The Best Outside Woodburners

Certified Models

• EPA-certified outside woodburners can burn wood gases more completely. In doing so, heat is extracted more efficiently and produces less smoke. Less wood is burned as well. Burners purchased in Vermont after March 31, 2008, must be certified to meet the state's emission standards. Dealers are prohibited from selling the older models.

Anti-Blowback Catch

• Doors should come equipped with an anti-blowback safety catch. The catch avoids flash burns by releasing the door slowly, allowing the gases to escape and avoiding the possibility of severe burns. A burner without this feature should not be considered, according to the Outdoor Furnace website.

Door Insulation

• Water-cooled doors are the most efficient, however, they are prone to corrosion and are the most expensive. Doors must have a minimum of 6 inches of insulation on the outside to be effective. Avoid hollow doors that have little insulation. The best door should offer air tightness to prevent overheating and boiling. Poorly insulated doors can warp and allow air penetration.

Adjustable Doors and Sizes

• Outside woodburners should have doors that are adjustable in four directions in case of warping. Door sizes should run from 20 to 30 inches in each direction. This makes it easier to load large, uncut logs.

Door Gaskets

• Doors should have a recessed lip running around the outer edge, according to Outdoor Furnace. Within the recess there should be a silicone-covered door gasket. If the gasket is not covered with silicone it will harden with creosote and break down. Creosote, a highly combustible by-product of burning wood, is the black or brown residue that can take many forms such as flaky and crusty, sticky and drippy, tar-like, or hard and shiny. A leaky door can cause runaway fires. If there is no silicone seal in the door recess, an adjustable door will not stop air leakage.

Rust-Free Models

• Outside woodburners can rust. Steel or stainless steel models will prevent corrosion. However, if the firebox has many welded seams, has dead spots that keep water from flowing all around the firebox, or uses several thicknesses of steel, corrosion can quickly occur. Ashes are a major cause of corrosion. Hence, the firebox is the place where corrosion is most likely to occur. A high heat model will reduce the amount of ashes.

Chimneys

• Models with manual or electric dampers should have a long chimney in order to draw air over the fire to keep it burning. If buying a furnace with a forced air draft, avoid extra chimney length as it will create more creosote. The chimney should also have a cap. During the off season the cap keeps out debris as well as rain which can rust the chimney. During heating season, a cap such as the cloverleaf style, will prevent downdrafts.

Models with Legs

• Outside woodburners with legs have advantages over burners that are skirted to the ground. Leg models save time and money during installation. Piping coming out of the ground is easy to see when positioning the burner. Additionally, because skirting and frames on all burners are made from mild steel, they are subject to corrosion when sitting directly on the ground. A model with legs can is less susceptible to corrosion because it can sit on four sidewalk blocks instead of a full concrete base.