- GoldenHas donated $ to the upkeep of GPL
The little bit of residential work I dabble in, we do Rigid out-sulation, taped seams, spray foam, etc. no humidifier needed.
I run an HRV 20-minutes every hour. Some days I will run it at constant low speed. This morning when I woke up, it was 32% in my house. It takes a lot to get it down into the 20%s. When outside air temps are in the negative teens or less for more than a day, we might drop to 26%-28%. We replaced half our windows 2 years ago with brand new Marvin windows. They still have condensation of the edge of the glass. Our older windows have frost and ice, a good 2″ up the glass and covering some of the sash.
It is all about dewpoint. If the glass is below the dewpoint in your house, they will show condensation. If the temp of the glass drops low enough, it could be frost/ice. My father’s 1950s house needs a humidifier, I had constant nosebleeds in the winter growing up, everything was static-y… No frost or ice on his old windows.
In Canada, they have even gone to triple pane glazing on some of their commercial and residential projects. We have done that on one project, and it was in Northern Minnesota. It just isn’t common here yet.
Get some outside fresh air coming in, either an HRV, running a bathroom or kitchen exhaust fan for awhile, etc. I would recommend keeping your furnace fan running (provided you have a variable speed motor) to keep air moving as well. Ceiling fans help to move the warm air as well, box fans can really only push air towards a few windows at once…
When it drops do double digits below zero, you’re likely to get condensation/frost unless your humidity is very low, or you have some ultra high performance glazing.
67 indoor temp with 40% RH gives a dew point of 42 degrees. Meaning anything less than 42 degrees will likely have condensation on it.
I keep my house at 64 at night, and with our 32% RH, dew point is 33 degrees. When it is -10 degrees outside, its a good chance my glass is less than 33 degrees. If we could drop our RH to 20%, Dew point drops to 22 degrees. However, I cannot get our RH below 26%, that’s the lowest I have ever seen it running the HRV constant with frigid outdoor air.