Wed, 10 Jun 2026 11:17:11 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47769#Comment_47769 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47769#Comment_47769 Sun, 15 Feb 2009 22:16:53 +0000 layperson My house was originally built in 1700 and is not listed. It is on 3 floors and the top floor is where we sleep. It has exposed beam work and has a pitched roof. It is very pretty but sometimes leaks. The renovation work started in Oct 2008 and due to end in May 2009! A big conversion beleive me.
My builder has removed the pasterboard to the pitched roof and the Rockwool is discoloured, is 2 layers deep (I estimate it is 8 to 10 inches), but we suspect most was done around 30 years ago (some improvement works were done about 7 years ago and there is some different coloured rock wool going on). The builder is putting new plasterboard back (with no insulation properties: just plain plasterboard). I am concnered about the following:
1) Should i be using a insulated plasterboard (e.g Kingspan 50 mm) or Spacetherm?
2) Would his exisiting solution pass Building regulations?
2.5) Would his solution allow for air pocket to allow ventelation ?
3) Given that i have leaks, should he not take out the rock wool and chekc for leaks (e.g where the felt has broken)?
Help please!!!
]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47770#Comment_47770 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47770#Comment_47770 Sun, 15 Feb 2009 22:18:21 +0000 layperson ]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47771#Comment_47771 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47771#Comment_47771 Sun, 15 Feb 2009 22:27:00 +0000 tony
The discolouration to the insulation is moat likely dirt.

sounds like you have a reasonable ammount of insulant though gaps will have a disproportionate effect on heat losses.

You must fix the leaks.

why is the plasterboard being changed? you are at an ideal moment to improve insulation.

If you were going to do sheet insulation then it is cheaper to use this and then plasterboard rather than a composite board.

Please concentrate on eliminating all drafts from outside to inside (air sealing)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47779#Comment_47779 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47779#Comment_47779 Mon, 16 Feb 2009 09:11:45 +0000 layperson ]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47781#Comment_47781 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47781#Comment_47781 Mon, 16 Feb 2009 09:32:56 +0000 TheDoctor
you need 50 mm to ensure ventilation here and prevent damp / rot.

make sure the rockwool is consistent and complete.
Make sure the renovation does not overly disturb and move it around leaving gaping voids in your insulation.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47784#Comment_47784 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47784#Comment_47784 Mon, 16 Feb 2009 09:47:49 +0000 Sigaldry
Element being renovated: U-value W/m²K

Walls 0.35
Floors 0.25
Flat roof or roof with integral insulation 0.25
Pitched roof (insulation at ceiling level) 0.16
Pitched roof (insulation at between rafters) 0.20


Where existing thermal elements are to be retained, and are below a specified 'threshold U-value', they will need to be upgraded to achieve the following U-values.

Element being retained or renovated Threshold U-value W/m²K Improved U-value W/m²K

Cavity walls 0.70 0.55
Other wall types 0.70 0.35
Floors 0.70 0.25
Pitched roof (insulation at ceiling level) 0.35 0.16

Pitched roof (insulation at between rafters) 0.35 0.20
Flat roof or roof with integral insulation 0.35 0.25

NB thats the minimum values you need to achieve to comply with England and Wales building regulations - as this is the green building forum - i'd suggest at least 20 to 25% better (lower) than those would be a good start!

I'd suggest contacting the technical departments of whichever insulation manufacturers you prefer (or look at their website's/technical literature and tell them the sizes and centres of your rafters and what the current build up is and what U-value you are aiming for. They should also be able to advise you of ventilation requirements for your given build up and whether there's any risk of condensation occuring.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47828#Comment_47828 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47828#Comment_47828 Mon, 16 Feb 2009 16:50:31 +0000 rowefamily
Many thanks. Russ]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47829#Comment_47829 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47829#Comment_47829 Mon, 16 Feb 2009 16:55:18 +0000 TheDoctor
they never look like the original rafters you are trying to mimic.
Generally detract from the aesthetic appearance of the room.

