Roof Insulation

Hi,
We live in an old house (1840)and the roof of this house has its lower part pitched and the upper part has a more conventional flat ceiling, rather like this (in x-section) /\ / \ /----\ / \ / \
Where the upper part (above the ceiling) is sealed. My problem is that the room is very cold so today I sawed a hole in the ceiling to see how much insulation was there. I was surprised to see that a previous owner has laid fibreglass wool perpendicular to the joists and not in between them. I can't think why this would have been done. Does anyone else know why? My plan is to re-lay this insulation in between the joists and to poke additional insulation wool down each of the channels (formed by the joists) in the the pitched part of the roof. Can anyone think of a better solution please?
Many thanks.
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Hmm, that'll help the temperature won't it? :) to see how much

Not normally a good idea to lay it perpendicular since you can't see the weight-bearing joists to stand on; also any wiring should be attached to said joists (and hence visible). However, I would think laying a given thickness of fibreglass perpendicular, rather than parallel to the joists would actually improve the insulating properties since there will be a layer of insulating air trapped between fibreglass and ceiling. Maybe that was why it was laid that way; the installer reasoning that since in his wisdom he didn't bother installing an access hatch, nobody was likely to be going up there for a wander round.
Count yourself fortunate there's any insulation up there at all! In the last place I bought, the roof void above half the house was totally inaccessible from below (no hatch) and there was a brick wall separating it from the attic over the rest of the house. However, I could just squeeze my digital camera through a small brick hole in the eaves[1] and shot off some flash photos - revealing that the whole area had no insulation at all (despite having a brand new, freshly skimmed and painted plasterboard ceiling.
Suggest you have a google for the thread "Loft Insulation - Best Type and Tips for Installation" in which a roof of similar construction to yours was discussed in this ng a few weeks ago.
David
[1] Very Useful Tip for exploring dark otherwise inaccessible places where you can't get you eye and/or light to the hole...!
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On Fri, 31 Oct 2003 21:53:15 +0000, a particular chimpanzee named
and produced:

I can't think of a worse solution.
You get less value from insulation between the joists than covering them, as heat is lost through the joists leaving up to 12% of your ceiling uninsulated. As other posters have said, the insulation has traditionally been laid between the joists to allow access, but as your roof void is sealed, then this is not a consideration.
You need to leave a gap between the insulation and the underside of the felt to allow for ventilation and for the felt to drape. Use a rigid insulation board such as Celotex or Kingspan to a depth of 50mm less than your rafters.
--
Hugo Nebula
"You know, I'd rather see this on TV,
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Sir
I did mine when the slates were off the roof. My firebglass runs both ways, first in the joists, and then over the top of the whole lot, there is about 450mm in all up there now.
For the sloping sides you have a problem, anything you poke down, will in time slide to the bottom. I would call round a few cavity wall type people and see if their cavity wall stuff is suitable - I have no idea if it is or not. You also see adds for people that spraf insulation onto the unserside of old roofes, maybe thay can help ? Squirting something in that sets sounds like the way to go to me .......
Rick
wrote:

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wrote:

about
and see

Nooooo!!!. If there is one thing I'd never do to insulate a roof, it is to have the underside of the roof sprayed with foam insulation. In all honesty it is probably the worst solution, restricting airflow over the timbers (causing damp/rot) and potentialy making future roof maintenance more difficult. Furthermore, I know of a couple of surveyors who will knock down the value of properties with this form of insultation simply because there is no way of assessing the state of the roof timbers.
If you want to insulate the underside of the roof, use a sheet material such as Celotex or Kingspan.
Cheers Clive
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