How (not) to reject or waste energy
November 13, 2022 2:12 PM Subscribe
The bulk of rejected energy is an unavoidable byproduct of combustion and heat engines. We can, however, avoid wasting energy when heating/cooling houses and apartments. Learn about thermal bypass, thermal bridges, wind washing, heat pumps vs furnaces, air leakage, the stack effect and building envelopes. Weatherproofing? Deal with air leakage, make sure that insulation is installed properly and seal your attic. *(Data on energy flows from Lawrence Livermore National Laboratory, including one for 2021).
The Energy Vanguard blog is an ongoing educational effort by energy consultant and lapsed (?) physicist Allison A. Bailes III, PhD (Twitter) with over a thousand posts since 2010. Green Building Advisor has a paywall for some articles but their webinars and video series are free to the public and the Building Science and Beer podcast is available on Youtube.
The Energy Vanguard blog is an ongoing educational effort by energy consultant and lapsed (?) physicist Allison A. Bailes III, PhD (Twitter) with over a thousand posts since 2010. Green Building Advisor has a paywall for some articles but their webinars and video series are free to the public and the Building Science and Beer podcast is available on Youtube.
Ooh lots of stuff on ventilation from Dr. Bailes. I'm still looking through the blog, tbh, but the balance seems to be avoiding infiltration (random air leaks / the fuzzy idea of letting a building breathe) and creating intentional ventilation. "Random leaks don’t bring in fresh air, so we seal up the house as tight as possible and then intentionally bring in air from a location where we know it will be as fresh as possible (i.e., not off the roof or over the garage)." Also a bunch of posts on cleaning indoor air due to covid and some shifting opinion on how high a ventilation rate is necessary.
posted by spamandkimchi at 2:25 PM on November 13, 2022 [2 favorites]
posted by spamandkimchi at 2:25 PM on November 13, 2022 [2 favorites]
This post "four ways to do balanced ventilation" includes opening windows, and then goes up in complexity.
posted by spamandkimchi at 2:35 PM on November 13, 2022
posted by spamandkimchi at 2:35 PM on November 13, 2022
Thank you so much! I didn’t mean to hijack the thread, I’m very excited to read these.
posted by sixswitch at 3:33 PM on November 13, 2022
posted by sixswitch at 3:33 PM on November 13, 2022
What’s the state of things around balancing “seal the building completely but also provide excellent ventilation with lots of fresh air because covid”?
This isn't a dichotomy, anymore than there is a choice between having lots of leaks in your fuel tank and being able to put new petrol in. Leaks are always bad. If you need sure changes, mechanical ventilation or just opening window works well.
posted by Dysk at 3:34 PM on November 13, 2022 [1 favorite]
This isn't a dichotomy, anymore than there is a choice between having lots of leaks in your fuel tank and being able to put new petrol in. Leaks are always bad. If you need sure changes, mechanical ventilation or just opening window works well.
posted by Dysk at 3:34 PM on November 13, 2022 [1 favorite]
If only some of this would be legislated into rental properties. Why insulate anything if the tenant pays for heat? (Or, if only home ownership was still a reasonable goal.)
posted by Ookseer at 3:54 PM on November 13, 2022 [5 favorites]
posted by Ookseer at 3:54 PM on November 13, 2022 [5 favorites]
Really interesting articles, thanks :-)
I wish we were better at this stuff where I live. Because we have a climate that means it's never very hot or very cold, we seem to mostly ignore the details. The local government does require that new houses are well insulated and that requirement is higher for a house with airconditioning and also takes into account the aspect of a house, size of windows etc, but it's still a pretty low bar and easy to achieve, with no real attention paid to sealing a house for air leaks. Our house (built in the '80s) leaks air like a sieve - from inside the attic space, you can see light coming in all over the place.
posted by dg at 4:55 PM on November 13, 2022
I wish we were better at this stuff where I live. Because we have a climate that means it's never very hot or very cold, we seem to mostly ignore the details. The local government does require that new houses are well insulated and that requirement is higher for a house with airconditioning and also takes into account the aspect of a house, size of windows etc, but it's still a pretty low bar and easy to achieve, with no real attention paid to sealing a house for air leaks. Our house (built in the '80s) leaks air like a sieve - from inside the attic space, you can see light coming in all over the place.
posted by dg at 4:55 PM on November 13, 2022
no real attention paid to sealing a house for air leaks.
The issue is, if you seal up a building from the 80s, you'd immediately get moisture and mould problems - they don't usually have the advanced vapor barriers modern sealed buildings have.
