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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 

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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 22ugfmembrane7.jpg

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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:

 

image.png.5a214bad9ac34d6b954f109e13d3c8a0.png

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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.

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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.

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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/

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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!

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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 22ugfmembrane7.jpg

 

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

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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.

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