Breathable alkyd paint?

[Penners]

Homebase sell an own-brand masonry paint that they call Weathercoat. The following is a quote from the brochure:

This advanced breathable formulation allows vapour from inside your house to escape whilst preventing water penetration from the outside.... [a bit further down the page] allows water vapour to escape

What do we think about this (the claim, not the lack of punctuation)?

 

[Nemesis]

In truth, I think it's really mainly skin which does that.

I think they are talking round objects.

 

[Gervase]

The trouble is, a lot of people are going to read that on the tin and assume that it's OK for the exterior of their period property.
Bloody snake-oil. Grr!

 

[Dave Alder]

Given that on a modern build of house the coating is breathable then fair enough. I would be very doubtful if Homebase would claim the same for a period property. Making alkyd or acrylic coatings breathable is not difficult it is just a question of by how much and to what extent does it effect the finish and the weatherability of the coating.

 

[biffvernon]

Ask them what the Sd value is.

 

[NT]

The current fashion seems to be to describe paints that pinhole badly as breathable. Whether thats whats going on in this particular case I wouldnt know.

NT

 

[middi]

I cannot really comment with authority on this Penners, but:-

As a P/P owner I would want clarification on a few points from the manufactures, and I don't mean a B&Q assistant, even if you are lucky enough to find one in their stores, only cash desks appear to be manned.

1).........How can the paint perform in the way they claim on a lot of modern or modernised buildings when impermeable barriers are introduced where the transfere of moisture from inside out or viceversa does not apply.

2).........How does this paint perform on a vast number of period buildings where evaporation of any moisture has to rely totally on the extreme porousity of the materials from which it was constructed , does it mean that this microporous/breatheable paint will only allow evaporation at a microporous speed and therefore not suitable for these buildings.

3).........Are they in a position to specify and/or clarify specific applications where this type of paint would perform to its best advantge, bearing in mind that the paint has a constant porousity rate, and the diverse masonary based stratas to which it may be applied has differential constant.

I have no objection to paints, they are necessary, at times, to protect and prolong the life of many building structures and keeps those of us which loves colour coordination very happy.

What I ( and probably most of you ) detest, those well chosen words on a tin of paint which does exactly what it says on the tin only to find a year or so down the line that we have used the incorrect paint for what we intended to achieve, stuck with the bl***y stuff and only forced to buy more and make another c**k up in order to cover up the previous one.

Only one winner there I'm afraid.

I don't know Penners, they may have a winner.

I prefere to see pigs fly first.

 

[NT]

Well, some paint is a kind of oinkment

NT

 

[biffvernon]

Ask them what the Sd value is.

Seriously, there should be a technical data sheet available giving values for water absorption and water-vapour diffusion. The word 'breathable' tells you very little. No data - no purchase.

Here are some examples from an honest paint maker.

 

[Penners]

Ask them what the Sd value is.

Can you explain Sd value, please, Biff?

 

[biffvernon]

er...nope. I was leaving that for you to explain.

 

[Penners]

sugar deflection

simplified drag

scientific demolition

southerly draught

silly definitions....

:?:

 

[Dave Alder]

Great post Middi,
Alas I'm afraid that the big manufactures will not see pp housing as a big enough market. Too many variables on building construction and most of the products are designed to keep moisture out of the fabric. if it does enter then the coatings stops it evaporating out and yes the coatings are really microporous not porous
dave