Diablo Posted September 11, 2019 Share Posted September 11, 2019 All, We are having our flat roof done and I want to move the exhaust vent from the pitched, as it is making a mess on our slate tiles. I called BPC and they want £210 for a cowl and shroud, which seems a bit dear to me. The roofer is using mushroom vents for about £10-15/each which don't look that dissimilar. Has anyone come across any more cost effective alternatives? Thanks, Rog Link to comment Share on other sites More sharing options...
mvincentd Posted September 11, 2019 Share Posted September 11, 2019 i have this https://www.roofingsuperstore.co.uk/product/ubbink-oft5-insulated-flat-roof-vent-terminal-180mm-diameter-black.html ....and a reducer like this https://www.roofingsuperstore.co.uk/product/reducer-167-149-for-pipe-connections.html to get into my ducting. I've picked those links at random but all different diameters available at https://www.roofingsuperstore.co.uk/browse/ventilation/flat-roof-vents-extraction/flat-roof-extraction.html Tin top hat supposed to go atop insulation below membrane (assuming a warm flat roof) but roofers weren't concerned with using it. pic installed here Link to comment Share on other sites More sharing options...
Jeremy Harris Posted September 12, 2019 Share Posted September 12, 2019 Are those roof terminals >3m apart? The MIs for our MVHR gave specified minimum separation distances for intake and exhaust ducts, both for roof mounting and for through wall mounting: Link to comment Share on other sites More sharing options...
mvincentd Posted September 12, 2019 Share Posted September 12, 2019 I think they're 2.2m apart, which is fine with regs, in excess of my mvhr design recommendations, and acceptable to me given the exhaust air is only air that had been in my house anyway. Obviously the further apart the better but routing the ducts internally can be a minefield and there's a playoff in achieving external separation at the cost of sending the ducts through more contortions internally to achieve it. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted September 12, 2019 Share Posted September 12, 2019 My concern was only that the MIs for the MVHR normally over ride any guidance in building regs, so technically a Genvex MVHR installed with the intake and exhaust only 2.2m apart on a roof would be non-compliant. Whether it makes any appreciable practical difference in performance is doubtful. I'd have thought a couple of metres apart should just about be OK, as long as the intake isn't downwind from the exhaust. Link to comment Share on other sites More sharing options...
mvincentd Posted September 12, 2019 Share Posted September 12, 2019 I appreciate your flagging the concern, especially given the Genvex 3m requirement and my picture, however i'm on a Zehnder q350 and it states 1.5m minimum. Had I gone for a unit with a 3m requirement i'd have had real problems meeting it....anyway I had to introduce two undesirable 90 degree turns in the ducting through the joist space to achieve the 2.2m Use of a MAICO KWH as suggested by this passivehaus consultant would have enabled me to keep dead straight runs both in and out of the unit....but something tells me you wouldn't concur with his advice! http://www.heatspaceandlight.com/space-mvhr-ducts-tight-combined-intake-exhaust-grille-solution/ Link to comment Share on other sites More sharing options...
Jeremy Harris Posted September 12, 2019 Share Posted September 12, 2019 1 minute ago, mvincentd said: I appreciate your flagging the concern, especially given the Genvex 3m requirement and my picture, however i'm on a Zehnder q350 and it states 1.5m minimum. Had I gone for a unit with a 3m requirement i'd have had real problems meeting it....anyway I had to introduce two undesirable 90 degree turns in the ducting through the joist space to achieve the 2.2m Use of a MAICO KWH as suggested by this passivehaus consultant would have enabled me to keep dead straight runs both in and out of the unit....but something tells me you wouldn't concur with his advice! http://www.heatspaceandlight.com/space-mvhr-ducts-tight-combined-intake-exhaust-grille-solution/ Not that I would or would not concur, just that I had similar problems getting enough separation with our Genvex system to make it comply with their MIs, and as our building inspector had never seen a house with MVHR, he used the MIs as the document that had to be complied with. I also had to fit 90 degree bends and some tight duct work to get this to fit! Link to comment Share on other sites More sharing options...
Diablo Posted September 12, 2019 Author Share Posted September 12, 2019 15 hours ago, mvincentd said: i have this https://www.roofingsuperstore.co.uk/product/ubbink-oft5-insulated-flat-roof-vent-terminal-180mm-diameter-black.html ....and a reducer like this https://www.roofingsuperstore.co.uk/product/reducer-167-149-for-pipe-connections.html to get into my ducting. I've picked those links at random but all different diameters available at https://www.roofingsuperstore.co.uk/browse/ventilation/flat-roof-vents-extraction/flat-roof-extraction.html Tin top hat supposed to go atop insulation below membrane (assuming a warm flat roof) but roofers weren't concerned with using it. pic installed here Brilliant! That's what I need. How do you get from the 180mm vent to the 167mm of the wider end of the reducer? Many thanks Link to comment Share on other sites More sharing options...
mvincentd Posted September 12, 2019 Share Posted September 12, 2019 I picked the links at random to illustrate the items....actually in my case I had 150mm diameter ducting so got the appropriate 'reducer' to fit that and go onto I believe a 160mm version of the chimney. Link to comment Share on other sites More sharing options...
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