about environmental issues.

There are exceptions, especially in the occasional environmentally controlled low-energy office block.

The reality is that it's possible to manage heating and cooling far more intelligently and effectively in most kinds of buildings. But it's considered a fringe eco-hippy interest and not something most of the population needs to care about.

> But it's considered a fringe eco-hippy interest and not something most of the population needs to care about.

Here in Arizona, if we built things for cooling more like in the middle east (windcatchers/solar chimneys/qanats + thick walled rammed earth and/or monolithic domes), it would probably be more energy efficient.

But I can't imagine that style would go over well with our current (overall) political climate here...

Do you have any recommendations or resources on this topic?

I've never visited Phoenix but isn't it the humidity combined with temperature that makes it unbearable?

Here in NY, with high humidity it can be upper 80s or low 90s outside but when you factor in the humidity you have no way to cool off. You can be laying down doing nothing but dripping in sweat. Combine that with being in an apartment that's on the upper floor with bad insulation and forget it. I imagine it's even worse in places like Florida.

It's also crazy how big of a difference there is between an upper floor that's poorly insulated vs a basement. You can expect a 15-20f degree difference.

Humidity makes a huge difference that is true. But even if it is 0% Humidity Phoenix regularly gets over 110 degrees Fahrenheit, which is more than hot enough to kill.

In North Central Florida where temps get up to 100 or 110 (we're not on the coast) AC feels like it is necessary but I've known of people who have lived here without it. A series of fans and knowing which windows to leave open and when is the key. It's all in the construction of the house too. When people immigrated from Europe to the southern United States the typical construction of these houses was a very tall house with giant windows which open up. Since heat rises these early houses were built around this premise and people around here have been here a long time. Otherwise ice arrived by train and was placed next to a fan which was mechanically operated or by hand in the old days. My native ancestors from this area lived in log cabins (not teepees or huts as commonly described in history books) and the wall-less thatched structures were communal gathering spots not their actual homes. Modern construction with all the prefab elements and insulation is suffocating in my opinion and this is why, by choice, I live in a wooden house although yes I do have AC and enjoy it very much.

I'm from FL and I remember houses used to be built to help with the heat. It was still hot, but you'd have porches and eaves to block the sun and windows situated such that you could open them to create airflow through the house. Now, everything is a sealed box so AC is absolutely necessary.

You should invest in a very good, decently large fan, and when this happens, have it blowing on you while you sleep. When truly miserable mist yourself with a spray bottle of water, and then sit in front of the fan. Evaporation of your sweat and evaporation of the sprayed water both hep bring down your body temperature.

A wet rag works great too

Design is a huge difference. Old houses have high cielings to trap heat and vent easily with windows open. Hallways are arranged to move air across the house. Modern construction generally doesn’t take any of this into account because ac is the bandaid for bad design.

Thick stone walls (well brick). I live in Hungary EU, lot of old houses (early XXth/late XIXth century or earlier) has really thick stone walls. In the summer it keeps the house cool (as long as you close the windows and shades) and in the winter it keeps the warm inside. Even if the temp outside is +35c the inside is between 23-25c (or even less)

As I understand it, the difficulty with this approach is that it depends on the night being significantly cooler than the day. Heat from the day can radiate away during the cooler night, preventing cumulative heat buildup in the stone, which acts as an insulator. But one of the effects we're seeing from climate change, even in Europe, is that nights are warmer as well.

(This was discussed recently on an HN thread, but I can't find it.)

Just got back from Rhodes in Greece and their architecture is interesting (given that day time temps where 32-35C and night time temps 27-29C) - everything was built thick and massive with overhangs on any windows that get sun, shutters on every window during the day (and AC but often off) and everything was painted white (or very pale shades of blue, yellow or pink).

It was interesting to see how they've built to adapt to their environment.

We had a north face hotel room and with the massively thick walls and double glazing (plus no direct sun) the room was just about bearable at night even without the AC (which was actually outputting much less cold air than the AC I had in a hotel in Manchester this year).

