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Comment by seniortaco | Hacker News Reader

Wood is already a poor insulator, so if it takes up less space and you can fit more insulation, that is better.

My uncle built his home from hardwood. No insulation. In sub freezing temps, you can put your hand in the wood and it isn't cold. Compared to my (poorly) insulated home, it b is significantly better.

That isn't a good way to measure because the inside of the house is warming up the walls. Hardwood is a poor insulator, but it is an insulator. If you touch wood it will feel warm, but it still loses a lot of heat compared to a properly insulated wall.

Are the walls solid hardwood? Is it a cabin? How thick are the walls?

Hearing this reminds me of the Dara O' Briain line that American houses seem to have been built by the first two little pigs.

Yes, but if it's a much worse insulator, the extra heat transfer through studs might be more significant?

I'm not sure if it's been measured, but I imagine this densified wood would probably have at least twice the thermal conductivity of typical construction lumber, since naturally dense hardwoods already approach that.

So it seems like we'd basically need to replace 2x studs with 1x studs, assuming the same stud spacing, in order to match the thermal performance of a traditional wall.

I don't think this would be a dealbreaker at all though, one could always use continuous insulation instead of cavity insulation, which has a lot of benefits anyway. Maybe it can end up being a competitor to metal studs for commercial builds, at least.

Not a materials guy but would densified wood lead to such a drastic increase in thermal conductivity?

Air has very low thermal conductivity, so for a lot of materials, thermal conductivity is primarily a function of how much air they contain and how it's structured (ideally in tiny pockets to minimize heat transfer through convection). Like spray foams, fiberglass insulation, etc are basically designed to hold air while minimizing convection.

I believe that's somewhat true of woods as well - different woods seem to range from 0.12-0.25 W/(mK) or so, which is somewhat less conductive than the underlying compounds like cellulose (0.4), thanks to the trapped air in wood.

It seems like densifying wood would mitigate the insulation contribution of trapped air, causing thermal conductivity to approache that of the underlying compounds like cellulose, though I'm not sure exactly what those compounds are with their process and how close they get to that air-free extreme.

if you dont make any other changes, it will have some detectable impact, but conductivity is linear with all of conductivity, depth, and area; and the other dimensions can also be changed like the screw diameter/pitch or the dimensions of the stud.

its very unlikely that this change will be an important consideration for house building or shopping though. theres simpler spots to reduce heat loss, like double paning your windows

If this just replaces steel beams or allows more post frame construction, the walls wouldn't change. Actually, if used in post frame style construction, it would allow for more space for insulation with less thermal bridging.

In modern construction we already put continuous insulation outside the 2x4 so that we don't have to deal with the studs and how much worse insulation they are.

I think that's the best practice, also for avoiding condensation, but isn't it pretty uncommon at least for residential builds in the US? Here in Washington, codes were recently changed to require continuous insulation, but I believe that's only with the prescriptive method. From what I've seen most builders seem to continue working around it and doing cavity insulation only.

Depends on where you live, but that seems to be fairly common anyway in new builds.

"poor insulator", seems like an odd statement, but it's all relative I suppose. It's certainly better than the masonry or steel that this will replace. But if you take the air pockets out of it, then it's not going to be as good, but likely better than steel.

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