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I've also built a simple and small (99sqm) PassivHaus in Romania, 5 years ago. Everybody, and I mean everybody from family to friends called me nuts, but I've got my payback this winter when the energy prices went trough the roof and I'm just slightly affected.

The house is elevated from the ground on 12 concrete columns so that I can insulate under the foundation beams using glass foam, insulation on walls is 30 cm of EPS graphite, underfloor 45 cm EPS and on the roof, 50 cm and the orientation is full on south. For heating it consumes about 1500-2000 kWh per year (December, January, February and a maybe a small part of March)

What is the big difference between houses built in North America and Europe is that the European houses are built using concrete and masonry which give them a lot of thermal mass which is crucial to this kind of builds.

Have a look here [0], this is the first PassivHaus in my area and is nicely documented. The cost of building a PassivHaus in my country typically goes about 20-25% more than a traditional one.

[0]: http://www.sdac.ro/site/archives/category/passivehouse

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People doesn't give the massive importance the isolation has. Some years ago we remodelled our home and added XPS (Extruded Polystyrene) to insulate the roof of the house. After that we use the AC only three or four days in the year, and before that we had to use it at least a complete summer month. That house is in the south-interior of Spain, so heat is no joke here.

If somebody are constructing or remodelling any house I recommend it to add any insulation they can in any shape, in less than five years you'll recover what you spend, and if you add PV panels for electricity or a thermosiphonic system to heat water, you'll recover the investment in about 10 years, with a healthy amount of available health in the devices to continue saving money with a proper maintenance.

> That house is in the south-interior of Spain, so heat is no joke here.

I looked up a few areas (Ciudad Real) to see what you meant by heat, but it seems quite similar to a good portion of the northern USA. This makes sense, I suppose, given the similar latitude.

Insulation is so, so important. I work out of my garage currently and Texas winters get reasonably chilly and of course summers are hot. I'm lucky enough that my garage is actually under a room in my house such that it's insulated (as you imply, roof insulation is one of the most important places to insulate). Even simply adding padded insulation and trim to the exterior door and garage door made it viable enough to stay cool in the summer with zero extra cooling and warm in the winter with a small infrared heater.

What people definitely don't give enough importance is CO2 buildup as well. The more isolated a place is, and smaller, the more environment friendly it is BUT the more likely it is to build up CO2, which leads to headaches.

I installed a CO2 meter both at my current home, and at my parent's home for when I go back for Christmas. In my home, it's a fairly big open place so it takes ~2 days of closed windows (0-3C outside) to reach 2000PPM (recommended under 1000, above 2000 starts affecting you, 5000 is the legal limit[1]). However, at my family home where I grew up it's a tiny room and it reaches 3000-4000 just by sleeping there with the window and door closed. So the headaches of "visiting family" might in big part be explained by this.

PS, incidentally in Spain!

[1] https://www.kane.co.uk/knowledge-centre/what-are-safe-levels...

that is why you need a Heat Exchanger

I suspect I'm experiencing some of this in a small home with poor circulation. Any suggestions for inexpensive room monitoring sensors?

I just bought one on my local Amazon version by searching "CO2 meter". While true numerical accuracy is "who knows", on rest/full ventilation it shows 400PPM and blowing at it (even gently) shows the CO2 increases drastically, as expected, so I'm happy with it.

These are starting to catch on, as someone else said Heat Exchanger, but that's a more general concept and this is the thing you'd actually want https://en.wikipedia.org/wiki/Energy_recovery_ventilation

What about windows? I find buildings with few or small windows to be unmanageably dreary, but the math works out that no matter how insulated you make the walls if you have a good amount of glazing on the walls the effective R value drops quite low.

You always can use isolated glass panels and wood or plastic frames to prevent that: https://www.energy.gov/energysaver/window-types-and-technolo...

I personally have gas filled glass panels and are pretty good at that, but I wish I had also those that have an IR filter coating that prevent IR heat from entering and from exiting the house. That was a lot more expensive when I installed mine.

It seems like historically people underestimated the insulation value of polyurethane because apparently it doesn't necessarily do well on the conventional R-value score.

Apparently a solid inch of sprayed polyurethane can provide 90% insulation, and 2 inches gets you to 99% insulation.

https://www.monolithic.org/blogs/presidents-sphere/r-value-f...

It is interesting that you insulate under the house.

One of the more intriguing passive house designs I saw was one where the insulation went down 2-3m into the ground all around the house footprint. This trapped the natural ground heat within that area and fed it upwards into the house. It took about 18 months for the ground to warm up, but once it was there, the ground/house warmed itself with virtually no input.

