Research Highlights

Energy Use Patterns in Off-Grid Houses – Case Study #11: Keswick Ridge, NB

House Description

A 8.5 x 9.1 m (28 x 30 ft.) 1 1/2 storey house built on a vented crawlspace with an unheated 4.9 x 6.1 m (16 x 20 ft.) summer kitchen/storage area off the east face of the house. The house was built in 1994 and is occupied by a farming couple. This well-insulated timber-framed house was situated to maximize the passive solar gain available on the site. A high-mass combination wood heater with water jacket/cookstove assembly (2 cords hardwood/yr, one each for cooking and heating) on the main floor provides space and water heat as well as all cooking requirements.

Thermal Envelope Summary
AC/H@50 Pa: 5.36
Walls: 3.5 RSI (R20)
Ceilings: RSI 7.0 (R40)
Floors: not insulated
Windows: thermopane, single hung openers
Doors: steel polyurethane core

System Description

Power is supplied by a 333 W rated PV array (10 re-used “Arco” panels – 3=100W – slightly mirrored, probably operating at 90% of rated output). Energy is stored in 12, 6V Trojan T105 batteries, wired to produce 12 VDC (1,200 Ah). A Trace DR1512 modified sine wave inverter produces 120 VAC for the house. A diesel generator supplies backup power. The system costs $6,000 CAD.

System Performance

The load on the system includes lights, a water pump, a computer, an answering machine, turntable and stereo system, TV/VCR unit, blender, juicer and food processor in the kitchen and skilsaw, sander and chainsaw (summer use only). A 360 W block heater is used on the tractor three or four times a year. The total possible daily load is approximately 7 MJ (2 kWh), while the actual load is estimated to be 3 MJ (1 kWh).Water heat is year-round off the heat coil within the heater/cookstove assembly.

The actual electrical use in this house is about 1,090 MJ (300 kWh) annually. The average annual lighting and appliance use for this vintage house in New Brunswick is 21,780 MJ (6,050 kWh) . There is a difference of 20,680 MJ (5,750 kWh), for a reduction of 94%. These figures do not include space or water heating.

Notes From Homeowner @ System Operation:

Generator is only used once or twice a year to equalize the batteries. Other than that, the PV array provides all electrical needs for this house.

Homeowners’ reasons for going off-grid:

Homeowners’ observations on living off-grid and energy use patterns:

This house doesn’t have a fridge. A “California Cooler” is installed on an exterior wall of the kitchen. This assembly is typically a small locker that has a venting system that brings cool air from below ground. In this case, the cool air comes in from the root cellar under the summer kitchen (which has a dirt floor) into the bottom of the locker, which is thermally isolated from the heated part of the house. A second vent set high in the locker acts as a chimney to pull warm air out of the locker and keep the cool air passing over the stored food. This, plus a large walk-in pantry isolated from the heated portion of the house suffice to keep all stored food in good shape. This approach to food storage is probably more successful in a vegetarian household.

1 The estimated baseload figure for a house of this vintage is 24, 500 MJ (6,810 kWh). A reduction of 2,720 MJ (760 kWh) was made from the baseload to compensate for the absence of an electric range. 24, 500 – 2,720 = 21,780 MJ (6,050 kWh).