Heating with Wood – Space Heating

BY: Dave Misiuk, Cold Climate Housing Research Center
Energy Focus: Fairbanks Daily News-Miner August 28th, 2008, Section A3

There are basically four different wood burning appliance types available that are considered “space heating” appliances. These are units which produce direct convective and/or radiant heat that can be used to heat a room, a house or other “space” and include woodstoves, pellet stoves, fireplace inserts and masonry heaters. Many people ask me, “Which ones are approved?”

Masonry heaters currently do not require certification by the EPA as do the other three appliances listed above. The EPA recognizes the clean-burning nature of masonry heaters which use a small, hot fire over a short period of time to heat a large masonry mass which then radiates heat slowly over a long period of time.

Since 1992, no woodstoves, pellet stoves or fireplace inserts can be legally manufactured or sold in the U.S. unless they are tested and meet the emissions standards of the EPA Phase II emissions program. So if you buy any of these appliances from a reputable dealer, you are pretty much assured that they are, in fact, EPA approved.

Additionally, the complete EPA List of Certified Woodstoves is available online here.

This document is 113 pages long and contains over 900 different models. It’s a long list but it contains good factual information that a consumer can use to help decide when making a purchase. As a caution, some brands on the list aren’t being made anymore but if you know a few brands that are being sold locally, you can jump directly to those brands to compare the specifications.

The list shows the manufacturer, the stove model name or number, the particulate emissions in grams per hour, an average assigned efficiency and the heat output in Btu per hour. It is important to note that the efficiency number listed is assigned by the EPA by stove type and is not tested for any particular model so you can’t use the stated efficiency for comparison within stove types.

The stove types listed are non-catalytic, catalytic and pellet. The emissions limits are 7.5 grams per hour for non-catalytic and 4.1 grams per hour for catalytic stoves. It was decided that a lower limit be established for the catalytic stoves because the catalytic elements tend to become less effective over their 3 to 5 year lifespan.

So if you have an idea of your home’s heat demand in BTU per hour, you can use the list to find an appropriately sized stove. You can also get an idea of a stove’s actual efficiency by looking at the grams of emissions per hour versus the listed heat output; use the lowest number in the heat output range since the certification testing takes place at a low burn rate.

The lower the emissions per heat output, the more efficient the stove is at utilizing all the available fuel and consequently, the less wood you’ll need to burn. If you purchase firewood the savings can be substantial. In fact, if you have an old non-EPA certified stove and you switched to a new more efficient model the savings can be even greater.

I was recently asked about a woodstove change-out program in light of the EPA’s recent declaration of Fairbanks as a non-attainment Area for particulate matter. While this is certainly a possibility for the future, an effective change-out program we have right now is the increasing price of home heating fuel.

In order to displace 1,000 gallons of heating oil by using wood, an older non-EPA woodstove would use about 11 cords of wood at a price of $2,750 if you purchase wood. Using a new EPA certified stove you could expect to use about 7 cords of wood at a price of $1,750. So the economics indicate that making a switch is a wise financial decision. At a savings of $1,000 per year, the cost of the new stove would be quickly repaid not to mention not having to carry those 4 extra cords of wood.

This is the third article in a series on residential wood heating. The series will include information about firewood, different heating appliance options, applications, installations and other aspects that will hopefully help us conserve our resources, keep our environment healthy and…keep us warm.

David Misiuk, P.E. is the Wood Energy Specialist at the Cold Climate Housing Research Center (CCHRC).