Insulating ceiling during winter construction?
Our house is currently at the stage where they are about to start interior framing. Unfortunately this means that there is a giant hole in the envelope (the ceiling!) and they are wanting to run temporary heat as it is quite cold (a typical daytime temperature this time of year is about 15F). Of course you can pump a lot of heat into a structure and not have it get too warm when you have no ceiling and a vented attic.
So my builder and I were discussing options for partially insulating the ceiling so that it would be warmer with much less heat used. My calculations show that even if we do R-10 ceiling insulation temporarily until after framing/drywall, we’d be able to get the building warm enough without using nearly as much heat.
As for context, we are planning R-60 cellulose ceilling, vented attic, airtight drywall method for the ceiling.
My builder’s idea was to staple insulation mesh netting to the trusses and then blow in a layer of perhaps 3-4″ of cellulose so that it would provide a decent insulation layer but not be so thick that it would be difficult for the plumbers to do their vent stacks (then we would have to blow in the rest of the cellulose after the ceiling drywall is on, so there would be an additional trip charge for the cellulose truck).
My question regarding this method is that it would seem to me like 3-4″ of cellulose would provide very little in terms of an air barrier, so there would be lots of air going up into the attic, which would not only take away heat, but moisture. This time of year the daytime temperature is about 15F and the dew point is around 10F — somewhere around 80% relative humidity usually. I know new concrete releases a lot of moisture so my guess is that the humidity of the heated interior (at perhaps 40-50F) would get high enough to get above a 15F dew point and then condense near the top of the cellulose insulation as air escapes up to the attic. So the cellulose would likely get damp all winter, and probably also make the bottom of the trusses damp as well. But the outside temperatures will be well below freezing until after the ceiling drywall is on (and we have an air barrier), so will this wetness in such cold temperatures cause a problem (mainly I’m thinking about mold)?
The other methods I have brainstormed are:
Instead of using the mesh netting, use a smart vapor barrier like Certainteed Membrain, and blow 3-4″ cellulose on top of that. This could provide a decent air barrier, but I don’t see data indicating it is designed to bear weight.
Sheet the bottom of the trusses with OSB, tape the seams with Siga Wigluv and then we have our air barrier and can build a service chase between that and the drywall. This would allow us to blow the insulation on top without worries as the air would be sealed and provide the benefits of a service cavity and probably better air sealing. Negatives are cost and loss of a couple inches headroom.
Has anyone done any of these methods or have any thoughts to share about them or winter construction (other than wait until summer!)? I greatly appreciate it, thanks!