Time for a THREAD about the details of our all-electric net-zero house.
Credit to @BrachDesignArch, Russell & Co Construction, and @CEsolar_com
cc: @energysmartohio and @Guay_JG
This thread is posted as a pdf at tinyurl.com/w2439yr
Credit to @BrachDesignArch, Russell & Co Construction, and @CEsolar_com
cc: @energysmartohio and @Guay_JG
This thread is posted as a pdf at tinyurl.com/w2439yr
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG Our annual generation covers everything the house uses plus one EV, with enough surplus for an additional 1,200 mi/yr of EV driving.
Gas service is on the property, but we didn’t run it to the house.
Gas service is on the property, but we didn’t run it to the house.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG Here is the breakdown again, just showing the house.
Total consumption is 31 kWh/day.
Total consumption is 31 kWh/day.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 4/ Why do this?
Lead the way on zero-emission solutions.
Don't give money to industries that contribute to climate change.
Be a more effective climate advocate.
It comes at no added cost.
Get a more comfortable house with no indoor air pollution.
Get a more resilient house.
Lead the way on zero-emission solutions.
Don't give money to industries that contribute to climate change.
Be a more effective climate advocate.
It comes at no added cost.
Get a more comfortable house with no indoor air pollution.
Get a more resilient house.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 5/
Climate Zone 6
8,000 Heating Degree-Days per year
High of 90 F, low of -9 F
Insulation: R70 ceiling, R52 walls, R64 floors over unconditioned space, R16 slab on grade
Air tightness of 555 cfm at 50 Pa (0.15 cfm/sq-ft)
Site Energy Use Intensity of 10.3 kBTU/yr/sq-ft
Climate Zone 6
8,000 Heating Degree-Days per year
High of 90 F, low of -9 F
Insulation: R70 ceiling, R52 walls, R64 floors over unconditioned space, R16 slab on grade
Air tightness of 555 cfm at 50 Pa (0.15 cfm/sq-ft)
Site Energy Use Intensity of 10.3 kBTU/yr/sq-ft
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 7/
Generation and consumption are both highly seasonal – and opposite.
We supply electricity to the grid in the summer and draw from the grid in the winter.
Generation and consumption are both highly seasonal – and opposite.
We supply electricity to the grid in the summer and draw from the grid in the winter.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 8/
Walls are double-framed with fiberglass insulation blown in between for a complete thermal break.
Windows are Alpen fiberglass-frame, triple-pane, gas-filled.
U-values of 0.15
SHGC of 0.27 for south-facing windows, 0.24 for all other windows.
Walls are double-framed with fiberglass insulation blown in between for a complete thermal break.
Windows are Alpen fiberglass-frame, triple-pane, gas-filled.
U-values of 0.15
SHGC of 0.27 for south-facing windows, 0.24 for all other windows.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 9/
The outside surface of the wall is the sealed surface. The siding is spaced off from the Zip board so the wall can dry to the outside in the summer. The house was blower-door tested three times during construction.
The final blower door result was 555 cfm50, or 1.0 ACH50.
The outside surface of the wall is the sealed surface. The siding is spaced off from the Zip board so the wall can dry to the outside in the summer. The house was blower-door tested three times during construction.
The final blower door result was 555 cfm50, or 1.0 ACH50.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 10/
Most windows face south. Roof overhangs block the summer sun angle and allow winter sun, for maximum solar gain in the winter. The awning roof is used for additional solar panels.
Most windows face south. Roof overhangs block the summer sun angle and allow winter sun, for maximum solar gain in the winter. The awning roof is used for additional solar panels.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 11/
This is a 3-ton (36 kBTU/hr) Mitsubishi Hyperheat Mini-Split. Average power consumption in Dec – Feb is about *one* hair-dryer (1,600 W). It's a bit undersized when the temp is in the single digits. We wired for supplemental resistance heat, but haven’t installed any.
This is a 3-ton (36 kBTU/hr) Mitsubishi Hyperheat Mini-Split. Average power consumption in Dec – Feb is about *one* hair-dryer (1,600 W). It's a bit undersized when the temp is in the single digits. We wired for supplemental resistance heat, but haven’t installed any.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 12/
The house is tight enough that it needs active ventilation.
A ground loop preheats the incoming ventilation air so it doesn’t condense and freeze in the HRV.
The ground loop also serves as cooling in the summer. It can cool the incoming ventilation air to around 55 F.
The house is tight enough that it needs active ventilation.
A ground loop preheats the incoming ventilation air so it doesn’t condense and freeze in the HRV.
The ground loop also serves as cooling in the summer. It can cool the incoming ventilation air to around 55 F.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 13/
The HRV brings in fresh air through a heat exchanger to retain heat that would be lost in the outgoing air.
The HRV inlet and outlet are the only holes in the house. There’s no fireplace, stovetop vent, or dryer vent. All bathroom vents go through the HRV.
The HRV brings in fresh air through a heat exchanger to retain heat that would be lost in the outgoing air.
The HRV inlet and outlet are the only holes in the house. There’s no fireplace, stovetop vent, or dryer vent. All bathroom vents go through the HRV.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 14/
The heat pump water heater moves heat from the room into the tank. It uses about half of the energy of a conventional electric water heater (net COP of around 2).
This is in our laundry room, so we don’t care if this room is a little colder than the rest of the house.
The heat pump water heater moves heat from the room into the tank. It uses about half of the energy of a conventional electric water heater (net COP of around 2).
