Should I take Free Cavity Wall Insulation In New House?

rew37

Hi All,

we have a bunch of contractors coming round our estate offering free cavity wall insulation. Now our houses are all less than 10 years old, built by Barratts (yes I know - they're crap!!!) but they are generally quite energy efficient.

To my mind (and I'm no civil engineer), the cavity on new houses is there for a reason; presumably to do with preventing damp/mould and maybe some other very sound reasons as well.

Does anyone know of any plusses or minuses to having this done in such a new house?

27col

A house that new will have been done whilst it was being built. That is why you can say that they are already energy efficient.

flashg67

My 10 year old (non Barratt!) house has the 'foam & foil' boards as cavity insulation which, I think, was required as part of the build,.So I suspect, as above, that you'll already have it?
Be interesting to sign up and see what they do when they come to install it...

rew37

The foam & foil boards are in my wall cavities. I won't be having installation - according to a builder on another forum I've looked at, the cavity is there to allow air to circulate and prevent damp so I'll be politely declining

MartinN_2

The cavity is there to prevent damp. however it can safely be filled with insulation so long as the insulation is water repellent, which all approved types are. Many builders used to be/are very firmly wedded to a cavity, so prefer to build a wider cavity and fill only the inner part of it. The insulation (either foam boards or rockwool batts) is then held against the inner leaf with modified cavity ties; IF they are poorly fitted the insulation will move and allow cold air to get behind it, making it useless. So personally I prefer a fully filled cavity.
With a fully filled cavity the insulation should work its way into every nook and cranny to give a continuous layer the full width of the cavity.If for any reason it does not (e.g. cement snots blocking the cavity creating a shadow area below into which the insulation does not fall), then in heavy rain water penetrating the uninsulated part of outer leaf will run down the inner face of outer leaf and puddle on top of the water repellent insulation, causing a damp patch on the inner leaf. The bigger the gap in the insulation then the wetter the damp patch. In theory at least it can be cured by injecting more insulation just above it.