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Comment by _spduchamp | Hacker News Reader

We moved to heat-pump a few years ago and disconnected from gas. It's been working great. Our biggest expense was insulating our house. It is an old house and the 2nd floor was very drafty. You could feel a breeze coming through cracks in the wall. When we opened the wall there were just a few newspapers in there and no insulation.

We had the 2nd floor siding removed, an extra layer of insulated wall added to the outside and then cladded with siding. It was like putting a big insulated hat on our house. Now the temperature is very consistent and absolute no drafts.

The architect said to me that we'll never fully recoup our costs of putting the hat on the house. To which I replied that we don't always to things for economic reasons, and just do them because they are the right thing to do.

My only regret was going with a Rheem heat-pump water heater in this mix. It does not perform well at all. With hindsight I would have looked for a way to perhaps have water heating integrated with our air heat-pump system. There is a company called Arctic that has those systems.

Also with regard to heat-pump water heater, out big problem is that a hydronic floor heating system (installed when we were on gas) is now constantly drawing off heat from our tank. I'd like to find a small standalone unit to handle floor hydronic heating separate from my main water heating.

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> The architect said to me that we'll never fully recoup our costs of putting the hat on the house. To which I replied that we don't always to things for economic reasons, and just do them because they are the right thing to do.

I am so frustrated with this analysis and sentiment when it comes to environmental investment. I understand that looking at it with a financial lens can and should be done to inform what we do, and it would be great if a project just paid for itself, but you look at all the other things we spend money on and the same calculus is not used.

People don't buy the cheapest car, house, clothing, or food they could possibly get by with, or analyze the marginal cost of moving up or down the possible price tiers available to them with only the financial payback as a guide. Yet we constantly hear the refrain that you shouldn't spend a given amount of money on solar, house improvements, appliances, etc. that might be better for the environment if the payback isn't somehow positive with a 10-20 year payback period.

I've constantly had to work with contractors to let them know that I still want to pay for the marginal costs associated with investment even knowing that the marginal financial benefit is smaller. For instance, with solar panels in less than ideal locations, tri-pane windows, etc. I have disposable income, and I think the world is trouble for the 8+ billion humans inhabiting it, so I think it's worthwhile that I would spend some of that to make it marginally better even if that means I don't have a positive financial return.

It's a much more complicated equation, but it's very possible the emissions from simply producing the insulation and having the install done are more than the saved future emissions.

Insulation pays back over a long enough time horizon (economically or CO2 wise). Although spray foam at the moment does have a large CO2 impact. If someone is putting in way too much insulation then we could say that the last 30% of insulation wasn't worth it. When people say something won't payback economically on a home, they are usually looking at a time frame of 10 years or less.

In this case the insulation itself will probably payback quickly. The problem is the cost of re-siding the house to get the insulation in- likely similar for CO2 impact.

I absolutely agree this kind of nontrivial work can be done in a way that is woefully inefficient/impractical. My EWI, approx 85m2 of graphite polystyrene with an embedded CO2[1] of ~15kg/m2 is equivalent to approximately 1.5 years of CO2 emissions (combined electricity & gas), or ~9 months of CO2 emissions before I replaced windows and old kerosene boiler that came with the house.

Actual installation and other materials excluded (adhesives, mesh, silicone render, 450 hot beverages, getting the neighbour's car repaired after the scaffolders hit it, etc.) excluded.

I don't have a full year of data yet, but all in it's looking like CO2 emissions are going to come in at well under 40%. This is in line with the independent assessment I needed to clear a grant for some of the costs[2]. It seems to me "carbon ROI" is about 1/4 the financial ROI (est 8+ years).

Now if it was PU instead of EPS that would be a different cost (10x the CO2 of polystyrene). Sadly I also ended up with some PU (PIR) in a small area of low-pitched roof void, I don't know if there were better choices there.

There's also a hidden cost in living in a cold, damp building - now there are winter days when I don't even turn the heat on at all.

[1] https://www.greenspec.co.uk/building-design/embodied-carbon-... [2] https://www.seai.ie/publications/Your-Guide-to-Building-Ener...

Is not impossible. It’s not likely either.

That’s very unlikely. Insulation lasts decades and is not that difficult to produce.

