
Passivhaus Detailing and Design - simonebrunozzi
https://architizer.com/blog/practice/details/passivhaus-complete-guide/
======
donquichotte
I remember seeing a very different approach with a very similar goal in
Vietnam.

In Hanoi, many houses have a small greenhouse-like glass structure on the
roof. The greenhouse has a chimney. When the sun is shining, it gets hot in
the greenhouse and the hot air escapes through the chimney. A hatch through
the roof into the greenhouse draws new air from below, essentially creating a
passive, sun-powere air-flow through the whole house, bottom-to-top. Usually
some windows on ground level are left open to let air in.

~~~
buckthundaz
FYI this is called a "solar chimney"

[https://en.wikipedia.org/wiki/Solar_chimney](https://en.wikipedia.org/wiki/Solar_chimney)

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upofadown
People tend to confuse the passivhaus idea with other energy efficient
methods. The passivhaus idea is that if the building has sufficient insulation
and is air tight, you can use the air from the heat recovery ventilation
system to do any required heating cooling. This simplifies the mechanical part
of the system.

As a result, such houses are very well ventilated when it is cold outside.
Mould is not a problem. The potential problem is instead excess dryness in
places where it gets very cold.

~~~
n1000
The dryness problem normally only occurs if the air change rate is higher than
the recommended 0.3. In large buildings this requires rather sophisticated
ventilation systems. There are also heat exchangers that recover humidity.

~~~
ip26
In fact I found that it seems ERV (recovers heat & humidity) is more common
than HRV (recovers only heat) these days. Possibly for the simple reason that
ERV suffers less from the exhaust icing up.

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nebulousmenace
There's a countermovement, the "Pretty Good House" idea (
[https://www.greenbuildingadvisor.com/article/pretty-good-
hou...](https://www.greenbuildingadvisor.com/article/pretty-good-house-2-0) .)
It has the goals like "simplicity" and "avoiding diminshing returns" (the
80-20 rule: 20% of the work gets you 80% of the improvements, in this case.)
It avoids certification and excessive rigor. (One article about it mentioned
the split between Passivhaus and Passive House. As I recall it was over the
amount of shading from one southern tree.)

My point, if any, is that it's not "Passivhaus or nothing."

~~~
simonsarris
Oh thank god. This is the approach I had when I built my house. This is IMO
the most desirable territory: Just try to maximize the easy assets of wind and
light using traditional methods, and add in modern insulation.

Few(???) architects and zero builders seem to understand
light/wind/circulation like people apparently intuitively did 200 years ago.
You might be better off with the average curious engineer designing a house
after reading a couple books than the average architect. Everyone is
astonishingly lazy, even mansions around here have terrible light/circulation
problems. But if you care, you can totally design a good one yourself that has
very low operating costs (our electric bills are 50-80 a month in a 2200sqft
house. We use maybe 3 cords of wood a year, but that's very approximate).

It does not take a lot of work to design a house, especially if you want to
build an efficient Colonial style. My goals were simple: Build something that
appears traditional, maximizes light and airflow and wood burning heat. Think
about ventilation passageways as the windows and doors, and think of the wind
as coming and going. Since heating is easier than cooling (we built in no AC
system and zero ducting), make your ceilings taller.

A little wood stove (Vermont Castings Encore) heats the whole thing. Spray
foam insulation in the walls (plus fiberglass), tall ceilings, and modern
windows (lots of them) is all you need.

Some pics of what I built, with design sketches:
[https://twitter.com/simonsarris/status/1183143604925190144](https://twitter.com/simonsarris/status/1183143604925190144)

~~~
pbowyer
> Few(???) architects and zero builders seem to understand
> light/wind/circulation like people apparently intuitively did 200 years ago.
> You might be better off with the average curious engineer designing a house
> after reading a couple books than the average architect.

Any book recommendations, especially around wind/circulation?

~~~
simonsarris
None of that specifically but read:
[https://en.wikipedia.org/wiki/Windcatcher](https://en.wikipedia.org/wiki/Windcatcher)

I realized that the cupola on my 1840's house growing up, this was it's
function. Wind pulls air through, which pulls air up into the attic, which
cools the first and second floors.

