Moisture intrusion puzzle

Trying to help a builder friend out on a new construction and wanted to see what the nachi brain trust thought.

This window had some substantial water damage to the Drywall directly under the interior sill after a driving rain storm. It was all bubbled up in the spot where he Made a cutout. I got there 4 days after the storm.

-He noticed standing water on the exterior sill.
-There is spray foam along the Inside of the exterior Wall.
-The loose fill insulation was damp when I looked at it.
-Moisture meter read as high as 16% in the drywall right next to the opening
-header and sides of frame are totally dry and didn’t show anything on IR when he looked after the storm.

  • There are two very small holes in the exterior sill. Looks like what would happen if a finish nail was driven upwards through it.

Guess where the builder’s shortcut was taken?!!

There shouldn’t be any holes in the bottom sill or standing water. As JJ eluded to, probably improper flashing also. Combination of issues here…

Thank you for sharing this article Jeffrey. I read the entire thing.

I’m still not confident in what shortcut the window installer took… I have some thoughts but nothing clear.

Could you please help guide this newbie further?

I’m wondering how the standing water got to the bottom exterior sill and stayed there… there is a gasket on the outer side of the sash on this window

What is this hot hot line inside the wall?
All that insulation and there still is heat entering under the window.
I suspect air.
All moisture is at the interior wall.
Is there a floor HVAC register under the window?

Condensation of outdoor air latent heat.

Just because the gasket is there doesn’t mean it’s sealing properly…

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Good catch David. It’s kinda weird to have such a small line of heat like that in a 2x and not be all the way across the width. Could be other issues.

I assumed the hot line was the sun beating down on the metal exterior sill and transferring through the wood frame sill… There is only a tiny amount of spray foam on the underside of the sill; the foam was sprayed along the inside of exterior wall and into the corner joint.

No HVAC registers near the window.

There is a whole house humidifier installed if that could have something to do with it…

Heat will not transfer through just one 2x in a window framed opening.

Lack of foam insulation will the the reason for air infiltration.

Don’t know where you are; so I can only guess about moisture levels.

No HVAC Register, but indoor air seems cool enough to cause temps below most OA Dew Points.

Whole house humidifier lowers humidity and vapor pressures. Low humidity and pressure causes accelerated moisture/air infiltration through the wall. The more moisture you suck out, the more that will pass through the building envelope.

Do not get tunnel visioned looking for liquid water intrusion, there are two other sources you must consider and eliminate.

What also happens when it rains?
Water vapor in the OA goes up, as well as the dew point temperature. Moisture is heat and will show up in IR as such. It will also show up as cool from evaporative cooling as a result of evaporation. De-humidifiers cause increased evaporation.

16% is not wet… but it will still show up in IR. That is why professional Thermal Training is a must…

Hi Jesse, It’s a little hard to tell from the photo but it looks like there’s a type of j-channel at the bottom of the virtical siding. From my experience it is very possible for a channel like this to act like a little gutter and deliver water to an unexpected place. You might consider taking a hose to the siding to the left of the window to eliminate it as a possibility.
Another high problem area is the flashing above the window but in this case it seems like it has a nice healthy overhang above.

Try this…

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Ugh, stupid photo uploaded rotated for some reason. You are correct Jeffrey that that is the correct orientation and it is horizontal siding, not vertical.

For starters…
1: Fenistation Sills or Thresholds must slope 15° degrees away from the fenistation.
2: Mechanical damage. Damaged sill flashing.
3: Insufficient or Lack of sealant between the window frame finishings and outer casement window.

Typically/usually the WRB and fenestration or penitration/protrusion are poorly installed and flashed.
Too bad.
So sad.
Been happening for melena. Keeps us working:-)

Didn’t see all these pics before. What the hell is this? It’s right outside the problem area.

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David… that may be an optical illusion as 1) the photo is 90 degrees off rotation, and 2) I believe that is a corner wrap-around window so is likely an optical illusion.

Oh OK. But that little gutter above the window and that black thing appear associated…

I believe it is a shadow from the frame that is actually running horizontal not vertical, as the glass is set-in and can’t be seen from the angle of the photo.
Guess we need the OP to confirm/deny, and hopefully has another pic that shows this phenomenon.

The window wraps around, so you’re seeing a bit of an illusion of something weird there at the corner.

One of the things I told him was that there shouldn’t be standing water on the sill and that it didn’t appear to be sloped down enough

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