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Comment by jschveibinz | Hacker News Reader

Some parameters to consider in the discussion:

1. We need buildings to live in

2. It takes materials to make buildings. What are the potential materials?

   A. Wood

   B. Metal

   C. Concrete

   D. Soil

   E. Rock

   F. Plastic

   G. Ceramics (brick)

   H. Others?

3. It takes energy to process materials for construction.

4. It takes energy to construct buildings.

5. Energy sources:

   A. Sun

   B. Wind

   C. Water/Ocean

   D. Nuclear

   E. Fossil fuels

   F. Others?

6. Other parameters? e.g. cost, speed, labor, quality, durability, aesthetics, etc.

If one takes all of the parameters into consideration, a model (with weighting) can be developed and one can attempt to optimize the model for either net CO2, or convenience, or whatever. It's a decision problem.

Calling all math/physics/engineering folks in this forum: please propose a way to help figure this out. And thank you.

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You forgot politics in your parameters, arguably the single biggest factor in building.

And personal preferences. People wanting bigger, fancier houses/condos/etc are a huge factor.

And those people want tear down the old house and build a bigger, fancier house where the smaller, less environmentally impactful houses stood.

In my old upper middle class neighborhood, our entire block of houses on our small cul-de-sac were all California ramblers. Small (under 3K sq ft), but on larger lots (some were 1/4 or 1/2 acre lots) near several natural ponds and wetland areas. Over the course of the last 15 years, out of the two dozen or so houses, only four or five are left as original. Thee rest were all bought, torn down and had huge, multi-million dollar houses which took up almost the entire lot built instead.

You're right, personal preference is a big one, and there are other obvious mechanisms at work here such as the city letting this happen because they benefit from the increased taxes they collect, but its not helping the environment at all.

many new houses are much more energy efficient, though. Modern building code basically guarantees that this is true. from an energy consumption POV, a bigger new, efficient house may be better. (within reason).

OTOH, modern tax laws and lot coverage calculations actively discourage energy efficient design. In many jurisdictions, you are taxed on the size of the house measured from the eaves, not the walls, and this encourages builders to maximize the house relative to the roof overhang. this reduces the ability to implement passive energy efficiency strategies like large eaves to increase shade on walls / windows.

A house that's 2x the size would have to be more than 2x efficient for it to be better. I doubt that new houses would be that much more efficient than an older house with some insulation and efficiency updates.

I don't think this is true. For heating and cooling you'd need to know surface area:volume ratios to tell.

https://www.pewresearch.org/fact-tank/2015/11/09/as-american...

this article suggests that newer homes are more than twice as good, but that the size cancels some of this out, so that the new homes are only a bit better than old ones.

Where's it say they're more than twice as good?

This isn't comparing new homes to old homes, but the overall homes over time. Obviously heat pumps, furnaces, etc are more efficient today than in 1970. If you updated an older home with efficient windows, doors, heat pump, and attic insulation, then I doubt there would be much difference.

Production of Concrete releases quite much fossil carbon (8% of all emissions), and you can't fix that with renewable energies. Growing wood does not require extra energy aside from Sunlight and sequesters carbon from the air. Switching from concrete to wood would surely make a big difference.

Isn't concrete neutral over its lifetime? Surely you'd want to take into consideration that wood an concrete are different materials?

Ingredient for concrete is calcium oxide, which is won from calcium carbonate, releasing carbon dioxide. Calcium carbonate is limestone. Thus: Making concrete takes carbon from the ground and puts it into the air. This is climate-wise as irreversible as a coal plant.

I'm under the impression there is a reabsorption of carbon over its lifecycle. Is that not the case?

It does, but in amounts i would consider neglegible for climate concerns. As a form of corrosion its relevant for materials engineering.

A holistic treatment would not ignore such things. Housing is obviously not a strictly climate constrained problem.

If we stop digging out carbon out of the ground to insert it into the carbon cycle, that would be a real good solution to be carbon neutral. I hope that qualifies as holistic to you, because its at the source of the problem.

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