Then read _The Timeless Way of Building_ and perhaps _A Pattern Language_

Then _Get Your House Right_ , or a condensed (...in a way) version is _Drawing
for Architecture_ by Krier.

Hmm there are probably others I cannot recall right now, but those are a great
start.

------
neilwilson
Just bought a brand new house here in the UK and the house has a SAP designed
footprint of 85kw/m2/a compared to the Passivhaus standard of 15kw/m2/a.

Unfortunately I have no choice. Unlike in Germany I don't get to buy the land
and pick the builder. The two come bundled in the UK. And will do until we get
political change that breaks up the building oligopoly.

~~~
brnt
Here in NL the two are also usually inseparable (you buy a house from a large
project, typically 100+ homes/apartments, sometimes even 1000+). But, just
looking around our two countries, it just seems requirements in the UK must be
lower. The average house just seems less well built.

~~~
tonyedgecombe
There were some improvements on the way but when the current Conservative
government came in they scrapped them at the behest of the big builders.

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choeger
Sadly it looks like that idea is not that sustainable. A Passivhaus (well,
every current Niedrigenergiehaus, actually) is a very complicated matter and
comes with some intrinsic problems:

> Airtight design resulting in draught free construction

That airtight design leads to problems with mold if you have any cold spots.
These spots can occur due to construction faults, material faults, or any kind
of acquired damage. For instance, you might not even notice that your windows
do not shut exactly as they were supposed to after a few years.

In the end, the repair of such a complicated design is again very complicated
(especially after a decade or two have passed and technology has again
advanced), expensive, and error-prone.

So for me, I'd rather prefer to take an existing, robust and dry building,
insulate it somewhat (especially roof and windows) and put in a regenerative
heat source (wood, electric) but not to focus too much on the actual energy
needed.

~~~
sourcesmith
The mechanical ventilation with heat recovery deals with the humidity problem.

~~~
Gibbon1
What if I don't want to live in a plastic box?

~~~
sourcesmith
What plastic box would that be?

~~~
Gibbon1
All the closed cell plastic foam needed to meat passive house requirements.

A point. All the energy savings disappear the moment you open a window.

~~~
sourcesmith
I think this has already been addressed by the sibling comment to my question.
Insulation does not have to impermeable. Its purpose to prevent the loss of
air carrying heat with it, not the transfer of moisture/humidity.

~~~
Gibbon1
If it's permeable then water will condense inside it and it will develop mold
and deteriorate. That is the fate of all of these passive houses.

~~~
throw0101a
Not necessarily. Mold grows in certain conditions: food availability, right
temperature, water/moisture.

Ideally you would want your insulation outside of vapour barrier:

* [https://www.buildingscience.com/documents/insights/bsi-001-t...](https://www.buildingscience.com/documents/insights/bsi-001-the-perfect-wall)

* [https://www.youtube.com/watch?v=rkfAcWpOYAA&t=22m58s](https://www.youtube.com/watch?v=rkfAcWpOYAA&t=22m58s)

* [https://www.youtube.com/watch?v=hTwq-qUnr9I](https://www.youtube.com/watch?v=hTwq-qUnr9I)

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adrianN
I don't understand why we don't mandate stricter energy efficiency for new
buildings. Why is it still legal to rely on fossil fuels for heating for
example?

~~~
im3w1l
The obvious answer is cost. How long do you want young people to live with
their parents to save up for the efficiency improvements you propose? How much
longer should their mortgage be? How many people become unable to afford one
at all and have to live on the street?

I have a friend who is a building a house by himself. I think that's really
cool. If you set standards too high that wont be possible.

Finally bureaucracy sucks. Even an "obvious" regulation that all houses
follows like "your house has to have a roof" has the potential to become
seriously annoying if you have to get an inspector who is only available in a
month and only on Mondays 9-10, to take a look and write a statement that your
house indeed does have a roof.

~~~
ip26
The sad thing is the cost is recouped in energy savings very quickly, and
there's never a better time to add inexpensive subslab insulation than right
before you pour the slab.

~~~
im3w1l
Don't get me wrong, I agree there are a lot of arguments in favor of building
efficient houses!

