SBMS Posted February 18 Posted February 18 So we have designed our roof using posi rafters. Originally our makeup was going to be from inside out… plasterboard battens propassiv 304mm blown cellulose 22mm Steico sarking counterbatten slates This Yielded 0.12 u value. We have really been struggling to get someone to do the warmcel blown insulation so I am now considering other options… I would rather not change out the posi rafers So I have 304mm Of rafters depth to work with. Could I just swap out the cellulose for 2 layers Of say 150mm mineral wool? Would I need batts or the roll? The warmcel was 0.038W/mk so I think a 0.035 or even 0.032 would give a better u value… does the above makeup support this or would I need to change it? Reason I went cellulose was to minimise issues with fitting which is the same reason I don’t want to go PIR..
crispy_wafer Posted February 19 Posted February 19 What kind of pozi’s, are they the metal web jobs or the I beam type? The metal web jobs are a PITA, to get between the webs on the joist without making a mess of your hands, or material, it’s doable of course just increases the amount of labour time to do it right without gaps etc. Just my thoughts just so you go into this with eyes open!
SBMS Posted February 19 Author Posted February 19 26 minutes ago, crispy_wafer said: What kind of pozi’s, are they the metal web jobs or the I beam type? The metal web jobs are a PITA, to get between the webs on the joist without making a mess of your hands, or material, it’s doable of course just increases the amount of labour time to do it right without gaps etc. Just my thoughts just so you go into this with eyes open! Metal web… I wouldn’t pick the easy option would I?! I’m going to speak to Steico today as they do a blown cellulose and a blown wood fibre product. I think their installer network is a bit more mature than warmcel…
Big Jimbo Posted February 19 Posted February 19 It's such a shame that Warmcell seems so hard to get done, and costly. In America, they seem to sell the stuff in Home Depot, and have the machines instore for hire. DIY in a weekend. 1
JohnMo Posted February 19 Posted February 19 Our roof is a similar construction, but I tried to go warmcell and they refused to do it. In the end I had all the interstitial condensation calculations done and went open cell spray foam - 300 to 350mm deep. 250m² of roof done in a day and a half. We used normal wood sarking boards with small gaps, no need for counter battens with natural slates.
Nickfromwales Posted February 19 Posted February 19 9 hours ago, SBMS said: So we have designed our roof using posi rafters. Originally our makeup was going to be from inside out… plasterboard battens propassiv 304mm blown cellulose 22mm Steico sarking counterbatten slates This Yielded 0.12 u value. We have really been struggling to get someone to do the warmcel blown insulation so I am now considering other options… I would rather not change out the posi rafers So I have 304mm Of rafters depth to work with. Could I just swap out the cellulose for 2 layers Of say 150mm mineral wool? Would I need batts or the roll? The warmcel was 0.038W/mk so I think a 0.035 or even 0.032 would give a better u value… does the above makeup support this or would I need to change it? Reason I went cellulose was to minimise issues with fitting which is the same reason I don’t want to go PIR.. Have you tried Gordon, the chap that does a lot of the MBC frames? I know MBC will be keeping him busy, but worth a call as you can do this at any time and shouldn’t really hold you up being in the queue.
Russell griffiths Posted February 19 Posted February 19 A lad on here called @Patrick bought his own machine and did it himself, he then sold the machine. have a look around there’s a second hand machine out there somewhere being used by self builders.
SBMS Posted February 19 Author Posted February 19 1 hour ago, JohnMo said: Our roof is a similar construction, but I tried to go warmcell and they refused to do it. In the end I had all the interstitial condensation calculations done and went open cell spray foam - 300 to 350mm deep. 250m² of roof done in a day and a half. We used normal wood sarking boards with small gaps, no need for counter battens with natural slates. @JohnMo - which foam did you use out of interest and what was your end U Value? Am happy to look at all options really, but have been very wary of foam for obvious reasons (mortgages being one)...
