ToughButterCup Posted October 23, 2018 Share Posted October 23, 2018 After much research we now know our flat roof can only be built using shaped insulation. And elbow grease. '... Much research.... ' disguises a long , nitty gritty detail process, much head and withers scratching. However, good progress towards conscious incompetence has been made. Not bad when you consider I started out unconsciously incompetent. Help me on my journey please.... One quote shows that, to create the fall, some of the PIR panels will be cut to shape by the producer - here's the twist we have to cut about 8 sheets to shape. Calamity, calamity. Just a simple wedge of cheese shape, but still currently - without a mountain of waste PIR - beyond me . Ah the joys of DIY eh? I know now that if I stick at this little sod of a challenge, I'll get there..... The lovely old guy who daily walks past our place -facing the friendly overtures of our fearless tom cat- says I should hot wire it. Memories of modelling glider wings Anyone done this before? Link to comment Share on other sites More sharing options...
jack Posted October 23, 2018 Share Posted October 23, 2018 29 minutes ago, recoveringacademic said: Anyone done this before? A friend used to hot-wire model aeroplane wings, as you said. Easy enough to build your own with nichrome wire, a frame and a variable current power supply. It would take a while to get it all together, which would allow you to put off actually doing the work. Link to comment Share on other sites More sharing options...
the_r_sole Posted October 23, 2018 Share Posted October 23, 2018 (edited) . Edited September 26, 2019 by the_r_sole Link to comment Share on other sites More sharing options...
PeterW Posted October 23, 2018 Share Posted October 23, 2018 You buy it pre-cut, it’s available from Kingspan Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 23, 2018 Share Posted October 23, 2018 And don't try hot wire cutting PIR or PUR, only EPS or XPS. PIR and PUR don't cut with a hot wire, plus the fumes given off it they did would be very unpleasant. Link to comment Share on other sites More sharing options...
ToughButterCup Posted October 23, 2018 Author Share Posted October 23, 2018 47 minutes ago, the_r_sole said: usually easier to use timber firring to create the fall and not cut any insulation Exactamento! Been there, got the T shirt - jus' cant do it (in the space available). Honestly we've gone into it in great detail. 42 minutes ago, PeterW said: You buy it pre-cut, it’s available from Kingspan They are the ones who are telling me I have to cut it..... ! Just now, JSHarris said: And don't try hot wire cutting PIR or PUR, only EPS or XPS. PIR and PUR don't cut with a hot wire, plus the fumes given off it they did would be very unpleasant. Gottcha! Link to comment Share on other sites More sharing options...
the_r_sole Posted October 23, 2018 Share Posted October 23, 2018 (edited) . Edited September 26, 2019 by the_r_sole Link to comment Share on other sites More sharing options...
PeterW Posted October 23, 2018 Share Posted October 23, 2018 Kingspan have a standard product called ThermaTaper Available here Link to comment Share on other sites More sharing options...
ToughButterCup Posted October 23, 2018 Author Share Posted October 23, 2018 2 minutes ago, the_r_sole said: so are you ending up with less insulation at one side of the roof than the other?! how have you managed to get into a situation with a flat roof, was it not properly detailed at the start and you've run out of space to build it properly? Yes. And when I asked the Kingspan man - how is that (less one side than the other) then ? - came the response that It didn't matter. Thats not how you calculate the U value for the roof. And a few alarm bells went off in my head: hence the post. I don't know what to expect so '...proper detailing...' means little to me. At the moment. I am now doing it myself. (CDM 2015 Domestic Client). When the architect did the drawing I think he expected to liaise with contractors - his argument is (and has been several times over different issues) that no matter what he draws on paper, contractors do it their way anyway. The MVHR piping was meant to run within the POSIs, but now - as specified- can't - so they need to run under the POSIs. Bang goes 200mm or so. I suppose I might get the MVHR people to squeeze the pipes into the available space. Maybe need to go down that rat run..... I don't want to get into a sideshow about how why or when. I just need to just bloody well do it (to misquote the Nike advert line). I know exactly why we aren't going down the cold roof route. 17 minutes ago, PeterW said: Kingspan have a standard product called ThermaTaper And here is their quote for exactly that.... Blocks 4,5,6,7 and 8 are the ones I have been told I need to cut to shape. Link to comment Share on other sites More sharing options...
