An obvious way to reduce your carbon footprint as well as saving you perhaps £300 per year is to insulate your loft and cavity walls properly.
You need to ensure that you do the job properly though: shoddy cavity wall insulation can lead to serious damp issues as the material can become a wick for moisture.
If you’re buying a new home, booking a homebuyer’s survey is an excellent place to start. Your RICS surveyor, if you’re buying a house, checks the roof and loft space and in doing so can form an opinion of how ‘fit for purpose’ any pre-existing insulation is.
They can also give you a valuable opinion on how good any cavity wall insulation is, although the caveat here is that home buyers surveys are not intrusive – a vendor’s reaction can only be imagined if a buyer’s surveyor started knocking holes into stud walls to check out insulation material, particularly if they then advised the buyer to pull out in the middle of the conveyancing process!
Which materials are used for cavity wall insulation?
- Mineral wool/rockwool – these materials are the speediest to install and the cheapest, however the compromise is that the lifespan of effective insulation is likely to be less.
- Polystyrene Beads – you’ll pay a bit more to have polystyrene beads installed and you’re well advised to get a professional in to do the job because if there are any gaps between the beads, damp might invade further down the line.
- Foam – the most popular types used are polyurethane and urea formaldehyde. Once again, you should get a professional to install it. It’s very effective, although eventually it breaks down which decreases its effectiveness.
Which materials are used for loft insulation?
- Blown-fibre – a professional contractor blows fibre insulation into the gaps between joists. The process is quick and very handy if a loft is difficult to access but you’ll pay the most for it.
- Batt or blanket – you can easily install this material yourself, which consists of either mineral, glass or rock fibre or foil-backed felt, and works best when you can easily access loft spaces. You should be particularly careful to wear protective gear when handling material like glass fibre however, because it is a particularly nasty skin irritant.
- Loose-fill – you can also look to install this material yourself, which normally consists of cork, mineral wool, cellulose fibre or recycled newspaper. You should use protective equipment and clothing to install it and there is some risk that materials will loosen, lowering their effectiveness, if you’ve got a particularly draughty loft.
- Sheet – this consists of firm sheets which are fire and moisture resistant and they come into their own if you have to tackle insulating a roof’s sloping side. The material is relatively expensive.
How much is it likely to cost you to fit cavity wall and loft insulation?
To insulate the loft of an average 3-bedroom semi-detached home might cost around £300 and upwards, increasing particularly if you choose to use blown fibre.
To insulate the cavity walls of an average 3-bedroom semi-detached home might cost between £400 – £500 and upwards, with costs likely to be higher if you choose foam as a material.
TIP The Government and British Gas often run schemes where you can get a subsidy towards home insulation; it’s always worth an online search to check before you embark on your project.