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Comment by lesuorac | Hacker News Reader

> Air conditioning was becoming common, making it possible to cool buildings with large expanses of windows that might otherwise get too hot in the summer.

I guess the cost of having to install and run AC is dwarfed by the savings in construction costs?

Or is this a case of operational costs being ignored in favor of capital costs?

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For a developer capital costs are the main factor, as operational and maintenance costs are passed to the tenant. With glass technology improving, the solar radiation component onto the HVAC system is now not much different from a traditional façade. After all there is no roof heat gains, other than on the top floors and maybe partially on some others. For the most part of a floor the heat gains for HVAC is lights, equipment, people and the cost of cooling the fresh air. People also add to that load. On the civil side, glass facades enable thinner floor slabs with the gain normally of some extra floors. I have been involved with many high rise buildings and they are highly complex beasts to get right everything, especially the costs. With flat slabs one can cast a floor on average every 7 days.

> is this a case of operational costs being ignored in favor of capital costs?

It’s driven by demand for “office spaces with high levels of daylight” [1].

[1] https://www.sciencedirect.com/science/article/abs/pii/S03601...

> Or is this a case of operational costs being ignored in favor of capital costs?

I would lean more towards this.

Because big windows cause solar gain in the summer, and you have huge losses of heat in the winter in more northern climates: even the absolute best windows maybe reach R-8 (U 0.125), while even sucky walls probably get R 20 or better (U 0.05).

>I guess the cost of having to install and run AC is dwarfed by the savings in construction costs?

No, otherwise warehouses would be made of glass and steel (they aren't).

But humans prefer natural light when they can get it.

The article has a chart that compares the total costs between the two types of walls. There's a column for "capitalized heat loss", which presumably factors in the HVAC costs. The article also specifically says

>The most obvious was cost. A glass and metal curtain wall wasn’t necessarily all that much cheaper than one made of brick in terms of the materials themselves, but it was much thinner and lighter. Its thinness meant that for two equally sized floor plates, the curtain wall framed one would have more rentable square feet than the stone or brick one. This more than made up for the fact that the thin curtain walls had worse insulation and were more expensive to heat and cool than masonry walls.

I'd assume they're going to install AC anyway, because who wants to be in NYC in the summer without it.

So the extra utility of big views etc outweighs running the AC a bit more.

I'd assume that more insulation and less insolation would make that A/C a lot cheaper and less polluting to operate.

A large floor area in a tall building means windows can only exist on the perimeter and almost definitely can't open for ventilation. Also the larger the floor, the more natural light the windows have to allow in and the more heat from the Sun they'll trap. In that space there will be lots of computers, screens, and lots of other electrical systems (even just for the lighting) generating a lot of heat.

So HVAC is anyway needed for the building to operate properly and the people to be comfortable even before you factor in the outside climate.

My understanding is that double and triple panes are an attempt to mitigate this.

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