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Comment by runxel | Hacker News Reader

There are even two subsequent standards: the Nullenergiehaus (zero energy building) and the Plusenergiehaus, which is better by having the ability to generate more electric energy than it needs.

However, those buildings are not as amazing as they might look. The "better" the standard, the greater the effort. What people didn't really took into account was the energy needed to actually build the house is becoming very large. At this point it takes the same amount of energy (embodied energy, called grey energy in Germany) to erect a Passivhaus as it will need operating over the next 50 years.

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Do you have a source for those figures? Given the very low energy usage of a passivhaus, 50 years worth of energy sounds like a good deal. But perhaps it would be more useful to compare like for like. How many kWh do we need to erect a passivhaus and operate is, vs a non-passivhaus?

I was also under the impression that many passivhaus implementations made heavy use of wood, and thus end up sequestering carbon for the lifetime of the building, but I don't know if that's mandated by the standard or just a preference of some builders.

> At this point it takes the same amount of energy (embodied energy, called grey energy in Germany) to erect a Passivhaus as it will need operating over the next 50 years.

That doesn't mean much since it takes less and less energy to 'operate' the house. For energy-positive housing it by definition takes more energy to build the house than to run it for a single day since the house is a net energy producer. Leave that fact out and use it as a headline and you can guess the reactions.

What is important is the trade-off between effort spent in creating energy-efficient infrastructure - whether it be housing or industry or roads or whatever - versus the expected returns, the projected lifetime, the means to distribute energy and more. Having an energy-positive suburb won't gain much if there are no means to transport the energy to the city centre or industry where it is needed. Insulating against -20° winter temperatures does not make sense on the Canary islands (and no, insulation is not the same as thermal buffering which can be used to lower inside temperatures during hot days, viz. adobe constructions).

> At this point it takes the same amount of energy (embodied energy, called grey energy in Germany) to erect a Passivhaus as it will need operating over the next 50 years.

Is that because the build energy is so high or because the energy usage is so low? I mean, by definition the energy used by a zero-energy house is zero. Shouldn’t you compare the build cost to a conventional house’s energy usage?

Our home is currently constructed from wood. The price is not higher compared to stone/concrete solutions.

Simply building a house in Germany at the moment results in a passivhaus. We also added the ventilation system which wouldn't be necessary, but I like the system, needing not to open the windows in winter that often or at all.

> energy needed to actually build the house is becoming very large

Why is it becoming larger? I would have assumed that we would use less energy rather than more to build buildings nowadays given the advances in technology.

Because you need all sorts of technology, and lots of materials that need high energy inputs to be manufactured.

Do you have a source on that?

You need permanent ventilation, better heat insulation, better doors and windows etc. for this to work. You still have to plan for some way of heating so you cannot just leave that out. This in all takes more energy to build and maintain.

That said, I live in a passive house and we turn on the heating only when one of us is sick or when it gets really cold.

> You need permanent ventilation, better heat insulation, better doors and windows etc. for this to work.

For many houses the better heat insulation is mineral wool and or styrofoam. Transporting either of these must be significantly more energy efficient than brick. If I look at how some old buildings are built here I have to assume that was not energy efficient during construction just from how much more material was used.

Do you have a source that better insulation requires more energy? Especially the extra windows must be more energy efficient during production as well if you look at how they are manufactured. They only extra material is a third glass pane but for that you save on a lot of extra fittings compared to old windows.

I would really like a source on why you think there is more energy used for building the house. It's very counter intuitive.

"Water is wet." "Do you have a source on that?"

I'm a real estate developer. This is elaborated on, ad nauseum, in 1000's of studies, for the last, oh, 40 years. Don't be That Guy(TM).

That is not quite true. The relative share of the life-cycle impact of material increases, because total impact decreases. There are a couple of reviews that discuss this matter and normally find that total life-cycle impact is consistently lower. https://www.sciencedirect.com/science/article/pii/S036013231...

There is quite a difference between a passive house and zero/plus energy buildings:

The focus of a passive house is on energy efficiency while Zero/Plus energy buildings try to have a positive net value.

While it certainly helps, energy efficiency is not required for a zero/plus energy building: You just have to produce more energy than you consume.

Regarding the building cost: As far as I know, the building cost is not greater compared to that of a normal building.

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