Replacing Roof Insulation

[Delaine]

Hi, We have a three story town house with the top floor rooms located in the roof. We have just found out that the builders have left out some of the "Kingspan" type insulation boards and the others have been cut undersize so are loose between the sloping trusses/rafters or whatever the correct name is. The developer has said that they can remedy this by replacing/fitting new boards without removing the ceilings or the roof tiles. Is this possible? We thought that these sort of boards had to be a friction fit between the timbers in order to be thermally effective. We don't see how these boards can be pushed up the roof timbers whilst maintaining an effective fit. Surley the easiest and only way to fit this insulation correctly is to remove the ceilings or the roof tiles?

We don't wan't a botch job carrying out, so any advice would be much appreciated please.

 

[PaulJR]

I think that you would be best having this conversation with the developers and ask them how they propose to achieve it.

If the joists/trusses are perfectly square, straight and parallel it might be possible to feed new board between them, but in reality I would be interested to see how they propose to do it.

I wouldn't be surprised if they aren't going to turn up with a box of spray foam and drill holes into the ceiling and fill it with foam - not the way I would want it done. but it would save your ceilings (as long as they don't over fill anywhere)

 

[Delaine]

Thanks PaulJR,
They are definately intending to fit the boards by sliding them up between the timbers. Can't see that this is going to achieve a better result than what I already have(if it is at all possible to get the boards up the timbers in the first place). I suspect they don't want to go to the expense of removing the roof tiles or ceiling plasterboard.

If they do turn up with some expanding foam it will be going back with them. Not having that stuff in the roof.

Going to have to try and persuade them to take the more expensive correct approach.

Would I be correct in thinking that the insulation boards have to be a snug fit between the timbers?

 

[PaulJR]

If there is any significant gap then you get air movement which defeats the object of having the insulation. It is normal to fit the boards as tightly as practical as you build the roof, but to be fair it is also normal to seal them up with spray foam - it is almost the same stuff.
If they are clever it should be possible to slide the new board up from the eaves or down through the loft space - not sure of your roof construction. It really depends how "square" everything in your roof is - and wood normally twists/warps/bends as it seasons, so I would be surprised if they were still dead straight. If they want to feed a couple of metres of insulation up like that they had best send a gynaecologist.

 

[Delaine]

A gynaecologist would probably do a better job than the monkeys that have lashed this house together.

I can't possibly see that they are going to achieve acceptable results fitting it the way that is being proposed. So I think I will insist that either the roof comes off or the ceiling comes down. That way they will have ample space to ensure that the boards are fitted correctly.

I have paid for a correctly built house, so I feel that I am entitled for the house to BE built correctly.

Thanks for the info PaulJR. Time to start emailing.

Delaine.