Which is (or are either?!) better for the environment? Glass fibre, or, better still if you can afford it, sheep's wool.

Rockwool has some big downsides for the folk who have to live downwind of the factory.

Hi,
Not only does your joiner have to cut it accurately he also needs to seal it properly to each other and to the surrounds in such a way it wont leak now or in the future. Not only tape it but mastic seal it all over.
I would look very carefully at the natural options. There are mmany recent treads on this. Just slapping in the Kingspan or Glasswool is not enough. Decide what you want and why you want it. Problem is this may present you with problems as joiner has only offered you what he can do or knows. Research all the many other options and ways you can use the two you mentioned then discuss with him. Make your judgement after he has given his views and take it from there.
Cheers
Mike up North

Hi,
I'd go with that every time ie:
less good well executed
is better than
top spec poorly executed

overall you have to consider the resources available within your area, so a less esoteric green option well done might be better in the long term than something that ticks current boxes but is poorly carried out. I think these factors do make a big difference to the overall result.

cheers

mike up north

In either case, it may be worth investing in a thermal image report (we paid £75) before you pay the final bill, then you can get any gaps rectified at the builders expense, also if you mention this, you'll find they'll fit it very carefully indeed!

I'm with the others here I am afraid.

I used PUR to do my skeilings & roof insulation but you need to pay a great deal of attention to joins and to ensure no air gaps are left where insulation meets the wood. This takes time and care using spray foam & sealant where necessary and very careful attention to creating an effective vapour barrier. If this is not done it will not be as good as a fleece material put in well, indeed it may well give problems in the future & end up not working.

Sheeps wool is lovely stuff & is currently believed to have the best ecological/climate credentials, sheeps wool is however very pricey. All fleeces suffer from reduced/lack of performance in drafty situations so as long as you have ensured no drafts can blow through it will work. With regard to the width lost you have to ask how much you will really notice when the job is finished & how much difference it will make to your energy use.

I have spent the last two days showing people around our house & the work we have done. One of the things I have said many times is that at the end of the day with renovation you have to work with what you have. If the space you will be left with will genuinely create problems when living in the space you can only do what you can do!

Sorry if you you have thought of some of this.

Regards & good luck in deliberations

S.

PS Not yet sure about the stories surrounding foam insulation as the only link I have seen appeared to be a press release describing a modeling exercise rather than any presentation of evidence collected in a real world situation over appropriate timescales. Whilst I would be unsurprised (& disappointed yet again) if it was true I would like to see actual proof. It may still be the case that PUR performs better than fleece in some situations even after these suggested losses in performance.

tell them not to cover the insulation til you've seen it

We have just insulated our chicken house with sheep wool donated by our friends sheep! We have about 3 inches of wool in the depth of the rafters. I know it is not cold yet but the temperature in the hen house is noticbly warmer than outside at night. It is probably helped by the dozen chickens warming it up though. I am quite impressed but the stuff is horrible to use as sheep dont wipe there a**es when thet go to the loo!

Mark

I can't use your link to get to the document, what is it's name?

Mind you as you say I wouldn't necessarily buy in to data presented in an industry leaflet. They have one which de-bunks the 'breathability myth' as well. Just don't say that around here or they will all go bonkers (I may even join in).

Can't remember where I saw it (possibly GBB or Whole House book) but apparently the fleece industry has suggested that the 'environmental optimum thickness' of their products is about 1m. I don't want to know how much a 1m depth of thermafleece would cost for an average loft (in fairness I do not think that the makers of the fire proof, non stinky, non rotting venerable woolen warm stuff claim this).

Sensible comment, as ever, Mike.

S.

Nice link!

As far as I can tell it is the overall 'ecopoints which matter (there are no data for sheeps wool of any flavour, warmcell insatalled dry, only cellotex of the foams & rockwool of the other fleeces) for our purposes they present an overall measure of the relative impacts.

Warmcell: 0.03 (Warmcel 500 recycled cellulose insulation (damp spray) with a density of 50 kg/m3 only)
Rockwool: 0.032 - 0.019 (here I have listed the range)
Cellotex : .041 (Celotex Pentane Blown PU Insulation Panels with aluminium foil/kraft facing on both sides)

All three get A+ rating for all construction types.

