We just completed construction of our timberframe home outside Calgary Alberta. We have radiant floor heating in the basement and a high velocity fan coil unit for the rest of the house. The basement walls are insulated concrete forms and the exterior walls are SIPs. This is our first winter in the house. Winters out here are typically long, cold and very dry.
Back in the spring I had stuffed fiberglass insulation in between all of the floor joists where they contact the outside rim joist.I did not put up any type of vapor barrier in these spots as I had never seen any put up in other homes. Needless to say I now have mold growing on the inside of the rim joist as a result of the trapped condensation. The bottom plate is soaked. When the mercury dips to the minus 20's and 30's (celsius) I get huge water on the windows.
Any suggestions as to cleaning up this mess, insulating the rim joist and dealing with wet frozen windows would be greatly appreciated.

Ian Mclean

Ian,
From my experience in the lake country of New York state our family post & beam frame (circa 1804-11) started to suffer from sill plate moisture invasion in winters to -20F. Over the years my brother and I had to selectively replace sections of the sill and the external waterboard below the clapboard siding. When doing this renewal we put moisture barrier from two courses of siding above the sill down over the sill and held in place by the new waterboards. We still had minor condensation on the stone foundation but not the rivers we used to have. My recent experience here in VA with northside (no sun) mold on both exposed wood and aluminum siding has created several lessons too.

Because of your northern latitude you can only do interior first aid until late spring.
Spraying with Clorox will help retard mold growth.
In the interior air space get a dehumidifier and an ozone generator air purifier running ASAP.
Scrub and wipe after your initial spraying then spray again. Wear rubber/plastic gloves to protect your skin along with some goggles for the eyes.

Not knowing the structual details of the wall/floor fit chat with some local builders about their techniques to avoid moisture penetration. The retrofit will not be easy or cheap.

I hope this missive is not discouraging.

deralte (aka Emmett)

Hi Ian,

It would be illuminating to see some digi pics of your problems.

Moisture migrates and condenses out preferentially on the coldest surfaces thus windows and particularily metal window frames become an obvious target for ice build up during winter. It can pay to have a deliberate cold surface area in your home where excess moisture will condense out in a controlled way thereby dehumindifying the air and reducing condensation problems elsewhere.

You should examine your floor plan to see what it is that is genenerating the moisture in the first place with the most likely candidates being kitchen (open plan), bathroom (shower) and people (breathing).

Ken Hume P.Eng. (Alta)

Vapor pressure is an amazing and powerful phenomenon and it may be that your box sills are seeing an unnatural amount of condensation (beyond the lack of a barrier) because it is presently that powerfully driven migrations path of least resistance.

Pull out the glass, it’s currently making matters worse and only acting as a sponge and retarding evaporation. When all fully dries out in the spring, treat with anti/mold/fungals and replace with rigid foil faced polyiso.

You made no mention of your enclosure system or a heat exchanger, but your condensation problems are telling. Your tight enclosure requires that you mechanically remove moisture, not to mention airborne pollutants.

Strategically placed dehumidifiers should help you get through the winter.

The above points are good,I would also consider moisture embedded into the house as a possible source problem that will lessen over time. Paint, drywall joint compound, wood but especially concrete can add moisture to indoor air. Perhaps, moisture is being released from the foundation walls and is escaping to air at the wall, sill and insulation boundry. Try to get relative humidity readings in the house and basement, and then vent or dehumidify problem zones.