Ask HN: House building hacks? Advice about green building materials?

[LunaSea]

Hi everyone,

I'm in the process of researching house building to study the feasibility of my future house project in Western Europe. Being a software developer, I'm of course looking to "optimize" things, especially around cost.

One of the most interesting topics I found was building materials, more specifically, green building materials like:

- compressed earth bricks

- rammed earth walls

- straw bale insulation inside wooden panels

- seashell crawl space insulation

These are all ecological, originate from renewable sources, recyclable and very cheap. This would seem like a nice "hack" to lower building costs?

The second interesting topic is building time. Some building materials are expensive but are much faster to install which means that in the end they could be more cost effective than their cheaper counter parts. For example: windows or precast concrete.

I haven't been able to find sources with specific examples of this concept though.

I wondered if any of you have house building experience or had gone through a similar process?

- This being Hacker News, what were the "hacks" that you discovered?

- Any tips I should know about?

I'm interested in lowering costs but not at the price of quality and durability of course. I know that there is no free lunch but reading about some of these building materials, it's not immediately clear to me why a regular brick costs 40€ while a compressed earth brick costs 4€ (x10 less !) while being larger. My sense of a building material is "worth" or not is terrible since it's not my field of expertise and so I sometimes I have difficulties accepting the prices of certain things and evaluating if they are fair price.

Thanks a lot in advance!

[jaclaz]

Western Europe says very little.

There are local building codes that may be very restrictive in the kind of structures/materials allowed, considerations about ratios between (external) volume and actual (internal) living space, local Laws providing incentives for some levels of energy efficiency goals, seismic/geological categorizations (only to provide a few examples).

Since you are a software developer you should be aware that "vague" requisites generally lead to "botched" results.

Unless you find the need to attempt to "disrupt" the building industry (AND also if you find it), you should be aware that - again generally speaking - the whatever construction techniques that are in use normally in your specific area is very likely to be the most efficient, cheap and fast. (not necessarily "green", or energy efficient, of course).

I am curious however of what kind of bricks you are talking about, 40 Euro bricks, are they gold plated?

4 Euro a compressed earth brick, is that rare earth brick?

A "normal" brick is something that ranges from 0.30 to 0.60 Euro each, a (much larger) concrete block something that may be 1.5 to 3.5 Euro.

[LunaSea → jaclaz]

Thanks for the quick answer,

I'll add some more details, the country would be Belgium, more specifically around Brussels.

I found local resellers for the building materials I listed and know that of some projects that have already used them in the past. So I assume that the materials are up to code.

Nice catch, the price for the bricks is of course wrong, I meant to indicate price per square meter.

Would you say that there is no point in using some of these materials outside of taste and lets say ecological benefits?

[jaclaz → LunaSea]

Good, so loosely you are in area where the ground is flattish, and with no easy to reach substrate.

I would say that basically you can go for a "light" (in weight) building (think of mainly wood) that will be "floating" or a traditional (or innovative) masonry one (that will likely need some deep foundations or at least an underground floor).

If you go for the first, there are firms that make pre-fabricated houses that are on par (or better) than anything you can build locally, the most re-known one (but of course not the only one) is HufHaus:

https://www.huf-haus.com/

they do have some operations in Belgium:

https://www.huf-haus.com/en-uk/europa/belgium/

AFAIK pre-fabricated houses of this kind - generally speaking - are not "cheap" but very good quality, though ultimately you get what you pay, so there are whole ranges of them, this is near the top (both for quality and price).

Having an underground floor can be an advantage (lots of space for technical apparata for ventilation, heating and what not, storage space, etc. and a good insulation from humidity.

Then the structure.

Costs (for a 1/2 storey) shouldn't be much different between an (again pre-fabricated) steel frame and a (cast on site) concrete frame (pillars and main beams).

Structural masonry should be slightly more expensive.

Decks can as well be concrete or steel (but you can also have wooden beams if you like them), cost should not change much between the types, unless you are going to have large "open space" rooms, in which case usually metal decks are cheaper.

What changes are the building times, metal structure is the fastest, concrete is second, traditional (or innovative) masonry third (think roughly of 1-2 months vs. 5-6 months vs. 8-10 months).

If you have a steel or concrete structure you are free to "wrap it" with practically any possible exterior wall/finish, with masonry you are a little more limited (in practice either esposed brickwork or plaster (there are also special wallboards suitable for exterior, but they are rather expensive).

But we briefly covered only the very basics.

What you have to understand is that a building is a complex assembly that - for some aspects - is additionally like a living being (it does "breath", it expands and contracts, it absorbs and releases humidity) so you cannot pick "arbitrarily" this (or that) construction material or method without considering how it integrates with the rest of the building.

What you need to choose first is a (good) architect and/or engineer and talk with him/her.

Such a professional should be - besides a technologist - also a sort of counselor that should guide/assist you in taking the "right" choices.

What I can tell you:

1) nowadays it makes sense when building a new house to have it higly efficient (thermically/energy wise) but you have to know that you are going to pay in advance in construction and materials the energy costs of what you will save in the next 15-20 years (i.e., example, if you will save 2K Euro/year on energy, this will have an added construction cost of at least 30K-40K Euro)

2) if you are going for an energy efficient house (class A, A+ or B) you NEED a PROPER mechanical ventilation system (easier to say than to design it) and you will have to consider its maintenance costs (filters and heat exchangers need to be cleaned periodically, fans motors may need to be replaced, controllers, like all electronics, sometimes do fry)

3) insulating materials - besides their costs - carry with them a number of "consequences", hay and rammed earth needs an exaggerated wall thickness, wool, wood and paper are hygroscopic (as well as rock wool) polistyrene (in foam boards or sprayed) is totally impermeable, personally (but of course it depends) I "believe" in other materials, like PET mats like:

http://www.maiano.it/eng/products/construction/sintherm.html

or cellular glass, like:

https://www.foamglas.com/nl-be/producten/

4) everytime you "deviate" from what is "commonly in use" in your area it will cost you something more or it will take some more time (either because the material will be more expensive or because its assembling will take more time because builders are not "used" to it)

[brudgers]

This is roughly analogous to a business that wants a web app and is reasoning that C, Java, and Haskell are the best options. And part of their rationale is the availability of programmers on Fivr at $5 an hour. And the other part is how hard would it be to write the app themselves.

The cost of the walls of a building are only a marginal contributor to overall upfront cost, while mistakes are a major contributor to overall cost.

Or to put it another way, there are really good reasons that houses are not usually built with the materials you mention in the area you live. That reason is more like the reasons houses aren't built out of palm fronds and blocks of snow where you live than wide-spread ignorance of the building trade.

If you're not an expert, the best course of action if you can afford it is to hire one.