Hello! I purchased a 50s era home last year and am looking at upgrading the attic insulation. Located in Calgary.
Right now there is cellulose almost up to the joists, and under that is a paper backed (both sides) layer of old fiberglass it looks like (it's black). So it could use a lot more. I had one company come look at it and they wanted to vacuum it all out, spray foam for a vapour barrier, and then loose fill. It was too much money for me, so I've decided to tackle it myself.
I have some recessed lights to seal and cover, bathroom fan to vent, attic voids above closets to seal, and baffles/insulation stops to install for ventilation. All that I can handle.
I had another contractor come out to take a look for quoting me on doing the loose fill once all my prep is done. He said to do all the prep I was planning, but not to worry about a vapour barrier; just loose fill right on top of what's there.
I found your website and I see some conflicting information.
This article (https://www.ecohome.net/guides/2216/why-is-there-frost-in-my-attic-how-do-i-fix-ice-dams/) stresses the importance of a vapour barrier: "But, if you have no air barrier at all, you really do need one. This requires lifting insulation, laying down a polyethylene vapour barrier over the whole surface (it can go up and down over joists) then reinstalling the insulation.".
But in this article (https://www.ecohome.net/guides/2299/painting-on-your-vapour-barrier/), specifically in the comments section, ecoHome suggests that a vapour barrier is not necessary.
Right now the attic has no serious problems. No ice or moisture build up. It's just poorly insulated and I want to get it to R50. I really don't want to introduce more problems by not doing this correctly.
Should I lay down a poly vapour barrier? It would be quite difficult with my truss design.