Is Aerogel/ Spacetherm the only way to go?

[RRRRRR]

Hi- going a bit mad here! I need to get the 0.35W/m2K minimum for wall insulation. Just got a Spacetherm-PP quote of about £650 with delivery for 10m2! Does anyone have any cheaper ideas? I've tried the free u-value calculators, but none seems to have all the materials I need so I can't find out. I want to use up as little space as possible. Would 25mm Kingspan and plasterboard scrape through?
Have-
Internal cement render 6mm
Internal Brick 103mm
Cavity blow filled Knauf rock/mineral wool 74mm
External Brick 103mm
Any help gratefully received.

 

[mointainwalker]

I haven't bothered adding-up all the bits and pieces but ( as long as the c-w insulation is rated same as loft-roll) 75 mm fibre gives R 1.875 and 25 mm Kingspan gives you R 1

R 2.875 = U 0.347

The other bits might add up to R 0.5 so you are well inside, probably close to U 0.3.

 

[alittlerespect]

Hi

I would agree with mountainwalker - if you go for a kingspan k17 board you will be well under 0.35 or to be more precise, in line with mountainwalker your total U value will be near to 0.31W/m2C (or substitute C for K for the more technically minded!)

Regards

 

[ajrobb]

My dodgy calcs show you could use 20mm of PIR (e.g. 32.5mm Kingspan K17)

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• ajrobb
• 9 Sep 2010
• 1

However, if you believe that a reflective cavity can have an R-value of 0.6, you could just about batten out with 19mm battens and put up Duplex plasterboard. (This also gives you a handy service cavity.)

Untitled

• ajrobb
• 10 Sep 2010
• 1

I don't think that British Gypsum make low-emissivity claims for their aluminium foil backing on Gyproc Duplex boards. If you need to convince BC, then you could line the walls with Proctor's Reflectatherm foil before putting up the battens and use ordinary plasterboard.

 

[RRRRRR]

Sorry to push my luck with another question after everyone's really useful help, but can I fix K17 directly to a cavity wall, or must I have battens/ dabs? (Very space tight).

And as K17 is 25mm Kingspan (£17 or so) behind 12.5 plasterboard (£7 or so), could I fix these together to get K17 at about half K17 cost?

Thanks again- Richard.

 

[ajrobb]

sorry - I should read more carefully before opening my keyboard

 

[RRRRRR]

Hi ajrobb- not really sure what you think you've, "not read carefully before opening your keyboard". Your help's been most useful!

 

[ajrobb]

Hi ajrobb- not really sure what you think you've, "not read carefully before opening your keyboard". Your help's been most useful!

I was about to suggest what you'd already suggested. You're welcome.

 

[mointainwalker]

Fitting the two elements together yourself will give you the same result as a manufactured component.

 

[RRRRRR]

Any ideas on how to fix plasterboard to Kingspan and then to the wall- or Kingspan to wall then plasterboard to that?

Can I fit Kingspan directly to wall with no gap?

Thanks!

 

[ajrobb]

Any ideas on how to fix plasterboard to Kingspan and then to the wall- or Kingspan to wall then plasterboard to that?

Can I fit Kingspan directly to wall with no gap?

Thanks!

Just an idea:
http://www.british-gypsum.com/produ...cialist_profiles/gypframe_board_jointing.aspx

Maybe spaced at 400mm fixed to the wall through the PIR every 300mm adjacent to the plasterboard screws. Overlap the PIR and plasterboard so the joins in one don't coincide with the joins in the other.

I don't know how you'd countersink the wall screws though.