This is in our laundry room, so we don’t care if this room is a little colder than the rest of the house.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 15/
Induction stovetop is amazing. It’s as good or better than gas in every way.
Heats quicker
Simmers better - no risk of flame going out
Safer – can’t catch things on fire
Smooth surface wipes clean
Instant response
No indoor air pollution
Induction stovetop is amazing. It’s as good or better than gas in every way.
Heats quicker
Simmers better - no risk of flame going out
Safer – can’t catch things on fire
Smooth surface wipes clean
Instant response
No indoor air pollution
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 16/
This is a condensing ventless heat pump dryer. 1.8 kWh / load is about half the usage of a normal electric dryer. It has long drying times, but they can be reduced by putting it in conventional electric mode. It takes about 1:20 in heat pump mode and 0:50 in electric mode.
This is a condensing ventless heat pump dryer. 1.8 kWh / load is about half the usage of a normal electric dryer. It has long drying times, but they can be reduced by putting it in conventional electric mode. It takes about 1:20 in heat pump mode and 0:50 in electric mode.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 17/
The eGauge monitors our electrical usage. CTs are on relevant lines in the electrical panel. It’s continuously monitoring: total usage, generation, heat, EV, and water heater. We move CTs around to see the other circuits. The graph is from the day that the low was -9F.
The eGauge monitors our electrical usage. CTs are on relevant lines in the electrical panel. It’s continuously monitoring: total usage, generation, heat, EV, and water heater. We move CTs around to see the other circuits. The graph is from the day that the low was -9F.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 18/
We underestimated energy used by the heating system because of ignoring the defrost cycle and overestimating COP.
Heating energy is largely predicted by temperature and date. The date affects how much solar gain we get through the windows.
We underestimated energy used by the heating system because of ignoring the defrost cycle and overestimating COP.
Heating energy is largely predicted by temperature and date. The date affects how much solar gain we get through the windows.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 19/
Overall – we underestimated the space heating energy, but overestimated just about everything else. So the total usage is almost exactly as predicted. The generation was overestimated a bit. We had no way to forecast snow cover on the panels, so there was some guesswork.
Overall – we underestimated the space heating energy, but overestimated just about everything else. So the total usage is almost exactly as predicted. The generation was overestimated a bit. We had no way to forecast snow cover on the panels, so there was some guesswork.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 20/
Financial considerations: We added $88,000 to the construction costs for: additional framing, air sealing, insulation, windows, HVAC systems and HRV, and solar panels - minus avoided cost of gas line and heat tape.
That gives an increased mortgage cost of $415 a month.
Financial considerations: We added $88,000 to the construction costs for: additional framing, air sealing, insulation, windows, HVAC systems and HRV, and solar panels - minus avoided cost of gas line and heat tape.
That gives an increased mortgage cost of $415 a month.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 21/
We save costs of $407 a month for electricity, natural gas, and gasoline for one car. So cost considerations are a wash, neglecting that: energy costs rise over time, mortgage costs may be deductible, and houses last > 30 years. Those make the efficient house a better value.
We save costs of $407 a month for electricity, natural gas, and gasoline for one car. So cost considerations are a wash, neglecting that: energy costs rise over time, mortgage costs may be deductible, and houses last > 30 years. Those make the efficient house a better value.
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 22/
Part numbers:
Mini-split: Mitsubishi MXZ-4C36NAHZ, MSZ-GE09NA, MSZ-GE18NA, SEZ-KD15NA, PAC-MKA30BC, MHK1
HRV: Ultimate Air 200DX, WCM12, TC2. Grundfoss Alpha 15-55F/LC
DHW: Bradford White RE2H80R10B
Dryer: Whirlpool WED99HEDW
Windows: thinkalpen.com
Part numbers:
Mini-split: Mitsubishi MXZ-4C36NAHZ, MSZ-GE09NA, MSZ-GE18NA, SEZ-KD15NA, PAC-MKA30BC, MHK1
HRV: Ultimate Air 200DX, WCM12, TC2. Grundfoss Alpha 15-55F/LC
DHW: Bradford White RE2H80R10B
Dryer: Whirlpool WED99HEDW
Windows: thinkalpen.com
@BrachDesignArch @CEsolar_com @energysmartohio @Guay_JG 23/
Thanks for reading this far! Hope this will be useful to others.
Thanks for reading this far! Hope this will be useful to others.
Actual house usage (excluding EV) is 11,300 kWh/yr. Generation is 15,500 kWh/yr.
Yes. Decembers have been almost completely snow covered. We would have gone with a steeper angle if we could. We are at 5 in 12 for the main roof, 7 in 12 for the awning roof. We were height limited by local ordinance.
This was a stab I took during construction on the cost and benefit of each of these steps. "Insulation" included the double framing, the extra wall insulation, and the windows, since I couldn't separate them out for the heating demand calcs.
We got most things right. We could have:
Added a transfer duct from the warmest room (the office) to the coldest (the mudroom in the basement).
Run a longer ground-loop tube to pull more heat out of the ground in the winter.
The things I was most worried about all came out fine.
Added a transfer duct from the warmest room (the office) to the coldest (the mudroom in the basement).
Run a longer ground-loop tube to pull more heat out of the ground in the winter.
The things I was most worried about all came out fine.
Here's a screenshot of the results for my house from @energysmartohio's excellent EUI calculator. He comes up with the same 10.3 kBTU/yr/sq-ft that I calculated.
energysmartohio.com/all-electric/e…
energysmartohio.com/all-electric/e…
