The Loom House is designed to create more energy than it uses by first reducing energy demand and then by collecting all the required electricity from a single photovoltaic array located on the South House. Around 40 percent of all US energy is consumed by the building sector. This means that reaching Net Positive Energy is first and foremost a team effort, especially between Miller Hull, WSP, and Clark Construction.
Architects have gotten very good at designing passive dwelling, homes that are so well insulated, they need little or no additional heat. These passive homes have to be very careful with the number and size of windows they allow. In the Pacific Northwest, we have a moderate climate but famously grey skies. "Sun breaks" are something that our weather forecasters describe in their forecasts. To battle this grayness and the rain, windows help bring the outside in. The rub: windows are about the least efficient insulation in any wall. Put in a window, and you put in permeable screen for cold air to get in and for warm are to escape.
Furthermore, the Loom house has spectacular views of the water and of the old trees on the land. We kept the window openings, (and we even expanded a few) and we resigned ourselves to some sort of heating system.
Miller Hull designed a building envelope that exceeds the requirements of the 2015 Washington State Energy code. We replaced leaky windows with triple-pane glazing. We blocked "thermal bridges" - building materials that wick outside cold into the inside of the house. And we redesigned wall and roof assemblies to add insulation. When Clark gets everything installed, the house should have a very tight building envelope.
Such a tight house requires a supply of fresh air, and, in fact, Washington State code requires fresh air in homes. However, cracking windows in the winter pulls in cold air. Instead, we use a small heat-exchanger air system and invite both sides -- inside warm air, and outside cold air -- to a party. The exchanger's "party" gives a place for warm and cold air to mingle. Before the warm air can make its escape, the heat exchanger uses the exiting air to heat up the entering cold.
Once we have a tight building, we need a less powerful machine (and less of an energy hog) to heat the house. (We require a unit with about half the heating capacity of a home insulated to current code standards.) The main house (approximately 2,000 sq ft) will be heated by hydronic radiant floor system that is embedded in the floors. Heating the water that runs through the floors is a Daikin Alterma, air-to-water heat pump. This system is approximately four-times more efficient than a condensing boiler furnace, which itself is generally considered "high efficiency". The Daikin heat pump also heats our hot water. (Hot water heating usually amounts to around 15% of residential electric bills, so getting hot water as a by-product of heating the house is a nice benefit.)
The North house consists of two rooms, which we use for office space and guest quarters. We will heat the rooms not with the c1972 electrical furnace that was there when we bought it, but with a single ductless split system. These systems have highly efficient air source heat pumps, similar to the Daikin. The heat pump warms (or cools) refrigerant, which it sends to a fan coil inside. There the air is warmed or cooled before it is blown into the room.
So we've greatly reduced the need for heating by sealing up the home. We've found super efficient ways to provide the heat and hot water that we do need. Now, we get to reap benefits by installing a smaller solar or PV system. We are fortunate that the south side of the South house is nearly perfectly angled and directed for solar panels. The entire PV system will live on the south side of the South house roof. During the summer, we will produce more power than we need, and we will sell it to the grid. During the winter, when we don't produce enough power day-to-day, we will draw from the grid. Over the year, our supply to and draw from the grid will equal out - even after charging our cars. Should dark and stormy skies reduce our solar production to nothing and rains knock out the power grid in our neighborhood, we will turn to a battery back-up.