Unity Blog

Wood Stoves In High-Performance Homes

Yes, it’s the holiday season, and you’d have to be a Grinch not to like the idea of cozying up to a fireplace or woodstove with a cup of hot chocolate while snow drifts outside. More than a few prospective Unity clients have this image in mind when they come to us. We try to let them down easy! Fireplaces simply don’t make sense in a high-performance home, and woodstoves have their own particular set of considerations.

Dissuading clients from including an open fireplace in a Unity Home is generally straightforward. They understand intuitively that a fireplace is more about providing ambiance than heating the home. In fact, traditional fireplaces are net energy-losers. That roaring fire might be throwing off radiant heat in the near vicinity, but it’s sending up the chimney lots of air that’s already been heated by the home’s heating system. And even if the damper is functioning reasonably well, the hole in the building envelope required by the chimney—a hole through which heat is continually lost—is substantial. Despite the romance of wood-burning fireplaces, we strongly advise against them in our homes.  

What are the alternatives? Wood and gas heating stoves can provide many of the advantages of a fireplace, without the serious disadvantages. Both types of stoves come free standing, or as inserts that look similar to fireplaces, with glass doors. Both fuel options—wood and gas—have pros and cons.. 

Although we strive to make our homes “all electric”—see this blog post for the reasons—some Unity clients end up using gas in their homes for cooking, a back-up generator, or even heat and hot water. If the house is supplied with gas, then a gas stove for ambience and supplemental heat can be a reasonable alternative to a fireplace. Gas stoves are relatively simple to install, and when supplied with a dedicated source of outside combustion air, they can function well in a Unity home. However, because they throw off a significant amount of heat, they can cause uncomfortably warm temperatures in our super-insulated homes.

Wood stoves have the advantage of using a sustainable fuel: either solid wood or wood pellets. While overheating the home can be an issue with wood stoves, our primary concern relates to their ability to draw properly in our airtight homes, so that the smoke goes through the flue, rather than into the house.

We recently surveyed the few Unity clients who have installed wood stoves in their homes, and generally they’ve been happy with the stoves—although they uniformly commented on the special care needed to install and operate them.

The impressive air tightness that we build into every Unity home has implications for wood stoves, because these stoves need combustion air to function, and that air has to come from somewhere. We strongly recommend that the combustion air be supplied by a pipe that provides a direct connection from the air outside to the stove. Without a source of outside air, the stove will struggle to burn, because the required air may not be available.

Appliances such as range hoods or dryers that depressurize the home have the potential to cause a wood stove to backdraft—sucking smoke down the chimney and into the home. One couple with a Unity home ended up having to call the fire department when their wood stove filled their new home filled with smoke the first time they used it. They’ve since learned the ins and outs of making the stove work for them.

A number of Unity clients have opted to put a wood stove in a three-season porch. This provides them with the warmth and ambience of a wood stove during the shoulder seasons and even into the winter, without the concerns that come from trying to burn wood inside an airtight home. 

The most clever option we’ve seen for introducing the ambience of a wood stove into a Unity home was in an owner-finished Nano in Greenfield, MA. The owner opted for a small electric unit that looks like a woodstove, with realistic-looking dancing flames and glowing embers visible through the glass front. The unit heats the Nano easily with comfortable infrared heat. To augment the illusion of a wood stove, the owner will sometimes light a “fireside”-scented candle with a wooden wick that crackles softly like burning logs, and wafts the scent of woodsmoke.

At Unity we’re all about authenticity, but we’re also willing to make compromises in the interest of saving the planet. As an alternative to “stockings hung by the chimney with care,” let’s hang them next to a fossil-fuel-free heating appliance that’s powered with renewable solar energy!