It is possible. You can't measure that in currency, though.

If there was a carbon tax you might be able too.

> People don't buy the cheapest car, house, clothing, or food they could possibly get by with... Yet we constantly hear the refrain that you shouldn't spend a given amount of money on solar, house improvements, appliances, etc. that might be better for the environment if the payback isn't somehow positive with a 10-20 year payback period.

I think the key thing here is that energy is 100% fungible unlike your examples. A kWH is a kWH.

But you’re not buying kWh in this example. You’re buying home energy systems. They have many tradeoffs, pro and con. Besides that, for many people, a kWh produced by a renewable energy source or that’s available to them when the grid is down is worth more than one produced by a coal plant that might be unavailable during an outage.

No, it really isn't. Your house might lose the same total energy as a super efficient house, but if all that energy happens to be lost through a cold spot by your dining room table, you're going to get pretty fed up with the situation.

Sorta, around here, a bucket of kWh at 2PM sells for more than the same sized bucket at 2AM.

It's not just an environmental consideration - efficient houses are much more pleasant to live in, particularly if they are designed holistically with proper ventilation systems and few cold spots.

It shouldn't be a surprise. Our economic system and even economics-related media puts individual short term gains above all else. Everything is viewed through the lens of "what makes me the most money today?" Long term positions are not valued. Positions that might benefit others are not even considered.

  Long term positions are not valued.

Stock market?

  Positions that might benefit others are not even considered.

ESG?

I agree, what kind of hat is your house wearing?

The outter layer wall that was added was wood studs, rock wool insulation, then wood siding. Looks great, no drafts, even temperature year round without having to run the heat-pump much. We also have an ERV to keep the air fresh in the house.

Imo you recoup the cost via the value of the building. Who wants to buy a drafty house with an oil furnace after 2030 or so?

No one will pay more for a house with a higher R-value. If this were a determining factor, it would be part of real estate listings. It's a secondary or even tertiary concern for most people.

> If this were a determining factor, it would be part of real estate listings.

It is part of real estate listings in the Netherlands, and it very much affects the value of the building. https://www.tilburguniversity.edu/nl/actueel/nieuws/meer-nie...

PEB grade systematically increases the value of a house less than 20% of the house value.

That's far too low to justify the huge sums involved in energy renovations.

If a home were priced as little at $200,000 then 20% would cover $40k in investments. Homes around here don't sell for the little.

Assuming your percentage is correct and home prices are much bigger it makes it seem like a spectacular investment. Actually too good to be true of an investment.

If the return were 2% or max 5% I could see it maybe not being worth it depending on home prices in your area.

20% is if you insulate your roof and walls, get triple-glazed windows, heat pump with floor heating and solar panels.

That is going to cost in the €150K-€200K range in Europe for a €400K, 150 m^2 house.

20% of the building’s value sounds like a very generous sum for new windows and insulation.

20% is if you insulate your roof and walls, get triple-glazed windows, heat pump with floor heating and solar panels.

That is going to cost quite a bit.

If you're buying a house without asking for the trailing twelve month energy bills, you are an unsophisticated real estate market participant and will pay for the ignorance over time.

Where I live you even get better conditions on your loan if you buy a house with better insulation, it’s that important.

In the US, this is so true and sad. After building my first home with insulation way beyond code I learned the sad lesson that it won't get you a dime more when it is time to sell.

We keep in touch with the new owners who have since thanked us for building so well. Their bills are much lower than any in the neighborhood and they had no idea.

The same goes for heat pumps. I'm living in my third build and we had room to do a ground source heat pump. It is amazing and my bills are half of what my neighbor pays for a similar size house. Mine is also better insulated. When it comes time to sell it, nobody will care.

The US needs to up the codes on insulation. Hot climate, cold climate - who cares, it helps.

In which country do you live? In Germany, it is 100% the other way around.

> so I think it's worthwhile that I would spend some of that to make it marginally better even if that means I don't have a positive financial return.

Your action is going to make close to 0% difference for the 8+ billion humans inhabiting the planet. So from a practical standpoint, you've failed, but that practical failure makes it clear that the gesture has pure symbolic value for you.

And since that symbolic value stands in stark contrast to incessantly chasing positive financial returns: task failed successfully. Congratulations!

