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Comment by toasty228 | Hacker News Reader

People still build houses like energy is cheap and abundant. A properly insulated house in any temperate climate require very little heating or cooling.

Spend 50k on insulation that will last the life of the building instead of 50k on heating and cooling devices which will need constant maintenance and replacement + fuel and end up costing 10x more over the life of the building.

A modern house with modern insulation in a mild climate shouldn't even need a central heating system. You can get by with 500w toaster heaters in each room for the coldest time of the year

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In the short term the math is usually bad. Can be a 20, 30, 40 year payback on insulation. For the builder? It’s almost for sure a loss unless he can play the green card. For any individual owner? They are likely to leave before they recoup a project like this. Appraisals on houses are price per square foot with a bedroom and bathroom modifier. Until people start pricing in energy efficiency in homes, say a price multiple of 0.8 to 1.2 based on the efficiency of the home? It’s going to be hard to math out. Which yes is sad.

Maybe a law forcing disclosure of average heating/cooling bills in the listing would do the trick?

I live in a moderately cold area and pay less than $2000 a year to heat a ~2000 square foot home. So something that improves the efficiency of the building would have to have a pretty low cost to even pay back at all.

There's probably a few lower cost things that I am overlooking, to the tune of netting out a few hundred dollars of savings after however many years they took to pay back.

That's an appraisal problem. Even cars are valued on more things but they do have mpg plastered everywhere.

> Can be a 20, 30, 40 year payback on insulation. For the builder?

In the UK, houses have energy ratings, which are largely not that useful, but they do allow estimated annual running charge.

The house that I live in we moved in and were spending ~1.7k on gas a year.

We needed to re-render the place, because it has a few missing pieces. we spent the extra £4 to put in 90mm of external wall insulation. We also had to replace the glazing. It was cheaper to get triple glazing (for some reason), however the results of that was that it was 6degrees warmer in winter, and 10 degrees (celcius) cooler in summer. Even with gas prices doubling, we spend about £70 on hotwater and heating.

There's also the simple reality that houses with better energy ratings are worth more when they are sold. If you own a house, it's a good way to lower your bills and increase the value of your house. The only thing you know for sure when you pay hundreds per month for gas is that it goes out of the chimney. Over ten years, that adds up. Most houses you can probably do some sensible things that definitely earn themselves back in that kind of period while also increasing the value of your property. The inconvenience and financing tend to be the big obstacle. Add incentives to the mix and it becomes an easy choice in a lot of places.

In northern Europe houses are insulated and have a rating. Cost to heat and electricity use are even standard part of a property listing and people do make it part of their total household cost calculation.

> For any individual owner? They are likely to leave before they recoup a project like this

How do you draw this conclusion? Like any other expensive, long-lasting part of the house, this should be seen as an asset which is “priced-in“ to the value of the building.

I could not retrofit my house for efficient heating with $50k. To do so would likely be cheaper to completely tear it down and rebuild.

same here. 1940's house with slate roof and vermiculite "insulation". You can't just use modern insulation techniques or blown-in foam because that would make exterior wood rot. You need to keep the air flowing the right way to dry out the wood.

I have to clean the eaves of my house myself because nobody I hire will believe me that you can't point a pressure washer at the eaves without water getting inside the walls. "I'll just avoid the vents" doesn't work when you can see daylight between the roof and the wall all around the house.

I'm guessing you don't live in a place with tropical storms or really severe weather.

Where I am your house would flood when 80mph+ winds blow the rain up your walls.

Indeed, that is the case. However the house is only 55 years old, so a freak storm destroying it isn't out of the question.

Same here... my walls are brick that need to breathe or they will crack and crumble within years if sealed up too tight.

Same goes with the cinder block foundation. If insulated, it moves the freeze/thaw interface inside the block and then you end up with a failing foundation.

And never mind ground-source heat pumps [1] (although I know the topic was specifically solar).

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

You don't even need to go that far, put 100m of tubing 2m underground and plug it in your heat recovery ventilation system, bam free winter freeze protection/pre warming and free summer cooling, all you need is a 30w pumps and you will save hundreds of kw per year

uh no... You still need a heat pump. The water coming from that system would be like 50 degrees, far too cold for heating.

I think my comment is pretty clear about the use case, this is obviously not water for your floor heating. You shouldn't even have that in a properly insulated house, way too much inertia.

There are electric floor heating graphene foils that put out 20w per sqm, they're more than enough, no moving part, no maintenance, no bs, not even 20% of the price of a hydro floor heating, you can even install them yourself

Heat recovery ventilation systems exchange inside air for outside air through an air to air heat exchanger (modern energy-efficient houses are built too tight for natural air exchange). If you make the incoming outdoor air an even 50°F (except when the outdoor temperature is between about 50° and 70°) then you spend less on heating and cooling.