My wife and I a couple of decades ago took a camping road trip down the middle of New Mexico, starting near the top of the state. One of our first stops was to visit the Acoma community, which is a pueblo built on top of a mesa; very few people still live up there. The various "apartments" are passed down matrilineally, which was an interesting thing to learn.

It was August, and very hot outside - well over 100F. Inside one of the apartments on the tour, someone was selling snowcones - a welcome relief. We went inside (had to duck under the doorway, as it was only 4-5 feet tall) and it was easily 20-30 cooler than the outside. The only thing we could figure was that being on top of the mesa, plus night temperatures, and the thick adobe construction, all acted as a thermal-mass barrier system or something. It was really amazing to experience. I honestly wish that kind of construction was more common here in the southwest.

Partially the curse of cheap energy - throw up a cheap shitbox and then use vast amounts of power keeping it cool.

Be interesting to see if that changes in a warming world, I hope so.

I have found (in mild but sometimes warm South Africa) that the best bet is to prevent the sun from getting through the windows.

Curtains/blinds are not nearly as effective as external shutters or some kind of external blind.

I make my own frames with light coloured textile stretched across it that I attach over the sun-facing windows, which has a dramatic effect without completely blocking out light.

One thing my wife and I have done to our house, which is a regular "ranch style" 1970s home - here in Phoenix, Arizona - is to add on our back porch "house curtains".

Our porch faces toward the west. We have a huge mesquite tree back there that shades the house during latter part of the day (plus our patio is covered), but in the later afternoon, sun will shine in as the sun sets, and heat the house up. So we strung aircraft cable with small turnbuckles and hung up colorful polyester fabric shower curtains (this was a recent change, originally we had used canvas dropcloths, which worked well too - but were difficult to keep clean). We can slide the curtains "closed" to block out the sun in the evening.

Between that, plus having double-glazed windows installed, extra insulation in the attic, roof ventilators, and the fact that our house is of concrete block construction (not stick frame) - while we still have to use AC, we find that we can keep it set higher most of the time, and during the early summer/spring and late summer/fall times - not at all (opening the windows at night and using fans to bring in cooler air - then closing things up in the morning before it gets too hot). It's noticeably reduced our bills, considering how old our house is (and we have two heat pump AC units on the roof - that has it's own interesting story, but not relevant here).

This is one of the key points of the PassivHaus standard: design your building to maximise sun uptake in the winter, but minimise it (with large over hangs) in the summer.

Yes, a building in San Francisco doesn’t need air conditioning in the summer, what a surprise. Make the same design work in Phoenix Arizona and we’ll have something.

This is a weird critique.

Even in Phoenix, the need for air conditioning can be reduced by designing houses well. As the article notes:

> Even in exposed, hot and arid climates, cooler temperatures are never too far away. In Jaipur, the capital of Rajasthan state in northern India, daytime temperatures regularly reach upwards of 40C in the summer months. But just a few metres below ground, the temperature of the earth in the region remains a much gentler 25C, even through the fiercest summer heat.

See also: windcatchers and underground aqueduct (qanats) in traditional egyptian and persian architecture.

> But just a few metres below ground, the temperature of the earth in the region remains a much gentler 25C, even through the fiercest summer heat.

That can be a risky bit depending how it's used specifically e.g. london's underground was pretty much freezing when it first opened but the clays have a hard time shedding heat so these days the walls warm up the undeground.

yes - but that's because there are big huge electric motors in there that spew out quite a bit of heat, as well as all the bodies, and the deeper (hotter) tunnels are very closed off.

This is talking about digging down a few metres and having a loosely covered courtyard in the space, very different.

At first, New York and London [0] metro lines were cool too. Pumping heat underground will not solve your problems in the long run. But this is only nitpick to this one particular cooling method. Maybe something like sending your heat to space[1] or better insulation will help.

[0] https://www.wired.co.uk/article/central-line-temperature-lon...

> When much of central London’s Tube network opened in the early 1900s, temperatures in tunnels and at stations were recorded at around 14C.

[1] https://physicsworld.com/a/keeping-buildings-cool-by-sending...

