Whats what with Cavity wall insulation? Alternatives?

timg147

Hi all,

Hoping that someone can shed some light on this for me. I need to improve the insulation/ energy efficiency of our house. I have been looking at cavity wall insulation. Firstly I'm not finding many installers whereas there used to be loads. I also keep reading horror stories about problems with damp etc after installation. Are these basically the same issue... down to bad installers/ installation?  
If cavity wall insulation is still a viable option can anyone recommend any installers covering the Midlands (North of Coventry).
Are there any other options for insulation - I can't do loft insulation as we have a flat roof. 
I did find someone on the internet offering the insulating render stuff as well as cavity wall. Does anyone know anything about this  as the front and back of the house are rendered and seriously need re rendering? 

Any help is greatly appreciated 

Bendy_House

By far the most effective way to insulate a room is to line the inside of the external walls with rigid insulation boards.

Any idea what insulation is in your ceiling/roof? Again, attaching rigid insulation to the ceiling is the best option.

The insulation can come ready bonded to plasterboard, so makes the job easier.

Two drawbacks - it steals inches from your internal room space, and it's pretty disruptive - it'll need skimming afterwards.

External insulation is another option, and if your render is poor, then that might make sense on these sides at least. I'm guessing it'll work best in conjunction with a cavity fill, and there certainly shouldn't be any issues with damp penetration as the ext insulation will be finished in a completely weatherproof option. Again, tho', it adds thickness that'll need accommodating.

FreeBear

timg147 said:  I did find someone on the internet offering the insulating render stuff as well as cavity wall. Does anyone know anything about this  as the front and back of the house are rendered and seriously need re rendering?

Insulated render is OK up to a point, but... You need a very, very thick layer to provide any worthwhile level of insulation - In the order of 100-150mm. A work colleague used a hemp/lime plaster to insulate her little cottage. From what I can gather, she is far from impressed.

As b_h says, insulating internally is probably a better option. If you have cavity walls, 50mm of Celotex/Kingspan will get you up to the current recommended u-value (or pretty close). You can also insulate the window/door reveals much more effectively and kill thr cold spot around the openings. In addition to the downside of losing a bit of floor space, any mains sockets and radiators will need to be moved. Some thought also needs to be given to adding in suitable fixing points for things like curtain rails.

On the plus side, you will end up with nice smooth walls, and any nasty cold draughts can be plugged in the process. If funds are limited, you can do one room at a time to spread the cost - This is the route I'm going down. Having done one room to date, it has been well worthwhile.