Yes you're right and I don't disagree. But a 500w heater isn't going to cut it when it's 20F outside. You actually have to run the heat as hard as possible when the sun is shining so you have some thermal momentum going into the evening.

The end result is you're going to make big lifestyle changes to accommodate the energy. For example everyone sleeping in 1 bedroom and only cooking with an electric pressure cooker or low and slow with an induction range.

A house built to passive house standards requires less than 10w per sqm of peak heating demand, a 500w toaster will warm 50sqm, which is a decent room already.

There are passive houses built at 2000m altitude in the Alps, some are made of wood and have literal strawbales for insulation, there are no excuses left in 2026 not to build good houses, it's more economical, more practical, more comfortable, more ecological

You could put that 500W into a heatpump.

Probably because energy is cheap and abundant.

> A properly insulated house in any temperate climate require very little heating or cooling.

A "properly insulated" house still requires something around 0,5 W/m2/K. Modeling a moderate 120 m2 house in the coldest months when the temperatures hit 15-20 negative you still need 2,5 kW of heat with domestic hot water on top. Put in the efficiency of a heat pump and you are still easily looking at half a mega watt-hour per month. ~1MWh for a whole house is very reasonable number during winter months, sans electric mobility.

That's entirely unrealistic to cover with batteries with current battery technologies alone, electricity generation is absolutely REQUIRED. Windmills can help soften the blow and storage needs substantially, but the TFA is about solar, which is effectively absent during the winter.

> 0,5 W/m2/K.

That was a good number in 1980 lmao (or in the US maybe), passive houses are often 1/5th of that. I'm talking 25cm+ of rockwool in the walls, 40cm on the roof and triple pane windows, mostly facing south, reasonably shaped house that conserve heat by design, etc.

0.5 W/m²/K is a good value.... for a window, certainly not for the overall house, for a wall it wouldn't even pass code in most of Europe

> That's entirely unrealistic to cover with batteries with current battery technologies alone

It already is a reality for many people.

> passive houses are often 1/5th of that. > 0.5 W/m²/K is a good value.... <...> for a wall it wouldn't even pass code in most of Europe

There's a mix of miscommunication and wat. I'm using approximate floor area values here, not perimeter walls. 0.1 W/m2/K for a WALL is definitely not a "passive" house, that's barely A++.

> I'm talking 25cm+ of rockwool in the walls, 40cm on the roof and triple pane windows,

Yep, this gets you something like 0.5 realistic, maaaaybe up to 0.3 in the models.

> > > That's entirely unrealistic to cover with batteries with current battery technologies alone

> It already is a reality for many people.

Megawatt-hour level home-battery installs? Show us a picture. That's literally a room full of batteries. The actual reality is having ten or so kilowatt-hours to balance rooftop solar.

It costs a lot more than 50K to retrofit a house towards passive standards.

Not everyone has the capital (even with gov subsidies) to make those investments, and it's generally the people who need to save a few bucks on bills the most that DONT have the money.

I'm replying to someone who bought a 30kwh battery and 24kwp setup, in my country that's already classified as a "local energy provider" I think they're doing OK financially.

People still spend literal millions on poorly built and poorly insulated mcmansions today btw, it's not a money issue.

GP's argument is the marginal cost when building new is roughly that amount, not that any house can be retrofitted for that amount.

However, it's not that far off for retrofitting, if you do it when your siding already needs to be replaced. Add 3-5" XPS foam to the exterior of any standard house; if a basement you bring insulation several feet down and out below the ground. If cathedral ceiling, when replacing the roof you put 6-8" polyiso down over the sheathing before the new roofing material. If vented roof, get 1.5x code minimum blown in the attic. Air seal first, of course (1-hour of air sealing is the best ROI of anything you can do in an old house).

But nobody wants to put that money up.

Would you be willing to quantify what "mild" means to you, maybe in terms of a USDA zone? There are maps for both US and Europe:

https://planthardiness.ars.usda.gov/pages/map-downloads

https://commons.wikimedia.org/wiki/File:USDA_hardiness_zones...

Passive house standards first gained popularity in Germany and Scandinavia but it seems the principles have been adapted to quite a wide range of climate zones now.

https://en.wikipedia.org/wiki/Passive_house

Why shouldn't energy be cheap and abundant?

Not saying it shouldn't, I'm just saying it isn't. Housing should be free and taxes illegal but here we are. Some retard decides to go to war with Iran and it costs 30% more to tank your car, I'm not making the rules. Solar panels got 15% more expensive over night in my country too. What happens when they decide to mess around with China? They make 70% of batteries and panels.

Take plants that can use enery from the sun 'freely'. Is it cheap for them? Not really when you look at the evolutionary battle between plant species. There is always another plant willing to take your place if you're inefficient, slow growing, not poisoning the ground around you, or some other trick to keep you alive.

Any means to keep energy cheap and abundant must be by force because it is not a natural order.

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