From the article on London:

> To understand how more of the Central line could be cooled down, just look at the Victoria line. In 2006, a similarly experimental groundwater cooling system was installed at Victoria station to lower temperatures in mid-platform areas. In 2011, TfL completed the installation of 13 ventilation shafts throughout the Victoria line, while the new fleet of trains running on the line allows TfL to operate a regenerative braking system, which returns power to the rails when a train brakes. And when a whopping 38 per cent of heat generation on the London Underground comes from trains braking, that’s a pretty big deal.

It's basically another example where sensible design can make a huge difference.

If you pump heat from the building into the ground, isn't that just a form of air conditioning? (Sure, it's a more efficient version than air-source phase-change refrigeration, but it's not without air-conditioning as I see it.)

The article is mostly taking about passive solutions. But yeah, geothermal heat pumps are just refrigerant based A/C systems with the condensor (or evaporator, or fancy reversible valve to switch back and forth for heat or cool) stuck in the ground.

I'm skeptical. Jaipur, right now during the day, has 60% humidity at 90F. If you lower your temperature with transfer into the ground then you're not lowering humidity but only temperature. That means relative humidity will go UP. I suspect even 80F at 90+% humidity will feel really unpleasant.

Boston here: yup, 90% RH at 80F is awful. 40% RH at 80F is merely warm, and a fan works well to alleviate that.

> I suspect even 80F at 90+% humidity will feel really unpleasant.

That's hardly likely in Phoenix.

Your quote is about Jaipur and not Phoenix. I am responding to your quote.

The article specifically indicates it (and other techniques in concert) works in Jaipur. It's not going to work 100% of the time in all places, but even in hot, humid areas improvements can be made.

> This allows air conditioning to be used very modestly, when it is necessary at all.

I'm not sure why every thread about energy efficiency improvements has people come in and do the "it's not a perfect solution for these edge cases" thing. Everyone knows that already, and it's totally beside the point.

Building office buildings in a way that makes them essentially giant greenhouses doesn't help with the AC bill either.

As you get into multi-story office and apartment buildings, your options for passive cooling get pretty significantly constrained.

Thick walls, passive roof cooling, maybe partly sunken... These things can work for a standalone house or certain types of commercial buildings but they're harder to work into bigger structures although evaporative cooling at least can be used.

There's a neat example of what can be done with multi-story buildings in Zimbabwe.


Neat design though, as the article says, Harare has a pretty temperate climate. In general, the higher elevations in a lot of East and Southern Africa have climates that are often as nice as the lower elevations are often not nice.

Phoenix isn't that bad since it's got cool nights and low humidity which you can work with. Florida on the other hand, good luck.

Eh, don't think you've been in Phoenix in the summer. Nights are still triple digits, which is the main thing that makes the summer so brutal.

Phoenix regularly has overnight lows above 90F. It's pretty bad.

The problem is all of the concrete. Get outside the heat dome and it cools considerably. You just have to rethink the building pattern. (White roofs with water collection would be a good start.)

Agreed. I lived in the southeast valley for 16 years. At the start of it, we were fairly near the edge of the sprawl, and now you have to drive another 20+ miles to get out of suburbia. It's definitely had an effect on temperature, particularly overnight.

I visited Savannah, GA this summer. In the 19th century houses were designed to have tall ceilings to capture heat, and large doors to verandas to capture wind. It was actually tolerable inside when touring these old houses.

Also, windcatchers are pretty cool too: https://en.wikipedia.org/wiki/Windcatcher

Interesting, is that why Victorian houses (in SF and elsewhere) usually have high-ceilings?

I thought the obvious solution is solar powered run AC. What am I missing?

That doesn't solve the problem of the refrigerants.

1234yf is the new refrigerant in cars. It has a global warming impact of 1, R-134a for example has a GWP of 1430. If we move to that it won't be much of a problem.

Solar powered AC would require a very large panel array and battery bank. ACs are quite the energy hog.

I have a 4.5kW solar installation and 26kWh of storage. I'm not sure what large or small is, but it didn't cost much and only covers about half of my house's potential solar roof space.

