Caulk drywall to floor?
 

I have read that a major air leakage area is where the walls meet the floor and roof. In new construction, they have the sill plate foam to air seal this area.

I have also read about air sealing using drywall and caulking behind the drywall at the top and bottom when applied.

I was wondering, for an existing house, would it be beneficial to seal the drywall along the bottom edge to the floor? I would think this would create an air seal and since most people have base molding, you wouldn't see the caulk.

I have heard the argument that drywall expands and contracts, but at the top it is normally attached to the ceiling using joint compound. This isn't always cracked so I don't think it is doing that much moving.

I had to put down vapor barrier underlay for a laminate floor in the basement and I used that red tuck tape to seal it to the drywall with the same thoughts. Not sure if it will make a big difference but I figure it can't hurt and it only cost a few bucks.

I agree with strider3700, for the price of a bit of caulk or red tape it is an easy upgrade. I will often use up part tubes of caulk and sealers for this kind of application, it helps tighten up the building, and diverts surplus materials from the land fill. Also, as a side benefit, it makes entry more difficult for small critters like ants!

There are acoustical sealant caulks (Tremco) that never dry out and can move with your building materials. I have seen 15 yr. old Tremco which is still sticky. It also will stick to poly and not much else will.

If you want to calk the gap between the dry wall and the floor using caulk backer rod seems like a good idea, it's a closed cell foam that you pack in to large gaps then run a bead of caulk over, they allow the caulk to be thinner so it can flex instead of cracking or separating.
As for caulking the vapor barrier to the dry wall, that is going to allow moisture to wick up from the floor in to the dry wall, calking it right to the floor using a polyurethane caulk.