From a practical standpoint, they have valued their energy savings closer to what the true cost of carbon emissions are (remember, most carbon emitters are in no way paying the true cost of their emissions [1]; this externality dumping continues with wild abandon).

You're arguing systems and scale. This person is simply early in the adoption curve. Consider what will happen when this happens more broadly. As the climate situation becomes more dire [2], the price of carbon emissions per ton will rise and the willingness to prioritize energy savings and carbon emission reductions should increase regardless of fiat return. Physical system outcomes are distinct from magic number in database goes up.

But sure, if you're already poor and have nothing [3], this won't matter to you and your life trajectory is already mostly locked in today. As nullstyle mentions, we need to compound in the positive outcome direction, and those decisions are being made today.

[1] https://www.nature.com/articles/s41586-022-05224-9

[2] https://www.npr.org/2024/04/09/1243595924/march-world-hottes...

[3] https://ourworldindata.org/poverty

This is a tough one, honestly. For one, being at the early adoption curve also has you on the low side of efficiency. If things aren't being done at scale, they are likely fairly low on that score.

More, though, moving to something that gets you a more climate controlled home in the name of efficiency is odd. You could almost certainly use smaller scale solutions to get more comfortable living that does not involve such a drastic change to the home. Clothing and lifestyle changes are things you can do, for one. For two, though, if the place was so drafty you could feel a breeze, it almost certainly did not have active heating/cooling to the level that they built up to. Such that is seems odd to justify how efficient you could do something that was just not getting done before?

No reason not to do it, of course. But insulation is an expensive thing to add to a house. Not just in raw costs, mind. Most insulation materials are of dubious carbon neutrality. And nothing lasts forever, least of all housing.

Insulation is one of the cheapest improvements than can be done to improve energy efficiency of a structure. Once insulated, those energy efficiency gains persist for the life of the structure. Nothing lasts forever, but homes have a 100+ year service life.

https://www.whitehouse.gov/briefing-room/statements-releases... (control-F insulation)

https://www.energy.gov/energysaver/types-insulation

https://www.energystar.gov/saveathome/seal_insulate/methodol...

Homes have a 100+ year service life? Where? I see the median age of housing stock varies heavily in the US. Quickly scanning other markets, I see EU has older housing, in general. Even there, though, they don't talk of 100+ year old houses as being that common.

Scanning websites on this claim, I see that "properly installed, with no damage" some types claim up to 100 years of service for insulation. I strongly suspect that that is a claim that will not hold for the vast majority of homes. More reading also strongly suggests that if your house was built prior to 2005, you probably need to get the insulation redone.

Worse, from my experience, the older the home the less likely you are to have subfloor/walls to actually install insulation. Heaven help you if you do one of those container homes. And if you live in an environment where you have heavy rains or hail, expect damage to creep in rather quickly.

Don't get me wrong, I support the idea that adding insulation is almost certainly a good idea where you can. I just can't bring myself to trust claims of 100 year service life.

Depends on the country. A well-built and properly maintained house in Germany can have a service life of 80 to 100 years or more. Some may even exceed this range, especially those that are regularly updated and renovated.

German building standards contribute to the longevity of residential buildings.

A well built and properly maintained anything can last hundreds of years. Proper maintenance likely involves heavy replacement of parts, mind. And is very contingent on no damage.

I will add I just moved out of a hundred year old house in Seattle. I know they can happen. I also know that house had no air conditioning and retrofitting one on would have basically meant a new house. Even if it looked the same.

> As the climate situation becomes more dire [2], the price of carbon emissions per ton will rise

Looking at what's happening here in Canada, where it looks like what has high chances to be the next government is campaigning on getting rid of the carbon tax, these days I'm somewhat pessimistic that carbon pricing will actually be implemented by the top contributors to global emissions. I hope I'm wrong.

There's no consumer-led revolution to come from early adopters accruing over time. It's fringe and luxury activity.

You... clearly haven't tracked the cost of solar panels. Learning curves are a thing https://ourworldindata.org/learning-curve

I know abt that. I'm replying to a post about insulation which is not innovation-ripe for industrialized optimization anytime soon

Literally every single accomplishment in human history was built upon millions of small "symbolic" individual actions. Good things don't just magically happen on their own.

