I have a question about an outlet and a light switch at our cottage.
We have a winterized cottage in the Interlake and a year ago we had a door installed in an outside wall that goes out to our screened in porch. Last winter the electrical outlet and light switch box on that outside wall, close to the door, began dripping water as the outside temperature dropped.
Any ideas as to how we can fix that?
There are probably a few different ways to stop the dripping water from the electrical boxes, but I will deal with two methods that should ensure it is fixed. One may be considerably more labour intensive than the other, but may be a better option, in the long term. I will also attempt to explain the cause of the moisture.
Cutting open the exterior wall in your cottage to install the door has compromised the air barrier and possibly the vapour barrier, which is the likely cause of your problem. This was done by cutting through the exterior wall sheathing and building paper or Tyvec on the outside and the interior wall sheathing and poly air-vapour barrier, if present. To elaborate on this, we must explore the details involved in construction of a typical insulated exterior wall of a home.
If we hypothetically cut a cross section through the exterior wall in your cottage, as was done to install the new door, we should find this typical form of construction, looking from the outside in: Siding, building paper, exterior sheathing, fibreglass insulation between wood studs, polyethylene air-vapour barrier, interior panelling or drywall. The exterior sheathing and the building paper provide an air barrier that should prevent significant air movement through the wall, but will allow moisture to escape to the exterior. The interior wall covering and polyethylene sheathing provide a partial air-vapour barrier that also prevents air and moisture intrusion into the wall cavity. If these building components were properly installed then cold air leakage from the outside and warm, moist air leakage from the inside should be minimal. This probably worked well for several years until the recent renovations.
Once a large hole was cut in the “building envelope” in this area, to install the new door, the seal on the interior air-vapour barrier was damaged and the exterior air barrier had been torn open. Also, the insulation may have been partially removed or compressed in the area near the door and electrical boxes. This will also be compounded if the new door was not properly insulated and air-sealed between the door jamb and new studs, installed to accommodate the renovation.
The results of this damage to the building envelope may be much more cold air infiltration from the outside when the temperature drops. This cold air will hit the warm, moist air leaking through the interior wall covering from the heated interior. The moisture in the heated air will condense and freeze in the metal boxes at night, as the temperature drops. Then, the frozen moisture will melt, when the warm morning sun hits the exterior of the wall. This may go on continually until the outside temperature drops sufficiently to prevent melting of the frost in the boxes, or warms enough to prevent condensation.
The solution to this problem is to repair the damage to the building envelope, or exterior wall. As I stated previously, there may be two different ways to accomplish this task. The first method, which is the most difficult, is to remove the new door casing, baseboards, interior wall covering, poly, and insulation in the area around the door and behind the electrical boxes. The wall cavity can then be inspected to see where the defects are and appropriate repairs made by replacing torn building paper, caulking, and air sealing as required. Then, the interior poly air-vapour barrier can be replaced and sealed before reinstallation of the wall sheathing and trim.
The second method of repair is to shut the circuit breaker for the light and outlet, remove the light fixture and receptacle and drill small holes in the siding around the electrical boxes. Through these openings, and knockouts or holes in the electrical boxes, blow-in foam insulation can be injected to fill the cavity around the boxes. If completely covered, the foam will also provide and excellent air-vapour barrier and prevent air leakage and condensation on the metal boxes.
Depending on the difficulty of the first method presented, I would suggest going that route for a couple of reasons. Firstly, this will allow you to properly diagnose the problem, which is somewhat speculative on my part, having not seen the problem area firsthand. Secondly, the door installers may have inadvertently removed or damaged the insulation in this entire section of the wall and replacement would require removal of either the interior or exterior wall coverings. Fixing that defect would not be possible by simply blowing in a small amount of expanding foam. Using the second method, you may stop the condensation and air leakage at the electrical fixtures but not in other areas. You may now have to deal with more condensation and moisture issues along the bottom of the wall or other vulnerable areas.