5 ms·

Information I have learned from reading the Green Building Advisors website over the past two years while building a new house (electric-only although I didn't

Information I have learned from reading the Green Building Advisors website over the past two years while building a new house (electric-only although I didn't start with that purpose): 1) Air source heat pumps have become incredibly efficient even in cold climates. 2) Ground source heat pumps are complex and very expensive and probably best suited for large installs like schools. 3) Ductless mini splits are the preferred way to heat and cool most USA (tight) homes. 4) Modern code dictates a tight (measured by air changes per hour) home and making an existing home tighter is usually the best use of time and money. 5) Induction is superior in many ways and air quality points to gas cooking being much worse than previously thought. 6) Heat pump hot water heaters (with tank) are the most efficient way to provide hot water. 7) Tankless electric is difficult because of the huge spikes of power it needs. Maybe if you have a battery with your solar setup, it can work better. 8) Tankless also seems to have more maintenance issues than expected (e.g., it's not maintenance free as I imagined). 9) Once your house becomes very tight (measured by air changes per hour), you will need to bring in fresh air. An ERV is efficient at exchanging stale, temp-regulated air with outside air. 10) Building tight, all-electric, with solar will provide a comfortable, clean, long-lasting house, but it will be quite a bit more expensive. Possibly 30%+ more expensive than using standard contractor choices.

