Help with Loft insulation

dave82_2

Whilst renovating our house I am replacing the loft insulation.

I have bought this

http://www.diy.com/diy/jsp/bq/nav.jsp?action=detail&fh_secondid=11127506&fh_reftheme=promo_159792389%2cseeall%2c%2f%2fcatal!!!1%2fen_GB%2fcategories%3c%7b9372016%7d%2fcategories%3c%7b9372050%7d&fh_view_size=10&fh_location=%2f%2fcatal!!!1%2fen_GB%2fcategories%3c%7b9372016%7d%2fcategories%3c%7b9372050%7d%2fcategories%3c%7b9372230%7d&fh_eds=%c3%9f&fh_refview=lister&ts=1289216615722&isSearch=false

To top up the 100mm between the joists.

So now for my question. We have sloped roofs in some of our rooms so there is a void behind these slopes.

There is a small gap where the roof joists go past the ceiling joists and down to the eves.

Sorry this description isn’t the best! But I am hoping someone will understand.

I want to insulate these sloped areas but don’t want to stuff them with insulation as I think this would be a bad idea.

Could I use a couple of layers of this (link below) which should still allow the airflow down into these voids to stop any dampness.

http://www.screwfix.com/prods/76477/Building/Roofing-Insulation/Thermawrap-Loft-Insulation-400mm-x-5m


Now I know that the m2/kW is going to be much lower in these areas am I likely to get condensation issues?

latecomer

If you mean the sloped section beyond where the sloped ceiling ends then there shouldn't be any need to insulate there provided the room walls are insulated. If thats not what you mean try taking a photo or drawing a diagram

Edit: Check this post:

http://www.diynot.com/forums/viewtopic.php?t=20661

dave82_2

Not really like that. The joists them selfs slope and the ceeling is sloped internally

latecomer

Do the sloped ceilings go down to the floor or is there a vertical section? Is so then are you talking about the area behind the vertical section?

dave82_2

Sorry this is very crude but it looks a bit like this

http://i52.tinypic.com/346kmqp.jpg

latecomer

Much clearer.

We have just done a loft conversion and had to leave 50mm air gap between the insulation and sarking boards. you have to be careful you dont block the airflow from the eaves up to the rest of the roof.

dave82_2

Cheers I will make sure I leave 50mm.

Thats why I was going to use the thin foil stuff for the slopped part as the gap where the roof joist passes the floor joist is tight! Anyone got any thoughts on the sloped bit having much less insulation than the rest of the loft will I get condensation issues?

dave82_2

The loft is very airy as there is no felt behind the tiles it is old and will probably need replacing before long!! the thin foil stuff I posted the link to shouldn't block the gap. So at least it will have some insulation on the slope!! It can be resolved properly when we eventualy replace the roof hopefully with a loft conversion in a few years time!

dave82_2

Actually coming round to installing some of this in the slopped areas to keep decent airflow not cheep but worth doing the job properly http://www.screwfix.com/prods/68120/Building/Roofing-Insulation/Superquilt-1500-x-10000mm

Any comments?

dave82_2

yes the gap it about an arms width my arm isn't that long but in theory I should be able to roll this stuff donw the slope! I will pratice with some buble wrap it is cheeper!!