You can think of it like Goretex ski pants, jackets and shoes - it's a close balance between being tightly woven even to be windproof and waterproof, yet loosely woven enough to allow your sweat to evaporate and pass through the weave it to keep you dry. These barriers keep your house airtight and waterproof but allow all the moisture generated from human activities - breathing, showering and cooking - to escape. A single human generates enough breath moisture to fog up the interior of a car in winter in 20 minutes, more if they had just exerted themselves.
Older buildings achieved waterproofing at the cost of also locking the vapor in, so the building codes actually mandated permanently open ventilation - eg in the bathroom or shower I'm told it actually used to be mandatory in Australia for the windows to have an open wire screen at the top if there's no extractor fan, and many older homes wouldn't have had a fan.
posted by xdvesper at 6:07 PM on November 13, 2022 [3 favorites]
The issue is, if you seal up a building from the 80s, you'd immediately get moisture and mould problems - they don't usually have the advanced vapor barriers modern sealed buildings have.
You can think of it like Goretex ski pants, jackets and shoes - it's a close balance between being tightly woven even to be windproof and waterproof, yet loosely woven enough to allow your sweat to evaporate and pass through the weave it to keep you dry. These barriers keep your house airtight and waterproof but allow all the moisture generated from human activities - breathing, showering and cooking - to escape. A single human generates enough breath moisture to fog up the interior of a car in winter in 20 minutes, more if they had just exerted themselves.
Older buildings achieved waterproofing at the cost of also locking the vapor in, so the building codes actually mandated permanently open ventilation - eg in the bathroom or shower I'm told it actually used to be mandatory in Australia for the windows to have an open wire screen at the top if there's no extractor fan, and many older homes wouldn't have had a fan.
posted by xdvesper at 6:07 PM on November 13, 2022 [3 favorites]
Yes, Australian homes used to be required to have a permanently open vent in bathrooms, but current regulations only require that a window is fitted of a size at least 10% of the floor space OR an extractor fan.
posted by dg at 7:36 PM on November 13, 2022
posted by dg at 7:36 PM on November 13, 2022
A single human generates enough breath moisture to fog up the interior of a car
Back when I lived in Chicago, during winter I could reliably fog up my side of a car (front, back and side) in less than five minutes unless the heaters were noticeably on (bare minimum heating, a favorite amongst my friends, would not have an effect so they'd always have to kick up the heaters and/or vents if they wanted to see out of the right side of the windshield.) The average time to fog was on the order of 3 minutes (you can tell we had super-exciting lives, such that anyone would actually try to monitor this).
I still occasionally wonder why I fogged things up much faster than anyone else I knew.
posted by aramaic at 8:02 PM on November 13, 2022
Back when I lived in Chicago, during winter I could reliably fog up my side of a car (front, back and side) in less than five minutes unless the heaters were noticeably on (bare minimum heating, a favorite amongst my friends, would not have an effect so they'd always have to kick up the heaters and/or vents if they wanted to see out of the right side of the windshield.) The average time to fog was on the order of 3 minutes (you can tell we had super-exciting lives, such that anyone would actually try to monitor this).
I still occasionally wonder why I fogged things up much faster than anyone else I knew.
posted by aramaic at 8:02 PM on November 13, 2022
I'll put two related links in here. The first is to the Passivhaus Institut which brings all of that into a set of standards you can build against. The next is for us Australians - YourHome which outlines sustainable building practices. Both are really detailed, but YourHome has all the information available online for free – including house plans.
posted by antipodes at 10:52 PM on November 13, 2022 [1 favorite]
posted by antipodes at 10:52 PM on November 13, 2022 [1 favorite]
The issue is, if you seal up a building from the 80s, you'd immediately get moisture and mould problems - they don't usually have the advanced vapor barriers modern sealed buildings have.
If you're going in to seal the air leaks on an older building, you can retrofit a lot of the stuff that you'd use with it too, including vapour barriers.
posted by Dysk at 11:32 PM on November 13, 2022
If you're going in to seal the air leaks on an older building, you can retrofit a lot of the stuff that you'd use with it too, including vapour barriers.
posted by Dysk at 11:32 PM on November 13, 2022
Also install mechanical ventilation like any other sealed modern home. Mould comes from moisture and you can mitigate moisture by venting it.
posted by Mitheral at 4:46 AM on November 14, 2022 [1 favorite]
posted by Mitheral at 4:46 AM on November 14, 2022 [1 favorite]
Also install mechanical ventilation
With energy recovery, if feasible.
posted by Stoneshop at 7:28 AM on November 14, 2022
With energy recovery, if feasible.
posted by Stoneshop at 7:28 AM on November 14, 2022
What’s the state of things around balancing “seal the building completely but also provide excellent ventilation with lots of fresh air because covid”?
