Wet Artic

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Posted by: from Calgary
1/23/2012 at 6:07:40 PM

We had a cold snap here in Calgary last week. Water drips through the bathroom vent this week as it warms up. I climbed up the artic to have supprisingly found water dripping off the underside of the roof. And I mean the entire roof surface dripped like rain in my artic. Roof sheething was either soaking wet or still heavily frost.

What happens? And what can I do?

I moved into this house 2 yrs ago and it seems every time after the cold snap, my bathroom vent leaked. Thinking that ice built up at the roof vent and melt from bathroom heat and and running down the hose; no big deal. I was so wrong! The problem must have been there ways before I purchased the house.

I did hire an inspector when buying the house. His advice was to add more insulation but no mention of any water damage. It was summer then. What and how bad is the damage?

Could someone help advicing me what to do?

Thank you so much in advance

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Date/Time1/23/2012 at 7:09:49 PM

If you have frost inside your attic there is too much moisture. If any of the bathroom or kitchen exhaust fans or leaking into the attic, that's one source. The most likely cause is no air flow through the attic. They are designed to be vented and the same temperature as outside,

The air comes in the sofit vents (by your eavestroughs) and out the roof vents near the top of your roof. If any are blocked or not big enough you will have a moisture problem.

More insulation will not solve the problem. A roofing or insulation company should be able to solve the source of your problem.

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Date/Time1/23/2012 at 9:04:41 PM

James is correct. It would appear that you have insufficient ventilation in your attic. Air must flow freely from the soffits and out through roof vents close to the ridge beam and there must be enough of both to ensure sufficient ventilation.

In addition, you should ensure as much air ceiling as possible of any penetrations into the attic space.


Kingsway Construction Inc

Glenn Rosborough

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Date/Time1/24/2012 at 7:14:49 PM

Was the vent installed proper on the roof, are the shingles layed out proper around the vent and is the vent the right one for your bathroom?

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Hung in Calgary
Date/Time1/26/2012 at 2:09:13 PM

Thank you so much for responding. And I can't believe how quickly you guys responded too.

I re-posted on the 24th, but for some reason I didn't see it showed up. I waited for a day just in case of site software update but it wasn't. I'm re-posting again.

My house is:

-Quite new, 10 yrs old

-Insulation is blown-in Celulos, about 6-10"

-I see 2 roof vents near the ridge

-There are 2 bathroom vents with insulated hose connected to the roof

-I see cardboard attached between rafters to prevent insulation falling into sofit space


I have not venture to the edges to see if sofit spaces are blocked. Neither I've gone to the roof to see if roof vent is thru.

How do you check & evaluate if ventilation is adequate? Is there simple method? must I hire someone and who would that be?

Leakage from ceiling:

Water dripped from one of the bathroom fan. This must be where the leakage is; but I looked and the surronding hose area is covered with insulation. Does this consider sealed? If not, how much leak must there be to cover the whole roof with frost and was melting and dripping. Roof sheething was soaking wet. It was the most frightening scene in my life as it was almost like raining in my artic.

This may goes back to ventilation; as if ventilation is working, moisture from leakage would have been blown out of the roof before it frosts? Well, it's my thought, and you may see how low it can be :- )

Is there method to detect leakage from ceiling other than the 2 bathroom vents?

Should I hire an inspector?

Note that I hired an inspector when purchasing the house 2 yrs ago and The only comment then was to add some more insulation. He went no further into the artic than half of his body intruded through the ceiling with a flash light. Also, it was the summer, the artic was nice and dry then.

It the same for me as I was no further into the artic than that. I called him for help and left a message but have not received a response yet for 2 days. Well, he may treated like a liability call and may never reply :- )

Thank you so much for your responses

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Date/Time1/26/2012 at 4:02:45 PM

Hi Hung,

You have a tough situation. James, Glenn, and Grant have all given you excellent responses and you seem to be developing an understanding of how your attic and insulation should function.

Your last post added some great information to work with and there are probably a few things you can do yourself to diagnose and possible repair your situation.

Roof and insulation in general - The minimum ratio for venting is 300:1 - in other words for every 300 sq ft. of attic, you should have a minimum of 1 square foot of venting, 1/2 at the bottom (soffits) and half at the peak (ridge, mushroom, whirlybird, etc) This is to allow the attic to breath properly and get rid of excess humidity before it condenses. Your attic would be about the same square footage as the floor below. The current recommended level of insulation is R50 - you have about R18 and should consider topping up as the inspection indicated. The insulation should have a vapour / air barrier underneath it, on the warm side. It should be continuous and all penetrations through it (plumbing stacks, exhaust fans, pot lights, light boxes, etc) should also be sealed to prevent hot humid air from going into your attic. This is extremely difficult to do with the insulation in place but it can be done. You can check your venting by going in the attic in the daytime and giving your eyes some time to acclimate to the dark. When they do, you can look for light through the roof and soffit vents. If you can't see anything through the baffles to the soffits, the insulation installer probably filled them when he was blowing it in. You should be able to see how many roof vents you have - if they are the mushroom style, they count for about 50 square inches each - you can do the math for your roof.

Exhaust fans - they should be vented through the roof, not just to the roof. You should see the exhaust fan vents from outside the house, looking up onto your roof - they DO NOT look like roof vents. The ducts should be sealed and have a horizontal run, sloping down from the fan, of at least 2 ft before turning up to the roof. This allows the air to build up some momentum before hitting the turn and gives condensation a place to settle before running back into your house. You should have a timer on your fans and run them an extra 20 minutes or so after a shower - this will ensure any residual moisture is exhausted.

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Hung in Calgary
Date/Time1/31/2012 at 4:53:12 PM

Hi all,

I went to the artic for the first time :- )

Everything seems to be in order. I see light comes in from most of the edges of the house.

I have 3 roof vents around 8x8" near the ridge. This is the size of the fixtures. The size of the openings are smaller (50-70%). the openings are actually holes that were knocked in by a hammer. They were not cut by a saw and definitely not to size. If using 8x8 and for all 3 vents, I got 1.3 sq-ft of roof opening. If only count the opening of the holes in the OSB sheething; it's only 3/4 of sq-ft.

My artic is about 1000 sq-ft; according to 300:1 ventilation ratio rule of thumb, I need at least 3 sq-ft which means the roof vent requires 1.5 sq-ft. Thus, it look like I have only half of the requirement.

My roof has 4 sides. It would be complied with 300:1 rule if builder installed 1 more vent on the 4th side of the roof. And cutting the roof sheething square with a saw would be nice too. And yes, cut to size of the vent would be a plus :- )

Insulation wise, I have at least 10" all around. Surpassing the ceiling joist of 2x6 and 3/4x5" brace nailed on top and across of the 2x6 joists. There is a plastic vapour barrier below the insulation. This explains why my ceiling is not damaged by water seeping through. I'm so glad.

To meet R50 requirement, I need to double up the thickness which may surpass the baffle guard for the soffit.

Is there a different way? Could I use the fibre glass style which may reduce thickness for the same R-rating? The existing blown-in can be moved to lay down the fibreglass and then put back on top.

Exhaust fans with 2" hose and insulated, do go through the roof; although, they are only run 4-6" horizontal before turning up to the roof.

The house is 10 years now, I suspect that the builder won't come back for warranty service eh! :- )

I will add insulation in the summer to allow time for the artic to dry up. It experienced winter rain after the cold snap.

I wonder of installing an addition roof vent this winter.

Thank you all for your help as you guys are extremely helpfull.

Could or should I post this as a project?

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