Thursday, 19 June 2014

Thermal Comfort in Older Houses

The Transition Energy Group forum on ‘Thermal Comfort in Older Houses’ went very well on Tuesday – a good turnout, with lots of new faces, excellent speakers and a very switched-on audience. As well as people with questions about their own houses we had a fair sprinkling of building professionals including several architects, a plaster/renderer and building managers – with lots of experience to share. Justin Smith from Cambridge City Council gave us the latest news about the grants available from the Cambridgeshire Solid Wall Insulation Fund (CSWIF) and the Green Deal Home Improvement Fund (GDHIF). Both of these are very new, launched only this month. They are quite similar in some respects – I have written a comparison here on our Green Deal FAQ page.
Jim Ross of Cambridge Architectural Research
explaining about window performance ratings
From my personal viewpoint, here are some messages I picked up that I thought were particularly interesting or important. You might also like to download some of the presentations.

 Damp can be an issue – breathable insulation will help.
Our first speaker, Andrew Mitchell from Natural Building Technologies terrified us with some horrific pictures of mould and rotten floor joist ends – all of which can happen if insulation is designed or fitted badly. However, using breathable insulation  - NBTs main product – reduces the likelihood of these problems.

Andrew would doubtless recommend using breathable insulation all the time but it is not the industry standard. We had insulation installed at home (single brick Victorian detached) 4 years ago and breathable insulation was never mentioned. I am still confident that we are OK with that, because we have no particular risk factors for damp: there was no problem with damp before, Cambridge is very dry compared to most of the country and the house is well ventilated. However, if you don’t have a damp proof course, or you live somewhere damp like Wales, or you are prone to flooding, or if you don’t have good ventilation or you are worried about damp for any other reason then you should seriously consider using breathable insulation. Andrew said that closed-pore insulation was now banned in Wales, or at least won't get grants.

NBT products have a reputation for being very expensive but Andrew claimed that the Pavadry system is not as expensive as the older Pavatherm and although other materials were still cheaper to buy they were more costly to install so the difference was not that great any more. I think we need some real cases to verify this.  

You can get grants for breathable insulation
To get grants like the GDHIF and the CSWIF you have to use a Green Deal installer and install an approved product.  NBT products are approved by the BBA. ( On the one hand it is good that products have to be approved – and without that they would be impossible to guarantee  - but it is costly and not all products have gone through this process so it does limit your choices a bit.  

You should get a 25 year insurance backed guarantee
When we insulated our home no-one mentioned guarantees but if you have measures installed under the CSWIF or the GDHIF they should come with an insurance backed guaranteed for 25 years. So if you do have problems  you should at least be able to get them fixed without being out of pocket.

 Details matter – and there is no one size fits all solution
 It isn’t just a question of which insulation you use, the details of how it is fitted, like what happens around windows and other junctions are very important. You need to keep moist air away from your floor joists and avoid cold spots which are magnets for condensation. Every house is different but there are existing solutions for most circumstances that should not need much adaption.  Good workmanship from the installers is important too, so it was good to hear that NBT will be involved in training installers in Cambridgeshire, for the CSWI and other Green Deal schemes.
Patrick's window with chamfered insulation to allow
more light in (the sill is  unfinished)

It was interesting to see Patrick’s chamfered insulation around a very narrow window. One problem with insulation is that it makes the window reveals deeper and less light comes in. The chamfering gets around that problem.

You can get an architect in and still use the grants
It can be helpful to get an architect or a building designed to help you choose insulation and develop a design for your house. The CSWIF and the GDHIF won’t pay for this but if you are prepared to bear the cost they will work with your Green Deal provider.  Peter Pope, the last speaker of the evening, is doing this. You can find an energy conscious architect through the AECB.

You can also shop around for Green Deal Installers/Providers (though at the moment the only provider registered with CSWIF is Action on Energy).  

You shouldn’t consider wall insulation as a standalone measure
Installers tend to be focussed on one thing but in practice wall insulation affects windows and lots of other things. For example, wall insulation needs to interact with window frames and it may be more difficult to change the frames afterwards. So if your windows are likely to need work in the next five or ten years, it may be better to do them at the same time. This is particularly true for upper floors if you have external wall insulation done because that needs scaffolding and since you will need that to do the windows later you may as well do them both at the same time.

Also, making the walls thicker may mean extending the ducts from your central heating boiler. If this is an old boiler you may as well get a new boiler at the same time. You can get a grant towards this from the GDHIF.

Finally, before you get insulation on your walls they do need to be in good condition first. So, you should have a thorough survey checking to see if they need repointing or if there are any cracks that need to be fixed.  Getting these things fixed can take time.  

More about windows
I was surprised to see that Jim’s presentation on Windows included the cling-film secondary glazing DIY option and he didn’t say anything bad about it except that it only works if your frames are in good condition – though this solution does not last so long. He also showed several other sorts of secondary glazing some of which were almost invisible. English Heritage loves secondary glazing because you don’t have to replace the original windows.  I have discussed secondary glazing options before in: Why doesn't secondary glazing steam up Jim also pointed out that the heat loss through windows depends on the frames as well as the glass – and window suppliers often only quote heat loss through the centre of the pane because the frames aren’t as good. Also, soft low-e coatings on double glazing have good performance figures but often don’t last long. There is an energy performance rating system for windows administered by the BFRC

The Cambridgeshire Solid Wall Insulation Fund needs to be spent quickly
The CSWIF is £5.7 million for solid wall insulation to be spent by the end of March 2015. That is a very tight schedule. However, Justin was clear that householders would not be rushed into getting insulation installed without proper surveys first and householders would be given the time they needed to evaluate their options.

Where planning permissions is required – which is likely for many cases with external wall insulation – using CSWIF doesn’t get you fast tracked automatically. However, Action on Energy will help you get through by filling in the application except for the bits that are personal to you.

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