How To Choose and Season Firewood

DIY Answer Guy — Wed, 25 Mar 2009 17:05:30 +0000

Effective do-it-yourself tips for choosing and drying firewood.

Many people burn wood as a source of heat for their homes. Many more of you may be considering doing the same, so I’d like to talk about two common problems you may be faced with in doing so.

One problem is how to choose the best firewood.

Many people buy the cheapest wood available, and that’s understandable in these economic times. But in doing so, you may be sending your hard earned cash up the chimney in a puff of smoke.

The other problem is how to properly store and dry (also known as “seasoning”) firewood.

The solutions to those problems in just a minute, but first a bit about how airtight wood stoves extract heat from wood and the problems associated with burning green unseasoned firewood.

How Does A Wood Stove Work

How does a wood stove extract heat from firewood?

The primary source of heat from a wood stove is from the combustion of the wood. The secondary source of heat is from the combustion of the gasified resins and unburned wood particles that result from the primary fire. This all occurs efficiently, providing you’re using dry seasoned firewood.

When you use unseasoned, wet wood in your stove, the water contained in the wood heats up and turns to steam. Unseasoned wood can use ½ of the heat it produces just to boil off the moisture and keep the fire burning. This production of steam will cut your heat output by up to 50%. Burning unseasoned wood results in cool water-laden smoke, filled with unburned particles and exhaust gases. All bad.

You see, this wet, heavy, high-density smoke travels very slowly up the chimney, where it cools even further, condensing onto the inside walls of the chimney and causing excessive creosote formation. Also bad.

Therefore, unseasoned wood produces less heat, creates more creosote, and increases the likelihood of a chimney fire.

Solution: to get the most energy efficient heat for your money and efforts, start by using high density dry seasoned firewood. Doing so is like upgrading your clothes dryer to a high efficiency model, it uses less gas or electricity to produce the same heat.

How To Choose The Best Firewood

There are different species of wood available in different parts of the country, and every species of wood has a different density (weight) and BTU output.

Why is this important?

Whether you are buying wood or cutting your own, you’ll want to get the most for you money or efforts. Right?

This chart shows the density and BTU output for the various species of woods, to help you do just that.

Remember you’ll get the best results burning properly seasoned wood with the highest density. Obviously there are more species of wood out there, but this covers some of the most common.

The following chart shows various woods by BTU content (1 MBTU = one million BTU’s)

Weight and Heat content figures are based on seasoned wood at 20% moisture content. One cord of wood is measured as 4′ x 4′ x 8′ = 128 cubic feet.

Woods by BTU content
(1 MBTU = one million BTU’s)
Species	Pounds/Cord	MBTU
Alder	3,965	25.8
Apple	6,150	39.8
Ash	5,320	29.9
Birch	4,650	30.4
Cedar	2,569	18.3
Douglas Fir	4,350	27.1
Elm	4,660	32.4
Hemlock	4,272	23.3
Hickory	5,748	36.1
Maple	4,386	28
Oak	5,625	36
Pine	3,339	21.9

Now that you have some background information on how to choose the best firewood to heat your home, the question remains, how best to season the firewood?

Do-it-Yourself Tips For Storing and Seasoning Your Firewood

Wood Preparation

Green wood contains up to 80% moisture by weight, and doesn’t always season properly due to improper storage. Also, seasoned wood will not always stay that way if improperly stored. That being said, to properly season your firewood, remove the bark, when possible, as this will speed up the drying/seasoning process and reduces the woods ability to re-absorb moisture.

Note: Pitchy woods, such as Douglas Fir, needs more time to season before it is dry enough to burn properly.

Firewood Drying Time

The drying process takes anywhere from 9 to 12 months depending upon the species of wood, the amount of airflow, and the humidity and temperature of the storage area. As moisture evaporates from the wood, air circulation is necessary to carry it away.

What Seasoned (Dried) Firewood Looks Like.
Here’s an example of a piece of properly seasoned Douglas Fir.

No bark, no mold, just dry and ready to burn.

Where To Store Firewood

Stack your firewood in a dry covered area with plenty of air circulation, meaning plenty of circulation under the wood as well as all around the sides and top. The best storage option is a woodshed with open slat walls, woodshed which allows air to circulate, and it’s best that it has an overhanging roof to keep the rain off the wood.

Note: Dry, seasoned wood stacked out in the rain will soak up enough water to revert to its original moisture content. When this happens the wood needs to be reseasoned until it is once again dry enough for use. This can take weeks, perhaps months.

Using A Tarp To Protect Firewood

If you don’t have a woodshed and will be storing your firewood under a tarp then you should be aware that a tarp creates a micro-environment. The evaporated moisture from the wood condenses on the underside of the tarp and drips back down on the wood and is reabsorbed.

The solution is to take a few pieces of wood and create a peak in the tarp at the top of your stack so the water will run to the tarp edges, instead of just dripping back onto the wood.

Be sure to fasten down the edges far enough away from the wood to keep the water away, but also tie the tarp edges down in a manner that allows air to flow under and around the tarp.

DIY Tip: Stacking wood off the ground using pallets or a few 2x4s or 2x6s will greatly improve air flow and reduce moisture problems. Also a few scrap 2x4s can be used to hold the tarp away from the wood and increase airflow.

There’s a ton of information out there about burning wood for home heating, but these important basics can help you can make informed energy efficient choices concerning your home heating.

Important things to Remember

Choose the higher density (heavier) woods.
Cut, stack, store and season your firewood properly.
And most of all, have your chimney cleaned every year!
Follow these simple tips you will certainly succeed with speed.

A Special Note of Thanks.

I’d like to thank my good friend and neighbor Mike for giving me all the great information on firewood for home heating. Mike has been using wood for home heating for decades and really knows his stuff. He’s currently helping me plan my move to wood heat.

Thanks again Mike, for all the great tips and information.
You’re the best.

If you have questions about your DIY projects, just ask your personal DIY consultant. I’m here to help you succeed with speed.