Fri, 16 Oct 2026 17:11:44 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18490&Focus=311713#Comment_311713 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18490&Focus=311713#Comment_311713 Fri, 16 Oct 2026 12:33:48 +0100 cc64
We're enclosing a previously open-sided porch to create an unconditioned entrance lobby. A vent serving the void below the beam-and-block floor, and positioned below the original front door, will vent into the new porch enclosure. Building control will not be impressed if we don't extend from the brick vent aperture and duct out to the side wall and through a new brink vent.

Naively I thought this would be straightforward enough. But am not finding suitably dimensioned ducting. It seems "there's not much call for that".

Has anyone else successfully grappled with this conundrum, and if so how? Having trawled through "countless" websites ( DOMUS, Manrose, Airvent, Mapthorpe, Wolseley, AirflowDevelopments, Timloc) I'm asking for a reality check; can this vent be re-established with a horizonal extension, a horizontal 90 flat corner, and another horizontal extension out to the new sidewall brink vent? Or is my architect havin a larf?

Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18490&Focus=311714#Comment_311714 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18490&Focus=311714#Comment_311714 Fri, 16 Oct 2026 13:20:49 +0100 build4less
You're on the right track. Once the porch is enclosed, that old brick vent is no longer open to outside air, so Building Control are right to want a continuous path out to a new external vent on the side wall.

The awkward bit is matching free area rather than the face size of the airbrick. A standard brick vent looks about 215 x 65 mm on the face but the actual open area is much less, so size the duct to that free area and do not pinch it down at bends. A short horizontal run with one gentle 90 degree bend is fine.

In practice people use either rectangular flat channel duct (Domus / Manrose style) with adaptors onto the airbrick sleeves, or 110 mm soil pipe with square to round adaptors at each end. Both are easy to get from merchants. Keep a slight fall to the outside so any rain that gets in drains out, seal the joints so porch air does not leak into the underfloor void, and fit a proper airbrick or cowl at the new outlet rather than leaving a bare pipe end.

So yes, horizontal extension, flat 90, then out to a new brick vent is a normal detail, not a joke from the architect. Just keep the run short and the free area up.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18490&Focus=311715#Comment_311715 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18490&Focus=311715#Comment_311715 Fri, 16 Oct 2026 16:23:18 +0100 Dominic Cooney
https://bpcventilation.com/collections/rigid-pvc-ducting-fittings

*edit to add that they even seem to have an "airbrick connector" on there.]]>