QUESTION: I recently came across one of your articles on wintering your cottage and I have a question concerning this topic. We purchased our first cottage last year on Lake of the Woods. Last October, I had a plumbing contractor come out to winterize the cabin. They drained the waterlines, septic line, the hot water tank etc. Before leaving, we turned off all the electricity and heat.
In January, I decided to check on things and noticed all of the windows and metal door handles were completely frost-covered. I've read many articles on condensation, however, I am more confused than ever, as I come across articles and people who say inconsistent things. Some people say to leave all the windows open a crack, for air movement, while others say don't do that because the moist fall weather will add humidity. Some people say don't heat your place during the weekend you winterize, as it will create a drastic change in temperature, especially that time of year. Yet, I have also read heat will help dissipate the moisture. Some people say leave a bag of charcoal to absorb the humidity.
Our cottage was built in 2007, has baseboard heat and is insulated. The windows are dual-pane PVC. My family used the cottage the weekend we winterized it. Certainly, that would have added moisture to the air. The cottage was heated for that weekend and then the heat was turned off. I know the temperature that following week dropped below zero. My feeling, based on what I have read, is the weekend we winterize, I might not want to occupy the cottage: leave the heat off and maybe run a dehumidifier for the day and leave the windows open a crack. But at this point I am just guessing. Is this necessary to prevent the frost?
Thanks, Rick Kaczmarz
ANSWER: This may seem like an odd time of year to be addressing the issue of closing up your cottage for the winter, rather than opening it up for the summer, but it may be the perfect time to plan ahead for the fall. Since we have just come through one of the coldest winters on record, with lots of frost, moisture and condensation issues, I feel this topic is very timely while that is still fresh in our memories.
You have touched upon one of the many areas of home maintenance where there may be numerous and varying opinions. I can empathize with your frustrations, because there is no cut-and-dried answer to your question.
While it does make some sense to prevent using the cottage in the days prior to closing it up for the winter, that may only help to prevent adding moisture to the air and building materials inside by using the plumbing fixtures. Heating up the air inside the cottage may seem like a bad idea, but should have little effect on the amount of frost buildup you see in the winter or spring. It is true increasing ventilation during the winter, if possible, should reduce your issue but that may be difficult. Leaving windows open a crack will certainly increase the amount of fresh, dry air that enters the cottage, but also may let in blowing snow or unwanted rodents. If the screens on the windows are fibreglass or nylon, mice or squirrels may find an easy way into the relative warmth of your summer home.
Because your cottage is like many, constructed right near a huge body of water, relative humidity in the outside air may be very high all year round. Even with the lower temperatures in the fall before close-up, the air inside and outside will contain a large amount of moisture. As soon as this air drops a few degrees, you will get condensation forming on areas such as windows. If there is decent air movement and some relatively warm temperatures inside, this will evaporate, especially during sunny days. The problem is this process will reoccur as soon as the temperature again drops, normally that same evening. When the temperatures drop below freezing, this condensation will freeze and may stay that way until there is a significant thaw, no matter what you do before shutting down for the winter.
The key may not be trying to dry the air inside prior to turning off the heat, but reducing it once the building is sealed up. Your suggestion of using a mechanical dehumidifier may offer some relief, but you will have to make accommodation to drain the reservoir and may require a few trips out there to ensure there is no malfunction and to shut it off prior to freeze-up. A better option is to try to get some passive ventilation that does not require frequent supervision. Leaving windows slightly ajar is one option, but will leave you vulnerable to moisture, pest and security concerns, as previously noted.
A better option may be to install an insulated fresh-air intake duct, with heavy duty metal screen over the openings, to introduce drier winter air into the building. However, this may only work well if you have another opening to let the damp indoor air out at the same time.
The simplest method to ensure some moist indoor air exits the living space in the cool, fall weather is to have an opening near the top of the building envelope. While I am not advocating cutting a hole in the attic or roof, many cottages have a wood stove or fireplace installed. While it may not be obvious, these wood-burning appliances have a natural vent, in the form of the chimney. Leaving the damper open, and any doors on the front ajar, will provide a good passive channel for air to escape by the natural "stack effect." This method has served me well for many years in my own cottage, but you must ensure you have a proper metal pest screen at the top of the chimney to prevent any critters from gaining access. This integral vent may not completely prevent the condensation and frost buildup, but may minimize it so it does not create any serious moisture damage, while eliminating your dilemma about heating the inside prior to closing.
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.
trainedeye@iname.com
