If I lose power how fast will my house cool down when the weather is cold?

Q:

If I lose power how fast will my house cool down when the weather is cold?

A:

The rate that your home cools down depends on a lot of factors;

1. The outdoor air temperature. The colder the outside air temperature the faster that the inside temperature will be affected.

2. Shape of the house. The shape of your home will affect the amount of surface area that is exposed to the outside air. So a simple box shape for a house will perform better where a T-shape, L- shape or a long thin home will perform worse. Longer homes have more exterior walls exposed to the outside air.

3. Insulation levels and air tightness. Insulation will have more affect on how fast the inside air temperature cools then almost anything else. The more insulation or R –value you have the longer your home will be able to stay warmer. This is applies to the walls and the ceiling or attic insulation as well. The more insulation and vapour barrier the more it slows the colder air from penetrating the wall cavity into the home.

4. Thermal mass. The thermal mass of a home is basically the ability of the homes building materials and furnishings to hold heat when the heat source has been turned off. The greater the thermal mass of the building the longer it will hold heat and the longer it will take to cool down.

5. Available Sunshine. Sunshine creates heat and it is amazing how a little amount of sunshine will heat up a house. Depending on the type of your windows (if they are solar gain) you could easily warm the home slowing the rate of temperature reduction.

6. Wind speed. The higher the speed of the wind the faster your home will cool down. It is called windwash when the wind blows against the outside walls of the home; this windwash cools the wall cavity faster than the normal cold air that penetrates the wall.

7. Internal Heat Gains. When the heat fails but the electricity is still active then things such as appliances, lights and other electronic devices give off some heat that helps slow the rate of the internal temperature drop of the house.

All these factors will affect how fast or slow your home will cool down.

Remember that when you lose power or lose your heat source do not use anything that uses propane to try and heat your home. The fumes and fact that propane heat sources use up all the available oxygen in the room make them extremely dangerous to operate inside.

Rob Abbott
Operations Manager
Village Builders Inc.

Some information for this post was found in the solplan review November issue #173