Here’s the floor after applying the insulation:

Yes, it looks just like the walls look. The foam insulation does dry solid, but it is full of tiny air pockets, so you don’t want to walk on it, since you will likely compress the air pockets and lower the insulation value. That’s why we applied the plywood floor as soon as possible:

Yes, this picture also shows the drywall on the walls, but that’s the subject of my next post.

There are many different opinions on the proper insulation technique. One school of thought says that you should install a vapor barrier (a plastic sheet) on the outer side of the wall, and then mount your fiberglass insulation, and then your walls. A vapor barrier is essential to keep moisture from forming in the wine cellar or behind the walls.

We decided to use a different approach: spray foam insulation. The insulation is applied as a liquid, and expands as a foam, and then hardens as a “solid”. Our contractor blew the the foam into place, smoothed it out, and let it harden.

This approach has a number of advantages.

First, it’s relatively quick. The entire job can be done easily in half a day. If you were to install a plastic vapor barrier, then cut and install fiberglass insulation, and fasten it into place, the job would take much longer. You may be able to simply push the fiberglass into place in the walls, but gravity won’t allow you to do that in the ceiling; fastening is necessary. With spray foam, it’s quick and it’s done. Here’s how it looks in the ceiling.

Second, since the foam dries hard, there is no need for a separate vapor barrier. Fiberglass insulation will retain water if it gets wet, so a vapor barrier is essential. With “solid” insulation, water cannot penetrate, so a separate vapor barrier is not necessary.

Finally, as you can see with the ceiling picture, foam is great for filling in every “nook and cranny” in a ceiling or wall with wires, pipes and other impediments. Fiberglass insulation will not fit as tightly.

Therefore, my vote is for spray foam insulation.