Installing a gas fireplace

It's hard to give up an old wood fireplace. The smell, the crackle, the fun of poking at the fire-they all make a home feel more inviting. But then there are the downsides. Traditional fireplaces are not very efficient heat sources. Cleaning up ashes, cutting and bringing in wood, and worrying about fire hazards are other reasons many homeowners look for alternatives, such as fireplace inserts.

Think of a fireplace insert as a closed box-really a kind of stove-that fits inside an existing fireplace. There are wood-burning inserts, which maintain some of the wood-fire romance but add efficiency, while pellet fuel inserts burn what looks like oversized rabbit droppings consisting of wastewood and other biomass. Electrical inserts, simple to install, are more for aesthetics than efficient heat. But the most popular type, especially in homes that already use gas for heating and cooking, are gas-burning inserts.

In this installation, in a city home built in the 1920s, a zero-clearance gas insert was the homeowner's clear choice. The existing fireplace hadn't been used in years and would have required a lot of work to make it safe for a wood fire. Wood was more expensive, and more trouble, than the homeowner wanted.

Because each installation is different, needing an experienced eye and a licensed gas fitter, putting in a gas fireplace insert is not really a do-it-yourself project, even though our expert, Wes Willard of Miles Industries, made it look easy. But you can do a lot of the prep work on your own. Before this insert could go in, for example, the fireplace surround needed some cosmetic surgery. The original brick had been clumsily repaired and coated with what looked like leftover cake icing. A simple drywall surround is an easy do-it-yourself solution that complements the sleek, modern renovation that's in progress in the rest of the house. If future owners decide to redecorate, they'll have a ready framework for a more traditional mantel and surround.

Is it Efficient?

No and yes. No, if energy efficiency is your only priority. In that case, first upgrade or at least tune up your home furnace, then block off the fireplace, never to be used again.

But if you want to use your fireplace, especially as a zone heater, a gas insert makes sense. You'll save energy if you use the smaller gas insert instead of firing up the main furnace, particularly in spring and fall.

Choosing a fireplace will depend on your budget and your tastes. You'll find just about any style, from Italian Renaissance to Victorian to High Modernism-even Southwest kiva fireplaces that will look perfect in your pueblo. But if you want your fireplace for supplementary heating, look for substance as well as style-a fireplace that's labelled as “heater-rated” is more efficient than one that is described as “decorative.” Manufacturers and testing agencies assume a heater-rated fireplace insert will be turned on much longer, so these inserts are built and tested to higher standards than decorative models.

Lower energy bills

According to Canada Mortgage and Housing Corporation, these are some of the features of the most energy-efficient gas fireplaces:

- a high Annual Fireplace Efficiency(AFE) rating
- direct venting
- an intermittent electronic ignition system, a pilot light that's easy to turn off and relight, or a two-stage pilot
- a radiation-transparent ceramic glass front
- a quiet “squirrel cage”-type circulating fan
- a secondary heat exchanger
- insulated outer casing
- the ability to turn the heat down

Right-sizing

The height, width and depth of the existing firebox opening can limit your choice of insert, simply because altering the size of the firebox is a big masonry job. Fortunately, most fireplace manufacturers offer models in several sizes.

A gas insert also has to be right-sized-not too big and not too small-for the space it will heat. Too little output, and it can't push out enough heat; too much and it will overheat the room, or cycle on and off too often to be efficient. While there are rough rules-of-thumb to estimate output needs, Steve Haagmans, eastern division manager for Miles Industries, manufacturer of Valor gas fireplaces, recommends against relying on them: “There are just too many variables-ceiling height, party walls, windows, doors and insulation levels.” Calculators such as the one at the Valor site, or at Hearth, include some of these variables and are therefore more accurate. For even more precision, a heating contractor can calculate a customized “modified heat loss” for your home.

But no matter what size the fireplace, don't count on it to heat all the rooms in a typical house; it simply can't move that much heat around that far.

Convection and Radiation

It's not just heat output that counts, but how the fireplace transfers heat-by convection or radiation-to you.

Convection is heat transfer when air warmed by the fireplace insert mixes through the cooler air in the room. It happens naturally because warm air is less dense, so it rises and gets into a flow.

Radiation is what you feel at a campfire when your face is hot and your back is cold. A fireplace, like any heat source, beams out infrared rays. The rays don't heat air much, but do heat the solid objects they “shine” on. For that reason, you shouldn't put a thermostat where those infrared rays hit directly: the rays will warm the thermostat and fool it into thinking the room is warmer than it is.

