BTU and Your Firewood

The British thermal unit (Btu or BTU) is a traditional unit of heat; it is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. This is part of the US Customary System. Its counterpart in the Metric System is the calorie, which is defined as the amount of heat required to raise the temperature of one gram of water by one degree Celsius.

BTU output is the way we gauge the heat value of the firewood we burn, and even if we cannot determine a numerical value for the heat in our home, we certainly can tell the difference between hot burning firewood and the “not-so-much” firewood we put in our wood-stoves. What are the factors? The type of tree that is burned will make a significant difference. Some types of wood naturally release greater amounts of heat, energy, than others, such as oak or ironwood. Some types of wood are best at holding coals overnight to make the morning fire easier to start, such as Hard Maple (wood types will be the topic of a future post). Yet the BTU output of each of these firewoods is susceptible to external influences, and one in particular – moisture content.

If your firewood is not fully dry you will NOT get maximum BTU heat from the burn. Wood that is wet or internally even still moist simply cannot burn as hot as it is capable of. Yet the wood will disappear in the fire and potential heat will be squandered. Correctly drying the wood is essential. Keeping the wood dry is a must. Burning the wood dry is a pleasure.

With this knowledge in mind Glenn’s Sheds was created, serving the Hudson Valley, greater New York, and reaching into NJ, CT, MA, and PA. A firewood shed that can breathe from all sides, as well as from below, will provide optimum drying capacity for any firewood. Loading a woodshed full of firewood in the spring will allow the wood to dry all summer and then be ready for use in the fall. Whether the wood is green or dry, destined for fireplace or woodstove, or for outdoors or in, will not matter. You will not need to worry that the wood you buy in the fall is fully dry, as you might be told, or that only a portion of it is dry. You will have had time to cure your firewood. (Note: Some woods, such as the Oaks may need more than one season to fully dry. A firewood shed that has a divider could provide a separate space for such wood to dry longer, and could be well worth the effort).

Firewood can also lose BTU value by turning “punky”, even to a small degree. Punky indicates that the wood has begun to rot – which is a common outcome of wood that is stored under tarps. Even though the wood may not be getting rained on directly, the tarp will hold in moisture which will cause a slow decay of the firewood. BTU’s evaporate. Firewood is compromised.

If you wish to be at the top of the game in regards to dry firewood, set up for one of Glenn’s Sheds as soon in the spring as possible. These sheds, with the “breathable below” design, will provide you with what you will need. And if you cannot set this up right away, consider this bit of wisdom – according to Chinese philosophy:

“When is the best time to plant a tree?”

         “Ten years ago”

“When is the next best time to plant a tree?”


For further information on “dry firewood” go to earlier post: “Firewood Dryness FAQs”. 

To get a quote on a new woodshed, go to “Get a Quote“.

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