Ceiling/Roof Insulation

[Andy_C]

I have a 1780 farm cottage. Two thirds of all the upstairs rooms ceilings are under a small apex loft but the remaining third has a sloping lath and plaster ceiling directly under the roof. This roof section has no insulation.

There is a gap of about 80mm between the ceiling and the felt which can be accessed via the loft to feed insulation in between the rafters. But what would be the best way to put in efficient and cost effective ceiling/roof insulation?

I had a quote from a roofing man for £1900 to remove the slate, put in insulation and put the slate back again.

The loft space in the small roof apex has been insulated with fibre glass

 

[Mark]

to be honest I think you're a bit tight for space. Most products seem to recommend a 50mm gap between the insulation and the roof. That doesnt leave very much insulation.

what was your roofer going to use ?

 

[BMcD]

Consider the problem of disturbing the lath and plaster ceiling. If you put insulatoin on top of the nibs which hold the plaster to the lath and this then gets compressed when the slate goes back on, the nibs could break weakening the ceiling. Like wise if you try to slide insulation in from the loft you are likely to break off the nibs. For 1/3 of a ceiling is it worth it?

 

[Andy_C]

Roofing man was going to use a thin 10mm insulation of which I can't remember the name. It was made up of about 12 different layers of fleece and a breathable foil type material. But too thin to push down from the inside of the loft.

 

[biffvernon]

You'd better look at this thread on Green Building Forum.
It's a long and convoluted thread, but I think the conclusion is that multifoils may not be quite what the manufacturers claim but if space is really limited it may be your best option.