This is a 3500 square foot custom home built in 2006. Everything about the house is really special. The design, site, workmanship and quality of materials are all carefully thought out and perfectly executed.
The heating system consists of three geothermal heat pumps. The main floor is serviced by a four ton unit, the second floor by a two ton split system and the ground level by a two ton unit. The main floor unit also heats the domestic hot water in tandem with the solar thermal collectors visible above. The ground level has radiant floor heating that is provided by its two ton heat pump using its water heating feature. The radiant is backed up by the ducted system that also provides for air conditioning. The second floor unit also incorporates a heat recovery ventilator.
The shell of the house is Energy Star rated and features spray foam insulation in the walls and rafters. All the ductwork is inside the heated envelope to eliminate duct loses. The ground level floor is completely underlaid with 2″ rigid insulation to reduce heat loss and improve the effectiveness of the radiant heat. The windows are low-e glass and of the highest quality.
There is no photo voltaic array, and the passive solar orientation could be better, but take a look below and you’ll see why. This is the view to the east.
We ran their electric bills through a calculator that breaks down electrical consumption into miscellaneous and heat pump based on the monthly distribution of consumption. It takes the last twelve months electric bills and determines the lowest daily consumption. This is then used to separate miscellaneous from heat pump consumption. In this example, I adjusted the dollar amounts to reflect the current rate for generation charges ($0.0899 per kwh). In the past twelve months the rate has moved between $0.0732 to a whopping $0.1897 when their six month contract expired. The results were:
Total consumption: $4,364.84
Lowest daily consumption: $7.39
Miscellaneous consumption: $2,698.49
Heat pump consumption: $1,685.32
The owners maintain a home office which tends to ramp up the electric bill, and at 3500 square feet and eight tons capacity, this house and system is almost twice the average house. Even given these disadvantages, monthly cost for heating and cooling of $140.44 is very good.