That's enough for our old house to be net zero in the Southern California summer, A/C and everything.

Modern houses with actual insulation in the walls, and windows that don't turn the rooms into solar ovens, would fare an order of magnitude better than even my modest solar setup.

Why not have solar panels on the roof absorb all the sunlight and keep the house cooler via an air gap?

Furthermore, I would love to have water heating this way. Solar panels heating a water container in the winter, that is mixed into showers and even small pools on demand.

Any observant Jews here who don’t want to use water heating on Shabbat? This may be a great idea.

PS: Heating a house is the only application of Proof of Work Mining that I approve of. But even then, I would rather it be useful work like SETI or protein folding:


There are also air conditioners that don't use refrigerated air. The principles of it are similar to the evaporative cooling mentioned in the article but with a fan and water pump. If your climate is dry enough to use it, it can be a great option and much cheaper than refrigerated air. You'll see one on the roof of almost every home driving through certain neighborhoods of El Paso.


This reminded me of zero electricity air-con made of plastic bottles: https://www.straitstimes.com/world/zero-electricity-air-con-...

The hot air flowing from outside through your windows could be compressed making it cool.

I wonder if there are existing, not so ugly commercial products providing that. This could be a green alternative for air-conditioning.

> The hot air flowing from outside through your windows could be compressed making it cool.

Compressing air actually makes it hotter, but that's not what's happening. Forcing air through a smaller space makes it flow faster, which ironically makes it less dense -- and hence colder.

It's the same effect that people claim holds airplanes up. (But doesn't. That's mostly the angle of attack.)

I don't understand this heat engine yet, one it exits the bottles it contracts again, heating up? it cools the window but heats up the air?

Alternatively, you could power an A/C with a micro wind turbine. Both have the same problem: no wind, no cooling. I'm currently in 30ºC and the tree leaves barely move.

Granted, I live 'up north' but it still gets hot in my new house. I mounted some exhaust fans in the ceiling to pull the hot air from where it naturally rises too. Combined with the forced air furnace fan to circulate cool air (pulled from floor level). Finds the inside of my house 9C cooler on the hottest days of the year.

This is especially important as the brick gets heat soaked and releases its heat well into the night.

Maybe one of you smart people can solve this "mystery": The old farmhouses here in the region (Flanders) were all built with their length axis on the north-south line, no matter where the road was.

An old farmer here claims that such a house is cold in summer and warm in winter. I once saw an architect on TV claim the same thing. But I was not able to find any explanation for this anywhere.

Ceiling fans are ridiculously effective. I'd seriously consider installing one in the bedroom after the past few years of heatwaves.

As long as the perceived temperature is below skin temperature, yes. But when it goes above and when humidity is high no fan can help you..

(It's a bit more complicated than that, but basically when you can't

You do need ceilings of a certain height. I live in an old farmhouse and the ceilings are just too low.

I agree that they're great if ceiling height supports them.

Even if you have 8-9 foot ceilings, consider a low profile ceiling fan rather than the sort that hangs down a foot or more.


The fingers of the next tall person to stretch his or her arms near your fan

My bedroom's just over 7 feet. Old New England farmhouse :-) So a ceiling fan doesn't really work even above the bed because I'm the tall person who will get nicked by it.

Why not? I've had one for years - they work very well.

Why not yet? Cost/effort for the so far relatively short amount of time it would be used. However that amount of time is increasing it seems.

Installing a ceiling fan is a pretty easy DIY project if the room already has an overhead light fixture. They can regularly be bought for less than $100 in many chain stores as well.

This guy grows oranges in Nebraska using very little electricity. He mentions in the video the same principals can be used for cooling.


I live in the southwestern USA, and have no air conditioning. I do have a solid brick house that is an awesome insulator. So we open up all windows and doors at night, and close the house up tight when the sun rises, putting heavy curtains over the windows. It still gets warm - up to 85 degrees inside on a 100+ degree day, but you get used to it.

It wouldn't work on all the suburban homes around us. The walls aren't insulated enough, there are so many windows that you'd never get them all covered.

