Cavity Wall insulation! Does is cause damp problems?

brawdy

I have a house that was built at around 1900 and it has a cavity wall. It is an end of terrace property, so has 3 external walls.

I have insulated the loft myself, but I am thinking about having the walls insulated by a company.

What I concerned about is blocking the cavity might cause damp problems. Houses in my area are prone to damp and I have a number of air bricks to keep it under control.

Any advice and opinions would be appreciated.

stevemcol

I had it done last year and up to now have been OK. Cavity wall construction, 1950s property. Not very scientific though. I did loads of googling beforehand and on balance convinced myself that with modern techniques and materials, damp should not be a problem. The 25 year garantee gave me more comfort.
The silicone treated insulation used should not transmit damp.
I'm very interested to see further replies though. I'm a sample of 1.

dave82_2

My mate had some installed in his flat and now has a condensation problem that he solves by leaving the window open! So I am not sure if there is much benifit as his heat is just lost through the open window instead!

If the houses have a history of damp problems I would be more worried about condensation than it actually transmiting dampness!

anotherbaldrick

It can cause problems, it all depends on how much care the original bricklayers took to keep the wall ties free from mortar droppings. If they did not bother the mortar can conduct moisture across the cavity from the outside face to appear on the inner wall face.
Before the cavity is filled there is air movement within the cavity to evaporate this moisture so you see no problem. When the cavity is filled the air movement reduces
and the damp can cross the cavity and appear as damp patches. Make sure who does the work checks the cavity and indemnifies you with an insurer .

PS I am very surprised a 1900 built house has a cavity wall ??

ormus

installers usually replace the plain airbricks with through airbricks. mostly plastic ones.

ie

deano72_2

i had mine done this year & no condenseation as yet.my house is 1930 detatched.it feels warmer this year but i dident have loft insulation last year
ps they did replace all the airbricks with plastic ones

tony6403

Most houses pre 1935 do not have a suitable cavity , however we did refurbish a semi built in 1933 which had a cavity of nearly 2" (but single course construction beneath the bay windows).
There are tales of rockwool insulation having voids and slumping. This in theory can cause cold spots which it is said can create mould growth due to condensation.
I would go for polystyrene beads which do not draw moisture and allow the wall to breathe.
In any event make sure that your pointing is sound , likewise your guttering.
Rising damp is a separate matter.
As regards airbricks , these are installed to ventilate the space below suspended wooden floors. Any airbrick above dpc should have a cavity tray over it to get rid of any moisture.

Johnjohn

Poorly installed cavity wall insulation or cavity wall insulation installed into unsuitable walls can cause damp problems - e.g. http://www.premier-heritage.co.uk/2009/08/the-dangers-of-cavity-wall-insulation-and-damp/

Daz2009

My 30's semi was done a couple of years ago under the warmfront scheme and I can't say I've noticed any problems

ormus

i reckon its another red herring jobby.
damp problems caused by a few bad installations. maybe.
but of the millions of houses done, i wonder how many have had problems?
personally, i dont know any at all.

ps
there used to be a lot of cowboys in the cavity wall trade. i think its better now.

Johnjohn

I think the idea of cavity wall insulation is a good one, however there do seem to be few bad eggs that have carried out inappropriate installations that have led to dampness problems. There is a British Standard (BS8208) that installers are supposed to follow to assess the suitability of cavity walls to be filled (not all are suitable). There are also a number of other standards covering the installation of different types of cavity wall insulation. This useful guide from the Energy Saving Trust contains some useful info - http://est.custhelp.com/cgi-bin/est.cfg/php/enduser/fattach_adp.php?p_tbl=9&p_id=806&p_faqid=806&p_created=1241189214