Home Weatherization in the Pacific NW Series, Part 1: Myths and Maintenance
This month I want to pass along some valuable weatherization tips to our clients and homeowners living in the Pacific Northwest. To me, no one offers better advice on this subject than my friend, Don Hatch. Don has spent the last 16 years inspecting prospective homes, giving guidance, and providing answers in his business, PDX Inspect. We asked him to share his best advice with you in this two-part series to help our clients protect their most personal of investments—your home.
– Lee Davies
With winter officially just a couple weeks away, you’re no doubt thinking about weatherizing your home against the cold snap. If you’re a veteran homeowner, you may think you have all your bases covered on the home weatherization front. But did you know that those home weatherization tips gleaned from most websites and magazines, are geared for general and national audiences, and could actually be detrimental to your home, here in the greater Portland area?
That’s because what may work in Michigan or New York could be exactly the wrong kind of advice for those living here in the Northwest.
A Home Weatherization Myth
In fact, an example of a popular myth or Old Wives’ Tale that could spell trouble in the Willamette Valley during the winter is that,“You should close your foundation vents in the winter and then re-open them in the summer.”
Although there is some validity to the idea of keeping a home with un-insulated floors warmer by closing the foundation vents, the truth is that closing your foundation vents in Willamette Valley homes during the winter can be an unknowing path to thousands of dollars’ worth of damage. A wiser alternative, to save money on heating bills, is to consider installing insulation to any un-insulated floor or un-insulated piping.
2. When the outside temperature is going to be continuously below freezing for greater than a 36-hour period.
Pro-Tips:
- If your plumbing piping is insulated, there is no reason to close your foundation vents. The only reason to close your foundation vents is to protect un-insulated pipes from freezing.
- It rarely freezes in the Willamette Valley—usually there are 2 to3 days a year that are constantly below freezing, and our winters are very wet. In areas like Bend, Grants Pass, and Klamath Falls, where they do have a hard winter, you should close your foundation vents for the winter. These places do not have wet winters, because their precipitation is snow instead of rain.
- Closing the foundation vents will trap moisture and water vapor in the crawlspace. The foundation vents are meant to allow this moisture to escape. Wintertime in the Willamette Valley is the worst possible time to close the foundation vents, because it is the wettest time of the year.
- The natural decomposing organisms in wood that begin the rot and decay process are active at around a 20% moisture level. Termites and Anobiid Beetles need a minimum of an 18% to 19% moisture content in the wood to be able to live or infest. The normal range of moisture in a well-ventilated home with a continuous waterproofing or vapor barrier during the summer is 12% to 14%. The normal wintertime range is 14% to 16%. Areas of the crawlspace that have limited or poor ventilation, such as areas behind garages, where there are no foundation vents, or areas where the plastic vapor barrier has been pulled back, can easily have up to a 2% higher moisture level than the rest of the house. Closing the foundation vents for more than 3 to 4 days can increase these moisture levels by 2% to 3%. Closing them for the winter will raise moisture levels to well over 20%. Anything above 17% is considered to be a high moisture level and will lead to damage.
Next Month:
Part Two: Home Maintenance Schedules — Small Investment, Big Payoff