Wed, 03 Jun 2026 06:06:26 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303735#Comment_303735 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303735#Comment_303735 Thu, 05 Oct 2023 09:25:32 +0100 blubb
I am retrofitting an MVHR into a pitched roof building. The idea was to have the inlet through the tiles at the bottom of the roof in the west-facing corner, and to have the exhaust at the top of the roof with a terminal going 1 m above the roof level. See sketch attached (sorry for the bad scan quality!).

Are there any issues with this layout?

An MVHR installer is telling me that the inlet needs to go through the wall of the building and never through the roof, which I find hard to believe.

Many thanks!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303742#Comment_303742 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303742#Comment_303742 Thu, 05 Oct 2023 10:30:25 +0100 an02ew https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303752#Comment_303752 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303752#Comment_303752 Thu, 05 Oct 2023 11:33:26 +0100 borpin
Mine are a little too close together but there doesn't seem to be any issue and are also not raised at all. They are a rectangle so 2 sides are open.

I do notice quite a lot of discharge on the slates though after 10 years.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303753#Comment_303753 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303753#Comment_303753 Thu, 05 Oct 2023 11:35:21 +0100 djh https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303762#Comment_303762 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303762#Comment_303762 Thu, 05 Oct 2023 18:57:48 +0100 revor Posted By: djhYou want both terminals in a similar pressure region, so the MVHR doesn't have to strain. The roof is infamous for varying pressure depending on which way the wind is blowing etc. So I'd have thought one terminal at the ridge and one on a slope was a poor idea. Better to have them both on the same slope but with separation between them, I'd have thought. Also site them well away from edges and corners.

Totally agree and choose if you can an elevation on the non prevailing wind side. Think they would be better on the wall easier access to clean grills etc. and away from turbulence. Minimum 2m separation is the general norm.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303763#Comment_303763 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303763#Comment_303763 Fri, 06 Oct 2023 09:02:14 +0100 GreenPaddy
An intake on the roof may well be covered with snow - the exhaust outlet unlikely, due to exhaust air direction and residual warmth. I never install intakes on the roof.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303767#Comment_303767 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303767#Comment_303767 Fri, 06 Oct 2023 12:16:38 +0100 djh https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303774#Comment_303774 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303774#Comment_303774 Fri, 06 Oct 2023 17:42:05 +0100 CWatters
Avoid putting the inlet down wind of your boiler flue.

I fitted a home made coarse filter to the inlet. Needs cleaning every 8 weeks.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303802#Comment_303802 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303802#Comment_303802 Sun, 08 Oct 2023 07:06:05 +0100 an02ew Posted By: GreenPaddyAn intake on the roof may well be covered with snow

Ubbink have a dedicated MVHR range of roof terminal (UB48, UB47 etc) these are insulated through to exterior have no fine mesh and stand 500mm+ above roof tile.

i have recentley taken the NICEIC domestic ventilation course at Vent axia (2 day course with a BPEC acceditation) lots of guidance lots of do's and dont's but no mention of wall vents prefered to roof vents]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303809#Comment_303809 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303809#Comment_303809 Sun, 08 Oct 2023 11:25:00 +0100 djh https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303851#Comment_303851 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17985&Focus=303851#Comment_303851 Fri, 13 Oct 2023 12:08:45 +0100 blubb Will adjust the design by moving the exhaust lower to be at the same level as the inlet.
The terminals are Ubbink UB49 160 mm inner diameter.]]>