Green Building Forum - suspended floor insulation - an interesting link Sun, 31 May 2026 12:52:30 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36418#Comment_36418 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36418#Comment_36418 Sat, 25 Oct 2008 22:07:51 +0100 Mike George
http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces?full_view=1]]> suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36425#Comment_36425 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36425#Comment_36425 Sat, 25 Oct 2008 22:39:48 +0100 tony suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36465#Comment_36465 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36465#Comment_36465 Sun, 26 Oct 2008 16:26:50 +0000 fostertom suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36468#Comment_36468 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36468#Comment_36468 Sun, 26 Oct 2008 17:35:07 +0000 skywalker
They've missed our wizard wheeze of using the magic gel though!]]> suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36475#Comment_36475 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36475#Comment_36475 Sun, 26 Oct 2008 18:48:17 +0000 Mike George Posted By: tonyIs this in a country where it very cold in winter way below freezing?

Washington DC, so yes I believe so.

Is any of it relevant to the UK?]]> suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36509#Comment_36509 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36509#Comment_36509 Sun, 26 Oct 2008 21:17:31 +0000 tony suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36520#Comment_36520 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36520#Comment_36520 Mon, 27 Oct 2008 00:20:44 +0000 JackyR
The reason given is that the cold side of the insulation will be at the same temp as the ground under the house, which is not sun-warmed. (If I've skimmed it correctly and not misread again...)]]> suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36538#Comment_36538 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=36538#Comment_36538 Mon, 27 Oct 2008 11:25:04 +0000 Ed Davies Posted By: tonyClearly there was no vapour check on the floor

But wasn't that exactly the point of the article? There was a vapour check on the floor which was preventing removal of vapour from the ventilation air. Moist ventilation air plus a cold surface can obviously be a problem sometimes in Britain though nowhere nearly as much of the time as in Washington D.C. This article, it seems to me, is interesting as a description of the general physics of what can happen but is not likely to be very directly applicable here.]]> suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139412#Comment_139412 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139412#Comment_139412 Wed, 14 Mar 2012 00:41:16 +0000 fostertom http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces?full_view=1
eventually led to http://uploading.com/files/ad26df12/285Ja-ufloor.pdf.
Building Inspector is keen to support it, wanted the 'argument' submitted - this is it. Hope he approves, as an02ew of this forum and I have just started building it!]]> suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139456#Comment_139456 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139456#Comment_139456 Wed, 14 Mar 2012 12:37:59 +0000 tony suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139527#Comment_139527 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139527#Comment_139527 Thu, 15 Mar 2012 08:20:23 +0000 Viking House suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139528#Comment_139528 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139528#Comment_139528 Thu, 15 Mar 2012 08:23:04 +0000 aa44
We live in Shetland where the wind gusts probably aren't a good thing for MVHR units. As a result I was planning to take the input for the MVHR from the solum, with lots of vents in the wall to allow a good airflow into it.]]> suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139533#Comment_139533 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139533#Comment_139533 Thu, 15 Mar 2012 09:37:06 +0000 tony
You could suck in scotch mist which would not be good as it is "wet"]]> suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139567#Comment_139567 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139567#Comment_139567 Thu, 15 Mar 2012 13:11:27 +0000 WillInAberdeen
He seems to be saying that the underside of the insulated suspended floor will stay close to yearly-average temperature, so will collect condensation from the ventilation air, if the dewpoint of external air in midsummer is warmer than that. (this bit is nothing to do with permeation through the floor)

For Washington DC the year-average temperature is lowish 12C (snows in winter) but the mid-summer dewpoint is very high 21C (US Capital was deliberately built in a hot swampy place). As 21 is much more than 12 there is a condensation risk.

For me the year-average temperature is 9C and the midsummer dewpoint averages about 11C so theoretically there is a slight risk of condensation, but in practice I suspect the timber will always warm up by a couple of C during summer and that will take care of it. During winter the air dewpoint is about 3C so that will dry the timber out nicely.]]> suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139574#Comment_139574 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139574#Comment_139574 Thu, 15 Mar 2012 13:57:38 +0000 Peter Clark Posted By: fostertomMike's first mention of this interesting paperhttp://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces?full_view=1" rel="nofollow" >http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces?full_view=1
eventually led tohttp://uploading.com/files/ad26df12/285Ja-ufloor.pdf." rel="nofollow" >http://uploading.com/files/ad26df12/285Ja-ufloor.pdf.


Hi Tom, I have still not managed to look at your pdf, any chance of making it available in a different way?

Peter]]> suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139612#Comment_139612 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139612#Comment_139612 Thu, 15 Mar 2012 17:52:48 +0000 Mike George Posted By: WillInAberdeenThis paper is entertainingly written, but I dont think it applies in my neck of the woods.

He seems to be saying that the underside of the insulated suspended floor will stay close to yearly-average temperature, so will collect condensation from the ventilation air, if the dewpoint of external air in midsummer is warmer than that. (this bit is nothing to do with permeation through the floor)

For Washington DC the year-average temperature is lowish 12C (snows in winter) but the mid-summer dewpoint is very high 21C (US Capital was deliberately built in a hot swampy place). As 21 is much more than 12 there is a condensation risk.

For me the year-average temperature is 9C and the midsummer dewpoint averages about 11C so theoretically there is a slight risk of condensation, but in practice I suspect the timber will always warm up by a couple of C during summer and that will take care of it. During winter the air dewpoint is about 3C so that will dry the timber out nicely.

Well said. Most seem to be overlooking the fact that the paper refers to a totally different climate to the UK.]]> suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139639#Comment_139639 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139639#Comment_139639 Fri, 16 Mar 2012 00:28:52 +0000 fostertom suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139643#Comment_139643 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139643#Comment_139643 Fri, 16 Mar 2012 07:51:54 +0000 tony
On the other hand warm and consequently with more moisture in it air from inside the house will tent to want to condense there.]]> suspended floor insulation - an interesting link https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139656#Comment_139656 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=2813&Focus=139656#Comment_139656 Fri, 16 Mar 2012 09:43:31 +0000 fostertom Posted By: tonyBecause a house is loosing heat the underfloor void will be warmer than outsideUsed to be true, but now minimal, given significant insulation - and that readily overcome by evaporative cooling esp in spring/autumn (the UK danger time), which alternates or is concurrent with condensation in the ventilated void.

Posted By: tonywarm and consequently with more moisture in it air from inside the house will tent to want to condense there
Not if there's a VCL.

Whatever, the benefit of the through ventilation is somewhere between irrelevant and actually a possible problem - so IMHO it's best eliminated. Then other benefits of the underfloor and/or subsoil can be brought into play, and hopefully the need for floor VCL eliminated too.]]>