oh and why are these used?

[Brian_A.MacNeish]

@bmullen

Those little ‘vents’ were used in Canada in the early 70’s when people were having UFFI sprayed into their walls. The vents helped with the off-gassing and supposedly helped vent the walls. (I never understood that part)

If the UFFI is still in there, it’s likely shrunk and hard to find.

Bill Mullen

The 1" holes were usually cellulose, Bill. UFFI went in through larger, usually 3" or larger holes. If they did use 1" holes for foam in your area, folks got ripped off worse than usual.

[jcampbell (Jeffrey Campbell, CMI)]

very good stuff guys… never realized foam dated back so far…

[badair (Barry Adair, EIFSTX#39)]

Brian the “Brain” always has very informative posts…as with may others around here a GREAT asset!!!

[Brian_A.MacNeish]

@cwhite2

Temperature differential between exterior dewpoint & interior = condensation

The venting increases the flow of moisture laden (interior) air into & thru the building & condensation builds.

Am I close?

Right on!!! Putting more holes in a house loosens it up and allows more air flow from the interior into/through attics/walls.

This phenomenon will usually only happen with any severity in very damp/wet homes. In others, there may be bit of condensation which will quickly dry up when conditions change, some times within hours so it is never noticed.

[Brian_A.MacNeish]

@badair

Brian the “Brain” always has very informative posts…as with may others around here a GREAT asset!!!

:oops: :oops: :roll: :roll: Well, thank-you, Barry!! It’s good to be in the company of people with a passion for the industry. Now, if…nah…won’t say it!!

[jcampbell (Jeffrey Campbell, CMI)]

this particular home had a stream running through the basement…

[Brian_A.MacNeish]

@jcampbell

this particular home had a stream running through the basement…

Certainly is one of, if not the main, moisture source they are trying to deal with by venting the siding!!

[Raymond_E.Wand]

Brian

I have seen larger holes for cellulose less than 3" and even smaller (1/2’ to 1") for UFFI. Cellulose is dense and takes larger opening to prevent clogging whereas UFFI was a foam.

[Brian_A.MacNeish]

@Raymond E. Wand

Brian

I have seen larger holes for cellulose
The larger blowing equipment (gas/diesel engine powered) would require larger holes for the cellulose simply due to volume of materials being moved. For example, for attics, my large blower would blow up to 120 30lb bags/hr while my small unit would only blow 25-30 bags/hour. When doing walls with the smaller blower, we used 1" holes.

less than 3" and even smaller (1/2’ to 1") for UFFI.
You could probably do a decent job with 2" holes for foam but with 1" or smaller you weren’t following the best techique for foam. Foam wasn’t injected under higher pressures as are the fibrous materials. The better technique for foam was to use larger holes, slip a flexible house into the cavity and let the foam expand to fill the cavity under virtually no pressure as you slowly removed the hose. If you just had a 1" hole high in an open 8’ cavity, no hose could be inserted down into the cavity; the foam would just fall into the cavity, not necessarily expanding to fill all voids.

Cellulose is dense and takes larger opening to prevent clogging whereas UFFI was a foam.

With high air/material ratio settings for cellulose using small equipment, you can blow cellulose through 3/4" holes.