Todd Fahrner recently published an excellent update on the Clever Cycles blog, outlining his family’s experience augmenting their central heating system with a free-standing wood stove. It’s an especially valuable article because, as Todd eloquently puts it:

“What does this have to do with biking? We can’t really tell where biking stops and the rest of life begins, but this connection to everyday biking feels as natural as that to, say, backyard chickens or slow food or knitting or beards. It’s just another thread of the Portlander good-life conspiracy.”

Todd’s free-standing wood stove sits directly in front of his fireplace hearth, venting out of the fireplace flue. This is a good example of how to retrofit an existing fireplace/hearth so you can achieve whole-house heat using a wood stove. In our home, we chose to seek ‘supplementary’ heat from a wood stove, as opposed to whole-house heat, with the primary goal of turning our home’s lovely, inefficient fireplace into a heat ‘provider’ as opposed to a heat ‘consumer’.

A traditional, open fireplace is like a vacuum, sucking perfectly good air right out of the room. When burning a fire in a fireplace, the room will receive radiant heat from the fire, but the fire requires a great deal of air, which it will take directly from the room. This will result in reducing the room’s air temperature as opposed to increasing it. Yes, the space right in front of the fireplace will be warm from the radiant heat of the flames, but the rest of the room will suffer.

Conversely, a wood stove or fireplace-inserted wood stove very carefully utilizes air to optimize combustion in a way that minimizes fuel consumption while providing maximum heat transfer from the firebox to the stove’s exterior walls. In this fashion, you get that deliciously dry radiant from the iron and/or stone of the stove without losing a ton of air through your chimney flue.

If you’re seeking whole-house heat from wood, you would benefit most from a free-standing stove, regardless of whether it’s vented through an existing fireplace or new flue. A fireplace-inserted wood stove –like ours, which sits inside the fireplace, as opposed to in-front of it– will not effectively heat your whole house unless you have a centrally mounted fireplace and ensure that the insert is extending beyond the hearth at the maximum distance allowed by the manufacturer. For our Vermont Castings Winterwarm stove, the maximum extension length is six inches from the non-combustible face of the fireplace.

For our family, we elected to have the wood stove insert flush-mounted into our fireplace, so it integrates seamlessly with the hearth and mantle, making it relatively safe for little people who like to play on the rug in front of a warm fire. The downside to this setup is that the majority of the stove’s iron is inside the brick firebox of our pre-existing fireplace, so the stove radiates less into the interior space than a free-standing stove. Yes, the stove does feature a ultra-low-wattage blower that circulates extremely warm air over the top of the stove into the room, but it’s still not as effective as a free-standing stove that is allowed to simply radiate all of its usable heat into the living space. This brings us to another intriguing point: architecture.

The Devil’s in the Design

There are several home designs that are especially conducive to whole-house wood stove use, while some are not quite as well-suited to the efficient transfer of heat from a stove to the complete living space. For example, a lot of old-Portland style houses and Portland four-squares (1900-1920) have centrally mounted fireplaces. This fireplace location makes these houses ideally suited to using a wood stove for whole-house heat as the heat can be sourced from the center of the home and radiate up and out in all directions –an extremely effective scenario.

Conversely, our house is a traditional 1923 bungalow with the fireplace located on the exterior wall of the front family room of the home, as opposed to a central interior location. The location of our fireplace is far from ideal for whole-house heating. The heat from the stove can move well from the front family room into the dining room –which it directly connects to)–due to large, open double-doors and the rooms’ close proximity. But the rest of the rooms in our home (bedrooms and bathroom) are at the back of the house, accessible only via a long hallway. What’s more, we have a 900 square foot finished basement that doesn’t benefit from the wood heat.

My point is that some houses are better suited to whole-house wood stove heat than others. We determined that our house would not be able to be heated entirely with wood, unless we used a wood-fired boiler, so we elected to simply supplement our bio-fuel central furnace with a cast-iron fireplace wood stove insert. And with this as the goal, the addition of the insert has been excellent. It does exactly what we need it to do, and helps make a wonderfully cozy front-of-house without sucking all the warm air out of the room like it used to.

Moving Air, Reducing Humidity

Also of note, we just replaced our legacy Sandberg furnace (which inefficiently burned pricey, local, recycled bio-fuel) with a new, Energy Star-rated bio-fuel furnace that features a variable-speed air circulation fan powered by a super-efficient electronically commutated motor (ECM). I mention this because the ECM-powered fan is configurable at the thermostat and can thereby be used at half-power to circulate air throughout the house. At half-power the fan uses less than 75 watts, so it’s quite economical considering the amount of air it’s moving throughout the house (500 cubic feet per minute).

When running the furnace’s ECM-powered fan while the fireplace wood stove is burning, we’re able to better circulate the radiant heat from the front room to the rest of the house, while running all the air through the furnace’s electronically-charged air cleaner. This makes for cleaner inside air throughout our home. Now, the fan certainly doesn’t end up blowing a bunch of hot, wood-stove-heated air throughout the house… there’s not that much heat in the air and that’s not the biggest benefit to running the ECM-powered fan. The real benefit is that the fan is moving warmer air that is much drier than the standing air in the other rooms in the house.

As a matter of course, the radiant heat created by the cast iron wood stove dries out inside air. In some climates this is a major issue (some people keep a pot of water on their stove at all times just to add steam humidity to the air), but in our climate –and with an older home– this drying effect is a major benefit. In essence, the wood stove is contributing to lower humidity in the house, which has the benefit of reducing the potential for mold and mildew and associated allergies. What’s more, by moving the air around in each room, you’re helping to eliminate cold/hot spots.

I’ve been very impressed by the combination of the ECM-powered fan and the wood stove. Yes, we are burning a small amount of electricity when we run the ECM-powered fan, but we’re also lowering the humidity levels in the entire house while increasing our whole-house comfort. It is an effective solution when choosing to use the wood stove along with the bio-furnace. Considering the architecture of our house combined with our desire not to have a free-standing stove in our small front room, it is a reasonable and very effective compromise.

In summary, choose your wood heating method based on your likely use of the stove along with the architecture of your home and how well heat transfers from room to room due to said architecture. If you have a duct-based forced-air furnace with an efficient ECM motor, you can also assist the transfer of heat throughout your home using the furnace’s built-in, low-power air circulation fan; this will have the added benefit of reducing the humidity level in your entire house.

Bottom Line: Keep the Heat In

Of course, the real overarching issue to consider when heating your home is whether you’re actually maintaining your interior temperature. Specifically, it’s important to make sure that you do your best to efficiently and effectively produce heat –and maintain proper humidity– but you also need to make sure you keep as much of the heated air inside your home as you can, for as long as possible.

With this in mind, I recommend that you first focus on sealing your windows as best as possible. This can be accomplished by installing new windows, or new storm sashes, or by simply using 3M window sealing kits to keep out drafts. Once you’ve addressed the most visible source of drafts (windows), insulate your living space. When insulating, start with the ceiling joists above your living spaces, and then move to the walls. If you’re windows are leak-free (or as close to it as possible), keep the heat from rising up and out and you’ll do a fantastic job of maintaining comfortable interior temperatures.

Once you can effectively keep warm air in and cold air out, then you’re ready to figure out how to heat your home, whether your criteria is purely economic, or environmental, or –more likely– a balance of the two. Remember, as Chief Joseph said… Endeavor to Persevere. The rewards for doing your homework are a lower carbon footprint and greater comfort for you and your family, not to mention the satisfaction of knowing you did your best to improve your life while treading lightly on the planet, as well as your fellow humans.