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Timber Frame wall insulation

Want to discuss the different types of insulation; this is the place to do so.

Timber Frame wall insulation

Postby grahamt » Sun Jan 02, 2011 12:26 pm

I live in a timber frame house which was built in the mid 80s. We bought the house in the mid 90s. At the time I was unaware of the construction type of the house and didn't become aware of the issues until I started investigating improving the insulation of the property. I have tackled the lofts and we now have double-glazing all around the property, although I recognise that double-glazing never pays back its capital outlay cost (generally agreed at 90 years!). We did it more for its reduction in maintenance and for its improved security.

When we came to look at the walls we had to reluctantly accept the general advice that it is inadvisable to add additional insulation to the cavity, due to the need to ensure that damp does not accumulate in the insulation and cause rotting of the plywood backing board that lines the timber frames in the cavity space.

However, our house is of an unusual construction: whilst the ground floor has the normal inner timber frame wall and an outer brick curtain wall, the upper floor has the timber frame sitting on top of the lower brick wall rather than on top of the lower timber frame! Rather than a brick outer curtain wall there is uPVC cladding attached to the facing upstairs, so the upper floor is just the thickness of the timber frame itself plus the attached cladding. The insulation in the timber frame is just the normal fibreglass blanket; the cavity is the usual 100mm that was used in the 80s.

It occurred to me that a substantial improvement in the insulation could be achieved by replacing the fibreglass insulation with something like 100mm Kingspan insulation board, cut to size. However, this is enormously disruptive as the normal way of doing this would be to remove the plasterboard inner wall lining and the vapour barrier beneath, replace the insulation and then replace the vapour barrier and plasterboard and redecorate. This is not something to be undertaken lightly.

However, upstairs, I realised, there might be an alternative and less disruptive solution. If the external cladding is removed then access would be available directly to the external board facing of the timber frame. I wondered if it would be possible to remove the boards, one-by-one and replace the insulation from the outside, then replacing the boards and the external breather membrane, before replacing the external cladding.

Has anyone ever tried to do this? Does anyone have a view on the possibility/advisability of doing this? Does anyone have any information on the improvement in insulation that might result from this?
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Re: Timber Frame wall insulation

Postby nrg-steve » Sun Jan 02, 2011 1:09 pm

How much insulation do you currently have? The U value should be about 0.45 or 0.4 which is pretty good, so I'm not sure why you want to improve this?

One suggestion is
The best thing to do is to take off the plasterboard every time that you redecorate a room and replace the insulation with the best that you can afford, for example extruded board. Then a vapour barrier and upgrade services and re plasterboard etc.
This seems a lot of work!

Steve
Domestic & Commercial Energy Assessor http://www.nrgsurveyors.co.uk
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Re: Timber Frame wall insulation

Postby grahamt » Sun Jan 02, 2011 1:45 pm

The timber frames appear to be built from 4x2 so the depth of the cavity between the inner and outer surfaces will be 100mm (4"). That will be the depth of the fibreglass insulation. Modern timer frames are, I understand, built from 6x2 (150mm) and I have seen them filled with 150mm Kingspan or equivalent, so I assume it was thought that the original standard of insulation was inadequate for modern heat-retaining requirements.

Bearing in mind that the recommended depth of fibreglass loft insulation is now 270mm and that Kingspan type insulation is rated twice as efficient as fibreglass it still seems to me that replacing the existing insulation should make a difference. The question is, how significant a difference, compared with the cost?
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Re: Timber Frame wall insulation

Postby JBrown » Sun Jan 02, 2011 11:01 pm

Happy new year everyone, hope you all had a great christmas.

To clarify you are wanting to replace 10 cm fibreglass with 10cm of kingspan in walls? I am not the best person for the clacs on this, sure the SAP/design experts should be able to give you the differing u values and benefits you could make.

Building regs changed mid 80s, do you know the exact date your property was built, pre or post 1982?
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Re: Timber Frame wall insulation

Postby grahamt » Sun Jan 02, 2011 11:45 pm

As I understand it, 100mm of fibreglass insulation will give a U value of around 0.32 whereas 100mm of silver foil faced phenolic panel will give a U value of around 0.20.
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Re: Timber Frame wall insulation

Postby JBrown » Tue Jan 04, 2011 9:54 pm

Hi Graham

What is the heat loss of the property ie external perimeter? Is the house detached, semi terraced?

At present the construction is plaster board, vapour barrier, insulation, external membrane and cladding? Can you upload a photo of the cladding?

I assume you are leaving the downstairs as is? Will this not create an issue with the benefit of the work being lost with alot of the heat being lost via the downstairs walls?

I cant see there being an issue removing the external cladding, there is various small projects on older local authority properties rebuilding timber frame sections with cavity. However, this is where the timber frame has limited insulation and the remainder of the property is cavity wall. These houses are built mid 1960 ish.
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Re: Timber Frame wall insulation

Postby mcginty85 » Fri Aug 23, 2013 1:29 pm

We are a company who can help. We have an insulation foam product designed for timber frame buildings that is a retro fit without pulling your home apart. For more information we can be contacted on 01236 879881 or mobile 07774 967036

Regards Jim McGinty
Director
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