Tue, 09 Jun 2026 12:54:47 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177560#Comment_177560 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177560#Comment_177560 Sun, 09 Jun 2013 15:28:48 +0100 Greenfish
Plenty of between rafter space to stuff with something.... Could fill it with cheap (0.044 W/mK) loft roll and still get a space heading towards a u value of 0.11 (not quite that because of the truss timber contribution), but how to keep the fluff up there before fitting the VCL and plasterboard? Could stick 400mm of PIR board in there, but it would be nice to save some build costs at this stage by using a cheaper material. Mineral wool bats perhaps? Pumped cellulose or foam?

How can I insulate well and economically given the depth of this between "rafter" space?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177564#Comment_177564 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177564#Comment_177564 Sun, 09 Jun 2013 16:19:53 +0100 PeterStarck https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177565#Comment_177565 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177565#Comment_177565 Sun, 09 Jun 2013 16:54:00 +0100 Ed Davies https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177567#Comment_177567 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177567#Comment_177567 Sun, 09 Jun 2013 17:05:05 +0100 Chris P Bacon
Our sloping roof is 500mm deep with an air gap formed under the sarking board with battens and hardboard.

The VCL was fixed to the inside face of the trusses and counter battened with 95x20mm battens to which the plasterboard will be fixed.

The resulting void was pumped with loose rockwool, this gives a calculated u-value of 0.082

The flat ceiling was similarly insulated to a depth of 750mm.

Not sure if the loose mineral wool is available in the UK (I'm in Sweden) but a similar job could be done with cellulose.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177568#Comment_177568 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177568#Comment_177568 Sun, 09 Jun 2013 17:05:39 +0100 Greenfish Posted By: PeterStarckIcynene or Knauf Supafil Frame would work but not cheap, but then are there any cheap loft rolls any more?Works out about £3600 for Icynene to be sprayed, compared to £1300 for "Supaloft" (the recycled plastic stuff) plus fitting costs, have yet to do the numbers for 27m^3 of other materials. But the Icynene will be nice and air tight in every nook and cranny, while the Supaloft will be lots of plastic dangling around my head!

If I could get a cheap loft roll, how could I install it between the rafters?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177570#Comment_177570 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177570#Comment_177570 Sun, 09 Jun 2013 17:10:55 +0100 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177571#Comment_177571 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177571#Comment_177571 Sun, 09 Jun 2013 17:14:52 +0100 Greenfish Posted By: Chris P BaconThe resulting void was pumped with loose rockwool, this gives a calculated u-value of 0.082 Yummy u value! Did each gap between rafters have to be pumped separately to avoid air pockets?

Out of interest what was your truss structure? Any pictures?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177572#Comment_177572 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177572#Comment_177572 Sun, 09 Jun 2013 17:17:05 +0100 Greenfish Posted By: tonyNo question about it, quilt, either fibreglass (my choice) or rockwoolBut how to keep it up there? Temp sticks and strings like Ed suggests?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177574#Comment_177574 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177574#Comment_177574 Sun, 09 Jun 2013 17:34:00 +0100 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177575#Comment_177575 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177575#Comment_177575 Sun, 09 Jun 2013 17:41:48 +0100 Chris P Bacon
Are Rockwool Flexibatts available in the UK? Here you get them in thickness's of 45, 70, 95, 145, 170, 195 & 220mm and I find that the thicker ones are stiff enough to stay in place by themselves if cut very slightly oversize, if they are too big they will bow and fall out. At the very most a bit of string or some light netting would hold them in place until you come along with the PIR or VCL.

If Rockwool don't have the flexibatts in the UK Paroc should have a similar product available.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177576#Comment_177576 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177576#Comment_177576 Sun, 09 Jun 2013 17:59:36 +0100 Ed Davies Posted By: tonyI always fix the ceiling first, insulate next, then wiring then fix the deck, have lunch… And there was me hoping to get the whole house built before elevenses. ]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177577#Comment_177577 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177577#Comment_177577 Sun, 09 Jun 2013 18:05:15 +0100 barney
Failing that, weed membrane is OK - youwant a narrow roll width though if it's trusses

Regards

Barney]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177579#Comment_177579 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177579#Comment_177579 Sun, 09 Jun 2013 18:29:49 +0100 SteamyTea Posted By: barneyFailing that, weed membrane is OKWhat I used in my loft. Just stapled it in place.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177581#Comment_177581 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177581#Comment_177581 Sun, 09 Jun 2013 18:41:38 +0100 Chris P Bacon
I wouldn't use the chicken wire if you are going over the top with VCL as they would be a danger of punctures.

See if you can get a price from a contractor to blow in the loose rockwool, it will be the easiest solution IMO.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177588#Comment_177588 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177588#Comment_177588 Sun, 09 Jun 2013 21:43:50 +0100 tony ]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177593#Comment_177593 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177593#Comment_177593 Sun, 09 Jun 2013 23:21:36 +0100 Rex
Rex]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177594#Comment_177594 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177594#Comment_177594 Sun, 09 Jun 2013 23:27:17 +0100 Ed Davies

That's what put me off Warmcel. Also the lack of DIY install (in the UK).]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177600#Comment_177600 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177600#Comment_177600 Mon, 10 Jun 2013 06:30:03 +0100 Chris P Bacon Posted By: tonyBut might settle

Mineral wool settles a lot less than cellulose (the figures I have seen are 2-4% vs. 10 -15%), I had a bad experience with cellulose in wall panels previously so was very cautious about using loose fill insulation again.

