richo106 Posted January 8, 2022 Share Posted January 8, 2022 (edited) Hi all With our build in its planning stage just trying to sort some finer details. Our existing bungalow only has a 70-80mm cavity (blown insulation in it I believe) we are going to insulate internally what would people use to insulate inside? 50mm celotex or 50mm rock wool? what is the best method to install it? New metal stud inside? Battens? All advice greatly welcomed as I am struggling for the best way to do this at the minute Many Thanks Edited January 8, 2022 by richo106 Link to comment Share on other sites More sharing options...
tonyshouse Posted January 9, 2022 Share Posted January 9, 2022 No studs, no air gaps, sheet material is best either composite or stuck together on site as it goes up. Composite is easiest and quickest but more expensive. should start with a target U-value and go from there i use fixing foam and the next day six insulation fixings per sheet belted well in Link to comment Share on other sites More sharing options...
nod Posted January 9, 2022 Share Posted January 9, 2022 Your best option if you can afford to loose a bit of internal room is Gpyliner with a 50 mil rock wool slab 10 mil off the walls Link to comment Share on other sites More sharing options...
Cpd Posted January 9, 2022 Share Posted January 9, 2022 Just had 75mm of PIR backed plasterboard put on my internal walls and it’s made an amazing difference, still a long way from perfect but it was a free government instal so not to be sneered at. The house is very old traditional Scottish two up two down with stone walls air gap and wood panelling on the inside, the installers used a both foam glue and screw fixings to to attach the sheets straight to the wood panelling and the plasterer came in a few weeks later and did a fine job covering up all obvious imperfections. I am a fan of PIR over rockwool when space is a premium and you can control the detailing but rockwool is a lot more forgiving if detailing is going to be a problem. Link to comment Share on other sites More sharing options...
richo106 Posted January 9, 2022 Author Share Posted January 9, 2022 4 hours ago, nod said: Your best option if you can afford to loose a bit of internal room is Gpyliner with a 50 mil rock wool slab 10 mil off the walls Thanks, this was my original thought with 50mm studs. How does rock wool compare to PIR in terms of insulation? Im guess rock wool a lot easier to use/install? Link to comment Share on other sites More sharing options...
nod Posted January 9, 2022 Share Posted January 9, 2022 The ones that are pictured where put in for sound While pir stats may look slightly better The rock wool give a tighter fit Behind the gypliner and around the brackets 1 Link to comment Share on other sites More sharing options...
richo106 Posted January 9, 2022 Author Share Posted January 9, 2022 4 hours ago, tonyshouse said: No studs, no air gaps, sheet material is best either composite or stuck together on site as it goes up. Composite is easiest and quickest but more expensive. should start with a target U-value and go from there i use fixing foam and the next day six insulation fixings per sheet belted well in So fixed 50mm pir directly to the wall? Tape them together? how would I attach the plasterboards? Sorry for the daft questions Link to comment Share on other sites More sharing options...
ash_scotland88 Posted January 9, 2022 Share Posted January 9, 2022 1 hour ago, Cpd said: Just had 75mm of PIR backed plasterboard put on my internal walls and it’s made an amazing difference, still a long way from perfect but it was a free government instal so not to be sneered at. The house is very old traditional Scottish two up two down with stone walls air gap and wood panelling on the inside, the installers used a both foam glue and screw fixings to to attach the sheets straight to the wood panelling and the plasterer came in a few weeks later and did a fine job covering up all obvious imperfections. I am a fan of PIR over rockwool when space is a premium and you can control the detailing but rockwool is a lot more forgiving if detailing is going to be a problem. May I ask how you got it via a free install? Link to comment Share on other sites More sharing options...
nod Posted January 9, 2022 Share Posted January 9, 2022 25 minutes ago, nod said: The ones that are pictured where put in for sound While pir stats may look slightly better The rock wool give a tighter fit Behind the gypliner and around the brackets You could always dab insulated pb directly to the wall Not as good as an air gap but easy option Link to comment Share on other sites More sharing options...
Cpd Posted January 9, 2022 Share Posted January 9, 2022 1 hour ago, ash_scotland88 said: May I ask how you got it via a free install? My ex partner lives in the house and claims family tax credits to top up the care work she does, just being on the register made her eligible and as I do not charge her rent I did not have to pay towards the upgrade. 1 Link to comment Share on other sites More sharing options...
Cpd Posted January 9, 2022 Share Posted January 9, 2022 1 hour ago, nod said: You could always dab insulated pb directly to the wall Not as good as an air gap but easy option i should know this but why is the air gap so important @nod is it just to do with the reflective property of the PIR boards ? Link to comment Share on other sites More sharing options...
A_L Posted January 9, 2022 Share Posted January 9, 2022 @Cpd, no air gap increases the heat loss by conduction 2 hours ago, nod said: You could always dab insulated pb directly to the wall Not as good as an air gap A 25mm air gap without reflective surfaces has a thermal resistance of 0.18m2.K/W, an air gap with a low emissivity surface 0.44m2.K/W. 25mm of PIR has a thermal resistance of 1.09m2.K/W and 25mm of EPS about 0.7m2.K/W. pages 19/20 of attached PDF BR443-October-2019_consult.pdf 1 Link to comment Share on other sites More sharing options...
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