This was in the UK. Colder climates may vary ofc.

We have an old house from 1988 located in Norway. Walking on the non-insulated wooden floor is very unpleasant. We will refurbish, and insulate under the floor, but it will not be anything near a passive house because of other construction shortcomings

well try non-insulated tiles here in Spain haha. I don't know why houses are built to such a low standard in Spain. Even the UK had better quality constructions when I was there, and that says a lot (single glazed windows, poor insulation, weak plumbing)

no harsh climate overall so much less insulation is needed?

Mainland Spain falls into the single digits at night at winter so definitely would need insulation, because there is also no central heating. People resort to heating with their aircons and portable heaters. I'm sad because I expected better infrastructure from 45% income tax at the highest bracket.

I come from Poland (sub-zero in winter; can be anywhere from -20C to +10C but typically 0-5C), but the winter I lived on the Spanish eastern coast was the coldest in my life: thin walls and windows, stone floor, no heating apart from little portable heaters, 5 degrees and rain outside.

Now I live in French southern coast, the buildings are slightly better but still poor. In my place even with all heaters I have on max, I'm nowhere near as comfortable as in properly built and heated apartments in my home place (actually when visiting friends in Poland in winter I'm almost overheating!).

Basically half of the year it's quite uncomfortable to stay at home for prolonged time: for ~4 months a year at winter; then again for ~2-3 months at summer (+26C at home with blinds down unless you put aircon on max for hours). Kinda suboptimal for WFH to be honest :)

I have an acquaintance in Madrid. Visiting her, I never know what to prepare for.

An Easter visit was miserable, because the condo building did not even have central heating. With night temperatures around 5 degree Celsius, I could barely sleep.

Then comes the summer and 40+ Celsius is at least as unbearable...

Spanish construction standards are pretty ascetic.

Portugal manage to be even worse. You’ll be stood there in someone’s kitchen wearing a coat and gloves, watching your breath condense, and they’ll be like “oh but we don’t get cold winters like you do in the northern countries”. That’s the rationale. The reason is actually more likely financial.

Exactly. Talking about thermal mass!

There’s also the movement of underground houses. They use the ground for cooling in summer and for insulation in winter. Also it apparently makes for great noise reduction, in spite of having lots of windows, light and views.

See the book “Recovering America: A More Gentle Way to Build”.

Underground houses can be a nightmare dealing with water infiltration, codes and the power of soil.

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.

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.

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

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.

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

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?

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.

What you expect may be different from what will eventually happen, and since the vast majority of houses are actually built by people that intend to sell them (builders), those make the market price, and - at least now - a passive house valued 30% more than average market is not easy to sell or rent, maybe this will change, maybe not.

You can very much rent a passive house for significantly more by including heating and cooling costs into the rental price. People can’t see what your heating bills are but they can compare with other properties that include heating.

Actual price differences at time of sale should be nowhere close to 30% not only because that’s an insane difference in construction costs but also because land isn’t free. A 200k house on 200k of land vs a 260k house on 200k of land isn’t a 30% difference in final price.

Still it remains 60K difference, or 20 years at 3K.

Assuming it is actually 60k, where in reality insulation is cheap. Having giant windows is useful for passive heat gain, but their mostly installed for aesthetics not practicality. Which means aesthetics are also increasing home values.

In terms of pure economics an extra 15k in insulation and 15k for a solar hot water system gets you further at much lower costs by actually providing hot water for showers not just lowering heating bills.

I think you are downsizing the project, from investing 60K to save 3K/year to investing 30K to save 1.5K/year.

No, I am saying you would save that much money more cheaply via other methods.

Sure, saving 3k/year on heating costs for a single family home is extremely high. An average 1,800sf house in Massachusetts on $1.87/therm natural gas is only projected at $1,243 / year in heating bills for 2021/2022. That said you can always build a larger house, so saving 3k/year isn’t impossible it’s just much easier when you include better methods to collect sunlight than covering a side of your house in giant windows which have low R factors because their giant windows.

PS: Insulation alone can only make so much difference. In other words you might save 1000$/year going from R10 to R20, but then going from R20 to R30 doesn’t also save you another 1,000$. Very quickly you’re better off collecting energy rather than reducing heat loss.

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.

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.

>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.

"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?

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.

>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.

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

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-...

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.

> It is interesting that you insulate under the house.

