thefoxesmaltings Posted November 2, 2022 Share Posted November 2, 2022 Following the typical makeup of a high spec/efficient timber frame building. The item in discussion is point no.7 - The Reflective Vapour Control Layer. Timber Frame Construction (Outside In) Brickwork Cavity Reflective Thermo Breather Membrane OSB Sheathing Timber Frame with 120mm Insulation Additional PIR Insulation (25-100mm) Reflective Vapour Control Layer 25mm Service void with Battens Plasterboard Is putting the Reflective VCL, (which is also designed to act as an airtight barrier) on the 'warm side' of the insulation, a counter intuitive idea? Surely, trades are just going to poke loads of holes through it for first & second fix, thus reducing the efficiency of the VCL and the air tightness? How would one even go about sealing this... Would it make sense to instead, place the Reflective VCL on the 'cold side' of the insulation, as the additional layer of shiny foil PIR (point no.6) would effectively become the VCL? Example where electrician has installed back box and fixed it through the Reflective VCL, effectively compromising the airtight membrane. Link to comment Share on other sites More sharing options...
Redbeard Posted November 2, 2022 Share Posted November 2, 2022 No wonder they call that lay-up 'super-advanced'. Read the first 3 lines: 1,120mm of PIR will give you 0.09W/m2K... Not as good as I thought, and a possible interstitial condensation risk? 1 Link to comment Share on other sites More sharing options...
ProDave Posted November 2, 2022 Share Posted November 2, 2022 26 minutes ago, thefoxesmaltings said: Surely, trades are just going to poke loads of holes through it for first & second fix, thus reducing the efficiency of the VCL and the air tightness? How would one even go about sealing this... No, you talk to them and lay down the ground rules. The whole purpose of the service void is for services, pipes and cables. The only time they need to penetrate the building is for services entering or leaving the building, like incoming supplies, and things like outside sockets, lights etc. Where such cables do have to exit the building it should be planned and sealed afterwards with air tightness tape etc. 2 Link to comment Share on other sites More sharing options...
thefoxesmaltings Posted November 2, 2022 Author Share Posted November 2, 2022 1 minute ago, ProDave said: No, you talk to them and lay down the ground rules. The whole purpose of the service void is for services, pipes and cables. The only time they need to penetrate the building is for services entering or leaving the building, like incoming supplies, and things like outside sockets, lights etc. Where such cables do have to exit the building it should be planned and sealed afterwards with air tightness tape etc. I get that, but in the example photo above the electrician has fixed the socket back box straight through the VCL - how else would you fix that to the structure securely, given the scenario? Link to comment Share on other sites More sharing options...
ProDave Posted November 2, 2022 Share Posted November 2, 2022 6 minutes ago, thefoxesmaltings said: I get that, but in the example photo above the electrician has fixed the socket back box straight through the VCL - how else would you fix that to the structure securely, given the scenario? I would use plasterboard back boxes. If he has screwed that back box through the VCL just what has he screwed into? I am not a fan of fixing the back box by screwing through the sides of the box into the stud, but if that is what he has done it won't puncture the VCL Where does the cable going through the VCL go to? The edges of the VCL don't appear to be taped to anything? Link to comment Share on other sites More sharing options...
Kelvin Posted November 2, 2022 Share Posted November 2, 2022 The VCL doesn’t look well fitted anyway. Link to comment Share on other sites More sharing options...
thefoxesmaltings Posted November 2, 2022 Author Share Posted November 2, 2022 39 minutes ago, ProDave said: I would use plasterboard back boxes. If he has screwed that back box through the VCL just what has he screwed into? I am not a fan of fixing the back box by screwing through the sides of the box into the stud, but if that is what he has done it won't puncture the VCL Where does the cable going through the VCL go to? The edges of the VCL don't appear to be taped to anything? I'm not too sure. It's not my build, but an 'in-progress' one we went round to have a look at - just a photo I took whilst there. Link to comment Share on other sites More sharing options...
thefoxesmaltings Posted November 2, 2022 Author Share Posted November 2, 2022 24 minutes ago, Kelvin said: The VCL doesn’t look well fitted anyway. Yeah, it doesn't seem too 'taught' and they haven't taped up the edges (yet) I'm guessing. It was a in-progress build we went to have a look at. Link to comment Share on other sites More sharing options...
markocosic Posted November 2, 2022 Share Posted November 2, 2022 Air barrier / vapour retarder goes on the inside in a heading dominated climate. Make the service void 45 or even mm and fill it with insulation if you're worried about "needing" to penetrate it. Plenty of space for cables and pipes that way. Really shouldn't need that much space though. That build is probably just badly thought through and badly supervised if the sparks and plumbers are needing to penetrate the vcl for admitting other than outside light fixtures. 2 Link to comment Share on other sites More sharing options...