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geff82
Interesting that this comes up now in 2019. I'd say, while a Passivhaus is not
the standard in Germany yet, you can simply go and buy one, like you can
choose a special version of a car and simply order it. Passivhaus is still
cool, but nothing extraordinary from the future.

~~~
jayalpha
It comes with several disadvantages. Like no air circulation (except air
condition, what is probably a must in such a house), mold problems etc. ...

~~~
n1000
That is simply wrong. The passive house standard requires ventilation systems
with highly efficient heat exchangers. This makes for good air quality. The
massive thermal insulation ensures that no condensation occurs in the
interior, i.e. no mold problems. A common problem, however (esp. if
inexperienced planners design the house) is too dry indoor climate in winter.
This happens if air change rates are too high and no humidity is recovered.

~~~
bipson
The regulations for Passivhäuser (or houses with the respective efficiency
rating) in fact require a ventilation system with heat recovery (since the
otherwise necessary open-the-windows-like-a-savage-system wastes too much
energy).

These nowadays come typically with moisture recovery (which arguably not
always works well enough, depends on how much you still need to heat).

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raxxorrax
> The Passivhaus has a continuous airtight barrier [...]

Theoretically that could work with a reliable air conditioner. In practice, I
know quite a few passive houses that have problems with mold.

And seriously, no air conditioner is superior to opening windows, don't kid
yourself.

A "normal" house with a good insulation (don't overdo it) would be my
preference.

~~~
AliAdams
Apologies for the tangent, but I'm interested; Are there problems with over-
doing insulation?

~~~
fyfy18
There's nothing wrong with over-insulating (although at a certain point it is
no longer economical), but you need to ensure the house is ventilated to
prevent mold.

You also need to ensure you choose the correct building materials, so they can
ventilate themselves. Modern building science says there should be a
continuous airtight wrap around a house with insulation either side. The
interior insulation ventilates to the inside, and the exterior ventilates to
the outside. What you don't want is multiple airtight layers as that could
cause it to become moldy inside the layers.

Passivhaus houses will almost always have a heat-recovery ventilation system.
These will bring in fresh air and take out stale air - like a bathroom fan.
But they also exchange heat from the outgoing to income air in the process.
Typically 80%+ of the heat is recovered (you can get systems that are 95%
efficient). They run at a low speed so consume minimal electricity (typically
under 100W for small houses) and don't provide a noticeable draft like air
conditioning or forced-air heating. They have filters to prevent pollen and
other contaminants from entering your house, so for allergy suffers they are a
big plus.

I live in a cold climate in an apartment built in 2015, which is well
insulated and has this system. Even though it has been below freezing
(currently 8c) outside, we haven't yet needed to turn on our heating because
of how well the building is insulated. We do actually have a typical vented
bathroom fan, but everything else (kitchen hood and dryer) are unvented, so we
keep all that heat inside.

~~~
zbrozek
Where did you learn about modern building best-practices? I just bought my
first single-family home and am excited to slowly transform it into a
comfortable-and-efficient modern building. But I'm finding it a little
difficult to penetrate this new-to-me space and would love to find some more-
complete resources.

My random web-crawling has certainly been moderately productive, but it's slow
and I can't help but feel that I'm not being adequately exposed to a
reasonable breadth of topics.

~~~
throw0101a
> _Where did you learn about modern building best-practices?_

Do searches on "building science":

* [https://en.wikipedia.org/wiki/Building_science](https://en.wikipedia.org/wiki/Building_science)

A consulting company specifically started around the concept because the
founder, Joe Lstiburek, got tired of seeing the same problems over and over:

* [https://www.buildingscience.com](https://www.buildingscience.com)

* [https://en.wikipedia.org/wiki/Joseph_Lstiburek](https://en.wikipedia.org/wiki/Joseph_Lstiburek)

This contractor based in Austin, TX, has a lot of good content:

* [https://www.youtube.com/user/MattRisinger/videos](https://www.youtube.com/user/MattRisinger/videos)

------
chmaynard
In 2016, I moved from California to Rhode Island to build a Passive House. It
was completed and certified by PHIUS, the American PH standards organization,
in 2017.

[https://www.corememory.io/this-new-house](https://www.corememory.io/this-new-
house)

------
runxel
There are even two subsequent standards: the Nullenergiehaus (zero energy
building) and the Plusenergiehaus, which is better by having the ability to
generate more electric energy than it needs.

However, those buildings are not as amazing as they might look. The "better"
the standard, the greater the effort. What people didn't really took into
account was the energy needed to actually _build_ the house is becoming very
large. At this point it takes the same amount of energy (embodied energy,
called _grey energy_ in Germany) to erect a Passivhaus as it will need
operating over the next 50 years.