Isn't that pretty normal, I mean maybe not three meters down, but modern foundations are required to be isolated in many places. The legal requirement in Denmark is at least 300mm of isolation under the house.

And that's not a new thing either.

In my 1970's house we have 150mm insulation under the house from the original build, 150mm in the walls and 200mm on the roof.

We added another part to the house a few years ago, and that was 300mm insulation in floor/walls/roof. Since the walls are made of brick with a depth of 7cm, it means the walls are 7+7+30= 44cm thick (plus some "slack")

Even my 1980's summerhouse has 100mm insulation in floor/walls/roof.

That depends of the the place where you live. In middle to the south of Spain, the floor of houses are normally made of marble (or other ceramic material) slabs on top of a little layer of some glue cement, on top of the armoured concrete slab foundation, but on the north is a lot common to have wooden floors with air chamber of a similar size.

It is indeed normal. I mentioned it by way of an intro to the unusual alternative I saw.

How would that work? Average temperature in the UK is about 15 C. If your house is at 24 C, this would mean you are constantly leaking heat into the ground from the bottom...

I guess one can consider the cube of earth an insulator, it's got a lousy insulation value per meter but it makes it up in thickness.

Don't think 15C is correct - looks more like 8.5C to 11C in England and 7C to 9C in Scotland.

http://projectbritain.com/weather/average.htm

You can look up ground temperature for your location here - https://weatherdownloader.oikolab.com/downloader.

Layer 4 is between 1m to 3m depth beneath the surface.

Apologies, I didn't appreciate you meant average temperature underground - that is definitely much warmer. We have a ventilation shaft for an old limestone mine near our house and on a cold day the warm air rising from it is very noticeable.

I wasn't the commenter so no worries about apologies... just wanted to point out where you can find this information. :)

Sorry, I was wrong indeed, thanks for the correction

> It is interesting that you insulate under the house.

Near our place in the countryside, required foundation depth is 1.4m to protect from frost heave. Use an insulated slab and that requirement goes away. The insulation keeps the heat in the ground. It protects the ground under the house from freezing.

Nobody cares about regulations here, but they do about getting proper foundations...

> The insulation keeps the heat in the ground. It protects the ground under the house from freezing.

If it is preventing the ground under the house from freezing, then it is supplying heat to that ground. That's a energy-negative process - some of the heat you generate is used to maintain the warmth of the ground.

Some of your heat is always going into the ground. The insulation prevents it from dissipating into the environment.

Au contraire, my dear Watson.

Without under-slab insulation, the heat emanating from the ground below the house escapes very quickly. This heat we don't generate. It occurs naturally. This is about using the naturally escaping heat to keep the ground under the house from freezing, about raising the frost depth.

This technique is especially interesting for holiday homes not permanently heated in northern climates. It's fairly standard in Scandinavia, up and coming in the Baltics, but less known in the US.

In the US, it's usually called FPFS or frost protected shallow foundations. [0]

[0] https://www.ncei.noaa.gov/products/land-based-station/frost-...

> It is interesting that you insulate under the house.

This is part of the building code in many areas: do a search for [under] "slab insulation".

* https://www.buildingscience.com/documents/information-sheets...

* https://www.finehomebuilding.com/project-guides/insulation/i...

It should be at least R-10 (RSI 1.8):

* https://www.youtube.com/watch?v=O2dNp9bicSk

* https://www.youtube.com/watch?v=XKp0wRzvR-g

> It is interesting that you insulate under the house.

I think anyone who's gone camping will appreciate the need for insulation between the ground and whatever you're trying to keep warm - a good sleeping pad is crucial for keeping warm.

Do you have a link on this? I’d love to read more about this.

We’ve just built a 45m2 log cabin to passive standards here in Portugal - heavily insulated in walls, floor, roof, lifted off the ground on concrete columns, double glazed, only heat source is a 2.5kw log stove. Everyone here (who all live in uninsulated concrete houses heated by open fireplaces) said we will freeze in the winter, roast in the summer. We situated the house on a north facing slope, to minimise sun exposure in the summer. Means little direct light in the winter, but we think (have yet to experience a summer in it) the balance will be good.

As I write this, the stove is out, having burned out overnight, it’s -11 outside, and 25 inside. We are getting through a ridiculously tiny volume of firewood compared to when we were living in a more traditional house for here - less than ⅛ the volume.

Insulation works. It’s also cheap. I don’t understand why people would build new structures without it.

> Insulation works. It’s also cheap. I don’t understand why people would build new structures without it.

