Sealing Floor Plates to Increase a Homes Efficiency

There are many means by which a homes efficiency may be increased resulting in lower utility bills. However there is one commonly overlooked area that is perhaps the best area to focus your efforts in increasing your homes efficiency; the junction between the concrete foundation (slab) and the wall. When it comes to energy efficiency, a house should be like a self contained bubble isolating the interior of the house with respect to air exchange and temperature fluctuation. Unfortunately, almost all houses leak air which results in a loss of efficiency.

During the summer months when the air conditioner is cooling the house, the air inside the house is cooler and thus more dense than the air outside the house. Therefore the air inside the house becomes layered with the coolest/most dense air near the floor and the warmest/least dense air near the ceiling. If the air near the floor is allowed to leak out of the house below the wall, a vaccuum is created within the house. This vaccuum is equalized when air leaks into the house from outside. It is by this continuous process that unconditioned outside air replaces conditioned inside air during the summer months. The inverse process occurs during winter months when the air inside the house is heated. As the heated/less dense air rises to the ceiling and leaks out of the house through light fixtures, etc., a vaccuum is created and air leaks into the house under the walls to equalize the vaccuum resulting in outside/cold air replacing the heated air inside the house. So the problem that must be addressed is air infiltration under the walls.

When your home was built the builder probably sealed between the slab and the walls with a product called "Sill-Seal", "Foam-Seal", or something like that. These are rolls of thin foam that are rolled out onto the slab before the walls are put in place. The problem with these products is that they don't work well since all slabs have low and high spots resulting in gaps between the slab and foam and between the foam and wall. The use of these products basically allows the builder to say that the sills were sealed when in fact there is still lots of room for air leakage. The solution to this problem is to caulk the plate line (junction of wall and concrete) on the inside of the house after the walls have been constructed. This is a very simple task with regard to homes under construction. You must first vaccuum the plate line with a Shopvac and then caulk the corner where the wood meets the slab with a very high quality caulking. Polyurethane caulk (NP-1, PL Concrete and Masonry, etc.) is best suited for this task since it is permanantly flexible and waterproof and since it sticks to almost anything. An average 3,000s.f. home will take approximately 15 tubes of caulking to seal the entire exterior plate line for an investment of ~$100. This investment will likely pay for itself in the first year once the house is completed.

Performing this process on an existing home is equally important, but slightly more complicated. The actual process of sealing the plate is exactly the same, but the carpet must be pulled back to expose the plate first. Despite this minor complication, this upgrade should still be performed as the energy savings will more than outweigh the inconvenience factor. In areas where wood or tile floors meet the exterior wall, the flooring can be caulked to the baseboard. This provides a similar benefit with far less hassle. In this case it is advisable to have someone that is really good at caulking perform the task since the caulking will be visible from within the home. Additionally, polyurethane caulk should not be used here. Instead an elastomeric latex caulk that matches the baseboard color should be used. Alternatively, the baseboards can be caulked with white caulking and painted once the caulking has dried.  Discover and share home improvement knowledge at www.HomebuiltHowTo.com.