Living Off The Grid

Can a fireplace be as good or perhaps better than a wood burning stove? That’s the question our guest author L. Fred Roensch asked himself not along ago, and his answers can be found below. I have also provided a few pictures of our own fireplace insert replacement. Notice the big pile of soot behind the old one, which happened because the old insert was too small for the fireplace, leaving a gap behind the insert for ash to fall – VERY dangerous! Our new fireplace is the HI300 Insert by Hampton.

By L. Fred Roensch, PhD

The use of a typical fireplace creates many problems and concerns in a home. A stove efficiently provides radiant heat and frequently is designed to provide other features such as a cooking surface, and/or an oven. Both fireplaces and stoves can use a variety of carbon neutral renewable fuels such as wood. However, most fireplaces create a significant draft and are usually an extremely inefficient source of heat compared to a stove. Of course both can be a source of significant pollution. Discussed below is a fireplace design that overcomes all of the negatives of conventional fireplaces and provides additional benefits.

There were at least three (and perhaps more) fireplaces built in homes in the mid west in the early 1980 that used a very innovative design for a fireplace. One of these homes was built and designed by me with the help of a very innovative architect-Bob Bland. The unique design features are discussed in the following paragraphs.

First, the fireplace was installed near the middle of the home as part of an inside wall. Positioning it inside the home, rather than on an outside wall significantly increased the mass of the home, provided additional earth tempering and provided the opportunity for other innovative features. To maximize mass contribution the fireplace was composed of stone from the floor to the roof and had a very dramatic appearance.

Secondly, a unique heat recovery system was built into the fireplace design to significantly increase the efficiency of the fireplace. The fireplace included two air intake vents near the ceiling (where the hottest air in a room exists) and passed it through the wall of the fireplace, into a plenum area isolated from the combustion side and then passed the air around the enclosed chimney and around the back of the combustion area. The plenum area then was attached to a duct that drew air down to the backup furnace fan and distributed it through the forced air ducts to the room registers located throughout the home. To complete the circulation the air in the home returned to the ceiling and passed again past the back of the fireplace and around the chimney.

Honestly, in the home that I built with this fireplace/backup furnace design, I believe the backup furnace would never have turned on if I had been energetic enough to get up in the morning and start a fire during the winter.

The fireplace was also designed to preheat the combustion air and eliminate creating draft. Unless the furnace is turned off, in homes with a conventional fireplace when you start a fire, virtually always the furnace will come on because a draft is created that causes the air temperature around the thermostat to lower. Of course, turning the furnace off creates a much lower temperature in other rooms in the house when the fireplace is used. This is certainly uncomfortable to those not in the room with the fireplace.

One method to prevent this problem requires installation of a combustion air register in the floor of the fireplace near the front. In the home I built the combustion air register was connected to a duct that led eventually to the space between the wall and the glass of the trombe wall outside the south side of home. As a result the combustion air was partially preheated during the day. Using this air source for the combustion air eliminates drafts inside the home. Because the combustion air is coolers it enters the front of the fireplace and permits the glass doors to be safely closed. The register also permits controlling the burning rate of the wood rather than using the chimney damper.

Another feature of this design permits installation of a conventional hot water heater directly behind the fireplace. A copper manifold is installed against the back of the steel fireplace to heat hot water in the hot water tank during the winter. The lines from the hot water heater tank run through the air space plenum area behind the fireplace. During the summer an active solar collector heats hot water in the hot water heater tank. This hot water heating system, which, incidentally, typically requires nearly 30% of a typical home energy use, is an alternative to installation of multiple, expensive point of use on demand electrical heaters at sinks, showers and the laundry.

Of course, if one wants to roast marshmallows or hot dogs or even use it as an oven, there is access to the heat by opening the glass doors. In some designs an oven is built into the side of the fireplace combustion chamber.

Because the fire can be seen through the glass doors it offers a vastly superior aesthetic experience compared to a stove. Personally, I prefer a fireplace to a stove because of this feature alone-certainly my wife and children did!

During the summer, the glass doors are closed tightly. On the other hand the dampers on most stoves and fireplace are usually not airtight.

Many states now require installation of air pollution control on wood burning chimneys, even in remote rural areas. These regulations usually apply to stoves and fireplaces.

Obviously, I believe a fireplace if properly designed can offer all the benefits of a stove and one important additional benefit – superior appearance.

Also see…
- Wood Burning Stoves VS Pellet Burning Stoves
- Making Your Own Pellets for a Pellet Burning Stove