Page 64 - Zero Net Energy Case Study Homes-Volume 2

CASE STUDY NO. 8
STRATTON-LEE DIY HOUSE
(Above) Making the sheet met- al ductwork for the mini-split system serving the Phase 2 bedroom area. (Photo by Wen Lee)
(Opposite page) View of the in- terior of the completed Phase 1 living area.
An ERV was selected instead of an HRV because of the sizable cooling demand in this location and the possible need for moisture control of the exterior air. (The climate of this area, however, is quite dry, so an HRV would have been a good choice also.) The ERV provides fresh air to all the spaces via separate 6” rigid steel supply ductwork and has continuous exhaust at the bath- rooms via ductwork back to the heat exchanger at the ERV unit.
The kitchen exhaust fan in the range hood vents directly to the outside. A low-power unit (150 cfm) was selected to avoid excessive exhausting of inside conditioned air and to reduce the fan load. The unit selected has high capture efficiency at rlatively low airflows. The performance has been good at this level of air flow speed. The owners preferred not to have a recirculating fan unit for air quality reasons in an airtight house.
Domestic hot water was supplied by a gas water heater until August, 2019, when it was replaced by an electric 50-gallon heat-pump water heater. At that point, the house became fully electric and zero-carbon. (The house was already performing at ZNE including the energy used by the gas water heater. See the discussion below in the section, Energy Use—Post Occupancy Mea- surement.)
Lighting and Plug Loads
All lighting is done with high-efficiency LED sources and all appliances are Energy Star®. A vent- ing skylight with remote control was added to the newly enlarged volume in the living spaces in order to bring daylight to the interior, which previously required electric lighting even on bright days.
Since the house is designed to be all-electric, the cooking is done by induction cooktop and electric oven. The owners had to use portable induction units when the temporary kitchen was set up on the back patio, so they developed a familiarity with the techniques of cooking on such units. The final plans called for an induction cooktop for a zero-carbon house, but the practice experienced in the temporary kitchen was useful to have.
The clothes dryer is a conventional electric dryer located in the unconditioned garage.
Control Systems
For cost reasons, the owners chose not to have any “smart technologies” other than the energy monitoring device to record energy consumption at each point of use. An on-demand recircula- tion pump was installed in all the bathrooms, activated by a simple button, to conserve water use.
Construction
The construction period was initially planned to be one year, but extended to two years and eight months, reaching a conclusion in October, 2019. (See the blog postings on “FrugalHappy” for a complete history of the work from start to finish.) While Chris largely worked alone and usually full-time, he was often assisted by relatives and neighbors.
Structural modifications required an upgrade of the foundation footings. For this design and con- struction task, the owners decided to hire a structural engineer and a foundation subcontractor. This was one part of the project that they concluded would be better accomplished with experi- enced help. This occurred a second time in the fall of 2019 when only finishing work remained to be done in the Phase 2 bedroom spaces and the owners’ first child was due.
50
Zero Net Energy Case Study Homes: Volume 2