Nickfromwales Posted November 2, 2022 Share Posted November 2, 2022 This is how I work with this type of system. I run more of the counter ( service ) battens horizontally, so they can be fixed side on thus not needing to fix through the membrane, and then the boxes get drilled and screwed up and down into the horizontal timbers. The Egger board was installed to take the wall mounted TV’s, so they could be fitted with the correct depth / length screws so again the membrane didn’t suffer damage from any such retrospectively installed equipment. Injecting 330 foam all round the Egger board would offer further insurance. The sparky should drop down and go through to the next room in the joist void imo, or create a penetration with a conduit which can be filled with Illbruck 330 foam and made airtight accordingly. As said, you must lead on this, as most trades still have little to no experience with airtightness disciplines / products etc, and you should be prepared to provide them with the correct foam / tape etc if you want this doing correctly. 8 Link to comment Share on other sites More sharing options...
thefoxesmaltings Posted November 24, 2022 Author Share Posted November 24, 2022 On 02/11/2022 at 22:47, Nickfromwales said: This is how I work with this type of system. I run more of the counter ( service ) battens horizontally, so they can be fixed side on thus not needing to fix through the membrane, and then the boxes get drilled and screwed up and down into the horizontal timbers. The Egger board was installed to take the wall mounted TV’s, so they could be fitted with the correct depth / length screws so again the membrane didn’t suffer damage from any such retrospectively installed equipment. Injecting 330 foam all round the Egger board would offer further insurance. The sparky should drop down and go through to the next room in the joist void imo, or create a penetration with a conduit which can be filled with Illbruck 330 foam and made airtight accordingly. As said, you must lead on this, as most trades still have little to no experience with airtightness disciplines / products etc, and you should be prepared to provide them with the correct foam / tape etc if you want this doing correctly. Nick, this looks great. Stupid question - but how and where do you fix the screws for the counter horizontal service battens? Do they just go through the membrane? Link to comment Share on other sites More sharing options...
Alwayslearning22 Posted January 23, 2023 Share Posted January 23, 2023 On 02/11/2022 at 22:47, Nickfromwales said: This is how I work with this type of system. I run more of the counter ( service ) battens horizontally, so they can be fixed side on thus not needing to fix through the membrane, and then the boxes get drilled and screwed up and down into the horizontal timbers. The Egger board was installed to take the wall mounted TV’s, so they could be fitted with the correct depth / length screws so again the membrane didn’t suffer damage from any such retrospectively installed equipment. Injecting 330 foam all round the Egger board would offer further insurance. The sparky should drop down and go through to the next room in the joist void imo, or create a penetration with a conduit which can be filled with Illbruck 330 foam and made airtight accordingly. As said, you must lead on this, as most trades still have little to no experience with airtightness disciplines / products etc, and you should be prepared to provide them with the correct foam / tape etc if you want this doing correctly. Does the egger board have the strength to hold heavy TV? How is the egger board secured to the battens? They don’t look to thick. I’d like to use this set up for heavy cabinets and tv’s. Just need to know how to secure the board. thanks Link to comment Share on other sites More sharing options...
Nickfromwales Posted January 23, 2023 Share Posted January 23, 2023 On 24/11/2022 at 15:23, thefoxesmaltings said: Nick, this looks great. Stupid question - but how and where do you fix the screws for the counter horizontal service battens? Do they just go through the membrane? Apologies, I seem to have missed this! They are screwed at the very ends only, and are floating for the full length. The screws go through the vertical battens and into the ends of the horizontals, with 2 screws in the pattern of a 2 on a dice. I cut the horizontals a mm or so oversized so they are a nice tight fit, and used 4x80mm screws. 1 Link to comment Share on other sites More sharing options...
Alwayslearning22 Posted January 24, 2023 Share Posted January 24, 2023 (edited) Is the egger board secured to the vertical battens? Edited January 24, 2023 by Alwayslearning22 Link to comment Share on other sites More sharing options...
Kelvin Posted January 25, 2023 Share Posted January 25, 2023 I'm at the stage where I need to think about this and have been speaking to the electrician. We've decided on fitting plasterboard backboxes. However I spoke with the Glidevale (we're using the same product) and asked about screwing directly into the airtight barrier securing to the OSB of the CPS panel. They said it's perfectly fine to do this as it self-seals around the the screw. The issue is when they've put something in the wrong place and remove the screw so you need to cover the hole with tape. They also said that once you've decided where the services are going you can fit butyl tape for them to screw through which doubles up the sealing for a belt and braces approach. Obviously poking cable through a hole in the air barrier is wrong and to be avoided albeit if you need to do it you can seal around the hole and cable. Link to comment Share on other sites More sharing options...