danans 5y ago
> 10) Building tight, all-electric, with solar will provide a comfortable, clean, long-lasting house, but it will be quite a bit more expensive. Possibly 30%+ more expensive than using standard contractor choices. I'm just finishing doing a high performance renovation ( <1 ACH50, all electric, heat pumps, HRV, etc.). For new construction, the difference is more like +5-10% - the materials are marginally more expensive, and the labor doesn't require extremely specialized skills. The HVAC equipment is the very expensive part. For a renovation, it's more like 20% more expensive but it can vary widely depending on the existing house's condition and the original build quality. I personally saved a boatload by doing the high performance air sealing work myself - it's not that hard once you get the hang of it, just laborious.
- lbotos 5y ago
  How did you do the air sealing yourself? were you concerned about your continuous air/vapor/water barriers?
  - danans 5y ago
    I taped all the exterior sheathing joints (including at the foundation with high-performance air-sealing tapes). Then I applied a fully adhered vapor permeable airtight membrane to the entire exterior sheathing surface, and caulked the wall/roof joint, which also provided redundancy for the joint taping. The general contractor applied a secondary bulk water shedding house wrap, a rain screen, and the finish cladding. There were other things I did internally during the drywall/plasterboard stage also to minimize air movement through walls and ceilings.
    - lbotos 5y ago
      Nice! Mind shooting me an email (mine is in profile) would love to ask you some follow up questions!
photojosh 5y ago
> 3) Ductless mini splits are the preferred way to heat and cool most USA (tight) homes. In Australia, but we just installed these in our house with in-ceiling cassettes and they're incredibly good. Also initially didn't care too much that they had WiFi control, but we ended up never using the remotes and just using the app. (Since you're typically sitting on the couch when you want to change the setting.) Every ducted system I've seen is incapable of regulating separate rooms properly. Presumably one would need temp sensors in each room to do that, and that isn't done on cheap installs. > 5) Induction is superior in many ways and air quality points to gas cooking being much worse than previously thought. If anyone knows some good arguments to use when your partner is an excellent cook and loves gas for the high heat (searing and wok frying), I'm all ears. With the kitchen upgrade I installed a monster extraction rangehood (external fan, 3x the typical extraction) to hopefully deal with the air quality issue.
- mjevans 5y ago
  If I ever have enough money to buy a house, I want a kitchen that's isolated anyway. It can still be attached to the main building, but I want to be able to cook in the summers and only heat up one room. I'd also like the kitchen to be on it's own sub-panel anyway since I'd like the option of using 20A appliances at each outlet anyway.
  - rudedogg 5y ago
    I think code requires 20A circuits in the kitchen. Not sure though.
    - mjevans 5y ago
      You completely misunderstand. The whole kitchen would have a sub-panel _in_ the kitchen; because EVERY OUTLET would be it's own independent 20A capable circuit, run back to that sub-panel. I don't expect to use 20A from every outlet all the time, but I don't want to be constrained from any mix-and-match of devices I need within the room's power budget.
- Dumblydorr 5y ago
darkteflon 5y ago
Is this (https://www.greenbuildingadvisor.com/ https://www.greenbuildingadvisor.com/) the one? I hadn’t heard of this before but it looks excellent. In your view, if I may, what makes this an authoritative source?
- bklyn11201 5y ago
  I thought it was a good combination of practical while being backed with data. They are big proponents of modeling out energy use with something called Manual J. They advocate for designing based on data instead of hunch which often leads to over-provisioning (less phone calls) and less efficiency. Posters also seem to be practical and focused on cost efficient solutions. This can be more rare than you think when dealing with passive house consultants or with efficiency consultants as I received many recommendations that had >= 50 year pay off times!
DannyBee 5y ago
"1) Air source heat pumps have become incredibly efficient even in cold climates. 2) Ground source heat pumps are complex and very expensive and probably best suited for large installs like schools. " This is not really accurate on the complexity/etc side. Expense we'll get to later. A. The GSHP is not complex at all, and often much easier to understand than the equivalent air source machinery. I could repair my GSHP. B. The efficiency of air source heat pumps vary a ton in the field. This is not conjecture. This is backed up by years of research. Of course, unlike ground source heat pump (which usually contain tons of sensors and can tell you exactly how well they are operating in a lot of ways), air source heat pumps rarely contain any of the performance measurement sensors necessary to validate their efficiency in practice for your install, and they are rarely accessible. So you are limited to a small number of studies that bother to test them in the field by adding that kind of metering. Oh and manufacturer "self-reporting" about how good they are. EER or COP of air source heat pumps in-situ can be easily 50% or less of claimed efficiency depending on real climate and how well designed they were for the situation. GSHP are 85-99% of designed performance over a much wider climate range (again backed up by research, and with much larger sample sizes, since most GSHP have the monitoring sensors built in). That's on top of usually much higher efficiency of GSHP over ASHP. C. GSHP not amenable to the random "don't want to have to care about real engineering" HVAC contractors that most people deal with. IE not even willing to do basic manual j load calcs. They are only complex in this sense - most air source heat pump folks don't really have to know what they are doing, and it will often work okayish in terms of ability to heat/cool when they size it wrong. It will just be very inefficient. If your ground source heat pump folks don't actually bother to do the work right and enter the calcs into the loop design program, it can fail. Just about 100% of failed GSHP installs i've seen were done by air source contractors badly trying to moonlight because they thought they margin would end up better (and who were bad at ASHP as well). Any good loop design program will give you the EER/COP of the system in your case based on historical temperature, along with actual yearly cost/etc. So you don't have to guess whether it will work out for you (and it will be very close to reality). It's also obvious if your contractor is giving you bullshit if you have a loop design report - IE if the page with the assumptions/data show clear nonsense. As performance standards increase (IE California), or any form of real in-situ efficiency testing of air source heat pumps was