Green Building Forum - thickness of Insulation required Mon, 18 May 2026 04:32:04 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115369#Comment_115369 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115369#Comment_115369 Wed, 24 Aug 2011 00:00:52 +0100 sinnerboy Posted By: CWatersI'm not sure the Building Regs allow you to insulate an existing wall that badly :-)

I think the worst it can be is around 0.3 but I haven't been back to check Part L.

Your right CW -

http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADL1B_2010.pdf

Table 3 Page 18 looks for 0.3 W/m2K .

It does footnote to state (paraphrase) that the U Value may be reduced where floor areas are affected by +5% reduction . And Item 1.7 page 2 states "the adoption of any particular energy efficiency measure should not involve unacceptable technical risk of for instance excessive condensation" . Page 23 refers to BR 262 Thermal insulation: avoiding risks (2002 edition) for guidance on risk assessment . Anyone have a copy ? ( I don't) . No mention of EN 15026:2007 Hygrothermal Performance Of Building Components And Building Elements - Assessment Of Moisture Transfer By Numerical Simulation - the method (using WUFI software ) that Joseph Little used to prepare his report.

Something JL stressed in his report is that " even the closest attention paid to micro issues, such as insulation type and membranes, are not enough if macro issues like driving rain, substrate type & U-value haven’t been dealt with"

So as in the case of the OP with a Victorian brick house - I would at the very least approach my local BCO with my concerns about the 0.3 W/m2K value.

Or find someone expert in WUFI to run a simulation based on local climate data. Last time I checked there aren't so many such folks around.]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115371#Comment_115371 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115371#Comment_115371 Wed, 24 Aug 2011 00:11:17 +0100 Saint http://www.treehugger.com/files/2010/02/passivhaus-renovation-of-heritage-home.php
acheiving U=0.1 http://ecohome.tumblr.com/page/5

Wookey they actually say they used an additional 50mm Kooltherm so 180mm in total. Even so there must be an airspace included as well unless Kingspan is claiming a TC of 0.019W/mK for Kooltherm.......nah they wouldn't]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115372#Comment_115372 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115372#Comment_115372 Wed, 24 Aug 2011 00:34:56 +0100 sinnerboy Posted By: seanieWell I think that pretty much answers any concerns about IWI.

Couldn't agree less seanie ( no offence )

Posted By: seanieFrom the article;

"But there is another problem with interior insulation of this magnitude: heat loss through the exterior walls will be virtually eliminated. A little bit of heat loss through old brick walls drives out moisture; if you get rid of it completely, there is the possibility of freeze-thaw cycles causing the brick to deteriorate. Fortunately London doesn't get too many of these."


1. The UK does not start and finish in London.
2. The most substantial risk with IWI is the accumulation of condensation immediately behind the insulation. This will happen even in the absence of freeze/thaw cycles which impact the outer face. And - London's housing stock is old - very old , and very attractive too visually. Taking such time spans into account how many freeze thaw cycles do we responsibly subject this brickwork to ?]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115373#Comment_115373 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115373#Comment_115373 Wed, 24 Aug 2011 00:40:47 +0100 sinnerboy Posted By: SaintHere is someone who has renovated their victorian terrace to passivhaus standards, including 130mm of internal insulation on the front facade:http://www.treehugger.com/files/2010/02/passivhaus-renovation-of-heritage-home.php" rel="nofollow" >http://www.treehugger.com/files/2010/02/passivhaus-renovation-of-heritage-home.php
acheiving U=0.1http://ecohome.tumblr.com/page/5" rel="nofollow" >http://ecohome.tumblr.com/page/5

Wookey they actually say they used an additional 50mm Kooltherm so 180mm in total. Even so there must be an airspace included as well unless Kingspan is claiming a TC of 0.019W/mK for Kooltherm.......nah they wouldn't

I hate to seem not wish this initiative well ... but Sir Humprie comes to mind. " Very courageous ! "]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115377#Comment_115377 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115377#Comment_115377 Wed, 24 Aug 2011 07:09:31 +0100 Dominic Cooney thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115381#Comment_115381 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115381#Comment_115381 Wed, 24 Aug 2011 07:55:36 +0100 seanie Couldn't agree less seanie ( no offence )

I was being sarcastic.]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115391#Comment_115391 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115391#Comment_115391 Wed, 24 Aug 2011 09:13:50 +0100 sinnerboy Posted By: seanie
Couldn't agree less seanie ( no offence )


I was being sarcastic.

:shamed:]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115394#Comment_115394 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115394#Comment_115394 Wed, 24 Aug 2011 09:41:48 +0100 CWatters Posted By: sinnerboy 2. The most substantial risk with IWI is the accumulation of condensation immediately behind the insulation. This will happen even in the absence of freeze/thaw cycles which impact the outer face. And - London's housing stock is old - very old , and very attractive too visually. Taking such time spans into account how many freeze thaw cycles do we responsibly subject this brickwork to ?

