It’s time to deep-six the fireplace. Banish it from building codes and never look back. Let’s be frank, a century ago, there were few amenities in the home that could compete with the hearth of a home on a cold winter’s night. Bad lighting, really cold with drafty spots but with occupants who took leisure time seriously and socialised around a fire for hours. Today’s home, if built well, has no drafts or cold spots and good lighting, so who needs the patriarch’s idle chatter when Wi-Fi feeds us a steady stream of YouTube, Instagram and Facebook. Add to that, if built well, a new home’s indoor temperature won’t drop precipitously in a power outage for several days, more so if there’s no fireplace.
The Rumford wood burning fireplace should be outlawed: everywhere. It’s doubly bad on an outside wall as it compromises a wall section’s insulation and is hard to get a draft in a cold chimney. Never mind the fact that it gobbles tons of air an effectively dries the house out.
Don’t get me wrong, I’m sympathetic to the nostalgic aspects of a fire in the home as humans are instinctively drawn to fire. I grew up on a hobby farm with an air tight wood stove and had such strong memories from those days of yore that I installed an air tight insert in my own 1913 double brick home in the city. A mistake I regret now. Nostalgia played a part but so too did the delusion that in a power outage the neighbours would all be lining up at my door to warm their hands by the fire.
A comfy place of yore for the neighbours to hold out in a storm… is there WiFi?
Too Hot and too Cold
My house I should explain is a 16’ wide semi-detached, two and a half story double brick home built prior to WWI. With the exception of the wide multi-flue masonry chimney surrounding the insert, the main and basement levels were gutted and insulated to R18 and air sealed really well. The 2nd and 3rd floor walls are still uninsulated, yes I feel shame… Incidentally, the furnace thermostat is on the main floor adjacent the insert.
How does it all work? 99% of the time, there’s no fire burning and the mean radiant temperature on the main floor is evenly comfortable – except near the fireplace when it’s really cold and windy. Without a fire burning, the area around the insert is cold and drafty, not because of air leakage, but due to accelerated heat loss though the uninsulated masonry.
This is typical of fireplace retrofits in the city of Toronto. No one knows what to do to insulate the wall and air seal it. Most throw in the towel and don’t insulation and air seal any where near the unit, consequently, it’s cold to stand next to these appliances when not operating. See corresponding IR image below.
A vintage fireplace with walls recently spray foamed yet the bare brick remains behind the insert. This is typical in Toronto.
On a cold night with the fire burning and the little circulating fan whirring noisily, the main floor gets excessively warm, lulls the forced air gas furnace’s thermostat into shutting down for the night and the top two floors get really cold. Without power, the insert’s noisy blower motor doesn’t push and mix the hot air into the cold room air, so there goes my emergency plan for a cold day. The other issue is wood storage, we have no room for wood storage in the house and our back yard’s wood pile is an eye sore.
Days of Yore..
Burning biomass in rural areas might be acceptable and sustainable, but not in urban centres. In densely packed neighbourhoods, it would be like forgetting where we came from with the days of burning coal and streets littered in horse manure. If you think the pollution from a VW’s diesel engine is bad, try wood smoke with an inversion layer. Adding insult to injury, there’s no regulation guiding what you can and can’t burn for fuel. I have an old time neighbour who picks through other neighbours’ garbage for wood and thinks nothing of burning pressure treated lumber in his wood stove. He burns often and the neighbourhood downwind fills with smoke that is a health risk. There’s no place for wood burning in cities; ban all biomass burning appliances in densely populated areas.
CSA-F326: Safety trumps Efficiency
To the lay homeowner who wants a fireplace, they’re either dreaming of hanky-panky on a bear rug in front of a roaring fire or wanting to recreate that warm social place that brings people together. What they don’t appreciate are the huge energy penalties that come with an open-face Rumford fireplace, or even an air tight wood stove. The CSA-F326 Residential Mechanical Ventilation Systems standard was developed to prevent combustion appliances in the home from polluting indoor air but also to ensure that air tight homes gets a constant small stream of healthy fresh air for the occupants. This is a tall order to balance when you install lots of appliances that suck air out of the conditioned volume of the house.
The appliances that pull air out of the house include large exhaust hoods for the 6 burner gas range, bathroom exhaust fans, clothes dryers, solid fuel burning appliances, some natural gas appliances, central vacuums and possibly HRVs if not balanced. That ejected air volume has to be replaced and sometimes, the easiest source of replacement ‘air’ gets pulled in through a chimney. This phenomenon is called back-drafting which is a health hazard to the occupants.
What a make up air supply looks like for a large custom home. This system wasn’t designed to CSA 326 as it doesn’t warm the incoming fresh air.
The installer was kind enough to install a damper on this 12″ combustion make-up air tube.
To combat the possibility of back-drafting, the CSA-F326 standard sets about helping the designer calculate how much fresh air to bring into the house when certain appliances are switched on. Incidentally, that incoming fresh air has to be heated, usually electrically, which gets expensive. Ironically, the home owner thinking their saving money on heating bills by making fire may be paying exorbitant electricity bills while basking in the warmth of the fireplace.
To the mechanical designer, there’s a paucity of acceptable make-up air systems on the market to make homes meet the CSA-F326 standard. To the installer who has to realise the designer’s instructions, they have to get creative in finding ways to switch on the make-up air which gets expensive too.
Here a gas chimney touches a supply duct in an attic and gets spray foamed with 2lbs foam, a potential fire hazard.
You’re only as strong as your weakest link
Thermally, the weakest link in many new homes is the wood burning appliance. Forget the fact that combustion makeup air has to be added and they introduce a steady cold draft in the vicinity of the firebox. The subtrades may not interpret the manufacturer’s installation instructions and err on the side of caution so tend to not insulate well near fireboxes and the continuity of the home’s air barrier system also suffers. This is true even for sealed natural gas fireplaces. With the many sections of chimneys often not sealed the skin surface area becomes a significant and large area of the house’s exterior envelope that has no R-value.
The effort and expense that went into making this double faux-flue chimney could have been put towards a more optimised building shape, better insulation detailing and air sealing. The flues say “classic wood burning homestead”, but the aluminum vent cap at the height of the stone/brick transition tells us its a gas appliance. See below for closeup.
The chimney flues are capped with mortar, sorry children, Santa won’t be coming this year…
In a nutshell, if you’re looking for a very comfortable home that can withstand long power outages, put your money on exceptional envelope detailing that’s air tight and has nearly twice the R-value of a ‘Code Built’ house. Turn off the Wi-Fi, pour some tea and pull out a deck of cards anywhere in the house event after a few days without electricity.