I now see that paint removal from stone is prior to covering it up again, in areas that are to be EWI'd - presumably to make it vapour permeable? Otherwise, why bother with paint removal and pointing when it's going to be visually covered and functionally weatherproofed by EWI? in this case, a vapour-check at that back-of-EWI position would be just what the strong-VCL brigade would recommend, so can't be too bad. Why not save your money and leave the paint on (and not bother with repointing) - it won't be a complete vapour barrier by any means.

Tom,
Having a vapour seal on the outer face of the masonry is always going to be dodgy, any moisture in the wall from rising damp or internal condensation will have nowhere to go except back inwards or up - wick effect. Of course this particular gotcha places severe constraints on the materials and detailing of the external insulation, it would be wrong to replace one vapour seal with another. The obvious countermeasure is to have a vapour seal inside, adding a whole load more work :-(

I'd want to have a look at the condition of the stone in the walls where they've been sealed, and any joists or wallplates embedded. If everything is in good order then all options are open, if not I would prioritise getting water out of the wall.

The lean to solar is a very good solution, I proposed the same for my client in Snowdonia but it has not yet been tried on planning.

<blockquote><cite>Posted By: fostertom</cite>bella, You say also wall vapour permeability to insulate and protect from driving rain - I don't get that, as the EWI will well protect from driving rain, and in that situation the wall won't be called upon to provide any insulation.</blockquote>

Probably not very clear - meant that treatment of wall surface and choice of EWI should both encourage water/ water vapour movement and evaporation (as well as provide weather protection and insulation) so yes woodfibre is on the list. I see the issue on thickness but for the moment come down on the side of encouraging external evaporation rather than higher U-value for same thickness. Maximum possible dryness of the internal layers of the wall seems the number one priority and I am not certain that this can be achieved by using an impervious layer on the outside.

Needs to allow water (liquid) absorption and movement as well? ie "wicking"

Tom , interesting article in GBM winter 09 page 39 ," making the right choices for insulation , revisited "
I presume its fro mthe NBT woodfibre side of the fence

Is aerogel vapour permeable, anyone?

I have assumed that the term hygroscopic means water (liquid) holding capacity. And evaporation means the conversion of liquid water to water vapour that can then be carried away by air movement (wind, rising currents, ventilation). I imagine, but honestly don’t know for sure, that absorbing and “wicking away” water must be “good” properties for materials exposed to moisture (condensation, rain) rather as lime or clay plasters seem to be – or cob or hemcrete for that matter. For example, I think I would feel safer having wood fibre or hemcrete rather that synthetics sitting next to wooden floor joists set into solid walls if I was insulating internally – see GBM vols 18 &19.

What I am not clear about is at what point hygroscopic materials used for insulation (woodfibre, hemp, sheeps wool, shredded paper) when “loaded” with water via condensation or rain lose their insulating capacity and what the dynamic sum of effects actually come down to in the relatively wet , and only briefly cold UK climate. Lots of evaporation means lots of heat loss – “run off” i.e. membranes, slates, timber cladding might be a much better property in certain situations. Conundrum – how to arrive at the right combination for the refurbishment of solid walled buildings without sending the planners into a tiz. May be it is easier than I know – or maybe more difficult – certainly expensive!!!

Posted By: Peter Clarkto ensure the insulation is dry as much as possible, make it capillary open so that when it does INEVITABLY get wet, it can dry out faster

Oh yes ineed, but that's not to say that the insulation should be intended as a way out for rising damp etc; not that the insulation should be expected to absorb liquid water by 'wicking'.

Anyway, is this moisture in the wall that we're trying to find a route out for really from rising damp, i.e. forever renewed? That's actually rare - what's often called rising damp is usually some kind of condensation and/or penetrating damp. If the latter, then EWI will permanently cure both of those and leave the wall dry, once it's dried out initially.

"Anyway, is this moisture in the wall that we're trying to find a route out for really from rising damp, i.e. forever renewed? That's actually rare - what's often called rising damp is usually some kind of condensation and/or penetrating damp. If the latter, then EWI will permanently cure both of those and leave the wall dry, once it's dried out initially."

If there is water in the ground and the wall is dry, the water will travel up the wall by capiliary action ( I think the limit is related to atmospheric preasure - a proper physicist could tell me). Water vapour will travel through fabric by responding to vapour preasure gradients, generally from cold to hot but also from wet to dry. In solid stone walls both processes can be happening simultaneously. How fast this happens depends on the physical properties of the stone AND the mortar.

My priority treatments for a wet wall would be
Drainage
Driven rain protection

Posted By: Peter ClarkIs rising damp a particular part of Bella's problem? Why has it been mentioned?

