Green Building Forum - How tight/ leaky should a new sash window be? Tue, 14 Jul 2026 13:51:45 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276050#Comment_276050 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276050#Comment_276050 Wed, 09 Oct 2019 19:22:13 +0100 Nick Parsons
I worked on a job a while back with high-spec timber 3G sash windows and yes, there was some leakage during the a/t test, and casements would have performed better, but the 'wind' did not whistle through in a/t test conditions.

I should have thought that a brand-new uPVC sash window should perform quite well. What would 'the panel's' expectations be?

Thanks,

Nick]]> How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276051#Comment_276051 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276051#Comment_276051 Wed, 09 Oct 2019 19:45:43 +0100 nigel
As the seals age most sashes leak though.]]> How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276052#Comment_276052 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276052#Comment_276052 Wed, 09 Oct 2019 21:51:12 +0100 tony
They are not suited to exposed locations. The draught strips ate likely brush type.

The frames have to be installed absolutely straight and square and parallel with in 0.3 mm]]> How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276053#Comment_276053 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276053#Comment_276053 Thu, 10 Oct 2019 01:16:12 +0100 djh Posted By: Nick Parsonsthe 'wind' did not whistle through in a/t test conditions.
IIRC the normal test pressure of 50 Pa corresponds to a F6, so if it's windier than that, or locally-concentrated wind, then that would be expected. Some places/regimes use 75 Pa test pressures I think.]]> How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276054#Comment_276054 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276054#Comment_276054 Thu, 10 Oct 2019 09:15:17 +0100 Nick Parsons How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276057#Comment_276057 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276057#Comment_276057 Thu, 10 Oct 2019 10:47:27 +0100 Mike1
Worth knowing that there are some alternative sliding sash technologies available - at least elsewhere Europe - where the sashes don't actually slide over one another. For example:

Adrik (Germany) https://translate.google.co.uk/translate?hl=en&sl=de&u=https://www.adrik.de/fenster/WIN-Hochschiebefenster/Holz-TypS.html

and Solberg (Denmark) https://www.solborg.site/enl - who also have a UK installer (Enlightened Window) https://enlightenedwindows.co.uk/products/german-wooden-windows/s-series-sliding-sash-window/]]> How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276059#Comment_276059 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276059#Comment_276059 Thu, 10 Oct 2019 11:37:56 +0100 nigel It also means the seals don't wear out.

They are on an exposed elevation and they don't leak and they are timber.]]> How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276060#Comment_276060 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276060#Comment_276060 Thu, 10 Oct 2019 11:39:50 +0100 nigel Posted By: Nick ParsonsNigel, you echo my initial thought, but djh has a valid point. I guess it's going to come down to a judgement re how often, and in what wind conditions, the wind comes in. It must be very disappointing with a brand-new set of windows. I don't know what prior advice manufacturers/fitters would give in such (potential) circumstances.

That would depend on whether they were told it was an exposed location.
If they were I would expect them to caveat that above a certain wind load they may leak.
If they said nothing I think it would be reasonable to expect them to be fit for purpose.]]> How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276064#Comment_276064 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276064#Comment_276064 Thu, 10 Oct 2019 12:08:07 +0100 djh
Posted By: nigelThat would depend on whether they were told it was an exposed location.

Even if they weren't they ought to be able to make a rough assessment given the address assuming they knew that. And especially if they visited site to measure up etc. I suppose it's all going to depend on the details of the manufacturer and installer. What expertise and knowledge they hold themselves out as having or might reasonably be expected to have, what the contract says, etc. It seems like a specialist solicitor or maybe an advice service like Which or somebody might be useful. Perhaps any professional institution they belong to, although that might be part of the problem rather than the solution.]]> How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276068#Comment_276068 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276068#Comment_276068 Thu, 10 Oct 2019 13:05:12 +0100 Nick Parsons Nigel, you echo my initial thought, but djh has a valid point. I guess it's going to come down to a judgement re how often, and in what wind conditions, the wind comes in. It must be very disappointing with a brand-new set of windows. I don't know what prior advice manufacturers/fitters would give in such (potential) circumstances.


Nigel replied:
"That would depend on whether they were told it was an exposed location.
If they were I would expect them to caveat that above a certain wind load they may leak.
If they said nothing I think it would be reasonable to expect them to be fit for purpose. "

Nigel and djh:

I gather it was supply and fit. Although I suppose it is possible that it was not windy during the survey and installation, I agree that one might expect local knowledge to give them an idea of the exposure.

Thanks for all your thoughts.

Nick]]> How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276085#Comment_276085 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276085#Comment_276085 Fri, 11 Oct 2019 14:31:29 +0100 Paul in Montreal
Paul in Montreal.]]> How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276088#Comment_276088 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276088#Comment_276088 Fri, 11 Oct 2019 15:20:58 +0100 owlman How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276089#Comment_276089 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276089#Comment_276089 Fri, 11 Oct 2019 15:23:02 +0100 owlman Posted By: Paul in MontrealSliding and sash windows cannot be made airtight, no matter what. Avoid at all costs.

Paul in Montreal.


+1]]> How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276098#Comment_276098 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276098#Comment_276098 Fri, 11 Oct 2019 20:42:31 +0100 djh Posted By: owlman
Posted By: Paul in MontrealSliding and sash windows cannot be made airtight, no matter what. Avoid at all costs.
Paul in Montreal.

+1
I'd tend to agree although the Solberg spec does claim reasonable performance. And FWIW my lift-and-slide patio door has good performance so I suppose something similar could be done for sash windows.]]> How tight/ leaky should a new sash window be? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276199#Comment_276199 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16274&Focus=276199#Comment_276199 Wed, 16 Oct 2019 14:11:44 +0100 passivhausfan
https://www.gowercroft.co.uk/timber-windows-and-doors/the-winston-heritage-sliding-sash-window/]]>