> you get used to [85 degrees inside]

I sincerely hope that my future places of work and residence will not regularly subject me to 85 degree interior temperatures on the assumption that I will "get used to it" -- which I strongly suspect actually means "live with it."

> actually means "live with it."

No, it means the human body acclimates to its environment. You really do get used it.

I spent a summer at those interior temperatures without AC. I stopped "noticing" it, but my subjective ability to focus and objective running & flash-card-app performance did not recover until the temperatures did. How long does it take to "get used to it?"

A couple weeks, according to folk wisdom, which matches my anecdotal experience.

I'm curious if you went home to cooler temperatures, or if your whole summer was spent in warmth? I definitely have experienced harder times going back and forth vs. always being in the warm environments.

I spent the whole summer in warmth, days and nights. A couple weeks is what it took me not to notice it anymore, except insofar as it affected my performance. That's what I meant by "live with it."

I spent Christmas in Florida and noticed that many people who lived there seemed to find temperatures in the 70s chilly enough to wear a hoodie or something while I had just a t-shirt on.

Conversely, I've noticed that when it first gets cold in NY, it's very biting and unpleasant, while late in the winter, the same temperature doesn't bother me at all and near freezing temps actually feel a little warm.

So I find that the timeframe for me at least is more than a week or two, but no more than about 3 months.

we've been living in our current house for 11 years. it is a little over a km from the beach in Denmark, it has big doors that open onto the front porch and in a direct line with those doors are the windows in the bathroom, in the summer if we had both open we never experienced the house getting hot. That has actually stopped this year - now we sweat inside. But until this year we had a pretty good way to keep the house cool.

Interesting that this article is posted on the eve of Burning Man. This year should be especially hot. Every year I bring a simple swamp cooler, this year I'm going a step farther and bringing 2, plus an active ventilation fan and ducting. My total power consumption is about 18w, not too shabby to bring down the temps about 15f in ~1000ft^3 space and well within my modest solar panel setup.

The article focuses on strategies effective in arid climates. In California, evaporative coolers worked really well for us except on the hottest days. No way they'd work for us here on the US East Coast.

OTOH, I'm pretty enthusiastic about the exchange systems that circulate fluids to exchange heat with soil beneath home. That's a really reasonable approach.

The best part about southern california is even if its 100 during the day, it will be a brisk and breezy 70 once the sun sets.

Funny that this article doesn't talk about keeping warmth out. Whatever you can keep out you don't need to cool. So invest in:

- Insulated glazing

- Sunscreens in front of windows

- Wall and roof isolation

The nice thing about this is that these measures also keep you warm in the winter (lower energy bill), it's a double-edged sword.

UV reflective film on the windows seems to be helping one room in my house which was consistently 10 degrees fahrenheit warmer than the others. Alternately, but a little uglier, taping white kitchen paper towels to the window solved the problem as a temporary solution.

Obligatory reading: The Revenge of the Circulating Fan https://www.lowtechmagazine.com/2014/09/circulating-fans-air...

I really wish I could have a well-designed (for electricity use) house. Unfortunately, they don't seem to exist unless you build it yourself, and I can't even dream of doing that (although to be fair I can hardly dream of buying a house at all).

My house has an attic, and an attic fan or vent helps a lot.

I have cheap asphalt roof shingles (even so, $10K to replace them)- I did look into reflective shingles, but they were much more expensive, plus I had to consider resale value..

Attic fans are great for cooling at night, but I've found they make a difference only at cooler latitudes like Michigan where night temps fall 15 or 20 degrees below daytime highs of ~85F, reducing the house to 65 or 70 after sunset.

In the mid-Atlantic where I live now, night temps don't drop more than maybe 10 degrees below daytime highs of ~90F. So bringing in the evening air via an attic fan puts the house at no less than a toasty 80 (with 70% humidity) -- still uncomfortable.

Attic fans are great anytime the air temperature difference between the attic and the outside is great. In the hotter regions (such as the southeast US) they're great for venting hot air out rather than pulling cool air in. Attics will often get 20 degrees hotter than the outside air, so forcing that out helps to insulate the cooler indoor spaces.