fix your boards directly through the lathe and plaster to the rafters using proprietary fixings, rather than no nails.
Insulated Plasterboard is heavier than you think.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47832#Comment_47832 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47832#Comment_47832 Mon, 16 Feb 2009 17:12:14 +0000 rowefamily ]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47840#Comment_47840 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47840#Comment_47840 Mon, 16 Feb 2009 18:16:44 +0000 layperson Been out to site today with the builder and the architect. We took down the rock wool and revealled that the felt was so brittle it crumbled in our hands. Architect is telling me we should re-felt and this will mean taking off the stone tiles of our huge and enormous roofing area. This place is around 4500 sq feet over 3 floors so you can imagine the area of roof we are talking about. I think the cost of this will be inexcess of £20K.
Any alternaitves??? Please please help!!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47844#Comment_47844 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47844#Comment_47844 Mon, 16 Feb 2009 18:29:44 +0000 jamesingram gap between the batton and top of the PUR board , then foamed in the edge to get a good tight fit
under the rafter I fitted more PUR board, a polythene vapour barrier and then plasterboard

at the eaves I angle up the PUR board so as if there are any leaks, water will run down the board and out over the cavity wall and into the sofit , not that great, but better than running down the cavity or internal wall
I'm not sure what the general opinion would be of this idea ,probably not by the book, but it saved me refelting

and so far I've had no leaks showing (5 years)
perhap taking the first couple of rows of tiles off and get the PUR to meet with the top of the fascia, with a bit of DPC involved somehow might improve it?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47845#Comment_47845 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47845#Comment_47845 Mon, 16 Feb 2009 18:41:31 +0000 betterroof https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47846#Comment_47846 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47846#Comment_47846 Mon, 16 Feb 2009 18:47:46 +0000 betterroof
Sorry - lots of things to think about ]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47961#Comment_47961 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47961#Comment_47961 Wed, 18 Feb 2009 06:24:36 +0000 layperson RE; Betterroof: we are in South yorkshire. What does PUR board mean?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47967#Comment_47967 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47967#Comment_47967 Wed, 18 Feb 2009 07:51:11 +0000 jamesingram pavatherm would be the greener material option
http://www.greenspec.co.uk/html/product-pages/pavatherm.php

my previous comment referred to your problem layperson
cheers
Jim]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47969#Comment_47969 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47969#Comment_47969 Wed, 18 Feb 2009 07:55:27 +0000 rowefamily https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47971#Comment_47971 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=47971#Comment_47971 Wed, 18 Feb 2009 08:01:01 +0000 jamesingram PUR -celotex,kingspan there much the same
phenolinic board (kingspan) is a slightly better insulator than polyurethane ,and more expensive
as a result
or there this aerogel stuff , do a search on this site , regarding]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=48012#Comment_48012 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=48012#Comment_48012 Wed, 18 Feb 2009 14:56:19 +0000 CWatters
Prior to the bombshell.... If your builder wasn't converting a room from a store to a habitable room (eg it had already been converted) nor was he making changes to "insulating elements" (just removing and replacing plasterboard) then technically I don't think he had to upgrade the insulation to meet current regs. Worth doing anyway though.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=64000#Comment_64000 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=64000#Comment_64000 Tue, 13 Oct 2009 23:40:52 +0100 spoonandfork
low to high - 1st floor space, plasterboard, VCL, 150mm joists / insulation, OSB floor, loft/storage space, 150mm rafters / insulation, air barrier (?) stapled to rafters, 25mm gap, sarking, felt, tiles]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=64002#Comment_64002 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=64002#Comment_64002 Wed, 14 Oct 2009 00:17:07 +0100 neelpeel Also, insulating and getting the loft hatch as air-tight as you can is very important as the warm air can be sucked through like a chimney.

If you need floor space for storage then you can install battens to gain more depth for insulation and then floor over the top.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=64010#Comment_64010 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=64010#Comment_64010 Wed, 14 Oct 2009 08:47:49 +0100 spoonandfork https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=64011#Comment_64011 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3586&Focus=64011#Comment_64011 Wed, 14 Oct 2009 09:15:34 +0100 tony