Stay green by choosing a high-efficiency fireplace that burns more efficiently

Stay green by choosing a high-efficiency fireplace that burns more efficiently and produces less air pollution.

The classic fireplace, with a blazing fire open to the room, is a traditional symbol of comfort and security. Many people include a fireplace among their "must have" features when planning for their dream home. On a more practical level, an open fireplace is notoriously inefficient as a means of heating a room. Its appetite for air, to keep smoke from the fire going up the chimney instead of out into the room, is what causes the inefficiency.

But lots of people, including many who already heat their homes with a woodstove, probably would consider a high-efficiency fireplace instead — if they could find one that would do the job efficiently. The enduring popularity of fireplaces combined with the choice many of us make to use renewable wood heat for our homes has prompted a number of changes in traditional fireplace design that attempt to address the inefficiency problem.

To be an effective heater, a fireplace must borrow some of the features perfected by woodstove designers over the last 20 years. These include gasketed, ceramic glass doors with an airwash system to keep them clean; firebox insulation and internal baffling. An adjustable combustion air supply also is needed to control the burn rate and, therefore, the output of heat.

Some fireplaces with all these features are on the market. The quick way to find them is to look for either factory-built fireplaces or fireplace inserts that are certified by the Environmental Protection Agency (EPA) as meeting the EPA smoke emission standards, which stipulate acceptable concentrations of air polluting emissions from freestanding woodstoves and fireplace inserts.

In designing these fireplaces to burn efficiently enough to meet the standards, the manufacturers have produced some beautiful units that also are able to provide significant heat to your home.

Here's what you need to know to sift through the product specifications, sales advice and marketing hype to choose a unit that will match your personal heating and decor goals.

Fundamental Fireplace Problems

1. High air demand reduces efficiency  above.

2. Open fireplaces demand more air than modern houses leak.

3. Unless conditions are perfect, smoke spills into the room.

Strategies for Fireplace Improvement

Add glass doors (to reduce excess air flow) to all the open fireplaces above and you can increase their net efficiency to some extent. In the case of masonry fireplaces, glass doors allow some of the heat from the fire to soak into the masonry for slow release into the room. In the case of fireplaces with air circulation chambers, glass doors can boost internal temperatures, increasing heat transfer to the circulating air.

The majority of glass fireplace doors, however, are not tight-fitting, so they reduce air flow only by about half. The tempered-glass panels also block most of the heat from getting into the room and they are prone to breakage when exposed to intense or uneven heating, making them unsuitable if you want large, continuous fires to produce heat for your home.

So, while tempered-glass doors can boost efficiency by reducing excess airflow, they also reduce radiant heating efficiency and that is why they don't tend to produce a large net increase in fireplace efficiency.

If you already have a conventional open fireplace, you will find a fireplace insert is a far better upgrade option than glass doors. Inserts are woodstoves adapted by their manufacturers to fit within the hearth of an existing fireplace. They are EPA-certified, so they have all the features of "the perfect fireplace" (read on). If you decide to get an insert, be sure to tell the installer you want a full stainless steel liner on the top of the chimney; full liners improve heating performance and keep maintenance costs to a minimum.

The Perfect Fireplace

For new homes and additions, a good selection of beautiful, efficient and convenient factory-built fireplaces is available. Here's what you should look for if you want a fireplace that will warm your home as well as your heart.

1. The firebox must roughly match the size of fire that most of us build. That means it must be smaller than a traditional open fireplace. Notice fires burning in conventional fireplaces and you'll see that they occupy, at most, a third of the hearth opening.

2. The door glass must be ceramic and the fireplace must have a "glass airwash" system. In such a system, preheated combustion air is released through a narrow slot just above and behind the glass. A good airwash system can keep the glass clear for a week or more of round-the-clock heating.

3. The door must be gasketed and the fireplace must have a combustion air control. The combustion air control allows you to adjust the firing rate of the fireplace; any fireplace with a controllable firing rate also must have a combustion system to convert the smoke from slow-burning wood into usable heat.

Although fireplaces are exempt from the EPA emission limits that all woodstoves must meet, some are engineered to achieve low emissions so they appeal to those of us who have an environmental conscience, and a desire for renewable, wood heat and the beauty of a fire. A by-product of these low-emission technologies is much higher efficiency than conventional fireplaces can achieve. Some of these advanced fireplaces have optional central heating packages with fans and ducts to send the heat throughout the house. 

Post time: Sep-13-2016
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