Friday, January 3, 2014

Warning: Insulated blinds can cause damage in winter

These blinds are causing condensation problems in an Ontario home.

When my wife and I bought new blinds for our kitchen, we bought ones which trapped a pocket of insulating air when lowered. This style of blind, ours are Duette by HunterDouglas, insulate our large kitchen windows when lowered each evening.

Thick ice at bottom of window after an extremely cold night.
By insulating the windows, the temperature of the inside surfaces of the kitchen window glass is now much colder than in previous winters. This is causing condensation to form at the bottom of each window. Last night the cold dropped into record low territory. In the morning we discovered condensation had turned into thick ice at the bottom of each kitchen window.

Some of the paint has already been damaged and is flaking off. The windows are almost thirty years old and are of the older wooden variety. They are not plastic. This constant soaking threatens to rot the wood surrounding the windows, especially the wooden sills. We may need replacement windows sooner than expected.

An unintended consequence of using insulating blinds is the condensation problem.

Homes are getting to be quite complicated. According to an architect I know, modern builders and renovators are not really up to speed on the pros and cons of the newly designed and redesigned stuff they are installing in homes. Water resulting from condensation is not just a problem on cold windows but often forms unnoticed deep within walls and ceilings, according to this architect.

"Keep the heat" in has become almost a mantra but the research, backed by good science, needed to accomplish that goal is sadly lacking. You may be keeping the heat in but also trapping structure damaging moisture at the same time. In many cases, "keep the heat in" should be accompanied by the words "let the moisture out."

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