Cavity wall insulation, should I???
Discussion
Hi all!! A few neighbours have had cavity wall insulation added to their homes recently. I've heard various things over the years about this form of insulation, some good, some bad! Does anyone know about this?? I've been told that the cavity is there for a reason, to let air circulate, and if you fill this cavity with insulation, there is a large risk of dampness coming from the outside wall.
The theory behind it all sounds good, but once it's in there, it's staying there, so want to try and find out some more information before deciding.
Thanks.
The theory behind it all sounds good, but once it's in there, it's staying there, so want to try and find out some more information before deciding.
Thanks.
Some reading for you http://www.ciga.co.uk/faq.pdf
Go with mineral wool and you'll be fine. Well worth doing.
Go with mineral wool and you'll be fine. Well worth doing.
in my view YES i live in a barn conversion and the walls didnt have any in it and managed from a mate working for a company to get a grant £60 for the hole house ow ye. they drilled holes all around the house and pumped it full of foam beads our gas usage has gone down massively since they have done this
I had Cape Insulation Services install UF foam in my cavities in 1980 and there has never been a hint of trouble. I live in an officially 'sheltered' part of Britain (Chilterns area), as opposed to the Highlands or Dartmoor for example and that is significant. Even in 1980 the BRS were recommending mineral wool fibres for exposed locations. And before any naysayers ask if it's still in place or lying as a powder in the crawl space under my floorboards - yes it is and there's ample of it to see wherever it has spewed out during the installation and visible in through-wall vents etc.
Visible through in-wall vents? Eeeekkkkk!
In theory the in wall vents are there for a reason so ifthey have been filled with insulation thats not too good! In fact iironically one reason for a vent is to provide air for a gas boiler. Seems daft to me especially in old houses without double glazing etc.
The cavity is there to stop water ingress. Bricks and mortar are permeable to water so with the cavity the theory is any water that gets through the external wall will run down the inside of the external bricks to the bottom of the cavity exiting at the various weepholes left by the builder to let it out. In theory the builder goes to a lot of effort to ensure that nothing bridges the cavity.
When houses are built now the builder will insert insulation into the cavity but it is in sheet form and attaches to the skin of bricks and maintains the cavity.
This does of course beg the question of how old is the house, as you might alredy have some insulation in the cavity!
But after market installations basically pump a product into the cavity and in theory they go to great efforts to ensure that there are no gaps in the insulation which will provide a nice bridge for water to cross the cavity.
The modern products also should not deteriorate. A friend who is an electrician has expressed a view that some pf the products used have caused the insulation on wiring in the cavity to degrade, which I guess you don't want!
The advantage of cavity wall installation is that it is cheap especially with all the grants. The disadvantage is the danger of bridging the cavity. Its up to you whether you have it down. My parents swore they would never have it down, but did last autumn.
I keep thinking about it, but not done it yet, leaving aside the issue of having to either move or drill through the neighbours shed in order to install it!
In theory the in wall vents are there for a reason so ifthey have been filled with insulation thats not too good! In fact iironically one reason for a vent is to provide air for a gas boiler. Seems daft to me especially in old houses without double glazing etc.
The cavity is there to stop water ingress. Bricks and mortar are permeable to water so with the cavity the theory is any water that gets through the external wall will run down the inside of the external bricks to the bottom of the cavity exiting at the various weepholes left by the builder to let it out. In theory the builder goes to a lot of effort to ensure that nothing bridges the cavity.
When houses are built now the builder will insert insulation into the cavity but it is in sheet form and attaches to the skin of bricks and maintains the cavity.
This does of course beg the question of how old is the house, as you might alredy have some insulation in the cavity!
But after market installations basically pump a product into the cavity and in theory they go to great efforts to ensure that there are no gaps in the insulation which will provide a nice bridge for water to cross the cavity.
The modern products also should not deteriorate. A friend who is an electrician has expressed a view that some pf the products used have caused the insulation on wiring in the cavity to degrade, which I guess you don't want!
The advantage of cavity wall installation is that it is cheap especially with all the grants. The disadvantage is the danger of bridging the cavity. Its up to you whether you have it down. My parents swore they would never have it down, but did last autumn.
I keep thinking about it, but not done it yet, leaving aside the issue of having to either move or drill through the neighbours shed in order to install it!
Not filling the vents, but visible through them. The cavity is not perfectly sealed off and the foam has escaped into the vents and the installers cut it away to preserve the airflow. There's also leakage into the sub floor space where breaches of the inner leaf occur where joists go in. The foam you find is bone dry and it is not hygroscopic so won't leech water across the cavity under normal exposure. Anyway, after thirty years you'd think I would know if there were any problems!
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