Indoor Wood Fireplaces

For those of us with access to low-cost firewood, it often makes sense to heat our homes with an indoor fireplace. Our property in Ontario's Niagara Peninsula includes a woodlot and, when we built our house, we included a functional wood fireplace in the living room. The builder installed a now discontinued BIS Ultra (Security Chimneys International) EPA-certified residential fireplace, which was rated for up to 60,000 BTU/hr and an 8 hour burn time. Although it does have beneficial impact on our heating costs, in practice, it does not perform up to its rating, presumably because we don't have the same fuel that is used by the test lab. With the silver maple, ash, and elm on our property, we had to reload the fireplace more like every 2-3 hours. Normally, if we could keep the fireplace stoked, we generally had no problems heating the house during the winter. However, heating the house on coldest days was often a challenge because we could not come close to reaching the 60,000 BTU/hr rating of fireplace.

The main issues we encountered with using the BIS Ultra to heat the house are:

• Difficulty in constantly attending to the fireplace to keep it optimally stoked.
• Poor ash-handling system.
• Frequent glass cleaning.
• Dry air.

Because the firebox only holds a practical maximum of 1.5 cubic feet of wood, the fuel must constantly be replenished if the maximum output of the fireplace is required. This is difficult to achieve as someone must constantly be monitoring the fireplace day and night. If you wait too long, more kindling must be added to the coals so as to relight the fire. This can be quite time-consuming.

After burning steady for 2-3 days, a significant amount of ash builds up in the fireplace. Although it could be possible to sweep most of the ash into the ash pan and keep some coals in the fireplace, it is simpler to let the fire burn out and clean it completely out so as to start fresh. This allows the still-hot ash and coals to be removed from the house in a single metal bucket

The other reason for doing a complete clean-out after 2-3 days of burning is to clean the ceramic glass in the doors. After 2-3 days, in spite of Security Chimneys' touted "air wash system", the glass tends to blacken with creosote build-up, especially if the wood used isn't completely dry. The normal air flow in the fireplace tends to cause the outside edges of the door to be particularly black because most of air wash comes across the centre of the doors. Also, there is smoke produced when the the fire is restarted (like first thing in the morning) and smoke condenses on the glass due to the air currents in the fireplace. Although many people just use to newspaper to clean the glass, we found that it was also necessary to use a Potassium Hydroxide (KOH) ceramic glass cleaning solution to get the glass clean. This is not a fun job once you've done it several times.

Although the primary combustion air for the BIS Ultra comes from outside, the secondary air for burning the smoke (introduced at the tubes in the top of fireplace) is drawn from inside the house. Although we have a modern house (built to the R-2000 standard) that includes a Heat Recovery Ventilator (HRV) with humidistat control, the air is dry during the winter because the significant amount of secondary combustion air.

After several years of use, there is now some spalling in the refractory so continued continuous use will require replacement in a few more years.

There is not much to heating your house with a wood fireplace but I have a few pointers to share with you.  The most important thing is:

Do NOT allow your wood to smolder! Smoldering wastes fuel and increases the risk of a chimney fire from creosote build-up.  It also makes more work in cleaning the glass.

Charcoal is easier to ignite than wood so I use a metal kitty litter scoop to recover charcoal from the previous burn's ashes.  Make sure that the overall length is shorter than the height of the fireplace.  I scrape the ashes into a pile on one side the fireplace and then sift the ash into a metal bucket.  The remaining charcoal is then placed into the other side of the fireplace.  This is a dusty process so work slowly to keep the ash from flying out of the bucket.  If you're cleaning out a hot fireplace, recovering the charcoal also helps to keep the ash bucket cooler.

Once the charcoal has been recovered, I make two long piles in the center of the fireplace (oriented front-to-back) and add short pieces of wood if necessary to raise the height of the piles.  The long piles are to support longer pieces of placed side-to-side and the empty space between the two piles allows air to circulate under the wood and towards the back of the fireplace.

For starting a fire, I use waxed corrugated paper boxes from the grocery store.  This paper is not recyclable so you're helping your local waste management by keeping this waste product out of the landfill. I place this paper in the empty area between the 2 charcoal piles.  This helps to ignite the wood I've placed on the charcoal.  As for igniting the fuel, I use a butane barbecue lighter but keep the wooden matches in case I run out of butane.

Depending upon your jurisdiction's recycling program, cooking grease can sometimes be recycled in green bins.  I collect cooking grease in paper coffee cups stored in the freezer.  Once the cup is full enough, I will put the grease cup onto the hot coals of the fireplace.  You need hot coals to ensure that the grease burn immediately and not run down underneath the fireplace's refractory.

Sometimes a fire will die down and it just needs a good blast of air to restart.  You can blow on the coals but it's better to use a bellows or blowpipe instead.  We got our blowpipe from the historical artisans at the reenactment of the Siege of Fort Erie.

If you're contemplating getting a fireplace for your home, give the following points some consideration:

• Use an EPA-certified fireplace. Besides reducing nuisance smoke from your fireplace for your neighbours, it also reduces your wood consumption because of its higher fuel efficiency. Smoke contains a lot of energy and it's pure waste when it goes up the chimney. EPA-certified fireplaces make very little or no smoke.  Do NOT allow your wood to smoulder!
• Provide a combustion air supply for your fireplace. All fireplaces consume a lot of air, which has to come from somewhere. If you don't provide your fireplace directly with combustion air supply, you will notice your house becoming very drafty when you are using your fireplace. HRV-equipped homes have minimal drafts because the make-up air comes in through the HRV's fresh air intake.
• Provide good circulation in your home. Obviously, the fireplace puts out a lot of heat so ensure that cool air from all rooms in the house can move to the fireplace for heating. This can be as simple as keeping all of the doors open or as sophisticated as tying the fireplace insert into your forced-air ducts.
• Avoid glass doors if heating is the prime consideration. Seeing a roaring fire behind the glass is nice in your living room but it can be a real pain to clean after a while.
• Keep the log length uniform.  The BIS Ultra has a tapered firebox which allows combustion air to flow to the back   If you pack the firebox with 20" logs in the front and 18" logs in the back, the logs in the back could potentially be starving for air, thereby reducing heat output.
• Use split wood if possible.  This creates more surface area for combustion and allows the wood to dry better while in storage.
• There is natural air circulation with a wood fireplace so additional fans and ducting aren't necessary.  Our fireplace has an insert blower as well as a ducting and and fan to move hot air from the insert into our gas furnace ducting.  We've found that we primarily want our main living space to be heated and it's better to keep the bedrooms cooler so lately we haven't used either of the 2 fireplace fans.
• You need to regularly sweep the chimney to remove creosote build-up.  Consider adding a roof hatch near your chimney so can avoid climbing around on the shingles.  Depending upon the layout, the chimney on a two storey house can be a challenge to reach with a ladder.  Traffic causes wear on the shingles which could require premature replacement.