Manufacturers often hype one method of heat transfer over the other. The inserts that are better at convection are promoted as providing an even heat throughout the room, like a forced-air furnace. Radiant inserts are promoted as feeling more like a real fireplace and warming you faster. In fact, it is not really an either-or choice between convection and radiation. All fireplaces deliver both; different designs just produce one more efficiently.

Look for features that help heat transfer, such as the materials in the glass front. Tempered glass doesn't let infrared rays pass through nearly as well as pyroceramic glass (similar to Pyrex ovenware material). Channels around the firebox and the exhaust system encourage heat exchange from the fireplace to the air around it and convection into the room.

Fans also speed convection by pushing that hot air out and, according to Don Fuegler, senior researcher at Canada Mortgage and Housing Corporation (CMHC), do tend to improve efficiency. CMHC suggests you look for a quiet, “squirrel-cage” fan-the kind that looks like a hamster's exercise wheel and is used in a forced-air furnace.

An insulated outer casing is another of the CHMC's recommended features. It reduces heat transfer to the walls on the back and sides, so that more heat goes out the front.

Opportunities to Vent

Combustion needs an air supply, and almost all combustion produces waste gases that need to be vented safely.

Natural venting is like a traditional open fireplace-room air is used for combustion, with exhaust vented outside. This simpler venting system is fine for older, drafty homes, because there's enough fresh air coming in to replace air going up the chimney. But in a tightly sealed, well-insulated home, combustion that uses room air can create negative pressure, sucking dangerous gases back down exhaust vents into the house.

The safer choice in tightly sealed homes is direct venting, where outside air goes into the firebox through one vent, while combustion gases escape through a second. The fireplace insert has a dedicated air supply, so it won't suck air out of the home.

Ventless (or room-vented) fireplaces use room air for combustion and vent exhaust back into the room. They are not approved for use in Canada.

Startup Decisions

How the burners ignite when you flick the switch affects efficiency, but Fuegler suggests this might be one decision, depending on your situation, where safety might outweigh efficiency. A traditional pilot is reliable in a blackout, but burns constantly-not very energy efficient. A two-stage pilot is better. It burns at a very low level most of the time, and flares up when you turn the fireplace insert on. When you're not using the insert regularly, extinguish the pilot to save gas.

Electronic ignition systems don't burn any gas, so they are the most energy efficient, but require a battery backup to ignite if the power is out.

Comfort Levels

Without any heat control, a fireplace is just a decorative blast furnace. Heat output can be controlled in three ways: by cycling the flames on and off, by adjusting the flame height, and by adjusting the fan speed. In some models, these adjustments are manual. There's a switch for a low or high flame, or there's a switch to control the fan speed. Other models come with a thermostat that adjusts automatically as the room temperature changes.

The range between minimum and maximum gas inputs (see BTUs In and Out, right) is a good indication of how much heat control an insert offers. If you plan to use your fireplace year-round, a fireplace that can be turned way down is a useful feature.

Steve Haagmans has a final tip on getting more comfort out of your fireplace, something he says people often forget: “Read the instructions, or get the installer to show you how to use your insert. Your fireplace can probably do a lot more than you realize."

BTUs In and Out

On the backs of those glossy insert brochures, you'll find numbers that will tell you how well each fireplace works as a room heater.

First, mind your BTUs. A BTU (British thermal unit) is a measure of the heat needed to raise the temperature of one pound of water by one degree Fahrenheit. For example, lighting a wood match generates about one BTU. The amount of gas a fireplace consumes can also be expressed in BTUs per hour. (With a flame that can be adjusted, you'll see a range of numbers-from minimum to maximum input.)

Even the most efficient inserts lose some heat or unburnt gas out the vent. How much? Look for efficiency ratings. An efficiency of 76 per cent, for example, means the insert turns 76 per cent of the gas into heat in the room.

Exactly how this efficiency is tested is an important “apples-to-apples” consideration if you're comparing brands. “Steady-state” means efficiency when the fireplace is burning at a constant rate. Since you're not likely to leave your fireplace on 24 hours a day, fireplaces are also tested for AFUE, or Annual Fuel Utilization Efficiency, which measures the efficiency with all the usual stopping and starting, heating up and cooling down. Steady-state ratings can be significantly higher than AFUE numbers, so be sure you know what you're looking at.

The third measure is the newer Annual Fireplace Efficiency (AFE) rating, which uses a made-in-Canada fireplace test, similar to AFUE. Ask the fireplace retailer for these numbers, as they haven't made it into many brochures yet.