|
| Author |
Message |
SubArcticGuy
Member
|
# Posted: 11 Apr 2013 10:36pm
Reply
It is not my cabin but my house...but I have seen some good advice on here and I hope to find some more.
My house is a 26x40 single story with a basement. We live on the 60th parallel so temperatures can be in the -30C for 5-6 months. I have vaulted ceilings with very little ventilation. The roof is composed of (from bottom up) drywall, 1x4 strapping, vapor barrier, 2x8 joists (3.5 in 12 pitch), pink insulation in the joists topped with a pink fiberboard (I assume about 1.5 inchs) that takes it to the top of the joist. The roof is then strapped horizontially with 2x4 and sheeted with plywood and shingled.
I never noticed any problems for the first couple of years, but when I replaced the old wooden windows with triple pane vinyl windows we started experiencing problems. Now in the spring as soon as the roof gets warm we get water steady dripping in around the frames of most of our windows. This year we also have been getting a bit of water around one of our interior doors as well. I have investigated this and the issue appears to be the lack of sufficient ventilation on the top of the roof. The air can only move laterally along the 40' of 2x4 strapping and then into the gable ends.
I have tried adding extra vented soffit and whirlybirds at the peak to try and move more air. But the small airspace near the whirlybirds is completely packed with frost.
I have inspected the inside of the house with a thermal imaging camera in -40C temperatures and found two spots each about the size of my hand that are about 10-15 degrees colder on the interior where there is obviously a fault in the insulation.
So the way I see it I can either rip off the top of the roof including the sheeting and build up a 2x4 roof on top of it and rebuild the fascia and soffit. I also might add 1.5" of rigid foam between the 2x4 horizontal strapping.
My other option might be to pull down the drywall and add more strapping and then sprayfoam the inside and re-drywall. My concern with this is that I still have the poorly vented airspace on the top side of the roof.
Any suggestions...I need help!!
|
|
ICC
Member
|
# Posted: 12 Apr 2013 12:48am - Edited by: ICC
Reply
Quoting: SubArcticGuy ---pink insulation in the joists topped with a pink fiberboard (I assume about 1.5 inchs) that takes it to the top of the joist. The roof is then strapped horizontially with 2x4 and sheeted with plywood and shingled.
Question about the pink fiberboard. do you mean pink rigid foam insulation board? Any way to confirm the thickness?
And is it on top of the rafters or joists as you called them?
|
|
SubArcticGuy
Member
|
# Posted: 12 Apr 2013 01:17am
Reply
It isn't foam, just a rigid compressed fiberglass board. I am not sure of the thickness. I haven't confirmed the thickness of the joists either. I think I may pull down a section of ceiling in the bathroom this weekend to see how bad the insulation is and to confirm the joist thickness.
|
|
Martian
Member
|
# Posted: 12 Apr 2013 07:24am
Reply
My thinking is that the solid panels are trapping moisture and preventing it from reaching the vented space. My suggestion is to rip off the roof (down to the rafters) run 2X4's on top of and parallel to the rafters, and reroof. Leave a space between the ends of the 2X4 spacing and a horizontal 2X4 at the ridge for air to flow to your whirly gigs or use ridge vent. Make sure you have good air flow from the soffits.
The solid panels above the insulation are trapping moisture in the fiberglass. The moisture travels up through the insulation and hits the panels. There is no where for it to go from there.
Your new windows don't allow the house to breathe like the old windows did. Now more moisture is migrating into the insulation.
Tom
|
|
toyota_mdt_tech
Member
|
# Posted: 12 Apr 2013 09:01am
Reply
How about tearing off the roofing ridge cap, expose the sheathing. Cut it back about 1.5" on each side with a saw set to 1/2" and then add the ridge vent. Do this the entire length of the roof except the overhang of course. Then top it off with roofing shingles. The cap can be the real nice plastic, its got a grille on it so bees cant get inside etc.
|
|
ICC
Member
|
# Posted: 12 Apr 2013 10:14am - Edited by: ICC
Reply
Quoting: SubArcticGuy It isn't foam, just a rigid compressed fiberglass board.
the 'fiberglass' panels sound like some sort of structural roof sheathing but it hard to say just what? If it's an inch and a half thick it sounds like a ZIP panel or something similar. ???
martians solution may solve the venting problem if soffitt and ridge vents are in place. Part of the questions though is whether or not you actually have enough insulation in that roof for the climate? If the rafters are 2x8 it is my opinion that is insufficient.
the air space above the roof sheathing is doing no good at all, it is a puzzle as to why it was installed like that ???
Does the inner side of the roof have any vapor barrier just above the drywall? so going up from drywall it would be drywall - vapor barrier - rafters ---- etc. it can be difficult to install an unbroken vapor barrier, one that does not allow moisture laden air to move up into the rafter spaces. venting with at least an inch of air space above the fiberglass can help but for the sever climate it is not the best solution. My guess is there will still be condensation and possibly moisture freezing to the underside of the roof sheathing because of the climate extremes.
