Preventing Condensation in Enclosed Porch
Hello, we built a new home and have an attached 20x20ft covered porch. We are in Ontario. Just west of Ottawa about 200km. Climate zone 5 I think.
I did seek advice from the GBA community on this home build and thanks very much!
The issue we are now having is the covered porch was intended to be a 3 season room with the ability to warm it up in the winter if we wanted. So it’s 2×6 16OC with r24 Bibs and R10 GPS sheathing. R70 blown in ceiling, r21 CC spray foam floor, then r21 batts between joists, then r10 gps board covering joists, then soffet. Floor is open on 2 sides floating about 2ft to 10ft off the ground as ground slopes under it down to our backyard. It’s on screw piles on the floating side and icf foundation walls on the home side.
Most of the 2 outer wall are big sunscape screen windows so a thin poly window. Very leaky. No r value. The room has a good sealed wood burning fireplace with fan, and a small electric heater.
So here is the issue. We are using it more then expected in the winter. When we warm up the room frm minus 15C it takes 5 hrs with a fire. Then when it cools, water is condensing above the ceiling vapour barrier. We have water puddles above the ceiling vapour barrier. They turn to ice until was warm it up again. We want to change out the windows to triple pane casments so we can still open up the screen room in the warmer months. Then warm the room permanently to maybe 10 or 15C and warm it up a bit more when we use it.
Would anyone have a solution. I think the floor is insulated sufficient. Would anyone add more to the floor? Enclose the floor to keep wind out? Heat loss it dominated by the windows that need to be changed. Would anyone add a minisplit for heat and air conditioning?
Thanks so much
I will try and post a picture
NOTE: The area in the pic that looks like batts in the ceiling is under our bedroom. Behind those r20 batts is 4 or 5inches of CC sprayfoam. That’s why there is no vapour barrier in the spot.
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Replies
Is the amount of water increasing? Could it be a leak in roof or plumbing? More pictures include some from outside. Drain water and see if it recurres.
Thanks for your thoughts. We will be in the ceiling with cameras and visual inspection for sure.
The roof is under a foot of snow right now, and no plumbing exists in the covered porch. It's a metal roof with hidden fasteners. Brand new. A leak is highly unlikely. For one, water is collecting in small isolated puddles all over the ceiling poly. The whole entire roof metal would need many small holes scattered all over to do that. Like it would need to be raining in the roof assembly.
The water only increases after we warm the room and let it freeze again. I'm confident this is condensation on the poly as the room temp, and therefore poly and insulation move to above dew point (22C last night) when we warmed in up, then fall to way below freezing again.
I hope this helps.
Thanks
How is the roof over the area vented?
Since the vapor barrier is the warm side air barrier, is it continuous and well sealed around the perimeter? Is the vapor barrier connected to the SPF under the bedroom?
If you are getting condensation above the poly, it generally means that warm moist air from the interior is getting into the roof and has no way to escape. When the space cools down, this condenses out and drips onto the poly.
Is the water all over the ceiling or just in some areas? You have a lot of roof/wall junctions which require detailed flashings. i still suspect you have some kind of leak from outside. Ice damming kind of thing. Your change in use makes things worse, more heating/chilling cycles.
Thanks for the input.
Akos, the roof is a full length ridge vent on a metal roof. Moore vents and soffet. We will need to get in there but it shouldn't be blocked off.
The vapour barrier is well sealed. We are going to look at it to make sure, but as far as I can see there is not a pinhole for air leak into the rooms assembly.
In my mind warmth is getting above the poly because heat goes right through the vapour barrier. The air up there is already laden with moisture so it's just the warmth causing a dew point?
Johnathan, the water is all over the ceiling in small puddles above the poly. No rivers, but doesn't seem to be running anywhere. I did see the construction of the and I think flashing was very well done but it is possible their is a leak. We will look for one once we get up there.
Darn, this seems like a big problem!
Again thanks for the input. Will inspect for ventilation and leaks.
Pinholes in the VB are not an issue. Either the venting is not working or you have some larger air leak from the house into the attic above the porch.
Looking at the picture, that is not a simple intersection with the room overhang into the porch roof, typically these intersections are hard to air seal properly. Hard to see, but the ridge cap doesn't look like a vented one.
If the air leak/venting is sorted out, the air in the attic space above the porch should always stay near outdoor dewpoint. Heating the poly will no effect this. This means even if the room cools down, you should not see any condensation (or just a very small amount) above the poly.
Thanks! Got it. So to recap, you suspect it is either air leak or vent obstruction. I will look into both with my GC tomorrow.
Thanks for the info. GC and I have looked and we believe it is the vapour barrier. As suggested above, it is complex to seal it given the bedroom above and steel beam down the center. There are many spots that warm air and vapour are able to get into the roof assembly.
So now we need to fix it. My first thought was to build down the ceiling with 2x4 and spray foam the entire thing with 2" CCspf. Air and vapour seal the entire thing tight as a drum. It adds R14 approx to the ceiling too.
I would appreciate any thoughts.