QUESTION: I own a 1-3/4-storey home with no basement, but a small crawl space. I installed a new high-efficiency furnace a year and a half ago.
Over this past winter, my tenant complained that it got very cold overnight in the house. I went to the house on several occasions in the evening and found that the house was a complete sauna -- the tenant had the heat cranked up to 30C. The tenant said that it wasn't until after midnight that the house got unbearably cold. He said that it's fine during the day.
I brought in the same man who installed the furnace and he said that everything is working fine. Could this overnight cold actually be happening? How can I stop it from happening again this year? Is there any way that the furnace could be cutting out overnight? It is an older home, built in the 1960s, and the tenant does complain that the doors are drafty even after I replaced the weather-stripping.
Any help would be greatly appreciated. Thanks, Richard May
ANSWER: There are many things that can go wrong with the various mechanical systems in our homes, but sometimes a defect can be suspected when nothing is wrong. This can usually be chalked up to either ignorance or misguided expectations by the occupants. This may be the case in your situation, but it could also be caused by improper settings or an actual malfunction.
Your description of the state of the home when you visited on various occasions leads me to believe that your tenant has unrealistic expectations about normal indoor temperatures during the heating season. If the home was anywhere near 30C, and the occupants were not walking around in bathing suits and sandals, they must be new immigrants from somewhere with a very warm climate. They may find our winter temperatures unbearable, and consequently turn up the thermostat to ridiculous levels.
Even very elderly homeowners, who may be understandably cold, rarely set the indoor temperatures higher than 23 or 24C. Any higher than that and the furnace may run almost continuously on very cold days.
If your tenant likes to keep the indoor environment very hot during normal daily activities, I can see why they may feel chilly when they become sedentary and go to bed. Even a slight draft from an older bedroom window may feel very cold to individuals not used to such extreme temperatures, especially when laying in bed. You may be able to minimize this issue by installing clear plastic sheathing on the inside of the windows, or suggesting your tenants purchase warmer bedding, but that may not be the real issue.
Keeping a home unseasonably warm during the heating season can have a real detrimental effect on the building. If the home does not have lots of attic insulation, excessive heating may cause several problems. A warm attic during the winter can cause ice-damming, premature roof deterioration or excessive condensation and frost buildup. This can lead to moisture damage in the attic or inside the home once the frost melts.
Your tenants may also be turning the thermostat up to maximum at night in a misguided attempt to keep the house warm. If so, the burners may be running for such a long time that they are straining the furnace. This will trigger sensors inside the furnace that shut of the gas valve to prevent overheating. This is even more likely if there is a lack of airflow to the blower, often caused by dirty air filters.
There is also a chance that the fresh-air intake or exhaust may be covered with ice or snow, especially if the furnace is constantly running. As the outside temperature drops at night, the furnace exhaust may freeze, partially blocking the vent and shutting down the furnace. Checking the area around these pipes on the outside of the home should tell you if this is happening.
Another possibility is a problem with thermostat function or settings. If you had a programmable electronic thermostat installed with your new furnace, it may be set to turn down the temperature at night automatically. This may have been inadvertently set by your tenant or the furnace installer, and not checked during the daytime by your HVAC contractor. I would recommend going through the program settings, cross-referencing with the owner's manual, to ensure that they are not set too low for the tenant.
If everything checks out with the thermostat, I would recommend adjusting your tenant's heating habits rather than the furnace. Even if they are paying the gas bill, it's unwise to heat a home above 25C in our winter climate. Adding more insulation to the attic and crawlspace and covering leaky windows with removable plastic may help, but only a more realistic indoor temperature day and night will prevent problems with your home and furnace.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the President of the Canadian Association of Home & Property Inspectors-Manitoba (www.cahpi.mb.ca). Questions can be e-mailed to the address below. Ari can be reached at (204) 291-5358 or check out his website at www.trainedeye.ca.
trainedeye@iname.com