“Close to 0% difference”, compounding over time was how we got here. I’m not saying personal responsibility is the only factor, but youre the wrong person in the exchange above, and OP has the proper attitude.

Better is always good

I don't know, I've always dreamed of a world where influential people like yourself saw the value in leading by example.

> The architect said to me that we'll never fully recoup our costs of putting the hat on the house.

Your architect is almost certainly right. I would bet that most of your improvements came from fixing the drafts, with the insulation providing a marginal improvement on top of that.

I’ve also dealt with insulating old homes, but I did draft fixes, wall insulation, and attic/roof insulation at different stages. The draft fixes provided the most improvement, followed by attic/roof insulation. Insulating walls had much less effect than I anticipated.

In friends’ houses I’ve used my thermal camera (which I didn’t have back then) and it’s easy to see where the heat or cold is coming in during weather extremes. These days I’d recommend anyone start with the thermal camera view before deciding where to spend money on insulation.

> Insulating walls had much less effect than I anticipated.

I wonder if that's due to air already being a decent insulator and walls have sizeable air voids. As long as you cut out the drafts, the air in the walls should remain a decent insulator. It's also my understanding that the draft treatments are at least as important as the insulation work which is done when retro-fitting insulation. One reason attic insulation would make a much larger difference is most homes with attics use vented soffits designed to encourage airflow. They are built to be drafty and you can't seal up those drafts without redesigning things.

Depends what your walls look like inside. If it’s balloon framed with no blocking, you’ll have a good convection current inside the wall.

The moisture concerns when trying to add insulation to an old uninsulated house are real, in service of saving a few thousand dollars of heating costs you could literally destroy your house and your health with mold.

Someone is going to come by and look at your comment and raise an eyebrow.

The building trade and construction is filled with nerds, amazing products, cheats and snake oil... so just like tech but less VC'c.

https://en.wikipedia.org/wiki/Building_science building nerds are on point and doing all kinds of cool stuff. If you want the modern version of bob villa this old house is probably this: https://www.youtube.com/@buildshow . It will give you some clues as to what is going on in modern construction.

Oh I’ve seen buildshow. I have also seen him talking about mistakes he made in the older designs he had. I would be real cautious about letting a builder at a lower tier than him beta test their ideas on moisture control inside my walls when I’m the test dummy inside.

Even if you don't use a thermal camera, just the thermal thermometers work as well. Sure, you have to take more readings, but the result is the same. A lot of people probably have one of these now after Covid, and can at least test things out before going to the step of a full thermal camera.

I have a bedroom that has a shared wall with a water heater which causes this room to be hotter than the rest of the house. Using the thermometer showed the temps after I added a barrier to the inside of the utility closest dropped significantly.

Thermal cameras have got really cheap: I found one on Aliexpress for less than £150, that plugs into a smartphone.

Have you tried it, though? Is it any good?

What kind of thermal camera do you recommend and what price range?

I bought a Topdon TC001 a year ago that in my experience is significantly more responsive and higher resolution than similarly priced FLIR or other name brand options at that price point. It appears there are even more low cost options now.

I find it rather interesting that companies like FLIR are limited by regulation (I believe US export bans) from selling IR cameras with greater than 9fps. there is also a resolution cap but I forget what it is off-hand. Strangely enough this doesn't stop US citizens from purchasing higher performing cameras from non-US companies. I think technology has come down significantly in price over the last few years and you can now get smartphone attached versions like infiray for a few hundred bucks.

For what use cases is 9 FPS not sufficient?

I have a seek thermal which plugs into my phone.

Very handy for checking for drafts and cold spots, and also checking the fuse box and other electrical for hot spots.

The resolution is not amazing, 206x156, but it's enough for this type of work.

I have a friend who is happily using a flir one, with a resolution of 160x120 at his day job as an electrician and it is also enough for checking for draft, water leaks insufficient insulation, etc.

There’s a couple of big problems with the heat-pump industry in the U.S. First, people get their advice about HVAC from the tradespeople, who are way behind the curve on heat-pump technology. Second, and relatedly, the trusted American HVAC brands are far behind China and Japan and Europe on heat pump technology, especially cold-weather capable inverter units.

