Insulated render - anyone used this?

[Kaymo]

Hi,
Just wondering if there are any plasterers out there that have experience of using insulated render for exterior, or anyone who has had this installed on their property. I have an old sandstone house that has had a cement render applied in the 80's and I am thinking of getting this replaced with a lime based render when the scaffold is up for chimney repair this spring.

Diathonite Evolution and Bauwer light are a couple of products I have come across and in addition to being breathable have decent insulation values, but I haven't come across anyone with experience of it.

Thanks

 

[rangorgubbins]

hi kaymo,
I'm in a similar situation. What product did you end up choosing?

 

[Kaymo]

Hi Rangor,
I didn't use either in the end. I've taken the cement render off one wall so far and had it pointed up with lime mortar, essentially put back to its original state.

I'm in a conservation area so it wasn't clear whether I could get planning permission, and I definitely wouldn't get permission for the front which Ashlar Sandstone, and wouldn't want to cover it anyway. I have turned my thoughts to internal insulation now.

My research into showed that Diathonite had the best insulation value, although the Bauwer I think was a bit cheaper so there is a tradeoff. If looking for external insulation here is also the option of something like wood fibre boards fixed to the wall then rendered over, which is seems to be the option that is most proven for heritage properties.

There wasn't anyone up here installing either Diathonite or Bauwer, but there are installers down south. If you look up Jordaya contracting they seemed to look quite good but the distance was too much to me. If you contact Ecological building systems for Diathonite or Bauwer have their own uk website, both were quite helpful and could recommend installers in your area for quotes.

 

[rangorgubbins]

Thanks Kaymo, that's really helpful. I've already contacted both Bauwer and Ecological building systems and had quotes from both. You're correct, the bauwer light render works out quite a bit cheaper but provides less insulation on paper. Having said that, I've read some posts on the greenbuilding forum from a Bauwer representative suggesting that Diathonite is not quite as insulating as the manufacturers make out. They base their argument on the density of the products, claiming that as Diathonite is a higher density it cannot be as insulating as bauwer light. I'm not quite sure on the physics behind that statement, but as both products are essentially insulating by providing air gaps in the render, and the more air gaps the less dense the material i can see there could be a valid argument that the bauwer light product *should* be more insulating than Diathonite. Of course if that's the case it means one of the companies has got their lambda numbers wrong!

This is for internal rendering as we want to keep our external walls as exposed brickwork. At the moment I'm leaning towards Bauwer as even if we go for an extra 10 mm thickness of the render its still cheaper than the diathonite; although the diathonite U-value would still trump the bauwer light u-value even with the extra 10 mm.

On a side note, anyone on here got an idea of what the labour cost would be for rendering internal walls in the South East (Kent). There's 5 rooms, covering 61 m2.

 

[Kaymo]

I've seen Bauwer's arguments about this, if its the same thread as I am thinking of the rep was ripped to shreds by other forum members because that statement about density taken on its own is total nonsense, I think there was a bit of pseudo sales science there! A stone has density but it doesn't make it a good insulator. It could be worth checking out if either company's statements about thermal conductivity has been independently tested.

One problem I was cautious about with diathonite is that I think it probably needs to be installed with a machine. If its compressed when installed by hand it could reduce its insulating value, that could apply to Bauwer too I don't know.

I think Jordaya were quoting about £90sqm for 50mm thickness supply and fit of diathonite if I remember rightly.

Both companies suggest that any plasterer can apply this stuff but I would be cautious about this and ideally get someone who has experience of it, or at least is willing to take the time to learn and follow the instructions.

 

[Spudgun888]

Any updates on this? I'm considering using insulated render internally and I'm eager to hear how you've gotten.

 

[rangorgubbins]

Hi Spudgun,
I'm still trying to organise it, but I'm almost certainly going to use Diathonite Evolution to insulate. Hoping to start this part of the work in July. I've chosen this over Bauwer Light because Diathonite is lime based and has a higher insulation factor. It is more expensive though.

 

[Spudgun888]

Hi Spudgun,
I'm still trying to organise it, but I'm almost certainly going to use Diathonite Evolution to insulate. Hoping to start this part of the work in July. I've chosen this over Bauwer Light because Diathonite is lime based and has a higher insulation factor. It is more expensive though.

Great, thank you. Are you tackling the job yourself, or getting someone in to do it? As the area I'm doing is pretty small I'm thinking of giving it a go myself but still a bit unsure.

 

[rangorgubbins]

I did think about doing it myself, but I've tried plastering before and vowed never to try again.
The area we've got to cover is about 60m2.

 

[jason61c]

have a look at ecocork from mikewye also.

 

[tomfe]

Thing is unless you go for ewi where there is a desent thickness >50mm it's not going to make a great deal of difference.
I'd imagine the price difference in render would not make financial sense either.

 

[Kaymo]

Thing is unless you go for ewi where there is a desent thickness >50mm it's not going to make a great deal of difference.

Insulated render can go on at >50mm.

 

[tomfe]

Insulated render can go on at >50mm.

What would be the point in that? You'd be better off with ewi which would give you a much better uvalue for the same thickness and it would be cheaper.

 

[Kaymo]

What would be the point in that? You'd be better off with ewi which would give you a much better uvalue for the same thickness and it would be cheaper.

How do you know? Have you made a cost/benefit comparison with a breathable insulation system suitable for period properties?

 

[tomfe]

Yes. For stone properties where a breathable outer finish is needed, they don't all need this, a wood or stone fiber batt would be best. This can be rendered with a breathable render through coloured or suitable paint.
These cork renders are not breathable at such thicknessess anyway I would not have thought, sure the amount of binder would mitergate any benefits.

Having said that Eps is quite breathable as well.