ever required, you would see this "really efficient" argument disappear really quick. (Heating has definitely gotten a lot better in lower temps, not gonna argue with that). D. It is true that GSHP is expensive to install, but that's mostly a factor of scale for drilling, and not size of install or unit cost. It's never going to be an effective way to deal with a single 2000sqft house. It will be a much more effective (and space efficient) at serving multi-unit complexes, regardless of individual house size. For example, when they do GSHP for a new construction community (out here they are doing 200 new homes for examples), it's not a lot more expensive than installing air source pumps. For single houses, again, it depends on your real in-practice performance of an ASHP, which is rarely ever measured. For a house i owned in MD, and compared to two ASHP's that were properly sized (and properly sized/sealed duct work/house/etc with actual leakage/r-value/perf testing), but just a really bad in-practice fit for my climate (neighbors had same issues, etc), it only took 5 years to pay back the GSHP cost (after tax credits, etc). This is uncommon case, obviously. But i'll also say being able to set the house at 72 and leaving it that way forever is worth something too. Ductless i've got no qualms with :) I think most folks with tight homes would be much better off in practice with lots of ductless wall/ceiling units than standard ASHP/GSHP.
zhynn 5y ago
Also heat pump water heaters essentially air condition/de-humidify your closet/garage/etc which is great in humid climates.
hourislate 5y ago
I would add Spray Foam to your list. Increases racking strength of walls, provides an airtight seal and vapor barrier (2lb- Closed Cell Foam), and will eventually pay for itself in Heating and Cooling savings. We have a a very large cottage in Northern Ontario (3000 sq/ft +) that has been sprayed foamed (Demilic Heatlok) and has in floor radiant heating and forced air AC all supplied by Geo Thermal. The electric bills a year are less than what some people spend at Starbucks. The comfort is incredible in -30F/-34c or +100f/38c and a bomb could go off outside and I doubt you would hear it. The costs to insulate the whole house and to install the Geothermal (including AC) was 55k, less than what some folks spend on kitchen cabinets and counter tops.
tootie 5y ago
> Building tight, all-electric, with solar will provide a comfortable, clean, long-lasting house, but it will be quite a bit more expensive. Possibly 30%+ more expensive than using standard contractor choices. Maybe a 30% higher price, but likely a lower cost when you factor in externalities.
- fy20 5y ago
  I'm building a new house like this - in my country the building code is on par with Passive House standards, so we don't have much choice :-) I ran the numbers for heating with gas vs an electric heat pump, and gas actually worked out more expensive. The house will need around 2000W[0] of heat in the middle of winter. For that usage, the most expensive part of gas would be the network fee, not the gas itself. An electric heat pump is a bit more expensive that a gas boiler, but considering we'd need to have a gas connection introduced to the property, the overall upfront cost is the same. The lifetime of both units is the same (10-15 years). Someone here mentioned a gas absorption heat pump before, but those units are much more expensive than an electric heat pump in my country, and it still has the same issue of the gas network fee being expensive. We'll also have solar PV, so that will cut the electricity running costs even lower once it's paid off (~7 years). It's interesting that once you have an efficient building envelope, technologies that you would think would be more efficient such as solar water heaters or ground source heat pumps don't actually make sense financially in the long term. I also ran the numbers for underfloor infrared heating vs electric heat pump + hydronic underfloor heating. Taking into account the higher installation costs, and expected life of the heat pump unit, the infrared heating - which is must less efficient - actually works out costing around the same. The unit we have will also provide DHW and cooling in the summer, so it's apples and oranges, but for a pure heating perspective it's worth considering that option, espeically if you want a lower upfront cost. [0] For a 160m2 / 1700sqft house. This doesn't take into account 'waste' heat from appliances, so our primary heat source demand will actually be less.
ta2162 5y ago
I thought ducted central heat pump with zones was the most efficient. Also, it filters the air centrally (and better, higher MERV possibilities), allows you to more easily manage humidity, and allows you to mix and bring in outside air. Not cheap though.
- BostonEnginerd 5y ago
  I understand that the ducted systems are less efficient, but the ability to better control filtration, outdoor mixing and humidity makes up for that.
  - ta2162 5y ago
    >I understand that the ducted systems are less efficient But they're not less efficient, ducted systems are more efficient. Mini-splits multiply your refrigerant lines, compressors, heat exchanger, condensing coils, etc., so you're multiplying your inefficiencies. A single variable rate, zoned, ducted heat pump is the most efficient, but they definitely cost more.
axiolite 5y ago
I agree with everything you've said, BUT, I find small tank (10gal or less) electric hot water heaters surprisingly cost-effective options if you are using very low-flow aerators and shower heads (0.5-1.0 GPM). And particularly so if you have a small household where everyone can be taught to hit the button* on the wall to turn-on the hot water 30 min before they want to take a shower. The installation cost is vastly lower than heat-pump based units, they fit in a cabinet under a sink much better, are easier to wire up to an on-demand on/off button, is even cheaper to operate during summer months, etc. Would work even better with a solar thermal panel for preheating the cold water. The button in question being a 30-minute auto-shut-off switch, actually.
belorn 5y ago
> 2) Ground source heat pumps are complex and very expensive and probably best suited for large installs like schools. Looking at prices for the unit, the difference between Ground source heat pumps and air source heat pumps is around 15%. This assume we want heated water. AC-only units are naturally much much cheaper, but since there does not exist ground source AC-only units it is not a very fair comparison. When it comes to extracting heat from the environment there are a few different choices. Air, solar, borehole, ground, and water. As I understand it, which one is the most cost efficient choice depend more on the environment which it is getting installed than the actually unit.
- jnsaff2 5y ago
  Big price difference comes from installation of ground loop. They either dig up your back yard and install a horizontal loop or you can have a vertical borehole (you probably need several of those). Boreholes here in NE-EU are about 35EUR per meter and for my house I'd need about 300m of them.