Not sure. She and others seem v concerned to not block escape of moisture from her walls - as if it'll be a forever-renewed ongoing problem (which, assuming no penetrating damp or leaking pipes leaves only rising damp - I think?) rather than just a one-off drying of existing water.

I'm in fact suggesting it's the latter, so no need to make the insulation transport moisture, once the source (condensation, I bet) is stopped by the EWI keeping the surfaces warm, and the old moisture's dried out.

In useing external wall insulation there are many points to look out , for instance to apply such a system to a old building with no cavity , brick, stone ,concrete , first check if there is a dpc installed , if not then install a dpc
second check your roof to insure there is no water /damp ingress that my be allowing damp/water to enter the old walls at this point , third if you are not installing a ewis in the complete facade [ perhaps facing stone that is not allowed to be changed by the planers] then ensure that you take steps to stop any damp/water ingress flowing from the unsulatied areas to the insulation facade
Once these steps have been taken you may apply a ewis system with no problems
Regarding breathing problems , there are none in this type of substructure as any of the back grounds i have listed above will allow the water vapour to dispers in a standard heated home [oil,electric, gas ,not open gas flame, ] if your building was old and/or damp when you installed the ewis system there will be some tempory problems with water vapour but these are not large problems and will disapper soon depending on the amount of damp/ water in the old substructure
it is important to rember that each builing type will be differant in applying ewis systems regarding detailing of dpc, new/old bild ,steel/timber frame ,masonry of all the differant types and indeed the cost will differ depending on the back ground , from Ă‚ÂŁ 55.00 m2 to Ă‚ÂŁ 120.00 per m2 ,

The other main factor in costs are thickness / types of insulation and finishs

regarding finance there are limited grants to be had ,and some very very good tax allowances for industrial buildings

In short go to an approved contractor who will use a eta approved system and can offer a indepant insurance
that is insured to the system and building

any question just ask nb I work In the feild I think I am to say so

from gjjjohn

''If guarantees for EWI by a registered installer depends on inserting a damproof course first I think I will pass. ''.

I think I am with you there. Some, if not all, EWI firms bridge the dpc -if there is one - (some changing material from porous above to non-porous below), so that if there's any capillary action you've blown it anyway. If there is not a (rising?) damp problem, why take measures to chase the (not a) 'problem' away?

I was presuming just making sure wall and ceiling insulation joined up would achieve the required complete insulated envelope. ?
this could be done by just lifting the first few row up from the gutters ,
also adjusting the rafter feet, sprocket to allow thicker EWI as discussed earlier.

One of the deciding factors in favour of external roof insulation for us is that the roof is open internally with exposed rafters and the original exposed pine sarking boards (so no ceiling) as well as purlins and three A beams, all in rather good condition but with work needed on lead valleys, down-pipes, drains etc etc. The planners want internal insulation (so did our professional advisors) - will keep you all informed of ultimate decision. This discussion is giving us extra confidence that external is the right approach for this particular building. It is interesting that the discussion with the planners has all centred round whether or not it is acceptable to raise the roof not what is the safest/most effective method of insulation. Ultimately the safety and integrity of the roof is the bottom line but with a calculated heat loss of around 6000kW/yr insulation is clearly essential if the building is to have a long term future as our dwelling.

Just come across this on Springvale site http://www.springvale.com/page_view3.asp?InfoID=559:

"Producing one square metre of Platinum EPS at a thickness of 100mm requires 5 litres of mineral oil. Over a period of 50 years the same board saves over 600 litres of heating oil (source BASF)"

That's 50 litres (nearly 11 gallons) of oil per m3 of EPS. That much oil would occupy about one ninteenth of a m3 - so EPS is 1 part oil to 18 parts air!

Posted By: Paul in Montrealit doesn't mean that there is 50l of oil in the m3

I know - artistic license - most of it prob goes as fuel for the process (or perhaps they're not actually including embodied energy?) It just seems a surprisingly large amount of oil.

That 9 gallons of oil contains about 315kWh of energy, or 420 carthorse-hours of work, or an Olympic cyclist pedalling non-stop for 3 months. To make 1m3 of EPS.

Posted By: Paul in Montrealusing oil to make insulation saves more oil than it uses in manufacture - and prevents some oil ending up as CO2

Absolutely - if oil's got to be used at all, it should be for EPS, even more so than other oil-based insulants - but there are non-oil alternatives to even this.

And having used precious oil to make EPS, it shouldn't merely save so much oil as fuel, in its lifetime - it should eliminate oil as fuel altogether, because the tiny remaining heating requirement should be supplied, year-round, by free solar heat, not by burning anything at all.