Mary and James’ Larkspur Home

ABOUT THE HOUSE:
Mary retrofit the home to Passive House standards, while James later pursued electrification. What’s interesting about this home is that Mary added insulation to the exterior of the old building, rather than the interior.

ENERGY EFFICIENCY:

Passive House principles prioritize high levels of insulation and sealing leaks.

  • Elastomeric coating was added to the existing T1-11 siding to seal leaks to PH Target of 0.6 ACH50

  • Triple pane, air tight windows and doors replaced single pane aluminum framed units.  

  • Insulated the building shell by adding a continuous layer of 3” of Rockwool mineral wool insulation over the airtight siding, breaking any thermal bridges through the walls.  Fiber cement siding was installed over the mineral insulation.  The siding and insulation were chosen for their fire resistance. 

  • Roof was insulated by adding a continuous layer of 6” of polyiso insulation beneath metal roofing, breaking any thermal bridges there. White color metal roofing was chosen for its heat reflectance. 

  • Heat-recovery ventilator brings in fresh air and exhausts stale air, tempering the incoming air to the same temperature as the outgoing air.  The exhaust air is extracted from the kitchens and bathrooms, and fresh air is continuously supplied to the bedrooms and living room.  

ELECTRIFICATION:

  • Induction Range

  • All-electric clothes washer and heat pump Miele dryer

  • Harvest Thermal system uses a single heat pump to function as both a space heater and a water heater.  The heat pump is a SanCO2, which uses CO2 as a refrigerant which has a global warming potential of just 1, much lower than conventional heat pumps. The SanCO2 heats water in a tank; the heat from the hot water is transferred to the existing forced air unit through a water to air heat exchanger, and heated air supplied to the rooms using the preexisting ducts.  In the Harvest Thermal system, the 200 gallon hot water tank enables the system to function like a Thermal storage battery: it makes it possible to shift water and space heating electricity needs to only when energy is cleaner and cheaper. 

  • Swimming Pool water is heated by rooftop solar water heating.

RENEWABLE ENERGY:

  • MCE Deep Green clean electricity supply

  • Rooftop Solar: PV panels provide 10KW

  • Electric battery stores solar energy during the day, which they can then use during peak hours instead of energy from the grid.

WATER CONSERVATION:

  • Low flush toilets

  • On demand hot water recirculating pump that brings hot water to the ADU, pushing the cold water in the pipes back into the cold water line.

FIRE HARDENING:
A building that burns in a wildfire adds enormous amounts of CO2 emissions!

  • The exterior of the home was covered with Rockwool mineral wool insulation and Fiber cement siding for fire resistance. 

  • External metal Vulcan vents have honeycomb structure covered with intumescent paint that expands when heated to close the vent holes, keeping fire from entering home through the vents.

  • White color metal roofing was chosen for its fire resistance.

  • Passive House air tightness eliminates any random places a spark can enter the house.

LANDSCAPE:

  • Mostly natural landscape, with some fruit trees added, native plants

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