danans 5y ago

> 10) Building tight, all-electric, with solar will provide a comfortable, clean, long-lasting house, but it will be quite a bit more expensive. Possibly 30%+ more expensive than using standard contractor choices. I'm just finishing doing a high performance renovation ( <1 ACH50, all electric, heat pumps, HRV, etc.). For new construction, the difference is more like +5-10% - the materials are marginally more expensive, and the labor doesn't require extremely specialized skills. The HVAC equipment is the very expensive part. For a renovation, it's more like 20% more expensive but it can vary widely depending on the existing house's condition and the original build quality. I personally saved a boatload by doing the high performance air sealing work myself - it's not that hard once you get the hang of it, just laborious.

lbotos 5y ago
How did you do the air sealing yourself? were you concerned about your continuous air/vapor/water barriers?
- danans 5y ago
  I taped all the exterior sheathing joints (including at the foundation with high-performance air-sealing tapes). Then I applied a fully adhered vapor permeable airtight membrane to the entire exterior sheathing surface, and caulked the wall/roof joint, which also provided redundancy for the joint taping. The general contractor applied a secondary bulk water shedding house wrap, a rain screen, and the finish cladding. There were other things I did internally during the drywall/plasterboard stage also to minimize air movement through walls and ceilings.
  - lbotos 5y ago
    Nice! Mind shooting me an email (mine is in profile) would love to ask you some follow up questions!

photojosh 5y ago

> 3) Ductless mini splits are the preferred way to heat and cool most USA (tight) homes. In Australia, but we just installed these in our house with in-ceiling cassettes and they're incredibly good. Also initially didn't care too much that they had WiFi control, but we ended up never using the remotes and just using the app. (Since you're typically sitting on the couch when you want to change the setting.) Every ducted system I've seen is incapable of regulating separate rooms properly. Presumably one would need temp sensors in each room to do that, and that isn't done on cheap installs. > 5) Induction is superior in many ways and air quality points to gas cooking being much worse than previously thought. If anyone knows some good arguments to use when your partner is an excellent cook and loves gas for the high heat (searing and wok frying), I'm all ears. With the kitchen upgrade I installed a monster extraction rangehood (external fan, 3x the typical extraction) to hopefully deal with the air quality issue.

mjevans 5y ago
If I ever have enough money to buy a house, I want a kitchen that's isolated anyway. It can still be attached to the main building, but I want to be able to cook in the summers and only heat up one room. I'd also like the kitchen to be on it's own sub-panel anyway since I'd like the option of using 20A appliances at each outlet anyway.
- rudedogg 5y ago
  I think code requires 20A circuits in the kitchen. Not sure though.
  - mjevans 5y ago
    You completely misunderstand. The whole kitchen would have a sub-panel _in_ the kitchen; because EVERY OUTLET would be it's own independent 20A capable circuit, run back to that sub-panel. I don't expect to use 20A from every outlet all the time, but I don't want to be constrained from any mix-and-match of devices I need within the room's power budget.
Dumblydorr 5y ago

darkteflon 5y ago

Is this (https://www.greenbuildingadvisor.com/ https://www.greenbuildingadvisor.com/) the one? I hadn’t heard of this before but it looks excellent. In your view, if I may, what makes this an authoritative source?

bklyn11201 5y ago
I thought it was a good combination of practical while being backed with data. They are big proponents of modeling out energy use with something called Manual J. They advocate for designing based on data instead of hunch which often leads to over-provisioning (less phone calls) and less efficiency. Posters also seem to be practical and focused on cost efficient solutions. This can be more rare than you think when dealing with passive house consultants or with efficiency consultants as I received many recommendations that had >= 50 year pay off times!

