[poseva]

Really interesting. I've read about also "foundation insulation skirt" that allows you to create a warmer earth mass under the house.

To be honest this was the biggest "complaint" that others had in regards of how a built the house, the general knowledge says that the earth is warm and you don't need to insulate against it... but the earth is maybe 5-10 degree, of course warmer than outside -5..-10 but still a lot colder than what we want inside the house, 20,21 degree C.

[jaclaz]

That depends on how deep you dig, but of course going deep enough has a cost that may be far greater than the kind of insulation you used.

The 20-25% of increase in cost is a good proxi (from my personal experience I would have said 25-30%), but, from an economical standpoint it should be compared with savings over time (in the same region).

To give you an example in Italy, last time I calculated it, this 25-30% increase of costs corresponds - loosely - to the costs of heating for 20 years or so (bar the crazy increases in prices of energy that just happened), so it becomes more a "philosophical" choice than anything else to go for passive or almost passive.

[Sankozi]

5% return per year (or more in case of price changes or regulations forcing you to change heating source) does not seem that "philosophical".

[jaclaz]

I don't understand fully your way of reasoning.

A normal house costs - say - 200,000 "units" (dollars, euro, whatever).

Making it "energy saving" costs an additional 60,000 units.

In 20 years time you will be spending 60,000 units (3,000 per year) less for energy costs (and here we are assuming that ventilation and heating/cooling machines in the "better" house have the same maintenance costs than the ones in "normal" house, whilst usually, since they are more complex systems they tend to be more expensive).

You essentially have a "break even" point 20 years in the future, from there onwards you start saving money.

First thing, you need, now, 260,000 units instead of 200,000 (and not all people may be able to afford this).

Then, if, for whatever reasons, you don't use the house at all times in these 20 years, or you need to sell it before that time you are unlikely to fully get the savings.

Additionally, in less than 20 years time it is possible that someone comes out with a mega-para-hyper-ultra climatization device that makes yearly energy costs go down by (say) 90%.

So, if you want to do the "right thing" from a climate/energy savings point of view, by any means choose to invest in a passive house, but it remains essentially a "philosophical" decision, not an economical one.

[maxerickson]

If you step back a bit, it makes sense for society to push for the construction techniques that minimize the lifetime cost of the building. Here, buildings typically last for much longer than 20 years.

And then there's the whole thing where energy costs may not be fully priced into the use.

[jaclaz]

Sure, but then that is a "political" decision at government level, not your "free" choice.

It is clear that the (good) trend is towards mandating "better" insulation (and thus less energy consumption) but it is not like a government can say "ok, starting tomorrow all new houses must be passive", as that translates to "ok, starting from tomorrow price of all new houses will increase by 30%".

They are introducing - little by little - minimal requirements, and introducing in parallel some (BTW badly implemented at least here in Italy) economic incentives to better existing houses but it will take many years before they can impose "only passive" houses, and in any case, "new houses" are such a trifling percentage of existing buildings that they won't make a dent in the overall energy consumption, it is much more effective, given the amount to slightly better the much larger amount of existing buildings.

Also it is not as easy as it seems, for the last 10-20 years a number of houses have been built in the (at the time) energy classes A-B-C without mechanical ventilation/heat exchangers, with - let's call them "not fully tested" - construction methods and now that they are aging they show the problems emerging (humidity/mould, maintenance of windows, decay of insulation packets/facades, etc.), as often happens with new technologies.

[beerandt]

>construction techniques that minimize the lifetime cost of the building. Here, buildings typically last for much longer than 20 years. And then there's the whole thing where energy costs may not be fully priced into the use.

It goes both ways. Investing in capex has to be balanced against potential capex and opex market changes, not just today's market.

Unless that 0% rate gets passed onto you, there's a fairly rigid payback wall at 30 yrs where no amount of investment is going to make financial sense. (It's why despite loan terms growing for everything else, mortgages are still capped at 30 yrs.

What happens when the market is flooded with cheap renewable electricity, as is promised? Suddenly your payback period is extended beyond what makes sense.

Or advances in technology result in a cheaper, better insulation material?

And then there's the potential external costs of not just energy, but material and construction. It wasn't that long ago that asbestos singles covered nearly every new house because of its fire resistance and insulating properties.

The cost there also seemed to pay for itself, until we discovered the true cost of asbestos mitigation and removal.

[ClumsyPilot]

"You essentially have a "break even" point 20 years in the future, from there onwards you start saving money."

That's exactly how a 5% roi investment works. There is nothing unusual here.

"in less than 20 years time it is possible that someone comes out with a mega-para-hyper-ultra climatization device that makes yearly energy costs go down by (say) 90%"

And it's possible second coming of Christ will happen, or an asteroid will fall, and you'd be better off soending money on hookers and cocaine.

A plan that relies on some unrelated events to solve your problems is not a plan. Why bother planning at all then?

[jaclaz]

>That's exactly how a 5% roi investment works.

Not exactly, in a 20 years 5% roi investment you normally get your invested capital (admittedly reduced in real terms by inflation) back.

In this case a the end of the 20 years you have something that has degraded and that probably needs replacing (talking of ventilation systems or solar panels) and/or needs repairs.

I find it more like a 5 year lease for a car vs buying it cash.

[renewiltord]

This was a problem that hit the first solar adopters. Their break-even was so far in the future because the technology really ramped up later. Of course, one could argue perhaps that wouldn't have happened without the adoption. And perhaps argue against that again that it was gov subsidies that really pushed solar to primetime.

[empiricus]

Not only "philosophical", better insulated houses are also more comfortable.

[jaclaz]

Sure, but not all houses are built for "you" to live in perpetually.

You build a house according to the minimal requirements of your local codes/norms.

If you next year go to another city you may either sell the house or rent it (at average market value).

You build a "passive house".

If you next year go to another city you may either sell the house or rent it.

Do you believe you can easily get 30% more rent or sale price because it is passive?

[Retric]

It’s rather pointless to go through the effort of building a house if you don’t expect to live in it for very long. So, the minimum standards should only be relevant to people building homes for sale.

As to insulation, it’s very cheap to add some form of solar heating outside of the arctic but cooling always takes energy.

[baq]

did you include heating costs rate of change growing? (i.e. prices rise more % yoy with each year?)

[tejohnso]

Insulation under the home, and skirted around it. You may be thinking of a Frost Protected Shallow Foundation[1]. A nice alternative to excavating in order to get below the frost line. I dream of doing this as part of a self built small passive house project.

[1]: https://www.greenbuildingsolutions.org/blog/frost-protected-...

[swader999]

ICF construction where the foundation form is Styrofoam Lego like blocks that concrete is poured into achieves this shallow and in full basement hooded. A lot more homes in Canada use this approach now.