Insulating void walls in dormer house

[tunido]

Hi guys

I am new to the site and new to DIY in general. I am living in a dormer house and with quite a lot of work needing doing, I have had lots of different tradesmen round and conflicting advice all over the place.

Anyway, my current project is insulating the walls surrounding the bedrooms. each bedroom has a void hatch door and you can pretty much walk at a crouch/crawl the full length of one wall in each bedroom.

(Not sure if this would be easier with pics but anyhow..) from what I can see, I have my bedroom wall which is like a breeze block and then there is my void which you can get behind and then it is the bottom of my roof/top of wall. There only looks to be a bit of wool like insulation between the rafters

What I am looking to do is basically just tag on some insulation to the back of the bedroom walls to try and hold some heat. The chap who I had round to look at it said he would just kingspan the back of the walls with a thin layer of polythene so the walls would still had airflow

I am no expert at all but I have just heard stories of people going over the top with insulation and then the walls sweating

What do you guys think would be best? I have seen foil-like insulation and all sorts but I haven't a clue

Thanks for your help in advance and keep up the good work, this forum seems a great community

Paul

 

[ree]

You would be best helped if you post some pics, and a sketch outline (plan view) of the walls in question.

 

[freddiemercurystwin]

Untitled

• freddiemercurystwin
• 25 Apr 2010
• 24

 

[geraldthehamster]

The chap who I had round to look at it said he would just kingspan the back of the walls with a thin layer of polythene

That's what I'd do, apart from the polythene bit. Fix foil-backed Kingspan/Celotex/Xtratherm to the back of the wall with expanding foam. Even 50mm will make a difference, but you might use 75mm or 100mm if there is room to do it.

No need to insulate the rafters in the void, but ensure that area is well-ventilated from the eaves.

Cheers
Richard

 

[tunido]

thank you for the quick responses. I will get some pictures together and draw a little sketch.

 

[tunido]

Hi guys, just a quick picture and sketch, can you give me a better idea as to what would be best to insulate the wall/space?

Thanks!

 

[theprinceofdarkness]

Back of door needs doing as well.
Frank

 

[geraldthehamster]

Hi guys, just a quick picture and sketch, can you give me a better idea as to what would be best to insulate the wall/space?

As already stated above.

Cheers
Richard

 

[tunido]

Thanks

How much expanding foam would I need and what is the best stuff?

How much do you apply to the wall and in what pattern?

I don't think I will be attempting to do it myself, although it looks pretty simple. I just like to have the best understanding I can have when someone turns up to fit it

The first chap said he would just glue and nail it to the wall straight on with no foam or polythene

 

[geraldthehamster]

I've glued it with low-expansion foam, I've also used PU glue. If you're not planning on doing it yourself, just let the chap doing it use whatever he intends to use - no point second guessing it based on advice from a forum.

Cheers
Richard