DannyBee 5y ago

"1) Air source heat pumps have become incredibly efficient even in cold climates. 2) Ground source heat pumps are complex and very expensive and probably best suited for large installs like schools. " This is not really accurate on the complexity/etc side. Expense we'll get to later. A. The GSHP is not complex at all, and often much easier to understand than the equivalent air source machinery. I could repair my GSHP. B. The efficiency of air source heat pumps vary a ton in the field. This is not conjecture. This is backed up by years of research. Of course, unlike ground source heat pump (which usually contain tons of sensors and can tell you exactly how well they are operating in a lot of ways), air source heat pumps rarely contain any of the performance measurement sensors necessary to validate their efficiency in practice for your install, and they are rarely accessible. So you are limited to a small number of studies that bother to test them in the field by adding that kind of metering. Oh and manufacturer "self-reporting" about how good they are. EER or COP of air source heat pumps in-situ can be easily 50% or less of claimed efficiency depending on real climate and how well designed they were for the situation. GSHP are 85-99% of designed performance over a much wider climate range (again backed up by research, and with much larger sample sizes, since most GSHP have the monitoring sensors built in). That's on top of usually much higher efficiency of GSHP over ASHP. C. GSHP not amenable to the random "don't want to have to care about real engineering" HVAC contractors that most people deal with. IE not even willing to do basic manual j load calcs. They are only complex in this sense - most air source heat pump folks don't really have to know what they are doing, and it will often work okayish in terms of ability to heat/cool when they size it wrong. It will just be very inefficient. If your ground source heat pump folks don't actually bother to do the work right and enter the calcs into the loop design program, it can fail. Just about 100% of failed GSHP installs i've seen were done by air source contractors badly trying to moonlight because they thought they margin would end up better (and who were bad at ASHP as well). Any good loop design program will give you the EER/COP of the system in your case based on historical temperature, along with actual yearly cost/etc. So you don't have to guess whether it will work out for you (and it will be very close to reality). It's also obvious if your contractor is giving you bullshit if you have a loop design report - IE if the page with the assumptions/data show clear nonsense. As performance standards increase (IE California), or any form of real in-situ efficiency testing of air source heat pumps was ever required, you would see this "really efficient" argument disappear really quick. (Heating has definitely gotten a lot better in lower temps, not gonna argue with that). D. It is true that GSHP is expensive to install, but that's mostly a factor of scale for drilling, and not size of install or unit cost. It's never going to be an effective way to deal with a single 2000sqft house. It will be a much more effective (and space efficient) at serving multi-unit complexes, regardless of individual house size. For example, when they do GSHP for a new construction community (out here they are doing 200 new homes for examples), it's not a lot more expensive than installing air source pumps. For single houses, again, it depends on your real in-practice performance of an ASHP, which is rarely ever measured. For a house i owned in MD, and compared to two ASHP's that were properly sized (and properly sized/sealed duct work/house/etc with actual leakage/r-value/perf testing), but just a really bad in-practice fit for my climate (neighbors had same issues, etc), it only took 5 years to pay back the GSHP cost (after tax credits, etc). This is uncommon case, obviously. But i'll also say being able to set the house at 72 and leaving it that way forever is worth something too. Ductless i've got no qualms with :) I think most folks with tight homes would be much better off in practice with lots of ductless wall/ceiling units than standard ASHP/GSHP.

zhynn 5y ago

Also heat pump water heaters essentially air condition/de-humidify your closet/garage/etc which is great in humid climates.

hourislate 5y ago

I would add Spray Foam to your list. Increases racking strength of walls, provides an airtight seal and vapor barrier (2lb- Closed Cell Foam), and will eventually pay for itself in Heating and Cooling savings. We have a a very large cottage in Northern Ontario (3000 sq/ft +) that has been sprayed foamed (Demilic Heatlok) and has in floor radiant heating and forced air AC all supplied by Geo Thermal. The electric bills a year are less than what some people spend at Starbucks. The comfort is incredible in -30F/-34c or +100f/38c and a bomb could go off outside and I doubt you would hear it. The costs to insulate the whole house and to install the Geothermal (including AC) was 55k, less than what some folks spend on kitchen cabinets and counter tops.