PeterW Posted October 23, 2018 Share Posted October 23, 2018 So you reduce the thickness of the slab insulation and make that stepped using standard thicknesses built up - 30mm would do it I think in layers..?? Link to comment Share on other sites More sharing options...
ToughButterCup Posted October 23, 2018 Author Share Posted October 23, 2018 1 minute ago, PeterW said: So you reduce the thickness of the slab insulation and make that stepped using standard thicknesses built up - 30mm would do it I think in layers..?? Hmmm, as ever a pragmatic approach, but how do I get a perfect gradient? I expect I'm being thick..... Roughly chop it to profile and then use a Surform rasp ? Anyway, why can't Kingspan just cut it for me FGS? They are cutting blocks 1,2 and 3 after all. Link to comment Share on other sites More sharing options...
PeterW Posted October 23, 2018 Share Posted October 23, 2018 ThermaTaper comes in standard thickness, standard sizes. So ThermaTaper is available in 1:60 and 1:80. You want the 1:60 stuff so that is 30/50 over 1.2m, or a 20mm rise. So under the whole deck, you put a full flat deck of 80mm, and add your first tapered board so you have 110-130 over the width. Now you lay another layer of 20mm across the next 1.2mm, stack the sloping one on top and you have 130-150 which now butts up to the first layer... you could just keep building with 20mm, or could be clever and buy a selection of 20/40/80 and build up from there. Link to comment Share on other sites More sharing options...
the_r_sole Posted October 23, 2018 Share Posted October 23, 2018 (edited) . Edited September 26, 2019 by the_r_sole Link to comment Share on other sites More sharing options...
ToughButterCup Posted October 23, 2018 Author Share Posted October 23, 2018 Just now, the_r_sole said: Is this not the same roof where you are looking to vent it and have a cold roof construction? If you have a warm roof construction, looks like the thinnest insulation you have there is 90mm, not sure how that is achieving 0.15 but anyway... What is stopping you add say 30mm of height and use timber firring? I know you are trying to make the height as small as possible but is it due to a parapet or something else Do you have a section drawing of what is going on in the roof? Yes: but my eyes watered at the cost of shaped insulation: and local 'advice' ? told me it could be done more cheaply. Neither am I : I think it's a case of 'S Passiv'ous innit mate - load a shite that ' The planning conditions: the parapet has to remain where it is in terms of level. Maybe its me, maybe I take Planning Conditions too seriously: when the very local evidence is that others couldn't give a stuff and just do what they want. Here you are Thats as detailed as it gets (got). Just been out to measure the gap in the POSIs 126 ish mm..... Originally the MVHR quote required a space of 165 between the top and bottom chord of the POSIs. Well, we've got 125ish . Rather than a Genvex which we'd set our hearts on. Bum. If we use this system instead, magically we can shove the pipes between the top and bottom chord and the height problem goes away . The ducting is 75mm. Jus' like that. Not like this, like that Link to comment Share on other sites More sharing options...
Declan52 Posted October 23, 2018 Share Posted October 23, 2018 2 minutes ago, recoveringacademic said: Yes: but my eyes watered at the cost of shaped insulation: and local 'advice' ? told me it could be done more cheaply. Neither am I : I think it's a case of 'S Passiv'ous innit mate - load a shite that ' The planning conditions: the parapet has to remain where it is in terms of level. Maybe its me, maybe I take Planning Conditions too seriously: when the very local evidence is that others couldn't give a stuff and just do what they want. Here you are Thats as detailed as it gets (got). Just been out to measure the gap in the POSIs 126 ish mm..... Originally the MVHR quote required a space of 165 between the top and bottom chord of the POSIs. Well, we've got 125ish . Rather than a Genvex which we'd set our hearts on. Bum. If we use this system instead, magically we can shove the pipes between the top and bottom chord and the height problem goes away . The ducting is 75mm. Jus' like that. Not like this, like that That's the unit I have. Not much to say about it other than it works away. Not much noise from it. Changing the filters is easy. About 10 mins to clean the heat exchanger only because the screws are the devils work. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 23, 2018 Share Posted October 23, 2018 We have loads of 75mm OD MVHR ducting going through Posijoists. The vast majority of our ventilation ducts run through them. From a DIY perspective, the 75mm semi-rigid ducting has to be probably the easiest stuff to use. Link to comment Share on other sites More sharing options...
