A new house (with insulation between rafters) would normally have provision for ventilating the roof above the insulaltion. This would typically consist of air inlets along the eaves and outlets along the ridge. This ventilation presumably has two purposes: first to prevent condensation accumulating on the underside of the sheathing, and second to reduce the flow of heat through the sheathing and roof surface, and thus reduce the melting of snow and consequent formation of ice dams on the roof.
Is a ventillating system necessary or worth the labor and expense in a summer cabin located at 8,800 feet elevation in the Colorado Rockies (not a humid environment)?
The cabin is accessible only for six snow-free months, normally mid-May to mid-November. At other times it is closed down and unheated, therefore the ice-dam problem seems unlikely.
The only heating is occasional morning or evening fires in a wood-burning stove in spring and fall, with fires kept on all day for a few weeks in fall. When the stove is not in use, the cabin stays close to ambient temmperature outside. When the stove is in use, the humidity inside is very low, therefore the condensation problem seems unlikely to arise.
So, is it necessary to ventilate? Comments? Advice?
Replies
The short answer is no.
You can prevent warm moist air from condensing on or in your ceiling cavity by installing a vb prior to intalling your finished wall product, be it drywall or wood or whatever.
Gabe
Humidity doesn't come just from the environment; a lot is produced by the occupants and their activities.
I agree that burning a wood stove will dry the place out pretty well; but if you're boiling a bit pot of spaghetti in the kitchen, it's going to put back an enormous amount of w.v. into the air in short order.
Question: Are you SURE the place is only accessible in no-snow conditions? Do back country skiers / snowmobilers / snowshoers travel in this area? Is the cabin locked down tight for the winter or left open as an emergency refuge (and to prevent squatters from breaking stuff to get in anyway)? Might YOU one day decide to do a back-country ski trip to your cabin...?
If you're going to the trouble to insulate the ceiling/roof, I'd say vent it. Raft-er-Mate-type polystyrene moulded panels go in fast and don't cost much, but they don't provide as much venting as the old standard: 2x2s nailed in the rafter/roof corners, with black joe nailed to them. This gives you 1½" clear vent space only 3" narrower than the bay itself, and should be sufficient even in your area.
Two footnotes:
Dinosaur
'Y-a-tu de la justice dans ce maudit monde?