tootie 5y ago

> Building tight, all-electric, with solar will provide a comfortable, clean, long-lasting house, but it will be quite a bit more expensive. Possibly 30%+ more expensive than using standard contractor choices. Maybe a 30% higher price, but likely a lower cost when you factor in externalities.

fy20 5y ago
I'm building a new house like this - in my country the building code is on par with Passive House standards, so we don't have much choice :-) I ran the numbers for heating with gas vs an electric heat pump, and gas actually worked out more expensive. The house will need around 2000W[0] of heat in the middle of winter. For that usage, the most expensive part of gas would be the network fee, not the gas itself. An electric heat pump is a bit more expensive that a gas boiler, but considering we'd need to have a gas connection introduced to the property, the overall upfront cost is the same. The lifetime of both units is the same (10-15 years). Someone here mentioned a gas absorption heat pump before, but those units are much more expensive than an electric heat pump in my country, and it still has the same issue of the gas network fee being expensive. We'll also have solar PV, so that will cut the electricity running costs even lower once it's paid off (~7 years). It's interesting that once you have an efficient building envelope, technologies that you would think would be more efficient such as solar water heaters or ground source heat pumps don't actually make sense financially in the long term. I also ran the numbers for underfloor infrared heating vs electric heat pump + hydronic underfloor heating. Taking into account the higher installation costs, and expected life of the heat pump unit, the infrared heating - which is must less efficient - actually works out costing around the same. The unit we have will also provide DHW and cooling in the summer, so it's apples and oranges, but for a pure heating perspective it's worth considering that option, espeically if you want a lower upfront cost. [0] For a 160m2 / 1700sqft house. This doesn't take into account 'waste' heat from appliances, so our primary heat source demand will actually be less.

ta2162 5y ago

I thought ducted central heat pump with zones was the most efficient. Also, it filters the air centrally (and better, higher MERV possibilities), allows you to more easily manage humidity, and allows you to mix and bring in outside air. Not cheap though.

BostonEnginerd 5y ago
I understand that the ducted systems are less efficient, but the ability to better control filtration, outdoor mixing and humidity makes up for that.
- ta2162 5y ago
  >I understand that the ducted systems are less efficient But they're not less efficient, ducted systems are more efficient. Mini-splits multiply your refrigerant lines, compressors, heat exchanger, condensing coils, etc., so you're multiplying your inefficiencies. A single variable rate, zoned, ducted heat pump is the most efficient, but they definitely cost more.

axiolite 5y ago

I agree with everything you've said, BUT, I find small tank (10gal or less) electric hot water heaters surprisingly cost-effective options if you are using very low-flow aerators and shower heads (0.5-1.0 GPM). And particularly so if you have a small household where everyone can be taught to hit the button* on the wall to turn-on the hot water 30 min before they want to take a shower. The installation cost is vastly lower than heat-pump based units, they fit in a cabinet under a sink much better, are easier to wire up to an on-demand on/off button, is even cheaper to operate during summer months, etc. Would work even better with a solar thermal panel for preheating the cold water. The button in question being a 30-minute auto-shut-off switch, actually.

belorn 5y ago

> 2) Ground source heat pumps are complex and very expensive and probably best suited for large installs like schools. Looking at prices for the unit, the difference between Ground source heat pumps and air source heat pumps is around 15%. This assume we want heated water. AC-only units are naturally much much cheaper, but since there does not exist ground source AC-only units it is not a very fair comparison. When it comes to extracting heat from the environment there are a few different choices. Air, solar, borehole, ground, and water. As I understand it, which one is the most cost efficient choice depend more on the environment which it is getting installed than the actually unit.

jnsaff2 5y ago
Big price difference comes from installation of ground loop. They either dig up your back yard and install a horizontal loop or you can have a vertical borehole (you probably need several of those). Boreholes here in NE-EU are about 35EUR per meter and for my house I'd need about 300m of them.