What size furnace for 1800 square foot house?

Answer 1

Based on square footage alone, it isn't possible to specify a certain size required to keep your home warm. The age of the home (having a direct correlation with the type of insulation that is used), the height of the ceiling in your home, the existence of skylights, the number of outside doors and windows and basically the extent of exposure to the outside environment and the sun and your geographic location are all factors that determine the heat loss of your home.

To give you a reasonable range, the power output of your furnace should be anywhere from 55,000 to 65,000BTU/hr. When I say output, I am referring to efficiency x Input Power. For instance, a 92% rated 60,000BTU/hr furnace has an output of 55,200BTU/hr.

Check out the three charts in the related link (There is one chart for bungalow-type, one for semi-detached and one for 2-story detached homes)

In each category home, there is an estimated size for a home built before and a home built after 1980. This is simply to count for the extent of insulation to minimize heat loss and mostly aimed at the type of homes constructed in Southern Ontario. Find your answer in any of the charts and depending the age of home.

Do also keep in mind that these estimates are mostly good for climates in or similar to Southern Ontario.

Answer 2

40000