Baumits DP85 is a lot cheaper than both these wet products. You can buy it from Back to Earth from Chris (he is great).

<< Thanks for the link and another product to consider, but I don't understand how the DP85 is a lot cheaper?

Looking at the coverage data compared against the Bauwer as they both have similar thermal conductivity I get:

£20 of Bauwer will cover 2m2 at 25 mm thickness
£20 for 1.8 m² at 30 mm application

There doesn't seem to be a lot between them in terms of cost. >>


Hello Kenny,

Bauwer is based on natural volcanic sand called Perlite which is inorganic, sustainable material.
More on Perlite at:
https://www.perlite.org/library-perlite-info/general-info/Sustainability_Factsheet_Perlite.pdf


As a result, Bauwer Light is much more breathable vs petroleum based EPS alternatives.

For example Bauwer's vapour diffusion resistance, vapour permeability coefficient µ is 4, which is two times lower vs EPS based alternative

You could see Bauwer sample breathing at:
https://youtu.be/-AbGjlX_c3A

<< Here goes. Hopefully I haven't made a complete mess of this, maths not being my strong suit! Please correct me if anyone sees any calculation errors.

Diathonite published thermal resistance is 0.222 at 10mm
Yield of 3.70 kg/m² for 10mm thickness.
18kg bag
So 18/3.7 = 4.8649m per bag?
Bag is apparently around £35
35/(18/3.7)=£7.1944 for thermal resistance of 0.222 at 10mm

Bauwer don't publish thermal resistance but if I am calculating correctly their published thermal conductivity at 0.68. would work out at 0.0147 at 10mm thickness
For Bauwer to achieve a thermal resistance of 0.222 the thickness would need to be 15.1mm
Bauwer is around £10 per 7kg bag
1bag will cover 1m2 at 25 mm thickness
7kg x 15.1/25 = 4.228kg
£10 x 15.1/25 = £6.04 for thermal resistance of 0.222 at 10mm

So, Bauwer is about 15% cheaper if the prices above are accurate, but needs to be 50% thicker for the same thermal resistance which will presumably affect labour cost, and requires around 15% more weight for shipping.

A very quick look at external woodfibre insulation and pavatex external woodfibre insulation with a very similar thermal conductivity to the Diathonite is around £10 per sq metre for 40mm thickness so around £2.50 to for the same thermal resistance as above (0.222).

If this is all correct then the wood fibre board is significantly cheaper, but not sure about labour costs/fixings etc, and I am not sure if a board could be applied to an uneven wall like mine >>


Hello Kenny,
In applications over uneven solid stone walls, Bauwer has a significant advantage vs insulation boards, as it could take any shape with no need to connect the boards (potential cold bridging).Also Bauwer leaves no gaps between the insulation and the rough stone substrate. Saying that, there are number of projects were Bauwer was used for leveling purposes, so wood fibre boards are applied on the perfectly leveled substrate while maintaining high level of vapour permeability.

Bauwer insulation is a relatively easy and cost efficient way to achieve a considerable improvement, thermal and "feel dry" wall effect, for traditionally built solid stone walls.

You could play with the different thickness using Bauwer simple U value calculator:
http://bauwer.co.uk/Calculator.html?#CALCULATOR

Posted By: BauwerBased on the laws of physics, the density of any insulation material is linked with it's thermal performance.

Not really true, and as far as I know there are no 'laws' that show this. We have Laws of Motion, Laws of Thermodynamics, Laws of Energy Conservation. The nearest to a law of conductivity is Fourier's Law. But that is not really the same thing.
Just compare Lead and Aluminium. 36 W.m^1.K^1 for lead and 236 W.m^-1.K^-1 for aluminium.
If you want a really weird material, look at Gallium, that has different conductivities over the 3 axis.

Insulation is really about trapping air, which affects the density of a material.
There is also the ratio between the bade material, the amount of air and the size/structure of that trapped air.
That is before radiative characteristics are taken into account.

<< Hi Bauwer,
I agree with your point about the gaps on an uneven wall with wood fibre, but you could level with a traditional, or an insulated render such as Bauwer and then put wood fibre on.

I think the point of my discussion though, was not whether insulated render is a good idea, it was more of a 'which one' discussion. As far as I can see Diathonite has a better thermal conductivity than Bauwer, and although Bauwer is a little cheaper it has to go on thicker to achieve the same u value as Diathonite, so factoring in labour costs Diathonite might be cheaper or at least around the same cost. Where thickness is restricted Diathonite looks like the better bet because for the same thickness a better u value can be achieved.

A lot of the guys on here would say that EPS is vapour permeable enough for old houses, I spoke to historic Scotland and they disagreed with that, but they were not completely convinced about insulated renders either, and seem to favour wood fibre for external insulation.

Ultimately, one of the deciding reasons I didn't go any further with this, was that I couldn't get anyone to do it, or at least no one who was keen to use it, and a couple of plasterers I spoke to online were not convinced about the finish.>>

Hi Kenny,
Bauwer Light is highly breathable with vapour permeability coefficient being at the benchmark level 4. Could you please see our demonstration:
https://youtu.be/-AbGjlX_c3A

Bauwer Light density is only 280 kg per m3 which is considerably lighter vs 360 kg per m3 which is the declared density of Diathonite:
http://www.ecologicalbuildingsystems.com/docs/DP001EN1415201-diathonite_evolution_DOP.pdf

We have a national network of applicators, please feel free to send us an email at info@bauwer.co.uk and we would advise the closest one to you.

Highly breathable Bauwer insulation, applied externally and finished with vapour permeable Vimark Arenino VK2 mineral finish.

Posted By: goodevansThere is a house 2 doors down from me that has a similar detail above the window - I quite like the look of the windows sunk into a 'pillow' of render. However I also see others strongly suggest a drip bead at the head.

How important are drip beads here for modern renders?

I'd say it is really up to a customer preferences, you just chose what you like

How to Insulate Solid Stone Walls of a Cottage, Barn Conversion or a Watermill? Extra care needs to be taken when insulating solid stone traditionally built homes which need to breathe. Bauwer effectively insulates your home with a highly permeable breathable light weight insulation render: http://greenbuilding.co.uk/insulating-masonry-walls-of-old-stone-cottages-and-listed-buildings/