You can bring fresh air in from outside through a heat exchanger, where it's heated by the warm stale air you're pushing out from the building. You still lose some heat to outside, but a lot less than just opening a window.
posted by automatronic at 7:42 AM on November 14, 2022 [1 favorite]
You can bring fresh air in from outside through a heat exchanger, where it's heated by the warm stale air you're pushing out from the building. You still lose some heat to outside, but a lot less than just opening a window.
posted by automatronic at 7:42 AM on November 14, 2022 [1 favorite]
More applicable to warm climate temperature regulation but I think the thermodynamic piston cylinder based window openers are super neat. No electronics, just a piston full of wax expanding and contracting to actuate window ventilation.
posted by neonamber at 8:24 AM on November 14, 2022
posted by neonamber at 8:24 AM on November 14, 2022
Also install mechanical ventilation like any other sealed modern home. Mould comes from moisture and you can mitigate moisture by venting it.
Exactly. Sealing a home that's already been constructed is far more difficult and expensive than installing a bathroom vent fan, which is approximately $300-$500 done by a professional. Or less if you are able to DIY - a quiet, powerful bathroom fan is less than $100.
posted by The_Vegetables at 8:52 AM on November 14, 2022
Exactly. Sealing a home that's already been constructed is far more difficult and expensive than installing a bathroom vent fan, which is approximately $300-$500 done by a professional. Or less if you are able to DIY - a quiet, powerful bathroom fan is less than $100.
posted by The_Vegetables at 8:52 AM on November 14, 2022
than installing a bathroom vent fan
Why would you assume those houses don't have a bathroom vent fan?
Reality is say your old leaky house gets 2 ACH or something, and you buy some cheap rubber seals for your doors and windows and you make it a point to close up all your windows and you reduce it to 1 ACH. Good, your energy bills go down.
Now suddenly you have condensation on your windows in the morning and it's creating mould issues. So now you need to run your bathroom fan or kitchen exhaust fan for longer and longer to vent the moisture build up in your home, and... you're back to 2 ACH.
Without the barrier wrap - which allows water vapor to diffuse through it - you're still relying on ventilation, whether indirect or direct. Retrofitting the barrier wrap isn't something I've seen happen before, though I'm sure if you REALLY wanted to do it you could find a company willing to attempt it - they'd have to take off all the exterior cladding (brick?), remove the non permeable waterproofing... and I'm not clear on the next step, since you normally wrap the entire building frame envelope nice and tight BEFORE penetrating the wrap with pipes / electrical, but now those penetrations are already there, so you'd need to... pre-punch holes in the wrap before trying to wrap the building?
Same for ERV systems, no ethical / sane contractor is going to recommend you retrofit an ERV system if the building isn't specifically airtight to passive house standard, since you lose most of the ERV benefit through leakage. Very few builders where I am are capable of building to passive house standards today, never mind talking about a house from the 80s.
posted by xdvesper at 3:30 PM on November 14, 2022 [1 favorite]
Why would you assume those houses don't have a bathroom vent fan?
Reality is say your old leaky house gets 2 ACH or something, and you buy some cheap rubber seals for your doors and windows and you make it a point to close up all your windows and you reduce it to 1 ACH. Good, your energy bills go down.
Now suddenly you have condensation on your windows in the morning and it's creating mould issues. So now you need to run your bathroom fan or kitchen exhaust fan for longer and longer to vent the moisture build up in your home, and... you're back to 2 ACH.
Without the barrier wrap - which allows water vapor to diffuse through it - you're still relying on ventilation, whether indirect or direct. Retrofitting the barrier wrap isn't something I've seen happen before, though I'm sure if you REALLY wanted to do it you could find a company willing to attempt it - they'd have to take off all the exterior cladding (brick?), remove the non permeable waterproofing... and I'm not clear on the next step, since you normally wrap the entire building frame envelope nice and tight BEFORE penetrating the wrap with pipes / electrical, but now those penetrations are already there, so you'd need to... pre-punch holes in the wrap before trying to wrap the building?
Same for ERV systems, no ethical / sane contractor is going to recommend you retrofit an ERV system if the building isn't specifically airtight to passive house standard, since you lose most of the ERV benefit through leakage. Very few builders where I am are capable of building to passive house standards today, never mind talking about a house from the 80s.
posted by xdvesper at 3:30 PM on November 14, 2022 [1 favorite]
IMO the passive house standard is kind of dumb, and doesn't fit well with most of the warmer US climates compared to Europe where it was created, but in your example, humidity-based higher energy bills and energy use is season-dependent, where as you seem to be considering them to be a constant. There are plenty of times (and places) where extra indoor humidity is not a problem.
