Tue, 19 May 2026 16:45:14 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18154&Focus=306146#Comment_306146 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18154&Focus=306146#Comment_306146 Tue, 02 Jul 2024 16:23:00 +0100 Huwblut
I’m still plugging away with my little bungalow project. Following on from my post about insulation I’m now trying to figure out how to get it into the eves but still leave a 50mm gap for ventilation.

I’ve manage to get a photo downloaded so I hope that it helps. There’s lots more photos which I’m sure would be really useful but I can’t seem to get more that one in…

I’m told that it’s a hipped roof in the shape of a pyramid. It’s got two little bays at the front.

The corners are of particular concern as it’s a real junction of timber! There was some insulation in there previously but it was patchy which left cold spots and which resulted in some condensation / mould.

The ceilings are down and there’s access from above and below. I’ll be insulating the main body of the ceiling / floor from underneath.

I’ve been looking Manthorpe Refurb Eaves Panels:

https://www.manthorpebp.co.uk/roofing/roofspace-ventilation/refurb-eaves-panel-0

but the irregular spacing of the joists and rafters make it difficult.

I’ve also been looking at their eves ventilation roll:

https://www.manthorpebp.co.uk/roofing/roof-ventilation-%E2%80%93-solutions-modern-day-problem/roll-panel-vents-1

which may do a job as well.

I’m wondering if all the roof needs a 50mm gap or could I compromise and do as much as I can do and hope that there’ll still be enough air movement?

All the soffits will be replaced as well so I could include some extra ventilation there.

Apologies if I’ve not explained this too well.

I’d be lost without the help of the forum!

Cheers

Huw]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18154&Focus=306149#Comment_306149 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18154&Focus=306149#Comment_306149 Tue, 02 Jul 2024 17:44:07 +0100 Peter_in_Hungary
Closed spaces are a potential condensation point.

You could drill (lots of) holes at the top of the jack rafters to allow air movement between the jack rafters and do so to adjacent jack rafters until clear roof space is reached. It is never a good idea to drill holes in structural timbers (holes are supposed to be in the middle 1/3) but given the shortness of the jack rafters they are structurally very over specified but are the same size as common rafters for ease of construction and tiling..

You could also put vent tiles at the points of closed spaces, although cutting tiles at the bottom of a hip is always a bit fraught without the complication of vents.

To me it looks like the 2 products you cite provide through ventilation but do not provide ventilation for what is below - and it is below that it will be needed. I can imagine condensation forming on the underside of either product either if the insulation touches it or they are put in a closed space (closed by the junction of the hip rafter and the jack rafter)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18154&Focus=306151#Comment_306151 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18154&Focus=306151#Comment_306151 Tue, 02 Jul 2024 18:09:54 +0100 tony
How much insulation will you be putting in the loft - I reckon 400mm while you are at it

It should be possible to place the eaves ventilation trays, push fibreglass roll down over the wall plate and into the top of the cavities, do the corners first.

Then the first meter of the ceiling, then I add a vapour/air tightness barrier then plasterboard

Happy insulating !]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18154&Focus=306163#Comment_306163 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18154&Focus=306163#Comment_306163 Wed, 03 Jul 2024 16:22:14 +0100 Huwblut
For context there's a couple of small rooms in the top of the pyramid which are insulated with Celotex and some low walls which I'll probably insulate with Celotex or similar. Therese's a crawl space around the perimeter which gives reasonable access to the roof, I'll insulate this as well hopefully to 400mm ish.

The idea of a vapour barrier underneath the plasterboard and insulated joists has been mentioned before but discounted due to the above space being a "warm" space rather than a typical attic.

I'm happy to do this but is it really necessary? There'll be adequate extraction in the kitchen and probably 2 small; dmev constantly running fans - one in the kitchen and one in the bathroom with a 10mm undercut on the doors.

Apologies for so many questions but I'm learning a lot here...]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18154&Focus=306165#Comment_306165 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18154&Focus=306165#Comment_306165 Thu, 04 Jul 2024 13:46:22 +0100 tony
I always worry about wind or outdoor air getting under the floors of loft rooms, that is where you don’t want ventilation]]>