# Calculating watts per square foot

• Bacat
In summary, the heat capacity of air is around 1,000 j/kg-k. The amount of heat that an air conditioner dumps into the air is a function of the Coefficient of Performance and the watts per square foot of energy being dumped into the air.
Bacat
I am working on a project to consider how much air conditioning in a metropolitan area raises the temperature outside. I am trying to figure out how to translate the temperature outdoors (say 32 degrees C) into watts per square foot.

Once I have the watts per square foot of heat already in the air, I plan to estimate the amount of heat dumped by an air-conditioner with a Coefficient of Performance of 3. Then I want to see how many watts per square foot are being dumped into the air by houses. So I will want to calculate the amount of temperature rise as a function of watts per square foot.

Do I need to use the heat capacity of air?

*EDIT

How would I calculate the heat capacity of moist/humid air?

Last edited:
Watts is a unit of power, whereas temperature is a measure of energy. They can't be mixed in the way you are trying to mix them.

All you really want is the heat capacity of the outdoor air (specific heat), some assumption about the volume of the air (and it's movement...) and the heat flow rate of the energy in buildings to the outside. That's a lot of assumptions that have a big impact on your answer. But you don't need to know the starting energy of the air in any other units but temperature.

For the specific heat of air, I would use 1000 j/kg-k (you can google that).

The big problem you will find with this is that air doesn't stay still. When heated during the day, bubbles of air over cities (and other warm land features) rise and cause convection.

Joules per square foot would be fine. But this still doesn't help me calculate the heat capacity of humid air, which is a critical point in the matter.

Air doesn't contain much moisture, so no need to bother with that. In a weird, but perhaps useful mix of units, it's .322 watt-hours/Cu Ft-F

No square feet here...

## 1. What is watts per square foot?

Watts per square foot is a unit of measurement used to calculate the amount of energy or power being used in a given space. It is a ratio of the watts (electrical power) to the square footage of the area.

## 2. How do you calculate watts per square foot?

To calculate watts per square foot, you need to divide the total watts by the square footage of the area. This will give you the amount of watts per square foot. For example, if a room is using 500 watts of energy and has a square footage of 100, the watts per square foot would be 5.

## 3. What is a typical watts per square foot for a residential space?

The average watts per square foot for a residential space can vary depending on factors such as climate, insulation, and energy-efficient appliances. However, a general rule of thumb is 10-15 watts per square foot.

## 4. How does watts per square foot affect energy consumption?

The higher the watts per square foot, the more energy is being used in a given space. This can lead to higher energy costs and also impact the environment. It is important to calculate and monitor watts per square foot to ensure energy efficiency and reduce energy consumption.

## 5. Can watts per square foot be used for commercial spaces?

Yes, watts per square foot can also be used for commercial spaces. However, the average watts per square foot for commercial spaces can vary greatly depending on the type of business and its energy needs. It is important for businesses to calculate and monitor their watts per square foot to ensure energy efficiency and reduce costs.

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