sheep's wool: can it be laid on top of other insulation?

[maggie73]

I am getting quotes for 100mm sheep's wool to lay on top of existing insulation. However, "Ecofirst" have advised that I shouldnt lay it on top, later clarifying that, " if the insulation is organic then you can put sheeps wool on top, if non-organic then there is the risk of moisture retention."
My existing insulation seems to have been blown in there: it is grey, and very dusty, fluffyish. The best way to describe it is like the stuff that comes out the hoover bag.
I would guess that it is breathable, not sure about organic cos dont have a clue what it is made from. I would guess that non-organic would refer to foil or plastic/polystyrene board insulation?
Has anyone topped up with sheeps wool and experienced any problems?

 

[Nemesis]

It's possible that your insulation is cellulose?

http://www.periodpropertyshop.co.uk/acatalog/Insulation.html


Bit more about it here if you scroll down:

http://www.reuk.co.uk/Loft-Insulation.htm

 

[Lime]

I'd find out what the insulation is first.
a friend of mine had a blown lumpy-powdery, fluffy grey insulation in his loft and it was an asbestos compound.
At one time asbestos was an expensive but accepted method of insulation.

 

[MdB]

Caveat - I am not an asbestos expert

A quick easy test for loose asbestos fibre is to take a photo graph of it with flash. Asbestos is a completely matt substance so won't reflect the flash. Glass fibre on the other hand is reflective so you will get reflections from the fibre as below.

I showed the above to a local asbestos company and they were able to tell me over the phone that it definitely wasn't asbestos due to the reflections in the fibres.

Any doubt though, get it tested. Costs around £25 if you collect the fibres yourself.

 

[plumbers mate]

That's a blow - I have the RocWool stuff in my roof , now covered with a layer of rubbish from when the roof was redone, but I wanted to cross the present insulation with sheeps' wool to make up for my single glazed windows. I'll have to rethink ...

 

[worms]

Does the Ecofirst quote on moisture retention mean anything more than the existing moisture retention that they would believe you are experiencing with the Rocwool?

The Rocwool plus fleece wool may not be as breathable as fleece alone, but is there any reason to believe that it is any worse than your current rocwool only situation? If not, and if you (like me) have no problems with the current inadequate layer of rocwool, then I can't see why there would be any greater risk from adding to the insulation using the fleece product.

 

[maggie73]

The Ecofirst comment was the first I had seen relating to sheep's wool and moisture retention problems. You would assume that as long as moisture can pass through whatever insulation you have, then it wouldnt just sit below the sheeps wool causing problems. If you are just laying sheeps wool only, then you would be laying it on plasterboard and that's not organic is it? Pictures of the cellulose insulation looks like what I have in my loft just now, though it looks a wee bit more fibrous than mine- mine literally looks like dust. Cant find many good pictures of asbestos insulation, only pelleted looking stuff - when was asbestos related insulation banned?
Anyway, I am now reconsidering topping up on insulation as it has been mega cold here on a couple of nights this week (-10) and we have had frost on the nails! All dried away nicely and I saw other (condensation free) roofs with frosty nails so not panicking as such, but it just shows you how cold the loft can get with half the recommended insulation! All pipes and tank lagged!!