Roof insulation advice please

[vicky whitworth]

Hi Amc, I found that really useful. Could you just clarify how you suggest laying the insulation in the loft? So one layer in line with the joists and one layer across the joists. Does that mean the layer in line with the joists goes down in between the joists or rests on the joists creating a gap underneath? How far away from the roofing felt should I keep the insulation at the eaves?
Thanks.

 

[dave]

Thank you AMC,

The house is a few hundred years old with long but low roofs with limited access. Seems to have minimal (20mm-30mm) rockwool, or similar, at present.

Really rather go for sheep wool even if it will have to be a bit at a time, as money allows.

On those figures I'm now thinking to try and cover the oldest part of the house with sheep wool to around 250-300mm and (try to) shift the old rockwool into the slightly later surrounding extensions, for the time being.

So around 40-50m2 of sheep wool @ 270mm now and roughly the same still to do.

Don't even have a phone at the moment. Does anyone have any idea what the delivery cost would be for approx. 250 miles from most of the suppliers.

Is there likely to be much of a saving in delivery costs if we can raise the money to pay for the whole lot to be delivered in one go ?

 

[dave]

Sorry. Forgot to ask. As the price per volume seems pretty constant is there any disadvantage in going for more layers of the thinner 50mm which would allow it to be shifted around between the various roof spaces more easily.

Other than the extra time / work involved in laying out more rolls to achieve the same depth.

 

[Flyfisher]

I'd like to know why sheep's wool is so expensive in the first place. I understand it's effectively a waste product, especially if you believe all the moaning farmers who claim the price of a fleece doesn't even cover the costs of shearing.

It would be interesting to know where all the extra cost of sheep's wool compared to rockwall is spent - filling up the Ferrari of some astute eco-entrepreneur perhaps?

 

[AMc]

Hi AMc, I found that really useful. Could you just clarify how you suggest laying the insulation in the loft? So one layer in line with the joists and one layer across the joists. Does that mean the layer in line with the joists goes down in between the joists or rests on the joists creating a gap underneath?

The first layer is tucked down between the joists resting on the ceiling, if you can do it in one thickness then all the better. The idea is to completely cover all the gaps but not squash the insulation too much. Then the other layer at right angles to cover down the gaps.

How far away from the roofing felt should I keep the insulation at the eaves?
Thanks.

As I understand it the insulation shouldn't touch the felt. Bear in mind it will probably spring up a bit after you've unpacked it and laid it. I left about 2" but that was guess work!. If there is a gap between the ceiling and the underside of the roof or a grill allowing fresh air in there you need to make sure that remains unblocked.

More info here...http://www.energysavingtrust.org.uk/Home-improvements-and-products/Home-insulation-glazing/Loft-insulation/All-about-installation

Make sure you find your lighting cables and bring them up over the insulation so they rest on top. The cables can get warm and if they're heavily insulated this can cause problems (I assume melting). Less of an issue with low energy light bulbs as they power is much lower but still better to be safe.

As the price per volume seems pretty constant is there any disadvantage in going for more layers of the thinner 50mm which would allow it to be shifted around between the various roof spaces more easily.

As I understand it, the thicker the individual roll the less chance there is for gaps which allow air movement. Even if you lay the same amount in thinner layers you will end up with pockets and gaps in it which wouldn't be there in a continuous piece. All the time you're trying to lay as air tight a layer as possible.

In practice I'm not sure it will make a massive difference and if using the thinner material makes it easier to get into the tighter spaces then I'd assume better coverage would offset any minimal loss where you could use the thicker stuff.

I added a layer of cavity wall rockwool this winter as it was sitting in the coach house doing nothing left by the previous owners. It came in 2' x 4' 'batts' which I laid across the existing layers of quilt - butting them tight against each other. I can't 'feel' a difference but it can't be hurting.

It would be interesting to know where all the extra cost of sheep's wool compared to rockwall is spent - filling up the Ferrari of some astute eco-entrepreneur perhaps?

I suspect that it's not that sheepswool is unreasonably expensive, but rockwool is ridiculously cheap. As it's stuffed into every available space in a new build as well as 1000's of other things I suspect the price has been squeezed to the mimimum. Whereas sheepswool is much lower volume and seen as a premium product that people are prepared to pay more. The fact you can buy it in B&Q is encouraging suggesting that it will get cheaper. As anyone who's worked with rockwool knows it's horrible stuff, itchy and unpleasant to deal with and I'd sooner not.

I think it's probably a Tesla Roadster not a Ferrari

 

[Flyfisher]

I suspect that it's not that sheepswool is unreasonably expensive, but rockwool is ridiculously cheap.

Maybe not 'ridiculously', more 'appropriately' perhaps - but I know what you mean and I agree about the likely reasons.

I was, of course, being rather tongue-in-cheek regarding the Ferrari, but I do think it's interesting to consider what happens to all the extra money involved in these expensive 'eco' solutions. For a start, you have to earn nearly 4x as much money to pay for the stuff, which has a significant environmental impact, then the receipients of the money end up spending it on maintaining their standard-of-living etc, etc. I still reckon that cheaper = greener in the grand scheme of things.

 

[AMc]

I still reckon that cheaper = greener in the grand scheme of things.

That one could go and go - and if I recall it did last year! Cardboard shoes are cheap but not very green in the long run