So, you’re thinking about finishing that basement or bonus room and your calculating the costs. A major expense when it comes to the finishing construction of rooms in completed homes is the heating equipment or the expansion of an existing system. It can be a real hassle, not to mention extremely costly when it comes to running duct work to the new space. Or maybe you just have a bathroom that no matter what you do, stays a little cool.
There’s actually a simple calculation that will help you determine how much heat or wattage you need from a heater to keep it at a comfy temperature.
The information you will need on hand is all available to you.
-You’ll need to know the cubic footage of the area you’d like to heat or provide supplimental heating for.
This is easily determined; multiply the width of the room by the length of the room and then multiply again by the height of the room. For example if the room is 10 x 10, with 8 foot ceilings: 10 x 10= 100,
100 x 8 =800
-You’ll need to know where you’re located for the next variable in the calculation. In colder, northern states, it is usually recommended that the variable for the amount of heat required is 1.5 watts per cubic foot. Or if you are located in the warmer, southern states, 1 watt per cubic foot is usually sufficient.
So, say you live in Florida and the bonus room is 12 x 12 with 9 foot ceilings.
Your formula would be:
12 x 12= 144
144 x 9= 1296
1296 x 1= 1296
Your bonus room will require 1296 watts of heat to maintain a comfortable temperature during the winter. The term “wattage” is used mostly in electric heating applications. For gas heat, the amount of heat produced by a heater is refered to in terms of BTU. There is also a simple calculation for converting your earlier answers to BTU. To convert watts to BTU, multiply the wattage needed by 3.4129. So if your wattage requirement was 1296 watts, your BTU requirement would be: 4,423 BTU/hr.
The above calculations are also mostly used for fan forced heating. Radiant heating allows for less wattage, normally around 4-7 watts per square foot. The maximum amount of heat required for the same room that we used above; 12 x 12 = 144, 144 x 7 = 1008
All of the calculations above are based on the theory that the room you are to heat will be well insulated when you complete the project. Without proper insulation, heat loss, through walls, greatly increases. All heaters should be controlled by some type of thermostat, be it a unit mounted, installed heater or a separate wall thermostat. Small portable space heaters that are used as supplimental heat should never be left unattended.