Also even a so-so bathroom fan uses far less electricity than an AC or heater, so energy efficiency improvements tend to net decrease energy.
Finally, the number of homes constructed has fallen off a cliff in the past decade, where the median age of a home in the US is pushing 50 years old, so retrofitting is far more important than building new unless something changes dramatically soon.
posted by The_Vegetables at 8:18 AM on November 15, 2022
Also even a so-so bathroom fan uses far less electricity than an AC or heater, so energy efficiency improvements tend to net decrease energy.
Finally, the number of homes constructed has fallen off a cliff in the past decade, where the median age of a home in the US is pushing 50 years old, so retrofitting is far more important than building new unless something changes dramatically soon.
posted by The_Vegetables at 8:18 AM on November 15, 2022
normally wrap the entire building frame envelope nice and tight BEFORE penetrating the wrap with pipes / electrical, but now those penetrations are already there, so you'd need to... pre-punch holes in the wrap before trying to wrap the building?
My parents lived in a building from the early 1800s in Denmark until very recently. Triple glazed all round, loads of insulation in the walls, no damp issues or problems with heat leakage. It definitely wasn't built to 21st century Danish standards originally, but it was successfully brought up to those standards at some point. And that's not an unusual situation in Denmark! I don't know the details of how the issues are solved, but it sure as heck isn't as intractable a problem as a lot of people in this thread are suggesting.
posted by Dysk at 8:22 AM on November 15, 2022 [1 favorite]
My parents lived in a building from the early 1800s in Denmark until very recently. Triple glazed all round, loads of insulation in the walls, no damp issues or problems with heat leakage. It definitely wasn't built to 21st century Danish standards originally, but it was successfully brought up to those standards at some point. And that's not an unusual situation in Denmark! I don't know the details of how the issues are solved, but it sure as heck isn't as intractable a problem as a lot of people in this thread are suggesting.
posted by Dysk at 8:22 AM on November 15, 2022 [1 favorite]
Maybe consulting with some contractors from Scandinavia and Northern Germany (and probably lots of other places with decent building standards and loud of old houses that I'm less personally familiar with) rather than asking around a bunch of anglophone builders (or contractors from elsewhere with sorry building standards) to see what's possible would be a good idea. Like, if the Brits thought it could be done better, they probably would've done it better. They clearly don't. But it's equally clear that it has been done elsewhere, so ask those guys what's possible.
posted by Dysk at 8:26 AM on November 15, 2022
posted by Dysk at 8:26 AM on November 15, 2022
The article is great, thanks.
Please run your home ventillation at slightly positive pressure relative to the outside, so any leaks push air out, then filter your air intake as much as possible.... because remember that the air outside is no longer fresh and increasingly polluted. Industrial pollutants, higher CO2 and Methane and nitrogen oxides, pfas, soot, wildfire smoke, brake pad dust and tire particles, PM2.5 etc. And while nuclear fallout from testing is slowly decreasing, we always stand on the precipace of more radiation accidents and wars.
We are still stick building oversized cottages 19th century cottages with holes cut in the structural members to hide new fangled technologies of plumbing, electricity and ventilation.
Also, remember that our normal weather going forward is the weather that would be a natural disaster in the past. (rain events in multiple inches, heatwaves that last weeks, season long wildfires, yearly "once in a 500 year" storms.
Aside from cranks building bunkers, it seems like no one is building homes that can survive the world our pollution has already commited us to.
posted by anecdotal_grand_theory at 12:25 AM on November 16, 2022 [1 favorite]
Please run your home ventillation at slightly positive pressure relative to the outside, so any leaks push air out, then filter your air intake as much as possible.... because remember that the air outside is no longer fresh and increasingly polluted. Industrial pollutants, higher CO2 and Methane and nitrogen oxides, pfas, soot, wildfire smoke, brake pad dust and tire particles, PM2.5 etc. And while nuclear fallout from testing is slowly decreasing, we always stand on the precipace of more radiation accidents and wars.
We are still stick building oversized cottages 19th century cottages with holes cut in the structural members to hide new fangled technologies of plumbing, electricity and ventilation.
Also, remember that our normal weather going forward is the weather that would be a natural disaster in the past. (rain events in multiple inches, heatwaves that last weeks, season long wildfires, yearly "once in a 500 year" storms.
Aside from cranks building bunkers, it seems like no one is building homes that can survive the world our pollution has already commited us to.
posted by anecdotal_grand_theory at 12:25 AM on November 16, 2022 [1 favorite]
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posted by sixswitch at 2:16 PM on November 13, 2022 [3 favorites]