People are a bit sceptical about many insulation forms... plastic-based stuff is either a fire hazard (see Grenfell Tower) or extremely toxic waste (if it has been treated with fire suppressants), asbestos is completely banned for good reasons, and rock/glass wool can also spread nasty ultra-fine dust.

We’ve purely used rockwool. It’s enclosed within a semipermeable membrane, so no possibility of dust escaping.

It would be very interesting to learn more about this build. Was it something pre-fabricated (I've seen "kit" log homes advertised) or something completely custom?

Pre-fab, although loosely so - about 1000 me-hours to make it into a functional home. I unfortunately can’t recommend the outfit I bought it from, as they screwed up and shipped only part of the order, sent me defective parts (bad and/or incorrectly machined timbers), and had the worst post-sales service I’ve encountered in anything - but there are plenty of companies out there that make decent kit cabins.

What do you do for fresh air? We have a very well insulated cabin heated by fire, but find the CO2 builds up, particularly overnight with no doors opening, and if we aren’t very quick to close the fire once it gets going, PM2.5 can jump quickly.

We sleep with the window open in the bedroom, and I air the place each morning. Also, it’s almost too well insulated, as it’s easy to accidentally make it 30C in here while it’s -9 outside - so more often than not we have a window cracked open for some air whilst sat in in the evenings. Our PM2.5 is often a silly number, same reason. I’m considering getting an air purifier, but to be honest, given all the crap I’ve inhaled whilst building the place, and given that I smoke anyway, it’s low on my list.

> What is the big difference between houses built in North America and Europe is that the European houses are built using concrete and masonry which give them a lot of thermal mass which is crucial to this kind of builds.

Here's a 500 sq. m. (5000 sq. ft.) house built with heating equipment that uses 1800W (the equivalent of a hair drier):

* https://www.youtube.com/watch?v=_vul4vMFdkA

The same person building his own personal home up to Passive House standards:

* https://www.youtube.com/watch?v=mBOvflXoWlw

You do not need concrete† and masonry to make homes efficient. Switching from using 2x4s @16" off centre (OC), to 2x6 @24" OC ("advanced framing") would allow for less wood use, less thermal bridging, and more cavity space for insulation.

† It should be noted that concrete creates a lot of CO2 emissions, as does baking bricks. Growing wood on the other hand is a way to sequester carbon.

I agree, you do not need concrete and brick but you also need to take into account the local traditions. For ex. building a wood house (framing or CLT) would have cost much more than concrete and bricks and was also much more prone to errors because of the builders lack of experience, at least in my area and country.

Recently in Romania it really took of building houses using CLT (cross-laminated-timber) but it costs so much more than a regular brick and mortar house that few people afford it.

When -15 outside and 20 degrees inside, my house requires 2000W to keep the balance. This kind of simulations are done using PHPP package from PassivHaus Institut.

L.E. What I wanted to point out, thermal mass can have a huge impact on the house energy footprint.. to give you an example, today and tomorrow will be sunny days and this will drive my interior temp to about 23-24 degrees, this heat will heat-up the masonry and slabs and then give me back the heat in the next days when there will be no sun.

Wood is fairly inexpensive in North America because there are still many forests (especially in Canada).

There is nothing "inherently better" with one material over another for most applications. A good structure mostly depends on proper drainage and cladding to protect against UV rays and bulk water (precipitation), good air tightness (with mechanical ventilation for filtered, tempered fresh air), and high insulation.

* https://www.buildingscience.com/documents/insights/bsi-001-t...

Modern codes have moved back to 2x4, then they put continuous foam on the outside of that to make the total the width of a.2x6 wall. Wood is not a great insulator and you have to have some

> Modern codes have moved back to 2x4, then they put continuous foam on the outside

Codes do allow for only external insulation, but it it also possible to have some exterior "continuous insulation" with the remainder being in the wall cavity.

The thicker the exterior insulation, the trickier it can be to attach it to the wall and then also have mechanical fasteners for your external cladding.

* https://www.buildingscience.com/documents/insights/bsi-001-t...

* https://www.buildingscience.com/documents/building-science-i...

However, AIUI, using 2x6s reduces the number of studs needed and so would generally reduce the cost on average from both a material and labour perspective (even if 2x6s are slightly higher each).

* https://www.buildingscience.com/documents/insights/bsi-030-a...

* https://buildability.ca/wp-content/uploads/2017/05/M400-Adva...

* https://www.energystar.gov/ia/home_improvement/home_solution...