The BRE appear to be overhauling their rating system at the moment so there may be a flaw in the current calculations:

"A comprehensive update and revision to the Environment Profiles methodology (BRE 370) as well as the ‘Green Guide to Specification' and the ‘Green Guide to Housing Specification' is currently being undertaken. The update work has resulted in changes being made to the Environmental Profiles methodology. This will ultimately affect the way in which we calculate the environmental impacts of materials and how the information is reported as Ecopoints. Details on the update work to the Environmental Profiles Methodology can be found at the Green Guide to Specification web page at www.thegreenguide.org.uk"

On the basis of the above all three can, at the moment, be regarded as excellent choices & warmcell is a bit better than some rockwool products.

The thick plottens!

S.

Me too

Although multifoils spring to mind! (I thought they were regarded as having met some sort of recognised standard)

The document at least cites it's sources & it's sponsors. Whilst biased towards rigid foam at least provides comparisons between the different insulants. I hadn't realised that the lambda had ben adjusted to mitigate for loss of propellant over the first few years.

S.

Thanks for a great response guys. Sorry I haven't replied sooner. I will have a good read through all the links and I think you are right about the rigid insulation being a no go if we are not going to be there to supervise and make sure everything is carefully fitted.

With regards as to what is on the warrant drawings - our u-values are calculated based on 150mm of Rockwool but our architect told us that if we switched to kingspan that would give us better u-values and building control would be more than satisfied with that - no mention of having to submit new drawings...

Unfortunately cost is a huge consideration for us so wool is most likely out. Will have a look at the other suggestions and will no doubt be back with more questions.

Thanks again

SW

Posted By: James Nortonhttp://www.insulation.kingspan.com/uk/ifs_full_version.pdf" >http://www.insulation.kingspan.com/uk/ifs_full_version.pdf

...that link above.

All very well choosing better lambda over eco insulation but.... what I'd be interested in is £ / C02 saved... with that then I'd reckon warmcel (if on a new build) and rockwool come out tops...

J

That is almost certainly true on the pure cost of the insulation. I did some rough sums recently and Warmcel is surprisingly good value - much better than rigid boards or fleece. However, if you choose to factor in the additional depth of Warmcell needed around the perimeter of the property and the cost of that lost space it's not so clear.

My proposed house is roughly 11m on a side over three floors, so has a perimeter of ~130m, factor in an additional 100mm depth of insulation to achieve <0.1U-value (300mm vs 200mm and ignoring the thermal bridging of a frame to support the Warmcell) and this is 13m2. At a typical build cost of £1000/m2 the costs swing clearly back in favour of rigid insulation. Of this course this doesn't properly take into account the incremental cost of floor space, and has lots of generalities but........ (You can prove almost anything with numbers if you choose to, even aerogel starts to look reasonably priced with this kind of thinking.)

CO2 is almost certainly a clear win for Warmcel for the initial installation, but it could be argued that this is insignificant over the lifetime of the building.

(I have a feeling that I should duck at this point - perhaps this is a hint of future guilt over my planned use of rigid boards.....)

My understanding of the BRE' information was that loose fill cellulose (Warmcell is the only one they have data for) was certainly the winner in CO2 terms. If the longer term slumping concerns are genuinely dealt with by controlled density damp spray installation & proper noggin spacing it may be 'The Best" (sensu Tina Turner/Carly Simon) where space is available (possibly a rash statement).

The important thing here is keep it balanced, which the BREEAM eco scores seem to aim for. Almost all insulants installed properly will work well.

There is however a great deal hidden in 'installed properly'. Construction type is absolutely key - there is, most of the time, a major difference between what can be achieved in new build, or virtual new build where old buildings are almost dismantled and normal retrofit/restoration.

Often with retrofit/restoration space restrictions mean that fleece & loose fill insulants are not relevant choices as either proper installation cannot be carried out or, more likely, you just cannot get a useful thickness in.

My house, & very many in the uk, are constructed in such away that only 50-100mm is available for insulation between & under the rafters forming skeilings/sloping ceiling surfaces which account for much of the surface area. Loose fill is almost impossible to install in these circumstances & fleece nearly pointless; with both variously adversely affected by air movement rigid insulation is the only sensible (i.e. 'The Best") choice (unless you need/have resources to replace the roof then 'new build' approaches can be used).

S.