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Comment by yongjik | Hacker News Reader

Sounds like a rare case of America's ubiquitous suburbs working out for the environment. Everyone has a "roof" that gets sunlight most of the day, so rooftop solar, while being less efficient, is still a viable candidate.

(Although, if you factor out all the extra driving needed for the suburban life, it would likely still come out negative compared to a proper city.)

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Yeah, don’t over look the fact that the thermal demand from space conditioning homes is way higher on a per capita basis in a suburban context compared to an urban context with multi-family housing/apartments etc. There’s just way more air volume to condition per person, generally more inefficient systems, etc.

Even for the same amount of living space, apartments are way more efficient. A typical apartment unit is surrounded by other units up/down/left/right, so only two sides are exposed to outside air. A single house is exposed on five sides.

> A single house is exposed on five sides.

Six. The most heat escapes through the roof, but thermal loss through the floor is generally about 10-15% of the total.

Yeah we refer to this as the heat loss form factor of the building, which is determined largely by the surface area to volume ratio (so you have a square-cube relationship at work) as well as the the number of floors in conjunction with the roof area. With more floors, the heat transfer through the roof (which can be substantial, as mentioned by a sibling comment) is less significant for the same roof area (after normalizing for the gross floor area).

Same goes for the slab/foundations (which can also have substantial thermal transfer in many contexts).

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