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They didn't intent to put in "Exterior Ventilation" - they retrofitted the home with blown-in insulation. It's possible that they used UFFI in the exterior walls and the slits in these caps helped the UFFI off-gas and cure more quickly, but I don't think the intent is to ventilate the walls. If the intent were to "ventilate" the walls why wouldn't we have it in every wall of every home?

We see retrofits of blown-in a lot here. Many times the plugs are solid and when you poke your finger behind you find cellulose. Many times the plugs are slitted like those and you poke your finger in there and you find UFFI. Sometimes you find the ventilated caps used for both types - sometimes the solid caps are used for both types.

You are correct, painting the slits in the caps reduces their "ventilation" ability, but it doesn't seem to make any difference in building performance unless water is actually getting into the wall and it usually isn't getting in through those.

ONE TEAM - ONE FIGHT!!!

Mike

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I've never seen those vents as an indication of added insulation. They're typically installed in areas where the paint persistently blisters, due to vapor getting trapped behind the paint "skin". The vapor doesn't have to be from water entering the wall. These are usually older homes without any type of vapor barrier.

Subsequent repainting always results in the vents becoming blocked. A simple metal wedge at the bottom edges of siding panels can be quite effective and not as likely to be completely blocked with paint.

bsi028_photo_04.jpg

From http://www.buildingscience.com/document ... enclosures

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I've never seen those vents as an indication of added insulation. They're typically installed in areas where the paint persistently blisters, due to vapor getting trapped behind the paint "skin". The vapor doesn't have to be from water entering the wall. These are usually older homes without any type of vapor barrier.

Subsequent repainting always results in the vents becoming blocked. A simple metal wedge at the bottom edges of siding panels can be quite effective and not as likely to be completely blocked with paint.

bsi028_photo_04.jpg

From http://www.buildingscience.com/document ... enclosures

Agreed, but not here.

I used to see siding wedges all the time back east but I've never seen then here and never seen a need for them here.

ONE TEAM - ONE FIGHT!!!

Mike

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I've never seen those vents as an indication of added insulation. They're typically installed in areas where the paint persistently blisters, due to vapor getting trapped behind the paint "skin". The vapor doesn't have to be from water entering the wall. These are usually older homes without any type of vapor barrier.

Subsequent repainting always results in the vents becoming blocked. A simple metal wedge at the bottom edges of siding panels can be quite effective and not as likely to be completely blocked with paint.

Agreed, but not here.

I used to see siding wedges all the time back east but I've never seen then here and never seen a need for them here.

That's interesting. We have lots of houses with blistering paint issues. Every winter, I see several where I can poke a hole in the water-filled blisters and have water pour out from behind the paint. You don't see that in your area?

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Hi Jim,

Yeah, I've seen the blisters before but I don't think they're indicative of an unusual condition for our neck of the woods. The houses where I've seen them didn't appear to have any moisture issues in interior walls, no warped window casings, no odor, nadda. Old houses, normal vapor drive to the exterior, film-forming paint and you can have a few blisters but there's really no need to ventilate the walls - at least not here.

I remember seeing some of the jobs where my Dad went out to investigate wet walls back east. In the winter, vapor would move outward through those old walls, condense on the back of the siding and literally coat the back of the siding with ice. Dad would 'wedge' those walls to make them dry better.

Down here in the Western corridor we just don't get that kind of weather. The number of nights a year that temps get low enough to cause that kind of condensation are probably in the single digits. Now, go 45 minutes east up in the Cascades or head out to the Olympia penninsula and you could see entirely different conditions. Oh, by the way, they closed Snoqualmie Pass ten minutes ago 'cuz they've had 11 inches of snow up there since this morning. Down here, we had a little rain.

The OP is in Northern California. The last time I drove through that area in mid-winter it was like mid-April is around here. How often do temps go really low there? Isn't that the coastal forest zone? I think he's got walls that are retro-blown and I don't think it's necessary to ventilate them. Maybe I'm the only one that thinks that.

ONE TEAM - ONE FIGHT!!!

Mike

Edit: Oops, strike that. The news just showed a video of I-5 in Arlington, 40 miles north of here. Apparently the snow is coming down heavy there. Nothing here but maybe we'll see some by morning. Hope not, a half inch of snow here paralyzes King County and they start whimpering about the "blizzard" conditions. If we get an inch or more, customers will probably start cancelling inspections because they "can't get there."

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Funny Mike. Same thing here. Half inch or so of snow and they start closing the schools and workplaces. Having grown up out in northwest Nebraska and walking a mile of so to school (uphill both ways) when there was SEVERAL inches of snow the night before, I find it strange. But, to each their own.

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Most of the houses I see are below 300 feet and within 5 miles of the ocean. Snows this low maybe once every other year an inch or two and lasts about an hour. Above 1000 feet it snows 10 to 30 times. I go inland about 30 air miles and up at 4500 feet there is a 4 foot snow pack for a month or more usually.

My wife who does independent insurance claims work sees burst pipes from cold weather once in a while. The number one claim for house damage is water and that us usually from water heaters, ice makers, and dishwashers.

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