Cavity wall insulation

techpro wrote:

Insulating blocks could refer to any number of lightweight concrete blocks used for the inner leaf - it does not mean the cavity will have any other filling necessarily.
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John.

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Thanks. I didn't know that's what that could mean. I thought it referred to actual insulation within the cavity, such as I have seen being used in houses being built recently (looks like some kind of expanded foam with a foil backing.)
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techpro wrote:

Often they use "cavity wall batts" for that - can be full fill that take all the cavity and are made from rockwool or similar. Or they can use a partial fill of a PIR foam like celotex. This is a ridged yellow board usually covered with foil on both sides.
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John.

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techpro wrote:

I don't think you have understood my post - there is no obligation for a builder to install cavity insulation - houses are being built today - now - without CWI and it's perfectly legal and above board, so long as the walls meet the U value requirements which they can do without insulation.

It proves that they issue CIGA guarantees, which is the industry standard
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Phil L
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I did understand the post. I thought the document we unearthed meant that the builders claimed to have installed it. Now it seems it just refers to the inner wall of the cavity...
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Phil L wrote:

But it's virtually impossible to reach the U-values required without some form of additional insulation in a cavity wall construction. Even with the best aerated concrete block, the best U-value will be about 0.7W/m^2K. This is the upper limit for any _part_ of a wall; the average must be no more than 0.35W/m^2K, and in reality for a conventional spec-build volume housebuilder to to achieve a DER anywhere near the TER, the walls would need to be somewhere around 0.25-0.28W/m^K.
Of course, if you're building a house that will have Kevin McCloud crawling round it, then you can make use of biomass boilers, sun-spaces, photovoltaic cells, etc. to reduce you carbon emissions to the point where it doesn't matter how much heat the walls leak. I just can't see it being built by Persimmons or Barratts.
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techpro wrote:

'insulating blocks' probably means something like thermal breeze blocks used for the inner leaf, not something inserted in the cavity, in which case you can have cav wall insulation too.
After the first couple of years you can only claim against the NHBC guarantee if the house actually falls down.

Well, no. All of that can be bought on Ebay.
Owain
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snipped-for-privacy@hotmail.com says...

There was a survey done in Aberdeen, AFAICR, that was designed to show how inefficient the old stone housing was. Using a thermal camera they "protographed" the heat leakage. They then went to new wood-framed houses only to find all the installed sheet installation stopped at the now-higher-level of the electricity sockets, with nothing below. Some had complete sections missing...
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John W
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techpro wrote:

The 2000 regulatins were very exacting insulation wise.
Its a con.

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techpro wrote:

When you say the house was built in 2001; was this closer to the start or finish of the estate? With any change in requirements, there is a lag between when the initial notice was given to the Council, and when the building was complete, and this can be up to three years from deposit to starting the work, and then as long as it takes to complete. The rules on this have tightened up in the last decade, but a big client for the NHBC can still get around this.
Up until about 1995, it was possible to achieve the U-values without cavity wall insulation by relying on a mix of double-glazing and aerated concrete blocks. In 1995, U-values were lowered (better), and I don't recall seeing any houses or extensions built to these or later requirements without some form of cavity wall insulation.
Cavity wall insulation is either built-in during construction or injected after. Built-in types are mineral-fibre batts (Rockwool) which fully fill the cavity, or partial-fill types such as expanded or extruded polystyrene (white, pink or blue boards) or polyisocyanurate or phenolic foam (Kingspan, Celotex, et al - usually dull yellow with foil on both sides). These leave a residual cavity of between 25mm-50mm. Injected insulation is either loose mineral fibre (white or yellow), foam (which sets solid), or polystyrene beads.
You may be able to see evidence of the cavity insulation (or lack of) around service penetrations (meter cupboards, badly-sealed gas pipes, etc.), or at the head of the cavity in the loft.
Even if you have partial-fill insulation in the cavity, you shouldn't go injecting any more. Partial-fill insulation isn't designed to prevent water tracking across it, and rely on a residual cavity to keep the inner leaf dry.
However if you do have a clear cavity with aerated blocks, you can still benefit from cavity insulation. It should lower the U-value from about 0.7W/m^2K to 0.35W/m^2K, reducing the heat loss through the walls by half.
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