SBMS Posted February 19 Author Posted February 19 Was speaking to another installer that blows in Supafil Frame (https://knauf.com/en-GB/p/product/supafil-r-frame-21496_4206) - anybody used this in pitched roof?
SBMS Posted February 19 Author Posted February 19 1 hour ago, Nickfromwales said: Have you tried Gordon, the chap that does a lot of the MBC frames? I know MBC will be keeping him busy, but worth a call as you can do this at any time and shouldn’t really hold you up being in the queue. Have you got a contact for Gordon?
JohnMo Posted February 19 Posted February 19 24 minutes ago, SBMS said: which foam did you use Icynene LDC-50 Used battens under posi rafter to kill of thermal bridges. U values Pitched 0.13 Nearly flat (12 degs) 0.12 Only issue with spray foam is numb skull installers that install in inappropriate places like holding a roof structure together with closed cell foam and a non vapour permeable membrane. Then wonder why the roof rots.
SBMS Posted February 19 Author Posted February 19 14 minutes ago, JohnMo said: Icynene LDC-50 Used battens under posi rafter to kill of thermal bridges. U values Pitched 0.13 Nearly flat (12 degs) 0.12 Only issue with spray foam is numb skull installers that install in inappropriate places like holding a roof structure together with closed cell foam and a non vapour permeable membrane. Then wonder why the roof rots. If you could have had warmcel over foam would you have used that instead?
JohnMo Posted February 19 Posted February 19 31 minutes ago, SBMS said: If you could have had warmcel over foam would you have used that instead? Not sure. Not seeing anything wrong with the foam, it's been in for nearly 4 years.
Nickfromwales Posted February 19 Posted February 19 2 hours ago, SBMS said: Have you got a contact for Gordon? PM’d you. 1
Nickfromwales Posted February 19 Posted February 19 1 hour ago, JohnMo said: Icynene LDC-50 Used battens under posi rafter to kill of thermal bridges. U values Pitched 0.13 Nearly flat (12 degs) 0.12 Only issue with spray foam is numb skull installers that install in inappropriate places like holding a roof structure together with closed cell foam and a non vapour permeable membrane. Then wonder why the roof rots. Decent spray foam guys will propose a very thin layer of closed cell, either before or after the bulk open cell stuff is loaded into the voids, to act as the barrier. Did this in a basement where we needed to insulate under the residence floors (swimming pool hall was its own heated and airtight envelope) and it worked a charm. As with every single thing in life, if it’s done great on paper and executed less than well, it’ll fail. Jobs like this need a clued-up client who can be on site and know what they’re looking at, or a good PM / site agent to do so in their behalf.
Gone West Posted February 19 Posted February 19 3 hours ago, SBMS said: Was speaking to another installer that blows in Supafil Frame Eleven years ago when I was considering what insulation to use, Supafil Frame was on my shortlist. I discounted Warmcel as a friend had used it in her house and had problems. In the end I used 350mm Icynene for the walls and roof of my timber I-beam portal frame. The only problem was trimming and cleaning up. I did use a similar product to Supafil Frame in the walls of the old bungalow I was living in, while building the house. When I dismantled the bungalow it was easy to see how well it had filled the old timber frame.
SBMS Posted February 19 Author Posted February 19 1 hour ago, Gone West said: discounted Warmcel as a friend had used it in her house and had problems What problems out of interest?
Gone West Posted February 19 Posted February 19 19 minutes ago, SBMS said: What problems out of interest? The Warmcel was slumping and as a result there were cold areas around the ceilings. All down to the installers I guess. What I liked about the Supafil Frame was that, at the time, they used a transparent membrane so it was possible to see how well filled it was.
SBMS Posted February 19 Author Posted February 19 1 hour ago, Gone West said: The Warmcel was slumping and as a result there were cold areas around the ceilings. All down to the installers I guess. What I liked about the Supafil Frame was that, at the time, they used a transparent membrane so it was possible to see how well filled it was. Anyone else had cellulose and had problems with slumping... I assume its an installer issue rather than an inherent problem with cellulose in pitched roofs?
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