Zip system assembly

Hi
I am currently building a house in Montreal Canada wich is cold in winter and very hot and humid in summer.
The wall assembly is:
– brick
– 1 inch air gap
– R6 zip system sheating
– 2×6 wall with R22 rockwool
– Vapour barrier
– strapping 3/4
– gypse
we install the wool and the vapour barrier inside and we closed the construction site for 2 weeks for christmas
we were using propane to heat the place. we were around 60% humidity inside and between 7 to 10 deg C
When we came back, we finally had electricity so we could proper heat the place so i put some heater and 2 deshumidifier to reach 35% humidity and 25 deg celcius to dry everything out
after a 3-4 days, i regulated the heating to normal like 20 deg celcius
Note that it was really cold and humid during vacation and also after until now its still really cold
I noticed a bit of condensation between the zip sheating and the rockwool. enough to make the wool a bit wet. i took out the wool in that area a dry with ventilator for 24 hour before putting the wool back in place.
it was fine for a day but after 2 days, the condensation is back but less, like the wool is not wet but its humid.
We still have heater at 20 deg celsius and dehumidifier is working and we have 25-30% humidity
Note that the vapor barrier is a 6mm polyethylene but its not sealed.
Is it normal since it was cold inside all vacation and it will take time to regulate the humidity since outside is really cold?
thanks a lot
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Replies
caronsbuild,
I would have expected to see a bit of condensation on the sheathing for a few reasons, and I wouldn't worry about any of them.
- Before the interior of the walls is complete - that is the poly is sealed and drywall installed - warm interior air is able to make its way through the batts and once cool condense on the sheathing.
- Although your interior air is now in the 30% RH range, the construction materials are all a lot damper, and will be for some time.
- In cold climates like Montreal's you do get some moisture accumulation in the exterior sheathing during the winter. This dries in the spring, and unless it is very severe causes no lasting damage.
I understand
Thanks for your info!
Might I ask how you used propane to heat the place? If it was by unvented combustion within the structure there would have been significant water vapor created by the combustion process that you're now getting rid of via dehumidification. About 1.6lbs of water vapor are created by the combustion of a pound of propane.
Hi
There was a bit of a window open and 2 ventilator working!
It was well vented yes