Excessive condensation on windows resulting in mold growth

renewablesnow-renewable energy advocate — Fri, 18 Jan 2008 21:27:52 GMT

My two story home is 2,000 square feet and is 8 years old. This past Spring I removed fiberglass batt insulation in the attic and basement sill joists and replaced it with blown foam (Demilac)- FYI- I donated the 8 year old fiberglass to the area Habitat for Humanity ReStore. I also renovated part of the home and used Demilac to insulate the new construction.

I have two full baths- only one had an exhaust fan. Now both full baths have high efficiency Panasonic exhaust fans that properly exhaust to the OUTSIDE (not the attic space). I replaced the cooktop fan to be a unit that exhausts outside.

The furnace is a closed combustion unit. The water heater has a power vent. My main source of heat is cord wood in a soapstone wood stove (I desire releasing current carbon to heat the home and not releasing fossil carbon for heat). Until recently I have NOT been cracking a window to supply replacement air for the wood stove.

I have been using Comfortex insulated blinds on my windows which are double pane argon filled double hung. I monitor temperature and moisture content on each floor, outside and in the attic. The relative humidity inside the house is between the low 30's and high 40's.

The condensation on the windows in the morning when I raise the insulated blinds this Winter is significant. If the outside temperature is in the teens or lower, when I raise the insulated blinds on the sliding glass door, there is a significant amount of ICE on the interior glass and wood frame. Interior ice is also found on north facing windows.

If I don't keep up with removing the condensation every morning - mold grows. I have noticed that mold growth is happening on the window frame itself and is streaked in such a way that makes it obvious that air infiltration is happening between the window and the frame. I believe that replacement air is coming through the windows since I have air sealed the sill joists in the basement and in the attic and part of the home that was renovated.

I was originally considering a heat recovery ventilator. Will this type of unit solve the condensation issues?

Can an HRV solve any negative pressure issues I may be experiencing due to exhausting water heater, clothes dryer and bathroom fans to the outside as well as the 15CFM the wood stove uses?

Have the seals in my 8 year old windows failed?

Should I install an outside air kit on my wood stove?

I am curious to some feedback to how to resolve the significant condensation on the windows. I dont want to stop insulating the windows using the insulating blinds- as it is clear they are making a difference.

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Excessive condensation on windows resulting in mold growth