Hi Bob, what system are you using?

Some, such as Parex offer a survey service Though beware they may insist on a recommended installer

Not very near you, but try Gerard Lynch (www.brickmaster.co.uk/).

Is Thermopor expensive compared with other proprietory renders? I have not looked at the spec, but insulating renders I have looked at before have had a v poor performance compared with, say, phenolic. I can't see the point (if, as I assume, it's more expensive than standard) in going for an insulating render instead of a bit more phenolic.

I got the impression the OP was talking more about pull-out of mech fixings than adhesion, no?

Yes, but do you want to go back in a few years if they are wrong..... I use the parex system but use mechanical fixings and maite. If you read their literature it says 'use mechanical fixings where specified' Doesn't say specified by whom!

then put mechanical fixings in as well to doubly guarantee it's not going to all peel off?

can't see that I'd every 100% depend on any form of bonding on an external wall to hold up an entire wall full of insulation and render, no matter what guarantees the manufacturer offered.

I just have a nightmare image of the entire skin getting ripped off one windy night, and me having to stand there the next day trying to explain why I'd thought it was ok just to glue it on.

belt and braces*



*well actually I don't wear either usually

"Humbug" to the lot of you.

This is progression, advancement, it’s probably some space age glue invented by NASA. This is where we are, all of as on the outside of conventional, striving for better and newer technology, inventing what has been invented, trying what hasn’t been tried, single minded in our pursuit of thermal efficiency so come on if it say no fixing, no cold bridge then BELIEVE.

There’ll never take our FREEEEDON

Mike, re IWI, when I was using Styroliner 25+ years ago the manuf recommended a cement-based (tile) adhesive, and made no mention of mech fixings, so we did not use them. My entire house is lined thus, and it's all solid as a rock (if not warm enough 'cos we thought 38mm of XPS was reaally good!). Now, though, I use at least a few mech fixings, and really would want to on EWI for the same reasons as Gavin A.

There has been discussion on here re this before, but I cannot remember where.

Posted By: Mike GeorgeSome seem to believe that the heat loss through bridges is disproportionate to the surface area but I cannot see how this is the case.

I can't see that either. I think it comes from doing dodgy arithmetic and using percentages.
People often think, or want to achieve a higher internal temperature when they insulate, this changes the temperature difference. It is easy to forget to recalculate for this.

I find it easier to just use the actual units of area and the conductivity rather than think of the thermal bridges as a percentage of the area.

I very really use them, tend to stick to decimal fractions (only have to multiply by 100 to get a percentage).
it is a similar problem to understanding W and Wh I think, throw in Temperature, which is just a scale and the problems get worse. Scalar and Vectors, they make a big difference.

Posted By: Mike GeorgeSome seem to believe that the heat loss through bridges is disproportionate to the surface area but I cannot see how this is the case.

If you've got a very simple set up with just insulation with uniform area fixings through then I too can't see why it would be disproportionate. The temperature profile in both the insulation and the fixing will be the same (i.e., linear from the internal to the external temperature - neglecting the effects of the boundary layer insulation) so there'll be no lateral heat flows between the fixing and the adjacent insulation.

However, if there are multiple layers things get a little bit more complicated. Suppose you have stud work with mineral wool insulation between then PIR outboard of that with (to make the case extreme) metal fixings. The inboard ends of the fixings will now be cooler than the inboard faces of the PIR. All the way through the fixing the temperature will be lower than the adjacent PIR. This means that a circle of PIR around the fixing will be more connected to the outside world than it would otherwise be and so will have a reduced insulating effect.

I think you'd have to do some finite element analysis or some such to see if this is actually significant, though.

Posted By: SteamyTea

Posted By: Mike GeorgeSome seem to believe that the heat loss through bridges is disproportionate to the surface area but I cannot see how this is the case.

I can't see that either. I think it comes from doing dodgy arithmetic

Depends whether the heat flow is tidily straight from warm inside to cold outside, in both materials - or not.

Posted By: Ed DaviesThe temperature profile in both the insulation and the fixing will be the same (i.e., linear from the internal to the external temperature

doesn't seem right to me.

Imagine a metal screw fixing through EWI. Tell me if I'm wrong, but the inboard one-third of the conductive screw will be kept pretty much warm by its contact with the warm interior; likewise the outboard one-third will be kept pretty cold by its contact with the cold exterior. Most of the temp gradient along the length of the screw will be concentrated in the middle third. That means there will be temp gradients laterally between the screw and the EWI, therefore the heat flow will spread laterally, therefore the effective heat-flow area surrounding the screw will be much larger than the screw's cross section.

Same with a gappy air filled joint, or filled with conductive adhesive, between EWI boards. Disproportional effect on overall insulative performance.

and then on to this one?
http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=9565&page=1#Item_21

Posted By: fostertom
Imagine a metal screw fixing through EWI. Tell me if I'm wrong, but the inboard one-third of the conductive screw will be kept pretty much warm by its contact with the warm interior; likewise the outboard one-third will be kept pretty cold by its contact with the cold exterior. Most of the temp gradient along the length of the screw will be concentrated in the middle third. That means there will be temp gradients laterally between the screw and the EWI, therefore the heat flow will spread laterally, therefore the effective heat-flow area surrounding the screw will be much larger than the screw's cross section.
Same with a gappy air filled joint, or filled with conductive adhesive, between EWI boards. Disproportional effect on overall insulative performance.

We put EPS into the recess of the discs on our fixings, so the end of the screw had about 25mm
over it.
Make any odds?

Posted By: MikeRumney

There has been discussion on here re this before, but I cannot remember where.

This one?
http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=7573&page=1

in which

Posted By: an02ewi dont think i would just trust to an adhesive. but would also use some machanical fixings

So we learn, things change!