I had our heat pumps replaced here in Maryland in 2019-2020 with mid-range Amana (rebranded Daikin) units. Decent efficiency, but output drops to half at 10F. The guys who recommended the system, a trusted local business, didn’t even tell me about that. Even in Maryland that means waking up to a cold house several weeks out of the year. That means we needed to keep our oil-based backup heat in place, which is a huge expense to maintain. (Also, our HVAC guys didn’t know that the communicating Daikin units can’t control external auxiliary heat, so they just left things with no backup heat whatsoever.)

After educating myself about this, I wish we had installed one of those Chinese inverter based units, like the Gree Flexx. But if I asked my HVAC guy about that they’d stare back blankly. And the folks who do know what they’re doing can charge whatever they want. The price of getting a mini-split installed here is several times the price of the unit. The $16,000 we spent just a few years ago for two condensers and air handlers looks downright cheap compared to what it would cost today.

Regarding your floor, we have a similar situation with radiant heat in our basement slab. I’ve been looking to ditch our oil boiler, but there’s basically no heat pump options that are widely available. (I don’t want to install some imported Chinese air to water heat pump that the local guys can’t fix.) With heating oil prices being over $4, though, I’m looking at just biting the bullet and installing an electric boiler, which is at least something I could probably fix myself.

I feel you. The lack of knowledge among American tradespeople is infuriating. As soon as you deviate slightly from the brands of furnaces they have been installing for decades, they don't know anything.

I think the biggest hurdle to heat pump adoption (at least in North America) is likely to be that it provides an experience that simply isn't as good as a gas furnace. On a chilly morning the air coming out of the vents just isn't that warm and it may take hours to bring the house up to temp, whereas gas puts out pleasantly warm air immediately and can quickly warm the house even on the coldest days. When it's truly cold (like < 20F) the heat pump will run continuously and struggle to maintain temp. Don't misunderstand, the heat pump is certainly _good enough_, but people typically don't pick the "good enough" experience over the "better" experience when the better option is available and they can afford it.

For reference I've lived in NC and TN near the mountains where heat pumps are pretty standard. I imagine we don't get the ultra high efficiency cold weather heat pump units that would be used up north, but they also get much colder temps than us. Several of the houses I've lived in have been recent construction (2008 and 2018), so well insulated and reasonably new & efficient heat pumps. For the last 2 years I've been in a house with gas, and it's just so damned pleasant... I know on paper that heat pump is better, but I really don't want to give up that furnace.

A relative recently upgraded their 120yr old house with heat pumps, and the warmth is so much better than where I currently live (a 40 year old home with a new gas furnace). In my experience you can't generalize about heat source.

It doesn't have to be all heat pump. You can have a backup gas heat for the coldest days, or even resistive heat. I'd bet there are heat pumps that integrate those technologies to ensure a nice experience.

When I got a quote to upgrade my resistive heater to a heat pump, the added cost to get a backup resistive heater (with the same capacity as my existing one) was only $500. Seems like as long as you're wired for it, it's very cheap.

> I think the biggest hurdle to heat pump adoption (at least in North America)

> When it's truly cold (like < 20F) the heat pump will run continuously and struggle to maintain temp.

Luckily, pretty much the entire Western and Eastern Coastal areas, it doesn't actually get that cold on a regular basis, except a few days in the winter. The US is actually in an incredibly advantageous geographical position for at least 60% of households to be on heatpumps, as opposed to, say, Finland/Canada/Russia etc.

Meanwhile it was estimated that half of Swedish houses were equipped with heat pumps in 2016. That number has certainly not gone down since given the steep rise in electricity costs we’ve had since. Many houses have been converted from horribly inefficient direct electric heating to heat pumps.

Part of the problem is that heat pumps aren't really well suited to a use case where you frequently have to bring a house up to temp in the way you're describing. If you have a big overnight set-back and then the heating comes on in the morning, that will require much more heat output than constantly putting out enough heat to maintain temperature.

In a well insulated property, the greater efficiency from operating at low output temperatures outweighs the additional heat loss from no / a low overnight set-back. In a poorly insulated property, the optimum set-back is higher and the efficiency at that optimum point is also much lower because the heat pump has to operate at higher temperature in order to ramp up the temperature.

