I know the theory of insulaiton, but not the practical side.

The builders are insulating the new roof. They have put solid kingspan foiled insulation inbetween the rafters Surely there has to be good contact with the insulated plasterboard that they put on top of it. Otherwise the cold air just goes around the insulaiton doesn't it (its a good fit between rafters, but not perfect)?

Should they be using insulation tape or something.

There's a dormer in the roof and insulaiton is cut & pushed into all nooks & crannies. It wont all touch the insulated plasternboard when it is added. its not a bad fit, but there are gaps in places, where the air is going to get around the kingspan.

What should they be doing?

Hope that makes sense.

If the air can get around the Kingspan, you've wasted time and money putting the Kingspan there. It should be airtight, joins in the Kingspan should be foil taped. If that is the case, no need for next layer to touch, but the plasterboard layer shouldn't be providing draughtproofing to any major extent. Sounds like they need to re do the Kingspan fitting with a lot more care.

The kingspan needs to be tight against the trusses – there must be a good seal all away around. Our building work is just finishing, and the kingspan is tight against the trusses. Any significant gaps have been filled with expanding foam. A gap between the pb and the kingspan doesn't matter.

Its all about thermal bridges innit 🙂

Couldn't agree more. I didn't want to quiz the builders, unless what I was suggesting was practical.

So… they should tightly fit the kingspan in (any gaps filled with foam)
Joins between kingspan should be taped.

Thanks for the reassurance.

Kingspan is a branded name…. Quintherm is exactly the same-non branded stuff and is a lot cheaper. Available at TP i think!

http://www.grownupgreen.org.uk/library/?id=280

I can reccomend this stuff as well,very efficient and also good for the environment etc etc 😉

Pic of insulaiton here
http://www.flickr.com/photos/43457617@N06/4043566119/

Am I being paranoid?