MY husband and I will be spending six months in Florida and I would like to know what temperature you would recommend leaving our Winnipeg house at over the winter months to avoid cracking of drywall or other damage. In the past, we have set our thermostat to 15 C, but I wonder if it would be OK for it to be a bit lower to reduce costs. We are leaving in three weeks from now, so if you can answer our question, I'd be very grateful.
THERE may be no definitive answer to your question, but there are several possibilities depending on the type of systems in your home and its age. There are several things you can do to prepare your home for a lower temperature issue should you decide to go that route.
For the purposes of answering your question, I will assume your home is a typical Winnipeg home, heated with forced air natural gas and on city water and sewer. Because of this, there is less chance of problems with uneven heating due to power failures or other environmental concerns. This will minimize the first of several possible issues with lack of heat in the home -- frozen water supply pipes. Probably the biggest threat to your home when you lower the heat in our frigid winter are the water supply pipes. If the temperature nears the freezing point at any time, with static water inside the supply pipes, freezing is a strong possibility, especially in remote areas like the basement. If you have copper supply pipes, they will conduct and lose heat very quickly, increasing the chance of frozen water. They are also very thin-walled, so are likely to crack or split as the water expands while freezing. If you have plastic water supply pipes, like PEX, the chance of bursting from freezing is reduced, but leakage at fittings is still a risk.
To further eliminate the possibility of frozen water pipes, shutting off the water and draining the pipes may be your best defence. Shutting off the water supply is something that should be done anytime you leave your home for an extended period of time. This is critical, since the water supply is a pressurized system. That means there is constant pressure on the pipes, fitting, fixtures and seals that prevent leakage. When these things remain unused, especially for an extended period, they can fail. Seals may dry out on faucets, weak fittings may spring a leak, or other vulnerable areas may fail. If there is nobody in the home to quickly identify and shut off the water, major damage can occur. Because of the constant pressure, even a small leak can spray unabated for hours or days before it is discovered. If the main water supply valve is closed, any leakage should only last a few minutes until the pressure drops, preventing a major flood.
Draining supply pipes is much more of a concern for seasonal buildings, but should not be difficult to do even in your home. Opening up faucets throughout the home and in the lowest level, after shutting of the main valve, is all that is needed to accomplish this task. The only caution is if your home is older, the main valve may not close fully, allowing a slow trickle of water to leak continually. If this is the situation, a call to a plumber to replace the valve prior to your trip, or closing the faucets after draining, will prevent wasting water while away. The only other concern with draining your pipes is the seals in some faucets or valves are more likely to dry out and fail once you turn the water back on.
The next two issues of concern when lowering the heat is potential damage to wall coverings and condensation. These are largely dependent on the age of your house and how well it is insulated and sealed. In a home built in the last decade or two, insulation levels and air-sealing methods will ensure maximum heat retention when the thermostat is lowered. As long as doors and windows remain closed, there should not be significant heat or air loss, even in the dead of winter. This should allow you to turn the settings on your thermostat a little lower than normal, preventing a freezing situation should the power fail. The only drawback in this age of home is the lack of air movement from infrequent cycling of the furnace when the temperature is down. This may cause condensation on walls or windows in some remote areas, but may be minimized with a simple adjustment of the controls. Setting the thermostat so the furnace fan runs on continuous low speed will improve air movement in the entire house. That will prevent condensation from static air in problem areas.
If your house is older, air leakage through older windows, doors and ceilings is more of a certainty. That will make the chance of any adverse effects from low temperatures much more likely. To combat that, you may want to keep the thermostat cranked a little higher to prevent problems.
For a simplified answer to your question about thermostat settings when you vacate your home in the winter, a setting below 15 C will be possible, but is dependent on the age and condition of your home. If your home is newer, well insulated, and especially if you have a monitored alarm with a temperature sensor, leaving the heat at 10 C or slightly lower may possible. If you have an older home with poorly sealed windows and middling levels of insulation, leaving the thermostat at 15 C may be a better choice to prevent problems.
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 emailed to the address below. Ari can be reached at (204) 291-5358 or check out his website at www.trainedeye.ca.