advice needed on cavity wall isulation

stedwell

HI
Apologies if this has asked before - I did do a search but couldn't find anything.

My council is offering free cavity wall insulation until March so I thought I would sign up for it.

Having looked at their website they use Knauf superfi mineral fibre. :huh: I have googled this but cannot really find out much about it.

I had always thought that the beads were the best to use. is this true? Does anybody know anything about this particular insulation?
Many Thanks.

anselld

http://www.knaufinsulation.co.uk/products/supafil_cavity_wall_insulation.aspx

It is a fibre wool blown in from the outside through small-ish holes. I would prefer it to beads personally - it seems to stay in place better.

reeac

We had Rentokil Rockwool blown into the walls of a previous house in early 1977, lived there until mid-1998 and encountered no problems.

Johnandabby

stedwell wrote: »

HI
Apologies if this has asked before - I did do a search but couldn't find anything.

My council is offering free cavity wall insulation until March so I thought I would sign up for it.

Having looked at their website they use Knauf superfi mineral fibre. :huh: I have googled this but cannot really find out much about it.

I had always thought that the beads were the best to use. is this true? Does anybody know anything about this particular insulation?
Many Thanks.

Knuaf has a really good reputation, and their superfi insulation is good. Non-bead type insulation used to have a problem with moisture ingress, but the Knuaf product details confirm that it will not transfer moisture across the cavity to the inner leaf. If it's free you should definitely go for it - you'll notice a big difference in comfort and energy bills

jamesingram

I agree with the above comment regarding the benefits if cavity fill ( though in certain instances it can cause problems)
If you do have a choice of product , take a look at graphite EPS (expanded polystrene) beads also knows as neopor, platinum eps ,Kay-cel super plus
This has a lower thermal conductivity than most blown in cavity fill products and will therefore perform better in reducing heatloss for a given thickness

Beads relative to wool are less likely to hold moisture so also reduce potential for condensation forming midway in the cavity ( intersitial ) which may cause future long term problems with regard to building fabric decay.
Though rockwool may also give the additonal sound proofing as it's denser relative to EPS beads, it is also fire proof unlike EPS, though in a brick cavtiy this isn't as important

Mattty

All Cavity Wall insulation should come with a 25 year CIGA Guarantee. Your property will need to be surveyed first to ensure your cavity is suitable. e.g. typically a 50mm clear cavity, no existing damp issues, pointing in good condition etc..

wobblegobble

I had SIG energy management round yesterday for survey on behalf of EDF for free cavity wall insulation. Apparently they cannot do it as house has been built in last 10 years and has thermalite blocks and complies to building regulations for insulation :cool:

I have already had a survey from Mark Group who confirmed that I have a 75mm cavity which is suitable for CWI. Cannot understand why SIG(EDF) won't do it????

Mattty

Energy companies give free insulation as they have to commit to reduce carbon emissions by X amount each year.

Because your property is pretty well insulated already. Adding more insulation won't save much more compared to adding insulation to an older property. Basically, it's not cost effective for them as they won't gain many carbon credits from your property.

Heat loss is measured in U-values.

For example the walls of a ten year old property would likely have a U-value around 0.4. By adding insulation to the cavity you may bring that value down to 0.25. Dropping the U-value by 0.15.

Whereas a 50 year old cavity wall might have a U-value of around 2 and adding insulation would bring it down to around 0.5. Dropping the U-value by 1.5.

There are 10 times the savings from insulating the older property even though the same amount of insulation would be added.