Talk:Cavity wall insulation

A bridge for moisture
If cavity walls are built as a barrier to moisture, what stops the insulation bridging between both walls and negating the barrier effect? --ML5 (talk) 09:58, 2 June 2010 (UTC)

A circular plastic disc clamped on wall-tie holds insulation panel firm against inner wall with an air space gap to outer wall (basically) Soviet99999 (talk) 18:36, 23 February 2021 (UTC)

Vapor-blocking effect
If the cavity is filled with a material impervious to vapor, one would think that this would prevent the movement of vapor toward the outside of the wall. Ideally, one would want an impervious vapor-barrier on the inside of a wall, to keep the vapor from migrating into the wall, and then condensing adjacent in the cold, outer part of the wall. The rule is that the vapor barrier should be inside, and vapor-permeable materials should be on the outside, so that the walls remain dry inside. That is necessary to inhibit rot and mold, as well as to protect certain insulation materials such as cellulose and glass fiber.Docbnj (talk) 15:22, 24 March 2015 (UTC)

Masonry walls have to breath all the way through. From inside the house through inner leaf(wall) and insulation bat and air space gap  through outside masonry leaf (wall) into outside atmosphere Soviet99999 (talk) 18:21, 23 February 2021 (UTC)

Houses originally built with completey hollow cavity walls are 100% perfect as they are.Nothing must be added to cavity later on(it would be detrimental to building),they must remain completely hollow wall cavities Soviet99999 (talk) 18:33, 23 February 2021 (UTC)

Sources/Physics or Architecture expertise needed?
I came to this wiki looking for more information on the points mentioned in talk above. In discussions in the past I've been told that insulation is often a bad idea, and anecdotally I've seen numerous cases where it has resulted in worsening damp conditions after cavity filling has been implemented, or where cavities have been otherwise filled... with trash (crappy builders).

Surely there was a reason why buildings were built with cavities in the first place; It makes logical sense, since a layer of air would act as an insulator and the gap would also serve to allow moisture going either out or in to condense and go out through the ground.

Buildings constructed with completely hollow wall cavities are 100% perfect as they are. Nothing must be later on added to a cavity wall of a building originally made with pure hollow wall cavities
 * it would be severely detrimental to building.

They must be left with there completely hollow wall cavities (as originally built (with) Soviet99999 (talk) 18:28, 23 February 2021 (UTC)

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Recent changes
The 3 types of cavity wall insulation BAT (rectangular panel)   ( Fibreglass, mineralwool or polyester fibre)   are placed in cavity wall against inner leaf (wall) ,and held firm against inner leaf (wall)  with a circular plastic clip that clamps onto metal cavity wall-tie. There has to be an air space gap of 3/4 inch from showing face of insulation BAT to inner edge of cavity wall-tie drip point, plus a continuation of air space gap to outer leaf (wall) Soviet99999 (talk) 09:50, 23 February 2021 (UTC)


 * I've reverted a number of edits on this talkpage from, not because of the content, but because they were scattered all over the talkpage and repetitive. Soviet99999 is encouraged to leave comments in this section, so they can be followed.


 * Please note that "cavity wall" is a broad term, with somewhat differing usage between India, the UK and North America. A masonry cavity wall is something quite different from a framed cavity wall. The article is mostly set up to reflect UK usage of the term. In North America a cavity wall would be framed with wood or metal framing, with fiberglass or mineral fiber or sometimes sprayed foam or high-density cellulose in the framed cavity. If a masonry veneer is present, there may be a layer of rigid foam or mineral fiber insulation on the masonry cavity section, separate from the framed cavity. If it is an all-masonry wall, there will be a layer of foam or mineral fiber between the two masonry wythes. Except for semi-rigid mineral fiber, fibrous insulation is never used in a masonry cavity in North America. Ar least in North America, the term for fibrous blankets is "batt."


 * Statements in the article need to be very specific about local practices, and must have published references.  Acroterion   (talk)   13:11, 23 February 2021 (UTC)

Some references

 * Brick Institute of America Tech note [
 * Masonry Advisory Council
 * An Indian source, which appears to reflect only Indian practice - "no foundation is needed" would not apply in other climates
 * Another Indian source, which reflects some of Soviet99999's comments about ties
 * UK-specific discussion   Acroterion   (talk)   13:52, 23 February 2021 (UTC)

Please include my contribution Soviet99999 (talk) 16:03, 23 February 2021 (UTC)
 * Please provide your sources.  Acroterion   (talk)   17:00, 23 February 2021 (UTC)

Sprayed foam is wrong to do in masonry walls. wals have to breath Soviet99999 (talk) 18:11, 23 February 2021 (UTC)
 * It depends on the circumstances. Open-cell spray foam is used in circumstances where a vapor barrier is not desired. In cold climates, or in hot climates where the interior is air-conditioned, a vapor barrier is often required to avoid condensation build-up. Spray foam is widely used in North America.  Acroterion   (talk)   18:16, 23 February 2021 (UTC)

Cavity wall Insulation
It is wrong to use sprayed foam in masonry walls. Masonry walls have to breath all the way through Soviet99999 (talk) 18:14, 23 February 2021 (UTC)