Cavity Wall Insulation Question

smellymel222

Hi
I am wanting to get cavity wall insulation installed in our home to save on our heating bills. However, my husband says that it blocks up all the air bricks in the house and someone has told him that this causes damp! Is this true?
Thanks
Melissa

Pew_Pew_Pew_Lasers!

I suggest you read this:

http://www.askjeff.co.uk/content.php?id=4

I'm of the opinion that cavity wall insulation is generally a bad idea on older properties.

alanobrien

If its done properly they should sleeve the air bricks so the air flow channel remains open. The question of whether it can cause damp is one that is often discussed. Again i am sure it could if done badly with sub standard materials. That said I know many people who had it done with no problems whatsoever. I guess the solution is to make sure the company that does it is professional and has references you can check.

andrewmoorcroft

Pew_Pew_Pew_Lasers! wrote: »

I'm of the opinion that cavity wall insulation is generally a bad idea on older properties.

and very difficult because they dont usually have a cavity!
Could you please explain your opinion. Please dont generalise by saying that new houses are designed differntly. Please be specific with technical justications. I have a 1930's house with a 3" cavity. I am thinking of cavity insulation and would be interested if your opinion is well founded.

Party_Animal

Its not just whether or not you have a cavity wall. A lot depends on the construction. A brick cavity wall won't present any problems and can be filled. In the case of stone, coursed stone is ok but random stone walls present problems as some of the stones protrude in the cavity and this leaves gaps when filling and consequently cold bridging. This is why some people have found that cavity insulation makes their damp worse.

andrewmoorcroft

Party_Animal wrote: »

Its not just whether or not you have a cavity wall. A lot depends on the construction. A brick cavity wall won't present any problems and can be filled. In the case of stone, coursed stone is ok but random stone walls present problems as some of the stones protrude in the cavity and this leaves gaps when filling and consequently cold bridging. This is why some people have found that cavity insulation makes their damp worse.

Not sure if you were trying to answer my question but my question was asking about old v's new houses of like construction, i.e, both brick as per most houses in the UK (assuming the old and new house had a similar size cavity).
Also, in this context what is meant by 'old' because it is a 'relative word'.

Party_Animal

Andrew, if your house is built of brick, both skins, there won't be a problem. Where I live most properties built in the 30s were built of stone, with brick on the inner leaf.

archroy_2

Have been reading this post with interest. I am a builder and have just last week opened up a blown filled cavity wall. It was brick outer leaf 100mm cavity and concrete block inner leaf. The area cut out was about three meters from ground level and about two meters in length. Thoughout the entire length cut out, the insulation was so wet that it could be rung out by hand.
My conclusion was that the wall was in a highly vulnerable exposed position: being on the coast the rain drives hard against it and had penetrated the outer skin. Without the natural cavity break inside the insulation acted as a candle wick and drew the moisture in.
Personally, I'd think very carefully about using cavity fill on such exposed walls.

archroy_2

Fair and and valid points.

In this situation:
The walls were (are) black inside and condensation has been investigated and ruled out. The client consulted a surveyor who recommended the installation of a remedial cavity tray on then gable end hence the cutting out.

There are no leaking pipes and the roof and overhang are fine. The insulation is white mineral wool. There is no problem with the dpc.

The bricks are a sixties fletton and not renowned for their quality (though a lovely brick to cut with the trowel). The original bricklayers laid them frogs down and the remaining voids along with the position of the wall may contribute to the wall being prone to penetration.
It was just one of those jobs were I felt like I was wasting both my time and the client's money. My builders instincts told me that if the insulation was removed the problems would be solved. I suggested to the client that they go back to the insulation company but they deferred to the surveyors decision. Now I suspect the warranty might be void due to the cavity tray installation.

My ideas are not just plucked from thin air. This house is actually in the same street as mine and those with cavity fill have problems. Mine, and others with the cavity in it's original state, are dry.

Do I reject cavity fill as a bad decision? No. It's a great idea and can save on the heating bills. We build with a full fill cavity and it's fine.
Do I think it can cause problems? Yes. I have seen it up and down my street.

The jury's out.

Archroy

across

before cavity wall insulation our house was very dry and warm no problems it was great but we thought save on the bills and had cavity wall insulation, since then we have a very damp back bedroom and my fitted wardrobe at the front is suffering from musty smell and constant damp and mildew,we also had howling noises and got the men to come back whereby they found lots of insulation missing it had not been done properly so they filled the patches missing in! anyway i hate the difference its made and the bills are no different so does anyone know if they can suck it all back out again? it must be sopping inside at the back and we only decorated before christmas but the pink paper is now yellow and black dots in a patch!:eek:

eco-worrier

Pew_Pew_Pew_Lasers! wrote: »

I suggest you read this:

http://www.askjeff.co.uk/content.php?id=4

I'm of the opinion that cavity wall insulation is generally a bad idea on older properties.

He's a journalist who makes his living out of being controversial. CWI is a proven technology. If it is installed badly it will cause problems. Is that any different from endless other things!?
In very exposed situations, I believe that mineral wool is not reccomended - a better choice would be the now much less-often used foam.