Doingit wrote: » Is it absolutely necessary to close the cavity before installing the windows? Wondered if we could install windows, apply airtight tape to inside (between frame and black) and then pump cavity right up against the frame! Would this work? Would it just move the dpc out of position?
john f 4g63 wrote: » I am thinking of doing the window detail this way as at least the pumped insulation will fit nice and snug up against the window and there will be no insulation gaps. In order to get over the problem of fitting the windows in my 200mm cavity, my window thickness is 82mm therefore leaving a gap of 118mm to the internal leaf. As this is too wide for the window straps i am fixing a 3x2 on to the internal leaf in the cavity, the straps from the window can then be fixed to the 3x2 timber and will also just make the internal leaf so can be fixed to that as well. I will then use the air tight tape to stop the beads when pumping the cavity. This way i know the insulation will be fitted right up to my window and reveals. Well that's the plan anyway!!
sydthebeat wrote: » are you sure youre allowed to provide a combustible cavity barrier in an cavity? I dont think you are.
john f 4g63 wrote: » Is it the 3x2 timber you are referring to? If so do you know why?
dfader wrote: » Hmm forgot bout that. how about friction fitted pir between 3x2 and dpc and doubled up plasterboard over 3x2 and reveal
sydthebeat wrote: » Sounds good, does your frame allow for that thickness?
dfader wrote: » How about friction fitted pir between 3x2 and dpc and doubled up plasterboard over reveal
john f 4g63 wrote: » That is another option I am considering as the pir has a better u value then the bead but the only reason I didn't want to do it this way is this must be done before the windows are fitted so this might leave a small gap between both. I know they usually pump foam in here then but I am hoping a avoid this.
dfader wrote: » he should step back the blockwork on inner leaf maybe 30mm to allow for this
fclauson wrote: » the window boys will have a spray foam - now make sure you get the really good stuff - but it has a good U-value - no idea on name - but mine is a blueish colour
fclauson wrote: » You need to step back the inner leaf enough to get both your insulation and your ply see picture Thanks for that great detail drawing any advise on where I could more detailed photos and info on passive build . Books etc
fclauson wrote: » can we have a pic from the outside too expanding foam is not airtight - what air tightness are you going for
ExtaticFob wrote: » Thanks for the reply. We’re going to be taping inside with air tightness tape. We’re also putting an insulated board on it. That might not answer your question but there’s a lot of learning as we go. Requested photo attached.
fclauson wrote: » Ok - see my tech arch picture further back in this post you need to look at how you are going to make it a) insulated correctly with no cold bridge around the window (this will require thermal modelling probably) b) airtight if you fail on (a) you could end up with a cold bridge (read mold) around the wind frame on the window return because the wall/frame fall below the threshold temp read about FRSI in the (google FRSI calculations)
ExtaticFob wrote: » I’ll check that out. Thanks again. In your experience is there a way around this without removing the windows? As well as the inconvenience, we are getting the external wall plastered from tomorrow.
