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Kingspan between rafters problem -way to proceed?


 
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eophi

from United Kingdom

Joined: 23 Oct 2008
Posts: 7
Location: Buckinghamshire,
United Kingdom

PostPosted: Wed Dec 17, 2008 10:58 pm Reply with quote

I'm having the pitched slate roof done under a council grant (i have to pay 25%). Part of the job requires that they insulate the roof with Kingspan between the rafters. I live in a fairly old house and the rafters, which were sawn by hand, arent 100% straight (no surprise here). I reckoned it's just about impossible to get the Kingspan to fit exactly between the rafters and that gaps up to an inch or so are pretty inevitable. In anticipation of this problem I asked an Architect friend of mine the proper way to do it. He said that he would insist on beading above the kingspan and attached the length of the rafter to plug any such possible gap.

Well, I told the builder about this and he laughed . He said he'd never done this and that anyway they are very careful to cut and measure the Kingspan precisely so there arent any gaps, and that if there are any they are plugged with slivers of Kingspan.

I asked another builder, a good builder who does a lot of work for the National Trust, what he does in such situations. He said that where necessary they fill any gaps between rafter and kingspan with Polyurethane foam.

I let my builder get on with the job without interference and by the time I got back from work the Kingspan had been done, the waterproof membrane was on and the wooden battens as well. In other words I was unable to get a good look at the work. However although I was able to move some of the kingspan through the membrane other bits were tight, so I didnt bother to say anything (xmas coming up I want to see the end of the job, the best of a not so bad job etc., etc.,)

Since then however the temperature has dropped and the wind has picked up and I'm aware that this part of the job may be worse than I thought . For a start I swear its colder in the house than it was before they started when I had some decently fitted 4" polystyrene fitted between the rafters. Moreover when the wind is strong its coming through at two points. Now I have been able to look up inside at one point and I can easily fit my fingers in the gap between rafter and Kingspan.

What should I do? (The slates are now on the roof which makes the matter more complicated). Should I (a) just accept it and move on (b) insist that its re-done (c) offer to cut a deal with the council whereby I let them get away with this so long as I dont have to pay anymore (66% of my 25 % share still owing).

There is a part of me which wants to confront the council. There's bucketful's of funding coming from government to insulate people's homes and they can't be botherered to do it properly. I hate to think how many hundreds of homes across the county they've done this to, how many hundreds of people are sitting in their house thinking it's nicely insulated and they've only got a 50% job.

So what advice can you give me? How should I proceed, if at all? Comments please.
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chappers

from United Kingdom

Joined: 27 Aug 2004
Posts: 1202
Location: United Kingdom
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PostPosted: Thu Dec 18, 2008 1:17 am Reply with quote

As the council are paying75% of the cost i would make them my first point of call.
with rgards to fitting kinnspan between irregular rafters, the best technique is to cut slightly over size the hold the insulation up to the rafters and give it a good sharp knock, then cut along the imprint made by the rafters you always get a good fit then.Gaps can be fixed with tight slivers or as second best a squirt of expanding foam.
The odd small gap shouldn't matter but numerous gaps you can get your fingers in are unnecessary.
If you have no insulation at ceiling level like before remember you are now heating a larger area and this may have more gaps than before at say eaves level or through vents in gabel ends etc, thus leading to more leakage than before.
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htgeng

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Location: Lancashire,
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PostPosted: Thu Dec 18, 2008 9:33 am Reply with quote

eophi wrote:

So what advice can you give me? How should I proceed, if at all? Comments please.

You say you can't inspect it, but can you see it from inside the attic? If I was doing it I would also take the route of sealing any gaps with expanding foam. However that takes time to do a proper job and as you say if they are doing hundreds of jobs that is a very easy thing to leave off.

If the drafts aren't stopped I would say the insulation levels are almost as bad as having no insulation in there!
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^woody^

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PostPosted: Thu Dec 18, 2008 11:05 am Reply with quote

Why has insulation been fitted to the rafters and not the ceiling?

What is being done about ventilation to the rafters?

This method is the least desirable for a loft as it relies on the loft being heated - which obviously reduces savings

I would not agree with your Architect friend though. His suggestion is more complex than need be.

There are insulation boards with precut slots which allow compression between rafters and awkward spaces

Or infilling gaps with slivers, fibreglass quilt or expanding foam will do the job
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eophi

from United Kingdom

Joined: 23 Oct 2008
Posts: 7
Location: Buckinghamshire,
United Kingdom

PostPosted: Thu Dec 18, 2008 11:57 pm Reply with quote

The loft space was converted into a bedroom several years ago. It is lined with plasterboard. Kingspan insulation is going in the pitched roof between plasterboard and slates with the requisite gap as well (a damp-proof membrane is there of course). This is the normal and proper way to do it. And the plasterboard is the reason I cant see to check it properly.

Do I accept the builders botch job with kingspan and gaps or do I do something about it?
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^woody^

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PostPosted: Fri Dec 19, 2008 1:18 am Reply with quote

Oh, so its not a loft then its actually a room icon_rolleyes.gif

In which case, it seems that this may come under part l1 of the building regs and be required to be insulated to todays standards, in which case it should be a lot warmer than it was with 100mm of polystyrene

I also can't understand how you have got the wind coming into the room at two points - surely the room has not been touched?
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The following user says thank you to ^woody^ for this useful post:
Jacob98 (10 Mar 2013)
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eophi

from United Kingdom

Joined: 23 Oct 2008
Posts: 7
Location: Buckinghamshire,
United Kingdom

PostPosted: Fri Dec 19, 2008 8:38 pm Reply with quote

The builders are putting in a new velux and in the process they have removed a bit more plasterboard than necessary and the winds streaming in at that point. Also there is no plasterboard above the water-tank and the winds coming in there. Okay, if these points are coverered with plasterboard then the wind wont stream in. But thats not really the point. The point is that the kingspan is badly fitted across the whole roof and this subtantially reduces the effectiveness of the thermal insulation (surely?)

Woody, thanks for the reference to Building Regs Part L1. If you have a reference for British Standards or NHBC standards or anything else thats relevant it would be much appreciated.
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