I've no idea if this is a real issue but what stops the outer leaf of a modern insulated cavity wall suffering the same fate? They seem to survive ok.]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115396#Comment_115396 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115396#Comment_115396 Wed, 24 Aug 2011 09:57:07 +0100 seanie
"As well as the thermal bridge issue, there is an additional concern - that the joist ends will be exposed to dew point temperatures. Wet joist ends are worrying because the wood can rot and, ultimately, break.

Addressing this issue is one of the major engineering challenges of our project, one that we have spent a great deal of time considering and one to which we are applying an extremely innovative solution. In brief, it involves cutting the floor joists away from the external wall, hanging a steel beam off the party walls, insulating outside the steel beam and then hanging the floor joists off the steel beam; i.e. now entirely within the thermal and airtight envelope. As with pretty much everything on this build, there is an enormous amount of fine detail that I haven’t covered here "]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115406#Comment_115406 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115406#Comment_115406 Wed, 24 Aug 2011 11:58:30 +0100 sinnerboy Posted By: CWatters
Posted By: sinnerboy2. The most substantial risk with IWI is the accumulation of condensation immediately behind the insulation. This will happen even in the absence of freeze/thaw cycles which impact the outer face. And - London's housing stock is old - very old , and very attractive too visually. Taking such time spans into account how many freeze thaw cycles do we responsibly subject this brickwork to ?


I've no idea if this is a real issue but what stops the outer leaf of a modern insulated cavity wall suffering the same fate? They seem to survive ok.

Well the cavity provides a safety release mechanism for water which drains down the inner faces of the outer leaf. From the inside vapour will condense here and so too , from the outside , penetrating rain water. The modern brick and mortar fabric can cope better with freeze / thaw action than our historic stock weathered for decades or even centuries . Such uninsulated walls have coped by absorbing the internally generated heat unhindered by insulation together with ambient external heat outside the heating season - in which case the uninsulated vapour barrier free wall back diffuses i.e. vapour is driven into the building. I hope the old building refurbished to passive standard copes .]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115407#Comment_115407 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115407#Comment_115407 Wed, 24 Aug 2011 12:00:36 +0100 sinnerboy Posted By: seanieLooking at that project website it's very impressive. And it shows how challenging the goal was. Look at how they dealt with the issue of joist ends;

"As well as the thermal bridge issue, there is an additional concern - that the joist ends will be exposed to dew point temperatures. Wet joist ends are worrying because the wood can rot and, ultimately, break.

Addressing this issue is one of the major engineering challenges of our project, one that we have spent a great deal of time considering and one to which we are applying an extremely innovative solution. In brief, it involves cutting the floor joists away from the external wall, hanging a steel beam off the party walls, insulating outside the steel beam and then hanging the floor joists off the steel beam; i.e. now entirely within the thermal and airtight envelope. As with pretty much everything on this build, there is an enormous amount of fine detail that I haven’t covered here "

That is impressive alright. It's akin to constructing a timber framed house within the existing walls. I wonder if they left ventilated cavity at the interface ?]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115409#Comment_115409 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115409#Comment_115409 Wed, 24 Aug 2011 12:24:28 +0100 brig001 Posted By: sinnerboySuch uninsulated walls have coped by absorbing the internally generated heat unhindered by insulation

Did anyone have heating 100 years ago, or even 50? We didn't 30 years ago, just a gas fire downstairs.
Cue Four Yorkshireman sketch :bigsmile:]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115415#Comment_115415 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115415#Comment_115415 Wed, 24 Aug 2011 13:00:07 +0100 sinnerboy

Luxury !]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115418#Comment_115418 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115418#Comment_115418 Wed, 24 Aug 2011 13:32:20 +0100 SteamyTea thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115422#Comment_115422 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115422#Comment_115422 Wed, 24 Aug 2011 14:21:37 +0100 djh Posted By: SaintWookey they actually say they used an additional 50mm Kooltherm so 180mm in total. Even so there must be an airspace included as well unless Kingspan is claiming a TC of 0.019W/mK for Kooltherm.......nah they wouldn't
Where do they say that, Saint? I can't find it. :cry:]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115424#Comment_115424 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115424#Comment_115424 Wed, 24 Aug 2011 14:35:10 +0100 seanie
"These Kooltherm 130 sheets (130mm thick) will go in the roof and the external walls of the top 2 floors. Eventually all the external walls will have it in, topped off with another 50mm, giving them a U-value of 0.1"]]> thickness of Insulation required https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115445#Comment_115445 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7715&Focus=115445#Comment_115445 Wed, 24 Aug 2011 22:01:11 +0100 wookey
It is a thoroughly impressive project, and it will be most interesting to know whether it really does have a problem with facade deterioration or not over the next few decades. I hope it does work, and I'm glad someone is trying it, but there are good reasons to worry.]]>