I don't know if they are available in North America, but in the UK we have hybrid systems available that use heat pumps for 80% of the annual heat load and gas for peaking / ramping. OpenTherm gas boilers can be retrofitted to be controlled in this way so you only add the heat pump. An air source heat pump driving a hydronic / radiator system in this climate can serve 80% of the annual load with a unit sized at 55% of peak heat load. Different climates will have slightly different numbers but it shows the power of a hybrid system as you save a lot on HP capex and also maintain redundancy.

The advantage of this system is that the failure-mode of an incorrectly sized system is an efficiency penalty rather than not being warm enough, the same as an incorrectly commissioned or sized gas system. (Most gas systems are not optimally sized or configured and are delivering 5% to 10% less efficiency than they could).

I don't know if these systems are available in ducted air configuration for the US market though.

Wait - you have a HPWH connected to a hydronic floor system? That's an extremely inappropriate setup - the heatpump on a rheem is probably like ~4000 BTU/hr, and it's pulling the heat from the conditioned space, then you're drawing it off and pumping it back into the space via the floor. If you don't have an air-to-water heatpump and don't want fossil fuels, just use an electric boiler.

I know! It is definitely something i need to fix. I just havent found the right thing to handle the hydronics separate from our water heating.

That's a shame about the Rheem. Ours has been overperforming my financial model in the standard eco mode. We do have an advantage in that it sits out in the open in the unfinished part of the basement, which runs slightly warm in the winter due to a ductwork problem. No venting was necessary.

It's definitely challenging to find trades who have both the knowledge and interest to innovate relative to standard HVAC installations in the area.

On the payback period, that’s probably just outlay divided by energy savings. I’m sure you’d get more enjoyment from a more comfortable house and the next owner will appreciate the modernisation too so those need to be factored into the investment appraisal.

I doubt the architect puts such a miserly lens on the other projects they’re involved in.

This is actually becoming an important point. In parts of the world where energy ratings matter, they have an impact on house value as well. They unlock incentives, etc. A house that is up to modern standards is simply worth more because any new owner does not have to do expensive renovations to modernize. In the Netherlands house flipping is pretty common. Buy something old, modernize it, live in it a few years and make a profit. The lower energy cost is both a nice bonus and a key selling point.

> My only regret was going with a Rheem heat-pump water heater in this mix. It does not perform well at all.

Heat-pump water heater's performance depends a lot on where its installed and the airflow+heat available. If the water heater is undersized or if there isn't enough heat in the air, it would perform worse than a standard gas/electric water heater.

Mine is installed in a closet under the stairs, which is not ideal, but as long as I keep the water heater in eco mode, and keep closet door slightly open, it works good enough for our usecase. Our annual water heating costs went down from ~$500 to ~$100 after switching to the heat pump water heater.

As in the cold end of the heat pump is inside the heated area of the house? That feels very weird. On the other hand with heat pumps, stacking multiple stages strategy isn't necessarily a bad thing! All inefficiencies are not really losses but merely resistive heating contributions (unless their heat escapes to the final cold sink aka outside) and in the end the real question is which configuration is good in terms of capex and maintenance.

In an environment where getting rid of humidity is a concern (mold!), a "cold end inside" heat pump for water might even double as a dehumidifier, with water condensing on the cold end sent to the sewers, contributing a little energy in the process.

That's not uncommon and is even beneficial in warmer climates. It will be parasitic in winter (even if externally vented) and symbiotic in summer.

What problems are you seeing with your water heater? I’ve had one for about a year and have been pretty happy with it after learning I needed to schedule high demand times of day. It is a bit louder than I’d like but it’s not horrible.

> The architect said to me that we'll never fully recoup our costs of putting the hat on the house.

That's only true if value your added comfort at a very low price. The problem is that it is hard to put a value on the comfort of a house, either while living in it, or while selling it. Hotels, however, do it all the time, but it's easier since they are in the business of selling comfort at various levels.

That's right. I remember a local "electrification festival" where some vendors and city officials teamed up to explain the various options. One of the most common questions was "will this lower by bill"? And the most memorable answer by a vendor was "probably now, but you won't have to be wearing that coat in your living room". Which hit home because at the time we had a drafty house with poor heat distribution.

Have you ever monitored the air quality levels in various rooms?

