It's Raining in My Attic!

Performed inspection August 15 of this year. No issues found, no moisture, sheathing looked good. About 10 inches blown in cellulose insulation, insulation baffles in place.

The client called yesterday, freaking out because it’s “literally raining in my attic”. He’s not blaming me, but wants me to come by and give a professional opinion. I visited the house tonight.

Yep, the attic sheathing is saturated, water is dripping off the nails. It’s OSB, it’s wet, and some is turning black. This is on the North side only. Doesn’t seem to affect the south side, or the two end sides (house faces south).

Only thing I can think of is the baffles may be stopped up, or there is too much infiltration of warm air from house to attic (from can lights, attic access, etc.) The warm air hits the underside of the roof (the OSB), which is cold, and condensates.

I’m trying to give him ways to reduce this moisture. I can’t figure out why this didn’t show up at inspection, no blackened sheathing or indications of moisture problems. House was built in 2008

Any suggestions on what this freaked out homeowner can do?

Are you sure that the bathroom and stove vents aren’t exhausting into the attic?

Is there insulation over the attic opening?

Is there an attached, heated garage that may be allowing warm air into the attic?

good hints Dave

Great points to consider, thanks, Dave. The bath vents are extended to the soffits. Not ideal, but I see it a lot.

There is no insulation over the attic hatch. It’s more or less a 1 1/2 story, so the un heated garage has its own attic, as does part of the rest of the house. The two attics are not connected, or adjacent

There is an electric heat pump up there. I checked for loose duct, didn’t find any.

I told them to get a de humidifyer and stick up there until I can figure out what’s going on. I’m thinking they should seal the attic hatch,light fixtures, wire holes, etc. but just haven’t seen this issue this severe, unless it was ongoing.

Just because you see it a lot, doesn’t make it right :wink: If there’s soffit and roof or ridge vents, that moisture laden air will get sucked right back into the building envelope.

I’m thinking you’re exactly right. It’s all about sealing the attic bypasses and keeping that conditioned air from escaping into the attic.

These extremely cold temps, furnace’s/heat sources working like crazy to keep up with demand, & insulation voids are causing a lot of people to find deficiencies in their homes that they didn’t realize they had.

If you or any inspector’s out there (where applicable) do not have a narrative in your report about attic bypasses and stressing the importance of sealing them up, you should.

I had one a few years ago like this. It turned out to be inside air (with elevated humidity) escaping up the interior walls to the attic along with unbalanced attic air flow. Interior wall penetrations/pipe chases need to be sealed.

Additionally, not sure about your area, but we’ve had high winds as well, which “accelerates” things as there is more outside air being vented/transfered through the attic, which in turn sucks up & out the conditioned air through those bypasses. Also, as Linas kind of alluded to, if there is only a ridge vent or exhaust vent and no lower intake vents, this can make things worse as it will try and “pull” air from lower areas (which aren’t there), which many times ends up being from the inside of the house/conditioned building envelope.

I’m sure you mean the air handler ;-). Anyway, was it and the ductwork elevated/suspended or lying on the joists/insulation? If so, that’s a common issue as the insulation gets compressed and/or not what it should be in those areas underneath the HVAC systems/components. All those duct penetrations, if not well sealed, are attic bypasses too.

All good points. The ductwork is insulated, but laying underneath (for the most part) of the blown in cellulose. They are securely fastened to the air handler (thanks Joshua), and are secured to the vent boots. I didn’t notice any air loss there.

I’m thinking that the baffles, though in place, are blocked, and as mentioned, the ridge vent is sucking the conditioned air through duct penetrations, light fixtures, etc., as well as the loosely fitted drywall hatch cover.

Strange this must have never been a noticeable issue before. House built in 2008, no blackened sheathing from this occurring over the last 10 years or so. Possibly the house didn’t have as many occupants before, there are 2 adults and 2 teenagers living there now, which may add to the moisture load.

Thanks guys!

Do you have a thermal camera? I had some blocked soffits and venting issues in my own attic and I was able to find warm areas where the conditioned air was being sucked into the space. Insulating the attic hatch and sealing it up tighter was a lot of work but it has made a big difference.

any pictures of house and attic

That’s what I was wondering, If this has not been an issue before, what has changed? Did you need to cut the seal on the attic hatch for the inspection?

These were taken at inspection in August

The last one was taken last night.

I don’t have an IR camera, no need for moisture meter–the sheathing was literally dripping with moisture

There are simply two things happening here:
1# Objects below Dew Point Temp.
2# Source of excessive moisture
3# A combo of both

I do not see “upper ventilation” (in that one exterior picture).

What is the source of moisture?

#1 Check the building pressure with reference to the exterior.
#2 Do a blower door test to determine tightness of the building envelope.
#3 Use thermal imaging, with a blower door to determine the pathway of indoor air to the attic.
#4 There are air ducts in the attic. If Thermal Imaging does not show anything, do a Duct Blaster test of the A/C Duct system.

Anything else is “Just looken around” conjecture.

If you can’t find it. I always wanted to go to “Almost Heaven”! :wink:

Hard to tell from my pic, but there’s a Ridge Vent up there. Another concern is the right side of the house(in the attached pic) does not have attic access. The attic I looked at is above that octagon window. I’m afraid there’s going to be problems there as well. I told my client he needs to cut an access so we can look up there. Poor design, IMO.

Well, I could definitely use your experience and expertise up here, David.

I doubt me, or the client, could afford it. Don’t get me wrong, I realize he can’t afford not to either. That’s really what I’d like to do…a pressure/blower door test, just don’t have the equipment or training. I’d like to start with IR. I’m sure that will reveal a lot of these guesses.

I know my location states “Almost Heaven”. And it usually is. But the last few days it’s been cold as Hell!

And it was warm when you took those pics.
Are you sure that ridge vent is open to the attic. My guess is excess moisture build-up in attic along with lack of ventilation.

I’ve been saying this since he called me–inadequate ventilation, coupled with warm air infiltration from bypass.

I’m relatively sure the ridge vent is open to the attic. When in the attic, and looking up, I can see the foam that’s under the ridge vent. I cannot see daylight, but I seldom do. Maybe the ridge vent is clogged somehow?

I am less concerned about ventilation than the source of moisture.
You can’t ventilate your way out of this.
Increased ventilation increases moisture passing through the build envelope. and that aint good.

Just like you don’t pump water out of a wet basement. You stop the source first.

Are they running a whole house humidifier, or any other type of humidifier?