This week the plumbers and electricians finished up their underground work on our office expansion project. Once that was done we carefully graded the floor level. Then we installed a heavy plastic vapor barrier. We do this to prevent moisture from the soil from entering the building through the concrete floor slab. Once the polyethylene sheet is in place we then crawl around and tape closed any tears in the sheet around the penetrations. I like to tape the polyethylene right to the conduits when they poke through the floor. Making a tight seal in the vapor barrier also helps keep any radon gas out of the building.
Once we were finished with the polyethylene vapor barrier we then installed a layer of 2″ thick extruded polystyrene foam insulation. The insulation really does a good job keeping the floor slab warm in the winter. We cut around the penetrations then squirt low expanding foam to fill the joints tightly. The end result is a very well insulated floor slab. On top of the floor insulation the heating contractor staples plastic tubing to circulate warm water to keept he floor warm and dry during cold weather. This tubing is manufactured in Apple Valley, Minnesota. It is a Wirsbo tubing product which I believe is now owned by Uponor. The plastic fasteners that staple the tubing to the insulation really work well to hold the tubing at the bottom of the concrete floor. I’ve used a lot of this heating tubing product and never had a problem with it. Since it is buried in the concrete floor is it crucial to use a top quality product as you cannot easily get at it to make repairs should there be a tubing failure. With the miles of tubing that we’ve installed I’ve never had a product failure….just two times when carpenters drilled a hole through the floor into the tubing!