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How long does cavity wall insulation last?

Discussions around pros and cons of the various materials and installation procedures.

How long does cavity wall insulation last?

Postby CRogers77 » Mon Jun 13, 2011 12:05 am

Hi,

Sorry if it's a stupid question but once you install cavity wall insulation, does it last forever? If not, how long before it has to be redone and is redoing it as easy as doing it for the first time?

Thanks
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Re: How long does cavity wall insulation last?

Postby Angib » Mon Jun 13, 2011 8:01 pm

In principle, yes, it lasts forever. But there are some practical issues - for example, some types of insulation bead are so light that they seem to get 'wafted' out of the top of the cavity in strong winds. If your loft has some mounds of beads in it, that's likely to be cavity wall insulation! But that only affects to top half meter or less of the walls, so it's not worth doing anything about.
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Re: How long does cavity wall insulation last?

Postby Justin » Tue Jun 14, 2011 4:17 pm

..and all those houses where windows have been replaced and the old type beads just fall out.

I was also at a clients house who made a claim against the cavity wall insulation guarantee people. Not sure how they worked it out but it was calculated only half the amount was put into the walls as is required. It came to light when the rendering had an issue with damp. They came back and apparently did a top up.
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Re: How long does cavity wall insulation last?

Postby JAG » Mon Jun 27, 2011 8:23 pm

It's about the only building product - with the exception of superior forms of flat roof coverings (the stuff they used on the millenium dome ) - that carries a 25 year guarantee. If it is installed correctly, then it should last well in excess of the guarantee period. But, like all building products, if you buy from a good company you get the assurance of a better job. The problem here is that the cowboys make more money by cutting corners. I see here that there are worries about beads dropping out. Two things. Modern bead installations are 'sticky' and don't drop out if a window is replaced. And beads can be topped up. The biggest hazard with cavity wall insulation is if the surveyor gets it wrong and doesn't spot an existing damp problem or a bridged cavity...Trust the big guys.
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Re: How long does cavity wall insulation last?

Postby Angib » Mon Jun 27, 2011 10:15 pm

JAG wrote:Modern bead installations are 'sticky' and don't drop out if a window is replaced.

I spent a hugely enjoyable ten minutes on an EPC with the client relating the tale of a patio window job he did that went wrong. The homeowner insisted the house didn't have CWI so they cut out the section of wall, releasing an avalanche of beads into the living room. He had obviously told this tale before, so he'd got his comic timing just right. The bit that had me on the floor was his retelling of the discussion between the two fitters about whether they should close the living room door, to stop the beads going into the rest of the house - and risk having the door jammed shut by the wall of beads - or keep the door open and increase the clean-up job?

And the way to avoid this is quite clever - turn up the day before, drill holes along the line of the intended cut and squirt expanding foam into the cavity - that 'sets' the CWI along the cut and holds them in place the next day when the bit of wall is removed.
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Re: How long does cavity wall insulation last?

Postby HEA » Tue Jun 28, 2011 8:05 am

Angib wrote:And the way to avoid this is quite clever - turn up the day before, drill holes along the line of the intended cut and squirt expanding foam into the cavity - that 'sets' the CWI along the cut and holds them in place the next day when the bit of wall is removed.


Top Tip !!! :D Be surprised if many fitters think that far ahead. Maybe we should start a thread with similar clever little tricks
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Re: How long does cavity wall insulation last?

Postby Angib » Sat Aug 06, 2011 8:02 pm

Angib wrote:some types of insulation bead are so light that they seem to get 'wafted' out of the top of the cavity in strong winds. If your loft has some mounds of beads in it, that's likely to be cavity wall insulation!

I did a job this week that made me remember this post, as it had the extremely rare combination (I've never seen it before) of cavity wall insulation but no loft insulation. Sure enough, there were these little mounds of wind-blown insulation along the eaves:

Wind-blown-CWI.jpg
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