Moisture around attic hatch

I have ran into this a couple of times. Moisture stains around the attic hatch. One on a 8 year old house and another a 3 year old house. Why??? The bathrooms vent outside and the attic appears to be vented enough. Any Ideas?





Could be they have the humidifier cranked up. Indoor RH should be 30%-50%. I have had many calls this winter because of this. First thing I do is pull out my hygrometer and check humidity. Usually it’s too high. Was there mold in the attic???

What was the moisture content at the stained area?

No mold in the attic.

Moisture content around 15% but a couple of inches from the stain there was nothing.


by looking at that pic, it does not look like moisture to me. If you look at the right corner of the panel it is raised up a bit. that yellowish brown streak is probably dried up oozy glue from the strip they put in there to prevent cold air from coming out of the attic and into the house. I see this alot, most of the time the hatch is stuck shut because of this stuff. then you have to bang on it to get in. Might be wrong but that’s my guess, can’t zoom in far enough to be positive.

Not glue. Moisture test confirmed.

The seal is not on the hatch it is on the ceiling.

Here is a picture of the hatch in the attic.



Hi Lawrence
In my area the hatches are not normally stippled. The stippling could be preventing the weatherstripping from providing a good seal. Moisture in the household air could condense around the edge of the hatch and leave that water mark.

Well, with that pic, then I would agree with John’s guess. Sounds conceivable.

If you’ve got 15% moisture content on wood, IMO…that is not a big deal.


Might not be much but the home owners were concerned. 3 year old house that has been a nightmare.

They answered yes to my sign at the trade show on the weekend. More pics to follow.

Lawrence 009.JPG


You are right, Lawrence, there appears to be warm moist air leaking up into the attic and that is never a good thing. That yellow tar could be from smoking, BTW. They may need ventilation improvements, the rest of the house is tooo tight! :stuck_out_tongue:

With the price of energy rising like it is, no house is ever too tight. Just need to know how and when to ventilate the interior spaces.

Not Smoke.

The house is anything but air tight. Did a thermal scan and found endless air leaks, and missing insulation.


Looks like we need to learn some psychrometrics.

Yes, it is beyond Home Inspection, but when you start with the IR stuff you need to know it.

Did you obtain any psychrometric measurements of the indoor air I can work with?

Here’s a start!!

Dry Bulb- 74 deg
Wet Bulb-60 deg

Are these from Lawrence?

DB 74
WB 60
RH 44.0%
DP 50.711

Moisture will condense at 50.7 degrees F.
I think we can find that at an attic hatch in AB.

This looks more like Texas to me. :wink:

Caulk around the ceiling hatch trim and around the framing inside the attic hatch.

No, just a reading I got in an award winning architect’s building the other day. There was severe condensation on all commercial steel door stiles/sashes…I’m there working for the owner in litigation against the arch and builder. I think the doors were designed for the warm Gulf Coast of Texas though!!

…I called it at 43% RH.

Thought I’d give you some #'s to start with so you could begin the course.:stuck_out_tongue: :stuck_out_tongue: :twisted: :twisted:

David what do you want?

I did not get any Relative Humidity measurements but the inside temp was 20C (68F) and outside 5C (41F)

Another thing they did say is that the windows would freeze up when it was about -20C (-4F). They also just turned down the humidity in the house and have no idea what it was or what it is or when they changed it.


Here is a hatch that is completely wet and covered in mold on the backside. Nothing else in the attic is wet. Directly above the attic hatch…a turbine vent.