I have over-filled the flat ceiling to a depth of 800mm so I would hope that this will compensate for any settlement that does occur.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177604#Comment_177604 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177604#Comment_177604 Mon, 10 Jun 2013 09:28:09 +0100 wavy http://www.tdpltd.com/netlon-products/insulation-support-net.html
Or you could use the green stuff from the garden centre.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177633#Comment_177633 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177633#Comment_177633 Mon, 10 Jun 2013 19:18:25 +0100 pmusgrove https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177636#Comment_177636 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177636#Comment_177636 Mon, 10 Jun 2013 19:56:10 +0100 Fred56 I've done this job and it works.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177637#Comment_177637 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177637#Comment_177637 Mon, 10 Jun 2013 20:18:01 +0100 tychwarel [URL=http://s1214.photobucket.com/user/nantcoly/media/Ty%20chwarel%20build%20blog/roof%20insulation/100_1305.jpg.html][IMG]http://i1214.photobucket.com/albums/cc492/nantcoly/Ty%20chwarel%20build%20blog/roof%20insulation/100_1305.jpg[/IMG][/URL]

[URL=http://s1214.photobucket.com/user/nantcoly/media/Ty%20chwarel%20build%20blog/roof%20insulation/100_1283.jpg.html][IMG]http://i1214.photobucket.com/albums/cc492/nantcoly/Ty%20chwarel%20build%20blog/roof%20insulation/100_1283.jpg[/IMG][/URL]]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177638#Comment_177638 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177638#Comment_177638 Mon, 10 Jun 2013 20:28:58 +0100 tychwarel https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177639#Comment_177639 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177639#Comment_177639 Mon, 10 Jun 2013 20:31:10 +0100 tychwarel https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177640#Comment_177640 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177640#Comment_177640 Mon, 10 Jun 2013 20:43:48 +0100 Ed Davies https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177667#Comment_177667 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177667#Comment_177667 Tue, 11 Jun 2013 11:31:02 +0100 Greenfish
Had a look on the internet at pricing of possible materials, comparing thermal conductivity and cost per cubic meter:
Loft roll - basic 0.044 at £15 /m^3 or 0.04 for £20 /m^3, convenient 200mm depth.
Flexible, semi-rigid slabs or roll - 0.032 to 0.038 for ~£55 /m^3 most 90 or 140mm(not filling 400mm) some 100mm.
"Rafter roll 32" - 0.032 for £100 /m^3 but 200mm depth available.
Wood fibre batts - 0.038 for £100 /m^3

Have to wonder what is the difference between Earthwool Rafter Roll and FrameTherm material that makes it twice the price by volume! You can also see why floppy loft roll is attractive to my budget.

Knauf, Isover, Rockwool and Superglass all make comparable categories of product so I should be spoiled for choice. I need to get some more prices, anything other than common loft roll is going to be a special order.

Do I need a sarking board, or will the permeable membrane held taught by counter battens and battens be sufficient?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177672#Comment_177672 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177672#Comment_177672 Tue, 11 Jun 2013 13:14:38 +0100 Ed Davies
It's a bit harder to decide when you've more freedom on the depth. The direct cost of insulation value for the more expensive materials is worse but the saving in structure around them needs to be balanced against that. Not easy when it's difficult to work out what the cost of the materials will be - one of many downsides to the lack of transparency in building pricing.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177674#Comment_177674 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177674#Comment_177674 Tue, 11 Jun 2013 13:17:12 +0100 davidfreeborough
The high density Rafter Roll 32 mineral wool is a completely different product to the low density Loft Roll 44. You'll find lots of voids in the latter, non-uniform density & non-uniform thickness. That said, its not worth paying the extra unless you're targeting lower U values.

The price doesn't just reflect the increased density & lower lambda, it also reflects the fact that the lower lambda allows you to use standard 200mm trussed rafters & still meet building regulations with a reasonable thickness of insulated plasterboard. I guess this is why the timber frame variant is more competitively priced.

David]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177684#Comment_177684 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177684#Comment_177684 Tue, 11 Jun 2013 15:14:22 +0100 Greenfish
I have poked about with some loft roll, it really is a "low density/variable quality mineral wool product" as David says. I now have concerns that it is so soft that stacking 2 x 200mm layers, the weight of top one will compress the bottom, or the whole lot shift down the slope over time leaving a gap at the top hidden behind the plasterboard. Going to take a closer look at product density and compression figures if I can find them.

The "rafter" and "timber frame" variants do seem to offer comparable thermal conductivity for wildly different prices. I get why they are more than loft roll, but do they differ from each other other than the target market?

The 400mm is for structural reasons Ed, but also offers an opportunity to hit better u values. Putting 500mm of (0.04) wool in the ceiling of the non-habitable loft parts, so it gives the space to match it in the attic. The remaining weak design is the flat roof (bit of everything in this build) that I have discussed that in another thread.

I do wish the cost of materials was more available, I will post what I find out in case it is of use to others]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177691#Comment_177691 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10761&Focus=177691#Comment_177691 Tue, 11 Jun 2013 17:26:33 +0100 joe90