How many btu to cool 1 sq ft?

Answer 1

It depends on the cooling heat flow required for a given application (btu's per hour).

The most common application is cooling a house. Presumably you are trying to size your air conditioning system. In that case the heat flow through a wall (or ceiling) is essentially the temperature difference across the wall in degrees Fahrenheit divided by the R value of the insulation. (There are radiative and heat buffering effects as well, but I won't go into that now).

In most houses in the US, the R value of a wall is 11. Let's say one summer day the outside temperature is 94 degrees Fahrenheit and the desired inside temperature is 72 degrees. In that case there is a 22 degree difference (94-72=22) and the R-value is 11. Thus the heat flow through the wall is 2 btu's per hour (22/11). Thus an air conditioner would have to provide 2 btu's per hour to maintain a 22 degree Fahrenheit temperature difference across one square foot of an R-11 wall.

To size the conditioner, you would need to find the square footage of the surface through which the heat flow is occurring (the walls and ceiling of a house). Note that there is a much lower R value for windows (~R-1 for single pane, ~R-3 for double pane), and some allowance needs to be allowed for heat generated inside the house from people, machines, lighting etc. If the house is drafty, more cooling is also needed to make up for cold air lost when, for example, someone attempts to cool the house more by opening a window.

Answer 2

The number of BTUs required to cool 1 square foot depends on factors such as the climate, insulation, and desired temperature. As a general guideline, a typical window air conditioning unit can cool around 150-200 square feet per 5,000 BTUs. So, for 1 square foot, you would need around 25-33 BTUs to adequately cool it.