Zero Energy Certified


Certification StatusZero Energy Certified
Version of LBC31
LocationBellingham, WA, USA
Project Area1,962 SF
Start of OccupancyJanuary 2015
Owner OccupiedYes
Occupancy TypeSingle Family Residence
Number of Occupants5
Photo Courtesy of [Bundle] Design Studio
OwnerDaniel Welch
Project Manager[Bundle] Design Studio
Architect[Bundle] Design Studio
Electrical[Bundle] Design Studio
Lighting Design[Bundle] Design Studio
Interior Design[Bundle] Design Studio
General ContractorTretwold Construction
PlumbingSpectrum Plumbing
StructuralBourne Engineering
CivilColleen Mitchell
EducationSustainable Connections
Photo Courtesy of [Bundle] Design Studio
Wall R value and section specification31. GWB, 2×6 w/ roxul batts, plywood, Prosoco R-guard, 2″ Roxul Comfortboard IS, rainscreen battens, metal/cedar siding
Roof R value60
Floor R value60
WindowsCascadia 300 & 400 series. U value = 0.18, SHGC = 0.46
Air infiltration rate and sealing protocol0.4 ACH. Prosoco R-guard on sheathing

The house was rigorously designed to have identical floor plans between the first and second floors. This allows the house to change use over time from a 3bed-2 bath family house to (2) 1 bedroom – 1 bath units when needing to downsize. Both floors were developed to take advantage of the expansive territorial views and used building elements to bring the landscape into the living space. On the first floor a large indoor solarium is used as a passive solar sink and bridges the gap between indoors and out. The second floor is surrounded by a green roof that adds insulation to the roof and brings the landscape to the face of the building visible from the floor to ceiling windows.

Photo Courtesy of [Bundle] Design Studio

The house was designed with significant passive solar gain. The majority of the windows are facing south, with a few windows to the east and west to bring in morning and evening sun and cross ventilation. Only 2 windows are facing North to reduce heat loss. The site was cleared of trees to the south providing excellent solar access and the house, with its blank north façade pushed tight against the existing trees to the North. The simple shed roof was designed with a 7/12 pitch to provide ideal conditions for an active solar array. This move created an opportunity for sleeping lofts in the two upstairs bedrooms and a centrally located mechanical loft that houses the HRV, DHW tank and radiant floor mechanics.

PV Array Size (kW)9.24
PV Output Per Capacity Nameplate (W)280
Panel Quantity33
PV Type and BrandItek 280 Fixed Panels
PV Inverter Quantity1
PV LocationRoof
PV OwnershipDan Welch

As the major energy savings strategy the building envelope was designed to eliminate nearly all thermal bridges and air infiltration(.4 ACH50), reduce framing lumber, cost effectively increase insulation values and integrate high quality south facing windows. Heating that is used to condition the house was treated as a valuable commodity. Heat recovery, from both the domestic hot water and air used for ventilation is mined for usable heat which is recycled back into the house. Other energy conservation strategies include CO2 heat pump for DHW and radiant heating, 100% LED lighting and induction range. The house was pre-plumbed for solar PV to reach Net Zero Energy. A 9.28 kW solar array was installed April 2016. The total energy use of the house for 2015-2016 was 5.6 kWh. The oversized solar array allows for increased energy usage over time as young children age and for the possible addition of car chargers and/or shop uses.

Actual energy use during performance period6,462 kWh
Actual energy produced during performance period9,481 kWh
Net Energy Use-3019 kWh
EUI10.7 kBTU/sf/yr