There are solutions that work, they cost more, but work well, save energy costs and make a building that will last longer.
|
|
SubArcticGuy
Member
|
# Posted: 12 Apr 2013 03:24pm
Reply
I have only seen the top of the fiberglass panels so I am not sure of the exact construction. There is a vapor barrier behind the drywall but in the few spaces I have exposed during renovations leads me to believe it is not the best sealing job I have ever seen. The house was not build by expert carpenters (and there is no such thing as building inspecters in my nect of the woods....we do have an electrical inspector but he looked at my electric furnace with a perplexed look and said "that furnace has a lot of wires". He had never seen the inside of an electric furnace.
The big issue is that the 2x4 strapping under the sheeting is running perpindicular to the pitch so that the air has to flow up to 20' laterally through an 1.5" space.
I think if I put a 2x4 roof on top of the existing joists and have that ventlilated with a ridge cap I could be alright. I may have to replace a bunch of insulation though.
The Persist method looks interesting, it might be worth pricing out...(fortunately my father-in-law runs a large commercial insulation business, I will have to get his input as well).
|
|
ICC
Member
|
# Posted: 12 Apr 2013 05:45pm - Edited by: ICC
Reply
Quoting: SubArcticGuy I think if I put a 2x4 roof on top of the existing joists and have that ventilated with a ridge cap I could be alright.
maybe i misunderstood, but i thought the roof system went like this from top down ---
shingles
plywood
2x4 horizontal
the fiberboard sheathing or whatever it is
pink fiberglass insulation batts
vapor barrier
drywall
if that is correct and you rip off the shingles and sheathing and the horizontal 2x4 and then install 2x4 running up and down the roof parallel with the rafters, that will not help the condensation problem. Venting between the fiberboard sheathing and the upper plywood just makes the fiberboard cooler. That does nothing to vent the moisture that is being trapped in the rafter bays where the finberglass insulation is. To properly vent the venting must be under the fiberboard and above the fiberglass insulation.
Maybe remove the top shingles, 2x4 horizontal and the fiberboard to expose the rafter bays and insulation and then apply 2x4 on top of each rafter to provide air space and venting. Then sheathing and shingles. but if you go to all that trouble i'd seriously look at improving the insulation with rigid sheet foam, r35 worth as the literature recommends for your climate
http://www.greenbuildingadvisor.com/blogs/dept/musings/calculating-minimum-thickness- rigid-foam-sheathing
scroll down to the section called -- Is there a similar chart for unvented cathedral ceilings?
http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_8_par100.htm
scroll down to
TABLE R806.5 INSULATION FOR CONDENSATION CONTROL
you are climate zone 8 i believe, maybe a 7
|
|
|
SubArcticGuy
Member
|
# Posted: 12 Apr 2013 06:59pm
Reply
Thanks for the feedback...I was trying to find that chart last night but had no luck. I am basically right on the 7/8 boundary.
Just to further clarify, the pink fibreboard is not a sheeting product. It is nested in the rafter bays. I wonder if it might just be to give the batt insulation some extra thickness. I may pull a section out tomorrow to have a better luck.
At least I am slowly making progress towards a solution. A couple of more warm days and the water should stop pouring in too... .
|
|
ICC
Member
|
# Posted: 12 Apr 2013 07:36pm
Reply
Maybe it is one of the rigid fiberglass products. ???
|
|
ICC
Member
|
# Posted: 12 Apr 2013 07:46pm
Reply
OK I got ther roof layers now, somedays i'm slow on the uptake. then turning the 2x4 and fastening them to the rafters will provide vent space, as long as there are soffit vents and a ridge vent that should help. question is whether or not it will be the best roof and amount oif insulation for the climate.
|
|
ICC
Member
|
# Posted: 12 Apr 2013 07:48pm - Edited by: ICC
Reply
more for thought , zone D = 8 and C = 7
note that cathedral ceilings are allowed to have less insulation than a flat attic floor/ceiling. i think that os only because it is a concession to it being harder ti insulate a cathedral than a flat ceiling (attic)
|
|
Martian
Member
|
# Posted: 12 Apr 2013 08:13pm - Edited by: Martian
Reply
If you buy 6" flange-headed torqx screws and screwed the 2X4's on edge, you'd gain another 3.5 inches.
I'd have a tendency to spray foam up to the top of the rafters, then put the 2X4's flat on top of the rafters, do the decking, make sure you have sufficient soffit and ridge vent, and reroof.
One thing heat loss will do for you is set up a good airflow. Any heat that migrates through your insulation will rise out of the vents if you give them a path.
Another advantage of laying the 2X4's flat is you won't need new fascia boards.
Tom
|
|
|
