Having read every thread, I decided to internally insulate my attic, and having fitted, filled, and sealed to the very best of my ability, - my final task is to seal my freshly PLASTERED ceiling.
It does break my heart, compared to all the lime restoration I have done elsewhere, but this bit if ecovation requires a final airtight seal.
Condensation study says GLOSS paint. Don't want to do that, it's inside the house, guests sleep there, even I sleep there if I've had more than XXX beer.
So I have insulated. airtight sealed. Gypsum plastered, and am still fearful of condensating interstiller moisture lader air, and the computer says GLOSS PAINT to make condensation risk be zero. Keep it all inside.....?
What can I use ?
need to treat 1 month old fresh plaster.
plaster to timberwork joins etc.
A good coat of gloopy thick oily slop might make the whole thing airtight, but is there anything a little more natural?
Wellburn??

PS - If you must question my thinking, - please also recommend an eco non-breathing paint!

50mm on cold side. agree gloss would look VERY odd.
Will emulsion make airtight?

Use an alkyd primer and then paint with 2 coats of whatever latex matt paint you like. This will form a good VCL. I personally can't stand shiny ceilings - I much prefer dead flat. The surface finish of the paint shouldn't affect its vapour transparency. The alkyd resins in the primer will be your VCL.

Paul in Montreal.

p.s. I presume emulsion is the same as what we call "latex" over here? Water-based acrylic resin paint? Even gloss paint over here is water based now largely as I read some companies are going to stop making alkyd based paint altogether

1 - just an oil based primer: http://www.house-painting-info.com/alkyd-primer.html
2 - maybe latex is the North American term for emulsion: http://www.paintcenter.org/rj/may05f.cfm
However, latex emulsions are thinned by adding water, alkyd emulsions by adding white spirit etc.

Seems that latex acrylic paints are harder wearing than vinyl paints: http://dundean.com/tips_what_is_latex_paint.shtml

Over here acrylic latex is available in flat, eggshell, pearl and semi-gloss finishes. I seem to recall from my time in the UK that vinyl paints are either "matt" or "silk" and that only oil paints provided the gloss finishes.

I would avoid oil based paints if you can, but oil-based primers are supposed to be vapour proof.

For the sort of primers we have over here, see http://benjaminmoore.com/bmpsweb/portals/bmps_en_ca.portal?_nfpb=true&_windowLabel=contentrenderer_1_3&contentrenderer_1_3_actionOverride=%2Fbm%2Fcms%2FContentRenderer%2FrenderContent&contentrenderer_1_3cnp=public_site%2Farticles%2Fproducts_specs%2Ffp_fh_interior_ca&contentrenderer_1_3np=public_site%2Farticles%2Fproduct_articles_ca%2Fpa_int_primers_premium_ca&_pageLabel=fh_findproducts_ca

For regular interior paints see http://benjaminmoore.com/bmpsweb/portals/bmps_en_ca.portal?_nfpb=true&_windowLabel=contentrenderer_1_3&contentrenderer_1_3_actionOverride=%2Fbm%2Fcms%2FContentRenderer%2FrenderContent&contentrenderer_1_3cnp=public_site%2Farticles%2Fproducts_specs%2Ffp_fh_int_paints_ca&contentrenderer_1_3np=public_site%2Farticles%2Fproduct_articles_ca%2Fpa_int_collection_ca&_pageLabel=fh_findproducts_ca

and for low VOC paint see: http://benjaminmoore.com/bmpsweb/portals/bmps_en_ca.portal?_nfpb=true&_windowLabel=contentrenderer_1_3&contentrenderer_1_3_actionOverride=%2Fbm%2Fcms%2FContentRenderer%2FrenderContent&contentrenderer_1_3cnp=public_site%2Farticles%2Fmain_page_articles%2Ffh_findproducts_ca&contentrenderer_1_3np=public_site%2Farticles%2Fproduct_articles%2Fpa_int_natura_ca&_pageLabel=fh_findproducts_ca

(sorry for the long URLs)

Hope this helps.

Paul in Montreal.

Posted By: bot de pailleIsnt latex called arylic in the UK?

Seems that, over here at least, latex is just a word to describe an emulsion. It can be made with vinyl resins (cheap and not so hard wearing) or with acrylic resins (more expensive and hard wearing) or a mix of the two. Looks like paint that says "100% acrylic" is best for high traffic areas. I found out, to my surprise, that "latex" doesn't mean the paint has any actual latex in it at all!

Hope this helps decode some of my earlier posts on this topic.

Paul in Montreal