ToughButterCup Posted October 23, 2018 Author Share Posted October 23, 2018 1 minute ago, JSHarris said: [...] the 75mm semi-rigid ducting has to be probably the easiest stuff to use. There's a man who knows just when and how to throw a life-belt..... Link to comment Share on other sites More sharing options...
the_r_sole Posted October 23, 2018 Share Posted October 23, 2018 (edited) . Edited September 26, 2019 by the_r_sole Link to comment Share on other sites More sharing options...
Dudda Posted October 23, 2018 Share Posted October 23, 2018 Tapered insulation is more expensive for such a small amount. It's fine on a large area but not worth it for such a small quantity. Multiple ways to fix this. Was the original MVHR for rigid ducts with branches? That's not necessary. Use radial semi rigid ducts and you can still use whatever heat recovery unit you want. You can use 75mm Outer diameter which has 68mm internal diameter (I think) or you can use 96mm outer diameter which has 75mm internal diameter. The 96mm is better for longer routes. Both these will fit very comfortably in the 125mm space you have. The drawing shows the parapet capping as flat. It will either slope in or out a few degrees. If you slope it out with a nice 30 degree pitch you'll gain another 50mm height in the parapet on the inside while it stays the same outside. Build the whole parapet up - nobody will notice and I don't think I'd worry about this. Build the parapet in timber. It doesn't need to be a block parapet and building it in timber will give you more room to insulate. Option one is by far the easiest and a potential saving on everything if you do the semi rigid radial ducts yourself which is very easy to do. Link to comment Share on other sites More sharing options...
ToughButterCup Posted October 23, 2018 Author Share Posted October 23, 2018 ? Its all coming together for what in my case, passes for a brain these days. First ManFlu of the season . ? Go on, show some sympathy I dare ya @Hecateh, @lizzie, @newhome. No point in asking more widely: they're all brutes Link to comment Share on other sites More sharing options...
newhome Posted October 23, 2018 Share Posted October 23, 2018 1 hour ago, recoveringacademic said: First ManFlu of the season . ? Go on, show some sympathy I dare ya @Hecateh, @lizzie, @newhome. No point in asking more widely: they're all brutes Well I could be sympathetic or honest or brutal Instead, I’ll use one of my favourite phrases from work and say MTFU! Hope you feel better soon ???? 1 Link to comment Share on other sites More sharing options...
Hecateh Posted October 23, 2018 Share Posted October 23, 2018 Manflu is your body telling you that you have a lowered resistance due to stress and it's time to take a break. There, there, you will feel better soon. Right, that's that taken care of - now - as @newhome has already advised MTFU 2 Link to comment Share on other sites More sharing options...
Hecateh Posted October 23, 2018 Share Posted October 23, 2018 (edited) I am pretty sure you would get more sympathy from the weaker sex - who have knowledge of and also suffer from this (none)complaint agreed @newhome? @Jude1234? @lizzie? Edited October 23, 2018 by Hecateh Link to comment Share on other sites More sharing options...
newhome Posted October 23, 2018 Share Posted October 23, 2018 9 minutes ago, Hecateh said: I am pretty sure you would get more sympathy from the weaker sex Oh totally! My sympathy level is evidenced by my second most favourite phrase at work SIUB or ‘suck it up buttercup’ ?. 1 Link to comment Share on other sites More sharing options...
lizzie Posted October 23, 2018 Share Posted October 23, 2018 So agree @Hecateh and @newhome.......manflu.........hot toddy, under a nice snuggly blanket in a comfy chair and latest car mag seems to sort it in our house! @recoveringacademic that is my prescription for you 1 Link to comment Share on other sites More sharing options...
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