Sizing up your wood stove or fireplace purchase
When purchasing a wood stove, it is important that you choose the appropriate size stove for your home. Most Wood Stoves will have a BTU rating which is the factor you will use to determine the proper size for your wood stove.The formula presented here is only a guideline as, unlike gas appliances that have a controlled Btu input, wood stoves are controlled by the user and the amount of fuel supplied to the stove or fireplace by the user.
BTU: Heat output is calculated in Btu's = British Thermal Unit. This is a measure of how much heat the stove or fireplace is capable of generating.
The size of the stove is dependent on the size of the area to be heated. To determine the space to be heated, multiply the width by length by height resulting in the cubic feet of area to be heated. If you are heating several rooms, then add them all together.
Next, take the lowest temperature you are likely to reach in a given winter. Then subtract that number from your target temperature. Let's say you expect 10 Deg/F to be the lowest outside temperature and you would like the room to be 70. That means on the most extreme days, you need a temperature rise of 60 Deg/F.
Next determine the cubic feet of the area you wish to heat. Take the length x width x height to determine cubic feet. Example: 10 x 20 room with 9 ft ceilings = 1800 cubic ft.
It takes 1 BTU to heat 55 cubic feet of air 1 degree under normal conditions. So in our example, we have 1800 cubic feet and want to raise the temperature 60 Deg. so the formula is 1800 c/ft div by 55 c/ft = 269 x 60 (temp rise) = 16140 Btu to heat the area.
That being said, there are other factors that have to be considered. First, is the area to be heated well constructed and insulated? If not, then add 10% (or more) to the total BTU required. If the area is extremely well constructed and insulated, deduct 10% (or more) from the total required.
The second issue in our example is we are heating the area based on the lowest temperatures of the season. However, with wood stoves and fireplaces, we are usually supplementing another heating system which can add heat power when needed in extreme weather conditions. Therefore, it is much better to use an average outside temperature factor - so we can de-rate our findings by 30%. In our example that would equate to 16140 less 30% = 11,298 Btu required to heat the room most of the winter days.
Purchasing the wood stove or fireplace for the area to be heated now becomes much easier given that you know the heat output you need. Some or most of your decision may rest on the appearance of the product so that it fits the décor you are dealing with. The important issue here is that if you do purchase a wood heating product with much more power than you need, you will have to compromise by not operating the stove or fireplace in the very mild weather. You must be able to operate your wood burning product at or near maximum temperatures to achieve maximum efficiency. Failure to do so on a regular basis will result in clogged chimneys and extreme build up of creosote in the stove or fireplace.
The staff at New Energy Distributing is very knowledgeable in all aspects of wood heating. We are always happy to provide whatever assistance you may need in determining the best wood burning product for your application.