Of course in older, not-well-sealed housing the venting poses the risk of drawing cooler air from the house to the attic, negating much (or all) of the benefit. So their efficacy is very situational.

Attic fans aren't for cooling attics. Ridge vents, and passive and powered roof vents, and turbines mounted in the roof surface can cool attics far more efficiently than attic fans which consume over 100 watts and must run continuously on summer days -- a very costly way to air out an attic.

Though old houses often have attic fans, they weren't there to cool attics. That was the purpose of widowed attic gables or breathing slats under wood shingled roofs. Attic fans are there to cool the house interior, especially the hottest rooms on uppermost floors. That's why the intake of an attic fan is the highest point inside the house and not the lowest point inside the attic. Even then attic fans aren't intended to run for more than perhaps 30 minutes a day after sundown -- just long enough to replace the hot air inside the home with cool air from outside.

To vent an attic, the ideal air flow is to intake cool dry outside air from along the attic soffet, pass it along the underside of the hot roof sheathing, and have it exit high where attic heat is at its peak. And do this passively without a powered fan if at all possible.

In Houston? No. Next question.

If you read the article you would see that in India, with daytime temps regularly exceeding 40c just a few metres down the temperature is only 25c.

So yes, in Houston.

Until relative humidity hits 100% at 80F and you hate your life (and your house due to the condensing moisture). Air conditioning is in large part about humidity control which using the ground will actually increase as best I can tell.

You know nothing about Houston if you think we can go "down" at all without digging a swimming pool.

Humidity is as much the enemy here as heat. AC is how we mitigate that.

Not sure how far down you can go in Houston before you're under water. Downtown is only 15m above sea level apparently.


What about everywhere else? There are other places. Some of them are not Phoenix or Dallas either.

Well, sure. There are lots of places in the US (and elsewhere) where you don't really need AC. It helps to have good ventilation, maybe some fans, and possibly other passive cooling. Maybe just deal with a week or two of uncomfortably hot weather during the summer.

Of course, it also helps to live in a house that is out in the country or at least suburbs rather than a city apartment. A window AC unit or two also can help for things like cooling a bedroom for the hottest nights.

I thought Houston is dry enough that you can use swamp coolers? (They work by evaporation.)

Houston is beside the ocean and in generally swampy areas. Its average humidity range is between 60 and 90 percent depending on time of day. Hard to evaporate in those conditions.

Shows how little I know about Texas!

Most people don't realize how large and varied Texas is. Driving across TX takes a day. West TX is what a lot of people think TX is, dry, hot, flat, boring desert. The area near the gulf, including Houston, is humid and green.

Texas weather isn't uniform because it's a very large place

Houston (https://en.wikipedia.org/wiki/Houston) is absolutely not dry in the least. I'm guessing here, but I'd be hard pressed to name a more consistently humid US city.

Obviously, Texas is a single place to people who don't live here, but be aware that at 269K square miles (686K sq km), it's fucking huge. It's almost 800 miles across (ie, the distance between Louisiana and New Mexico).

So there's LOTS of variety in climate. The dry climate you associate with movie-Texas does definitely exist, but mostly in the western half of the state, & especially as you move down towards the Mexican border.

Houston, however, sits on the Gulf Coast. (Houston proper isn't on the water, but the overall metro area includes Galveston, which is an island in the Gulf.) The Gulf Stream curves over us and keeps us warm and wet.

Not for nothing, but our annual rainfall is pretty insanely high (~49 inches).

See more:


Anyway, in a very humid place like this, swamp coolers that depend on evaporation are of limited utility.

This article ranked 50 US cities by humidity:


Houston got the #3 spot. Only New Orleans and San Francisco are more humid.

(Another city on the list: El Paso, TX at #47.)

No even close. It's basically on the gulf coast and for the hot half of the year at least very humid.

Also, barely above sealevel, so lots of techniques don't work.

Climate wise, it's a pretty uncomfortable place to live.

It's not bad in winter though...

... but not good either. And "extended" summer is gross.

Same in LV.

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact