Loft insulation

Loft, wall and other types of insulation and energy related topics

Loft insulation

Postby PatK » Fri Feb 09, 2007 10:20 am

In my 1920's house the slate tiles were lime mortar plastered on the back. Over the years this has been dropping down onto the fibreglass loft floor insulation making a real mess. I have nearly finished chipping the remainder of the plaster off the back and when finished wish to put some form of insulation between the rafters. I was thinking of using Screwfix silver breathable roof membrane, or Screwfix airtec double insulation. Would this be wise and should I leave a gap between it and the slate tiles when I tack it into place? Many Thanks.
PatK
 
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Re: Loft insulation

Postby John Gallon » Sun Feb 11, 2007 10:04 am

Hi Pat,
The lime mortar will have been used to stabilise the slates originally. Although I have never used it, you can get a spray foam to replace the mortar to hold the slates and also keep out the wind but I think it may be a specialist job. As for your thoughts on insulation it would be better to increase the thickness of your existing to around 250mm rather than insulate the rafters. Unless you use the loft space insulating the rafters means that you are heating the loft first before you feel any benefit in the rooms below,
John
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Re: Loft insulation

Postby PatK » Sun Feb 11, 2007 12:12 pm

Many Thanks John, that was helpful, but I intend to board out the loft floor with tongue and grooved chipboard, and to use the loft space for storage. I intend to replace the 4" of fibreglass insulation between the joists with a modern silver bubble insulation, would this be OK? It is supposed to be the equivalent to 20cms of fibreglass!
The plaster has been falling off the back of the slates for the last 30 years and we have never lost any and they are secured with copper nails. I would rather not go down the spray foam route unless I have to. Yes we do get a bit of a breeze between some of the slates but it seems to stop any condensation problems, and if I put the foil breathable membrane between the rafters but with a good gap from the slates, this should, I hope, keep the breeze out.
Thanks John, would this be OK?

PatK
PatK
 
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Re: Loft insulation

Postby John Gallon » Sun Feb 11, 2007 5:53 pm

Hi again Pat,
Not too sure about the equivalent insulation of the silver bubble insulation, the 25mm bubble I have seen is only equal to 55mm of polystyrene. I would leave the 4ins in place and top up if the joists will allow or lay your bubble insulation on top. There should be no problem fixing a membrane, breathable or not, over the underside of the rafters but there should be an airspace of at least 50mm under the slates,
John
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Re: Loft insulation

Postby PatK » Sun Feb 11, 2007 6:56 pm

Many Thanks John, I will do that, your info. was most helpful.

PatK
PatK
 
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