~~~
the_mitsuhiko
> energy needed to actually build the house is becoming very large

Why is it becoming larger? I would have assumed that we would use less energy
rather than more to build buildings nowadays given the advances in technology.

~~~
roel_v
Because you need all sorts of technology, and lots of materials that need high
energy inputs to be manufactured.

~~~
ntp85
Do you have a source on that?

~~~
stewbrew
You need permanent ventilation, better heat insulation, better doors and
windows etc. for this to work. You still have to plan for some way of heating
so you cannot just leave that out. This in all takes more energy to build and
maintain.

That said, I live in a passive house and we turn on the heating only when one
of us is sick or when it gets really cold.

~~~
the_mitsuhiko
> You need permanent ventilation, better heat insulation, better doors and
> windows etc. for this to work.

For many houses the better heat insulation is mineral wool and or styrofoam.
Transporting either of these must be significantly more energy efficient than
brick. If I look at how some old buildings are built here I have to assume
that was not energy efficient during construction just from how much more
material was used.

Do you have a source that better insulation requires more energy? Especially
the extra windows must be more energy efficient during production as well if
you look at how they are manufactured. They only extra material is a third
glass pane but for that you save on a lot of extra fittings compared to old
windows.

I would really like a source on why you think there is more energy used for
building the house. It's very counter intuitive.

------
Gravityloss
Air tightness can easily be a problem. Something gets wet and can never dry
out. There is mold. The only solution is to dismantle the structure.

One problem with complex buildings is the limited average skill of the
builders and variable quality control in the business. Building technology
should take that into account.

Probably one reason is the volatile nature of the business - you have to hire
anyone you can get because everyone else is building too at the same time.

So I guess if one were to "disrupt" construction, one would have to start from
the financing...

~~~
supermatt
It sounds like you are confusing air-tight (draught free) and breathable
(vapour permeable). These are the passivhaus definitions.

~~~
Gravityloss
I guess I am.

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danans
A more general learning we can take from Passivhaus building techniques is
that habitable buildings should be designed to work in conjunction with the
natural environment they inhabit, like they used to be before the era of cheap
fossil fuels. But such site and solar-orientation aware design isn't today
part of the practice of building mass produced homes, and absent forces that
push that industry that way, things aren't likely to change.

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buboard
Is this kind of design fit for non-german climates?

~~~
adwww
The new Austrian embassy in Jakarta is Passivhaus certified, a first for that
climate.

[http://www.passivhaustrust.org.uk/news/detail/?nId=527](http://www.passivhaustrust.org.uk/news/detail/?nId=527)

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n1000
Given that we should be carbon neutral in 30 years from now (2050) in order to
have a shot at the 1.5° C target and given that average building lifetime is
>30 years, it would be irresponsible to build anything else than a passive
house or a zero energy building today.

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Nasrudith
I know it is a fringe case relative to the lifetime but I am curious how well
the designs handle power extended power outages and say high ambient
temperatures compared to other house types.

~~~
n1000
Thermal insulation helps to decouple indoor climate from the outdoor climate.
It depends a bit on what kind of heat period you consider. When high ambient
temperatures occur it will remain cool for longer indoor and night ventilation
can be used to cool the house. The cold produced by the AC is also better
trapped inside, ie used more effectively. There has been a case of extended
power outage in Germany due to heavy snowfall. I saw a report that showed how
the indoor temperature remained almost constant for the first two days of the
outage.

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dr_faustus
While not entirely "passive", houses built to the KfW 40 Plus standard in
Germany are pretty close (without some of the inconveniences of a real
Passivhaus)

~~~
scotty79
What are the inconveniences of Passivehaus?

------
rebuilder
How does a passivhaus maintain airtightness in the face of e.g. rodent
incursions?

