Discovering the Behaviour of my Small House in Each New Season

By Gary Martens, Kleefeld

I moved into my small house at the end of September so I am experiencing each season for the first time. My house is 20 by 24 feet with a high cathedral ceiling and a loft 10 feet wide over the bathroom and mechanical room. I insulated the entire house with spray foam insulation, R60 in the floor and ceiling and about R32 in the walls. My south and east facing windows represent about 10% of my floor space. On a sunny day at minus 25 degrees Celsius I do not require any heating source except the sun. The total energy from the sun is approximately 1000 watts (1 kilowatt) per square meter. My triple pane low e Argon filled windows block some of the heat coming in but provide the best insulation at night or when it is cloudy. Solar gain is measured by a g-value or SHGC (solar heat gain coefficient). A value of 0 means no solar energy is transmitted by a material and a value of 1 indicates 100% of the sun’s energy is transmitted through a material, windows in this case. My windows have a g-value of about 0.33. That means only 33% of the sun’s total energy is transmitted through the window as heat or about 330 watts per square meter of window. With my east and south windows totalling 13.7 square meters I receive about 4,300 watts (4.3 kilowatts or 14,700 BTUs) per hour of sunlight. That is more energy than I need to keep the house warm and the temperature rises to 25 degrees Celsius. At night a 1500 watt electric heater is just able to keep the temperature constant at an outside temperature of minus 25 degrees.

I have a high efficiency HRV that is labelled to recover 65% of the heat of the exhaust air at an outside temperature of minus 25 degrees Celsius. I used to leave the HRV running constantly but the relative humidity in my house was low at about 30% RH (I am obviously not making enough soups) so I turn off the HRV at night to try to raise the humidity a bit and to save the 35% loss of heat at night. During the day I can afford to lose that 35% but not at night.

I have yet to experience the hot summer sun but my southern overhang is adequate to keep direct sun out of the house and I intend to plant deciduous trees to the south of the house so that I have shade from leaves in the summer and sun through bare branches in the winter.

Gary hosted an Open House at his new Small Home on November 8. This attracted many people.