Sheepswool Insulation

Gordon Gekko

Hi all,

I've been looking at insulating the attic for oh, about a year now .

News of Bord Gais and ESB's monopoly price rises (yet more!) has finally convinced me to get the finger out and start insulating. I have no insulation in the attic at the moment.

Being a wannabe green sort, I'm almost definitely going to get this stuff. Obviously, it works out a good bit more expensive than conventional fiberglass insulation, but that aside, does anyone have any thoughts?

I've heard it is more effective than the fiberglass quilt insulation, but does anyone know if this is indeed the case?

I know 200mm is the minimum nowadays for fiberglass insulation - could I get away with slightly less sheeps wool insulation?

I've come to terms with the price difference, and feel it is worth paying more for the environmental benefits (both globally and in terms of not having nasty particles of glass fibre floating around my attic), so it is really just the technical aspects and peoples' experiences I'm after.

Mellor

Gordon Gekko wrote:

Being a wannabe green sort, I'm almost definitely going to get this stuff. Obviously, it works out a good bit more expensive than conventional fiberglass insulation, but that aside, does anyone have any thoughts?

How much more expensive is it?
The idea behind environmental materials is low embodied energy. Natural doesn't automatically equal enviromental (for example if it a natural material needed masses of energy to process it into a building material) but it nearly always takes little energy to process them. Sheeps wool has very low embodied energy.
BUT low embodied energy is no good in the long term if it cant match preformance, and you mentioned .........

I've heard it is more effective than the fiberglass quilt insulation, but does anyone know if this is indeed the case?

Sorry but thats not the case. It is less effective that fiberglass. And most other common insulations. It has a conductivity of 0.037W/m2K. Common insulations have values of 0.022 - 0.032.

I know 200mm is the minimum nowadays for fiberglass insulation - could I get away with slightly less sheeps wool insulation?

To match fiberglass insulation you'd need more sheeps wool. You could use less and justify this by the fact that sheeps saves energy in manufacture, but in a short period of time the sheeps wool would of wasted more energy through heat loss.

I've come to terms with the price difference, and feel it is worth paying more for the environmental benefits (both globally and in terms of not having nasty particles of glass fibre floating around my attic), so it is really just the technical aspects and peoples' experiences I'm after.

The wnviromental benefits aren't exactly what they are on the tin, fibreglass isn't that bad in the attic unless you touch it. I gave you a bit of technical info, hopefully somebody can share an experience.

Viking House

Fibreglass has a conductivity of 0.044W/m2K which means it has a worse U-value than Sheepswool.
If you used 200mm of sheepswool you would need about 225mm of Isover fibreglass to give the same U-value.

But sheepswool has a lot of properties that are least known as people usually only look at U-values.

Sheepswool has strong Hydroscopic properties which enables water vapour to be drawn through the material and vented to the outside without condensation occurring. This also occurs in nature when a sheep overheats and sweats or gets wet. Because of this quality some people have questioned the need for a vapour barrier internally.
The Hydroscopic properties of sheepswool is perfect for keeping the wood dry/healthy in a timber frame construction, any excess moisture in the wood is sucked out by the Sheepswool and vented to the outside by the higher surface area of sheepswool.

Sheepswool also has an ability to maintain its U-value when it gets moist and no reduction in performance was measured at moisture levels up to 17%.
Fibreglass on the other hand has a loss of 3% U-value for every 1% moisture, so 17% moisture would give a drop in performance of 51%.

Sheepswool has a much higher Decrement Delay than Fibreglass because it has a higher Density and Specific heat capacity. This means that an attic insulated with Sheepswool lets in the midday heat a lot slower than fibreglass and is less prone to summer overheating.

Fibreglass, Polysterene and Polyeurethene all have a low decrement delay and let the heat/cold through quickly. This is commonly known as the "caravan effect".
On a hot summers day, an hour after the sun comes out, your caravan is like an oven.
Denser fibrous insulations like Paroc are used around your dishwasher and you can turn your dishwasher at 10 O Clock and you will still get a waft of heat off it at 9 in the morning.

All in All insulating your house to the same U-value with sheepswool insulation means spending much less on heating your house.

The only other insulation with these same properties is Paroc Granitewool from Finland.

Mellor

Sorry was rushing late last night and i got mixed up. Should of been a bit clearer. Standard mineral fibre insulation would need to be thicker. The standard stuff from moyisover has a conductivity of 0.040W/m2K. As opposed to sheepswools 0.037W/m2K. I was refering to the better grade mineral fibres that have values of 0.034W/m2K. Sorry my first post is a bit of a mess. Hope that clears it up. But VH is right too, poorer quaility fibreglass would be down further to 0.044w/m2K
I have heard that sheeps wool had the hydroscopic properties viking house mentioned, damp without suffering heat loss. Was also told that it absorbs heat from vapour as it passes through, but couldn't confirm either of these, thanks VH for comfirming the first. Ever heard of the second one?

Gordon Gekko

No worries Mellor, cheers for clearing that up. I have read that wool actually generates heat if it becomes damp, never enough to heat an area but enough to prevent condensation. I've looked at so many webpages on the subject now though I have no chance of remembering where I read that .

Your point about the low embodied energy of sheeps wool, which is another point in its favour.

FrankGrimes

Very informative post Viking House. Unfortunately for me I'm reading this too late for renovations on my current house, but next time round your advice will be taken on board.

Mellor

Gordon Gekko wrote:

No worries Mellor, cheers for clearing that up. I have read that wool actually generates heat if it becomes damp, never enough to heat an area but enough to prevent condensation. I've looked at so many webpages on the subject now though I have no chance of remembering where I read that .

Your point about the low embodied energy of sheeps wool, which is another point in its favour.

Thats pretty much what I heard, can't remember where. Would like to know if somebody could explain it better.
It might be the fact that its a small amount of energy used to evapourate water

RazzaMataz

I've been looking at green insulation. I got a quote for sheepswool and also for shredded newspaper from the same supplier. The shredded newspaper is half the cost, and the supplier reckons you get the same performance from it.

Surely there must be some advantages to sheepswool for it to be a competitive product. Any one got any suggestions on how they compare? Google isn't being very helpful.

netwhizkid

I'd say go for the sheep's wool, The other fibre glass stuff is damn itchy, I was messing around in an attic last month running TV wires and I was itchy for a week as well as coughing and spluttering. I reckon it must be some sort of asbestos (yellow fibrey stuff) and having that in any-one's house is not good.

I was told by a builder once that he doesnt use Plywood anymore for flooring due to some cancer causing gas it gives off. (I never heard it but with all the building codes who knows??) Go for sheep's wool as it will help make a market for the poor Irish farmers wool too, Wool has the price cut out of it now to heck and for a farmer to hire a shearer means a loss with what the wool will make unless he can shear it her/himself. Either that or shredded telephone directories.