Curious if getting rid of those drafts may be unknowingly affecting your health in other areas.

My understanding is that any house that isn’t built ‘tight’ by today’s standards will have a fast enough ACH that you don’t need to worry about ventilation as you would with a tight house. And only a ‘deep energy retrofit’ of an older house would result in tightness like that, so ERV and MUA etc are not necessary. Local code, build detail, and age of house are factors, YMMV, but this isn’t a problem you’d cause by accident with anything but a very invasive retrofit.

Mechanical ventilation is not necessary in a drafty house, but it’s still very nice to have. Bonus points for a well-filtered system. (None of the major brands will sell you a system that is well filtered out of the box. But it’s straightforward, if rather space consuming, to put a monstrous filter with effectively zero pressure loss in series with the system.)

Bonus points for taking advantage of a balanced ventilation system’s ability to continuously extract air from stinky areas, e.g. bathrooms.

Even more bonus points for avoiding negative pressure due to conventional bathroom exhaust, which can defeat stack effect-based exhaust from non-power-vented combustion appliances, which are, for some reason, still legal.

(Seriously, WTF. There’s a straightforward design that could safely created a forced draft even with legacy leaky ductwork: put the fan on the exterior vent terminal, so the duct is under negative pressure. The wiring could be fished through the existing duct using class 2 / SELV wiring with high-temperature insulation. A pressure or airflow-sensing interlock in the appliance could prevent gas flow if the fan stops working. Sadly, I’ve never heard of a system remotely resembling this. The choices appear to be stack effect (category I or II) but basically crossing fingers and hoping the pressure works out) or positive-pressure sealed but not tested “category III” or “category IV” pipes and crossing fingers and hoping that the pipes are actually airtight.)

Yeah I believe GOLogic’s designs have the ERV exhaust in the kitchen, bathroom, and laundry, and the fresh air return in the living spaces and bedrooms. I definitely like the idea of that, especially with filtration.

We installed an ERV so there is always fresh air circulating in the house.

How noisy is it? I heard of people installing them, and getting complaints from the neighbors.

They're as noisy as an AC. So here in Arizona no one cares. But in Belgium this was an issue as they run more in winter and in winter sound travels further.

Just installed heat pump systems (daikin) this december.

The exterior unit is basically silent even when there was a cold snap (below freezing but not northern alaska cold).

I suspect an interior air source heat pump hot water heater, being smaller, will be noisier, and likely less efficient.

I'd love to switch my 240v/30a water heater to use a 120v/20a service, but will wait a bit longer for the technology to mature. Ideally it'd have the heat collection part outside.

In the winter everyone has their triple-paned windows closed. Is noise that much of a problem?

Is triple pane common in Belgium? It’s not in the UK (as far as I recollect) and they’re colder than Belgium

I built a house in 2014 there. Triple pane. Pointless. You never recoup the cost.

Uhmm...I see a problem for countries where you have wall to wall connected urban environments...If all 60 connected houses on a street, install external heat pumps, it will add up.

Turns out cities are loud! In NYC, at least, heat pumps are far more quiet than the endless window unit A/C's, or larger traditional A/C's, in my experience.

Outdoor noise is less of an issue in the winter in big cities because windows are closed.

Most of the noise in cities is cars. One idiot on a Harley drowns out a warehouse of heat pumps

Sounds like an installation can be really tricky or you will end up with something like this: https://youtu.be/1rKNT7-42J0?t=1510

Also, when talking about noise it's important to talk about frequency. If they produce low frequency noise, that can be far more irritating. Shutting the windows won't help much

Depends on the installer. A lot of noise results from units that are not properly mounted or mounted at a slight engine. The fan then starts getting more noisy and wears out earlier. There are other problems to not installing units properly.

>My only regret was going with a Rheem heat-pump water heater in this mix. It does not perform well at all.

Sorry to hear that. My Rheem heat-pump water heater works fantastically, although I do live in a hot climate so that could be why.

Drain water heat recovery seems like the best efficiency boost for water heating. Completely passive, 60% extra heat energy. At least for cold climates. Heat pump water heater might be phenomenal in a Phoenix garage.

A heat pump water heater seems phenomenal to me in an Austin attic. And I use the cold air generated to cool a wiring/server closet. Win/win.

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