* https://www.protradecraft.com/article/advanced-framing-dos-a...

And it's not like it's a new technique: it's been around for (at least) forty years.

I should have said modern building and not codes. there are a lot of ways to satisfy good codes, 2x4 tends to be cheapest for single family houses, but others are not far behind and may be worth it in the long run. Consult a proper engineer if you are building a house of course.

Moving insulation outside the frame also helps reduce the effect of thermal bridging although with timber that's not so important as it is with steel.

High thermal mass is definitely more energy efficient in the summer, when you can "store the cold" from the night into the next day.

A friend of mine, who is an architect, told me the technology is ripe to build houses that produce even more energy than they consume, but people simply don't want to live in them.

The article talks about "using the best windows", the problem my friend saw in many of such houses was simply that the dwellers would either open the windows too often, losing all the heat, or feel miserable because they weren't allowed to open the windows. A pure psychological effect of course, even with the best ventilation people still had the urge to open a window and felt bad if they couldn't.

I recently lived in a house with no external ventilation in one big room. Huuuge windows looking out onto a huge backyard full of trees and flowers. Yeah I missed being able to open the window and hear the birds. But then when lawnmowers started buzzing and dogs started barking, and later when winter hit, I was quite glad for the peace and quiet and no need to open them!

I never open my windows unless I'm trying to air out something.

how do you ventilate without losing all the heat?

Recuperator ventilation, presumably?

Heat recovery ventilation [1] can bring in fresh air and output old air while recovering the vast majority of the heat.

[1] https://en.wikipedia.org/wiki/Heat_recovery_ventilation

These are only compatible with forced air systems, correct? I.e. using in-floor radiant heat would require an entirely separate ventilation system with heat recovery?

Correct.

https://www.energy.gov/energysaver/whole-house-ventilation

Energy recovery ventilation systems gives a good description

> the technology is ripe to build houses that produce even more energy than they consume, but people simply don't want to live in them

It's called solar. Unless the house has a small footprint most can fit enough solar panels to more than cover their energy use.

> A pure psychological effect of course, even with the best ventilation people still had the urge to open a window and felt bad if they couldn't.

I wouldn't want to live in a house where I couldn't open the windows all the way. Near-perfect energy efficiency is something to strive for but there is something to be said for being able to open the window and get a nice breeze blowing through the house. Even if it isn't the most energy efficient it's okay with me.

> A pure psychological effect of course, even with the best ventilation people still had the urge to open a window and felt bad if they couldn't.

Even if it isn't the most energy efficient it's okay with me. I mean if we really wanted to get good energy efficiency we'd just remove all the windows completely. But we don't because we design building for the enjoyment of humans, not just for energy efficiency.

Salut! Could you please share more info / photos / tips, besides the sdac.ro link? How high is the elevation? What kind of heating do you use? How do you refresh the air? (opening the windows or heat recovery system) Thanks

So with home solar panels and storage getting cheaper and cheaper and better and better, where is the optimization point of investing in better insulation vs just buying more solar panels?

Especially if the solar panels may produce profit on sunny mild days about 40-50% of the year if there is reverse metering and the like?

Insulation beats solar panels. It’s not only much cheaper to get, but also to maintain.

The body heat of a family of 4 is enough to heat a well insulated house.

Solar panels are there to supply electricity for use. The last step of passive houses are zero-energy houses, which means that they don’t get electricity from the grid.

> small (99sqm)

Is that correct? 99 is not small at all.

Small in comparison with a typical single family homes that goes >150 sqm in my area. I completely agree with you, 99 sqm is more than enough for a 4 people family.

it depends on how you can use the space. 4 people can mean three bedrooms. in some parts of asia the average 3-bedroom flat is 150m². a few years ago i did a search in a european city and likewise was unable to find 3-bedroom apartments with less than 120m². 4 was 150m² minimum.

the problem is huge living rooms that can't be divided up and repurposed to make living space for more people.

work from home doesn't need a lot of space, but with young kids i absolutely need a lockable room. my current office room is 5m². plenty of space. but finding an apartment with that kind of room is rare.

> I did a search in a european city and likewise was unable to find 3-bedroom apartments with less than 120m². 4 was 150m² minimum.

You simply chose the wrong European city :) Try Dublin, the city of 70sqm 3 bed apartments (in fairness, these aren't allowed under current planning regs, but there are quite a lot of old ones).

The average size of homes in the UK is under 80 m2. See https://shrinkthatfootprint.com/how-big-is-a-house

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