Older furnace doesn’t necessarily require replacement
QUESTION: I recently had a problem with my furnace that turned out to be a worn out sensor. While the man from the heating company was here he noted because my furnace is 15 years old I should seriously be thinking about replacing it, soon. The furnace is a Rheem Criterion two, mid efficiency gas furnace, in a typical 50’s bungalow. It is serviced and cleaned regularly and the filter is changed every couple of months. The only other issue with the furnace was a wire which needed replacing a few years ago. I called Manitoba Hydro to see if they could do an unbiased inspection and let me know the condition of the furnace. They said I would have to call a heating or electrical place, but they all sell furnaces. Is the fact that a furnace is 15 years old grounds for considering replacing it? Also, are there any Winnipeg companies that do furnace audits and don’t sell furnaces? Thanks so much. Sincerely, Mindy B Answer: Upgrading a furnace to a newer, high efficiency unit will depend on several factors, with age being one of those criteria, but not the only one to rely upon. Other items that must be taken into account are recent home upgrades, furnace location and condition, and economic considerations. We will explore these and others, while discussing your specific situation. While not the most critical of all the factors to be considered while deciding on whether to upgrade your older furnace, age is certainly important. Even more critical than knowing the age of the current heater, is determining the normal life expectancy. For some older, standard efficiency furnaces with cast iron burners and high quality heat exchangers, that could be in the 30 year plus range. For some lower quality units, 15 years may be nearing the end of the road, but most of those furnaces would be long gone by now. For your mid-efficiency unit, 25 years is a reasonable time frame to expect the furnace to operate properly and safely, if well maintained. That is not to say it won’t last 30 years, or develop a damaged heat exchanger and need to be junked before the 20 year mark, but planning for an upgrade in that range would be practical. Another factor in deciding whether to buy a new gas-fired furnace is efficiency. Many older models, built in the early 1980’s or earlier, had efficiency rates in the 60 per cent range. That means that 40 per cent of the fuel input is wasted, mainly from exhaust going up the chimney with dilution air from the basement. Mid-efficient units like yours are often 80 per cent efficient, or slightly higher, so are a considerable improvement over the older ones. New furnaces, which are all high efficiency models, have ratings of 90 per cent or higher and waste very little energy by venting mainly water vapour through PVC pipes to the exterior. To upgrade from a standard model to a new High-E furnace makes sense regardless of condition, because fuel savings would be considerable. That’s not the case with your mid-efficiency unit, as the extra 10 per cent or so would not be a sufficient economic inducement to replace a furnace in good condition. Evaluating recent home improvements or upgrades is the next step in deciding whether to make the switch to a newer gas-fired furnace. If you have recently taken advantage of various government incentives and recommendations, you may have newer windows and insulation in your home. Not only would those upgrades have improved the energy efficiency of your home, and made it more comfortable, they would also have tightened up the building envelope. That will prevent air leakage and normally create a more humid environment inside your house. Upgrading from a mid-efficiency furnace, which vents through a traditional chimney, will further increase the relative humidity in the home by removing that natural vent to the exterior. If you do decide to change your furnace, upgrading or adding bathroom and kitchen exhaust fans, or installing a ventilation system (HRV), may be needed to take care of that extra moisture. A less critical, but often overlooked, area to explore is the location of the furnace for venting of the new High-E model. Since the new furnace is normally vented horizontally through the top of the foundation wall, location can be important to prevent the need for other modifications. If the furnace is beside a foundation wall where the exterior is too close to tall fences, neighbour’s homes, garages, sheds, or thick vegetation, installation of the vent may be tricky. If the furnace is near the centre of your home, with drywall ceilings and finished basement walls surrounding it, other renovations may be required to install the vent pipes in a proper location. The final item to address is your question about locating an impartial entity to determine if your furnace is truly in need of replacement. You have already discovered Manitoba Hydro is reluctant to inspect furnaces to see if an upgrade is required. However, they may come and evaluate the safety of a unit, if a contractor has suggested a damaged heat exchanger, or other defect, has made the unit unsafe for operation. You are correct to assume that some HVAC contractors will give you a biased evaluation because they may benefit in recommending upgrades, but not all. I suggest calling two or three contractors, preferably small independent ones not tied to larger franchise operations, to check your furnace. Trust technicians who evaluate other criteria, and not simply age, in determining the need for a change. Just because a furnace is 15 years old should not imply it needs to be upgraded, if it is in good working order and well maintained. Finding an HVAC contractor that takes this approach may not only answer your questions, but provide a more reliable company to do your furnace maintenance in the future. Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the past president of the Canadian Association of Home & Property Inspectors — Manitoba (cahpi.mb.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out
his website at trainedeye.ca.