Many clients ask what type of furnace or HWT should I choose to replace my current heating appliance. In Calgary we typically assume gas service so although there are many types of furnaces and hot water tanks, gas appliances generally fall into the two broad categories of direct (sealed) vent or open combustion.
Most furnaces and water tanks installed in the past 50 years were open combustion and they require two sources of air to be brought in from outside – combustion air and fresh air (for the home).
Recently the code changed so that only direct vent furnaces may be installed when replacing a furnace and for new construction. That’s good news because these furnaces operate at a higher efficiency of typically 85-95% compared to the older open combustion furnaces which operate around 65% efficiency. Theoretically you should automatically save 20% or more in efficiency by upgrading to a direct vent furnace, but it actually gets better.
Because the new furnaces are direct vent, they eliminate the (usually 6″ vent) supply of cold outside air freely entering into the furnace room next to the furnace. Unless your furnace room is insulated and sealed from the balance of your home (and they rarely are) then this outside air infiltrates your home unabated. So a great benefit of updating to a direct vent furnace is the elimination of this combustion air that freely enters your home. You will still require a fresh air supply for the home fed into the furnace, but this directly enters your return air duct and becomes blended with heated air as it flows through your system, so it usually does not cause the nuisance of cold basement floors, etc. that the combustion air causes which is fed to the open furnace room.
But what about the hot water tank? Good question, because unless your HWT (hot water tank) is also direct vent or electric, you will still be required to maintain that supply of fresh combustion air into the furnace room to service that appliance. If you are due to replace the HWT then seriously consider a direct vent or electric HWT as this will allow improved efficiency in the heating of your hot water while allowing the benefit of reducing cold air infiltration that we described above. Electric tanks are less popular locally because of the higher cost/btu of electricity, but the savings in heating and lesser cost of an electric tank could offset this. In fact many builders have reverted to incorporating electric tanks in their standard spec in Calgary.
The range of selection for direct vent hot water appliances ranges from direct vent (40-75 gal) tanks to tank-less, instantaneous water heaters. There is much debate on which is the better option, but without going down that rabbit hole I suggest that if you decide on an instantaneous heater you should also couple it with a storage tank.
Another important and often overlooked piece of equipment is the type of blower used in the furnace. There are two types of blower fans used in modern furnaces run from AC or DC electric motors. Newer model DC motors operate at 40 to 85% higher efficiency than conventional AC motors and operate at variable rates of speed. This more readily allows continuous operation of the fan to provide more comfortable air circulation in the home. DC fan motors are highly recommended and can make a significant difference in your monthly electrical bill, so if you are replacing your furnace you would be wise to ensure it is equipped with a DC motor.
Aside from all the benefits mentioned above regarding cost savings the benefits of eliminating the combustion air extend to a more comfortable, draft free environment and the potential bonus of more room if this is coupled with removing the (brick or metal) chimney and chase. Of you plan to leave the chase intact perhaps it could serve as a mechanical chase for a future solar electric or solar hot water system.
Additional benefits can also be derived from installing a good set back thermostat. Our current favorite is the NEST but the competition offers some great products that may be a better fit and the available choices increase every day. In any event, check with your contractor to ensure compatibility.
With all the benefits discussed above, we hope that upgrading your furnace will be an easier decision, but if you have any questions don’t hesitate to call the team at Sano Stante Real Estate at 403-289-3435 or [email protected]