Cavity wall insulation

AWD_2

Hi, I have a 3 bedroom detached house which was built approx 1960. There is no cavity wall insulation, the boiler is oil fired (no gas in our area).

We are considering having cavity wall insulation to hopefully make the house a bit warmer and also reduce the bills. I am a but concered with reports of damp etc after people have had it fitted.

I had two companies come to quote me.

Company 1 offered white wool insulation at a cost of £199.00 for 130m2 of walls. They then called back later the same day to say that they could now do it for FREE as they had a better grant which they could use. I should also add that neither me or my partner are over 70 years in age or on benefits.

Company 2 offered a wide range of options. They also mentioned that the best option is polystyrene beads which are glued together (to stop them coming out of the wall if ever you drill a hole). They said that these are best as they allow any water which does get into the wall to drain down properly. They offered me 3 pricing options

Option 1 Mineral wool 130m2 £274.36
Option 2 Polypearl white 130m2 £424.20
Option 3 Polypearl platinum £507.15

I think company 2 is the more reputable of the two companies.

I am not really sure what to do, can anyone offer some advise?

Thanks,
Andrew

AWD_2

Anyone?

Thanks,
Andrew

iamcornholio

If the property is suitable for CWI, and if the external brickwork is in good condition, and if there are no existing damp issues (not condensation but damp) then it is worth having and there should not be any problems

If you like to live in a sauna, then you may need to provide extra ventilation afterwards

You can get blown fibre fill for about £100 from many installers as they get a government grant nowadays. Poly beads may not be included in this grant arrangement so you pay for that system

I don't think that there is any real advantage in poly beads, and there will be a longer payback time. Loose poly beads will fall and blow out of any gaps, and if you make holes in the walls (new doors or extension etc) it tends to all fall out like an egg timer

greenlaws

Cavity insulation is dangerous. The cavity is there for a reason. Take it out / fill it and you risk major problems with condensation and water build up. NOT a good idea. Better to look at how your house works, and introduce insulation in the roof, run the heating more efficiently, put curtains or blinds over windows - anything but screw up the cavity and how it works...

iamcornholio

greenlaws wrote: »

Cavity insulation is dangerous. The cavity is there for a reason. Take it out / fill it and you risk major problems with condensation and water build up. NOT a good idea.

Oh dear.

So what is to happen with all the properties built since the 80's and the ones being built and extended today - all with cavity wall insulation?

AWD_2

This is the problem I have, it gets mixed reviews so I'm unsure what to do. The idea of wool insulation (The free one) seems like a bad idea as wool usually just holds water so I can imagine it would make the walls damp.

My house is located down a road that is surrounded by woodland so it is a fairly damp area. I'm beginning to think that I would be best to just leave it be.

Andrew

neiljules

I have not personally looked into this but my Dad has done a lot of research and came to the same conclusion of dont do it... The other post was right.. The cavity is there for a reason and should not be messed with.. I have even heard of companies setting up a second firm to deal with the problems their origional company caused.

anotherbaldrick

You need to be particularly careful if you live in an exposed situation such as on a open site with elevations to the wind driven rain or on higher ground .
Be aware that external bickwork is water permeable ie the bricks and mortar joints are not waterproof. The way cavity walls work is that any water penetrating the outer skin will meet the cavity space and run down to a drainage gap. The water then evaporates and the bricks dry out in the days when the rain has ceased. If you fill the cavity with anything you stand the chance of disturbing this cycle and allowing water to cross to the inner wall skin, particularly if in building the wall, mortar has been allowed to drop onto the wall ties which span between the inner and outer brick leaves. In such conditions you need to ensure the contractor inspects the cavity by CCTV camera or removal of some bricks to ensure cavity is clear of mortar droppings.

phead

AWD wrote: »

This is the problem I have, it gets mixed reviews so I'm unsure what to do. The idea of wool insulation (The free one) seems like a bad idea as wool usually just holds water so I can imagine it would make the walls damp.
Andrew

Its not wool, it doesn't absorb water.

The general opinion is that as long as its fitted correctly, and you don't live in an area where the walls will be constantly wet (that means typically where the walls are often exposed to driven rain) then fitting it is fine.

The posts you get in MSE tend to be a load of old wives tales, as said below new houses already have insulation fitted. If you believe the things said below then every house built in the last twenty years would have a damp problem.

anotherbaldrick

phead wrote: »

Its not wool, it doesn't absorb water.

The general opinion is that as long as its fitted correctly, and you don't live in an area where the walls will be constantly wet (that means typically where the walls are often exposed to driven rain) then fitting it is fine.

The posts you get in MSE tend to be a load of old wives tales, as said below new houses already have insulation fitted. If you believe the things said below then every house built in the last twenty years would have a damp problem.

You have forgotten to say that in new build houses the insulation does not fill the cavity. It is in the form of bats (slabs ) and these are fixed to the inside leaf of the wall so that their is still a void left to maintain a seperation from the outside skin.
Also mineral wool might not absorb water but as a cavity fill it will prevent air circulation within the cavity, stopping water which has ingressed from drying out by evaporation and wicking back through the outer skin

iamcornholio

anotherbaldrick wrote: »

... in new build houses the insulation does not fill the cavity.

... cavity fill it will prevent air circulation within the cavity, stopping water which has ingressed from drying out by evaporation and wicking back through the outer skin

The majority of new build does use full fill insulation

As for cavity air circulation being needed to dry cavities, that is not what happens or required according to established thinking. Anyway, air circulation in cavities negates the purpose of an insulating barrier - ie a cavity should be sealed