Alwayslearning22 Posted January 28, 2023 Share Posted January 28, 2023 On 02/11/2022 at 22:47, Nickfromwales said: This is how I work with this type of system. I run more of the counter ( service ) battens horizontally, so they can be fixed side on thus not needing to fix through the membrane, and then the boxes get drilled and screwed up and down into the horizontal timbers. The Egger board was installed to take the wall mounted TV’s, so they could be fitted with the correct depth / length screws so again the membrane didn’t suffer damage from any such retrospectively installed equipment. Injecting 330 foam all round the Egger board would offer further insurance. The sparky should drop down and go through to the next room in the joist void imo, or create a penetration with a conduit which can be filled with Illbruck 330 foam and made airtight accordingly. As said, you must lead on this, as most trades still have little to no experience with airtightness disciplines / products etc, and you should be prepared to provide them with the correct foam / tape etc if you want this doing correctly. Sorry to be a pain. Are those battens strong enough to hold up a heavy tv? I need to do this in my home but I’m concerned about the battens strength. Link to comment Share on other sites More sharing options...
ProDave Posted January 28, 2023 Share Posted January 28, 2023 28 minutes ago, Alwayslearning22 said: Sorry to be a pain. Are those battens strong enough to hold up a heavy tv? I need to do this in my home but I’m concerned about the battens strength. I did very similar. What you have to remember is the battens follow the vertical lines of the wall studs. When mounting the tv you screw through the battens and into the studs behind them. I used a wide tv bracket, the sort you screw a wide plate to the wall and a pair of brackets fix to the back of the tv and hang on the wide plate. Mine has been holding up our old 50" plasma tv that is a 2 man lift for a few years now, way heavier than any modern tv you will buy now. 1 Link to comment Share on other sites More sharing options...
Alwayslearning22 Posted January 28, 2023 Share Posted January 28, 2023 (edited) 35 minutes ago, ProDave said: I did very similar. What you have to remember is the battens follow the vertical lines of the wall studs. When mounting the tv you screw through the battens and into the studs behind them. I used a wide tv bracket, the sort you screw a wide plate to the wall and a pair of brackets fix to the back of the tv and hang on the wide plate. Mine has been holding up our old 50" plasma tv that is a 2 man lift for a few years now, way heavier than any modern tv you will buy now. Oh I see. My wall that I plan to use is a shared party wall so I didn’t like the idea of screwing that far into the studs. What length of screws did you use? nickfromwales is using the egger board I wonder is he avoiding drilling into the studs incase of vcl damage? Edited January 28, 2023 by Alwayslearning22 Link to comment Share on other sites More sharing options...
Nickfromwales Posted January 28, 2023 Share Posted January 28, 2023 On 25/01/2023 at 14:52, Kelvin said: I'm at the stage where I need to think about this and have been speaking to the electrician. We've decided on fitting plasterboard backboxes. However I spoke with the Glidevale (we're using the same product) and asked about screwing directly into the airtight barrier securing to the OSB of the CPS panel. They said it's perfectly fine to do this as it self-seals around the the screw. The issue is when they've put something in the wrong place and remove the screw so you need to cover the hole with tape. They also said that once you've decided where the services are going you can fit butyl tape for them to screw through which doubles up the sealing for a belt and braces approach. Obviously poking cable through a hole in the air barrier is wrong and to be avoided albeit if you need to do it you can seal around the hole and cable. Your chaps are spot on here, and it’s great to hear them saying this to you as they obviously know theirs stuff. 👌👍 Link to comment Share on other sites More sharing options...
Nickfromwales Posted January 30, 2023 Share Posted January 30, 2023 On 28/01/2023 at 21:13, Alwayslearning22 said: Sorry to be a pain. Are those battens strong enough to hold up a heavy tv? I need to do this in my home but I’m concerned about the battens strength. Yup. Bang a few extra 130mm x 6.0 screws in for belt & braces. 1 Link to comment Share on other sites More sharing options...
TerryE Posted January 31, 2023 Share Posted January 31, 2023 (edited) On 02/11/2022 at 18:24, thefoxesmaltings said: Is putting the Reflective VCL, (which is also designed to act as an airtight barrier) on the 'warm side' of the insulation, a counter intuitive idea? Surely, trades are just going to poke loads of holes through it for first & second fix, thus reducing the efficiency of the VCL and the air tightness? How would one even go about sealing this... We had a simple rule: no tradesmen were allowed to touch the VCL. We basically pre surveyed and agreed all through penetrations and fixings then we added tall of the through holes using appropriate diameter ABS pipe, the outside of which we sealed and taped, and this left the necessary through-hole for the tradesman to run cabling / pipework. Ditto we fixed dwangs / mounting plates where anything needed fixing or hanging. For example the PB was screwed to vertical service battens but we also had 60° reveals into out windows, we added horizontal fixing strips in the reveals to allow the crew to screw the plasterboard to this. If the electrician or whatever needed another hole then we would do this within a day or so. Prior to the Air tightness test, we went around and foamed + siliconed up the through holes to ensure airtighness. We passed the test first time, with no tweaks. Edited January 31, 2023 by TerryE Link to comment Share on other sites More sharing options...
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