Elevating A Slab Home - The Concerns
Raising an existing home, slab or pier and beam, is done for numerous reasons throughout the Greater New Orleans Area.
- It is an important way to reduce damage from possible future flooding.
- It can reduce flood insurance costs and increase the value of the house.
- It can also prevent tremendous future inconvenience and suffering.
However, since several years have now passed since slab homes have been elevated there have been growing concerns from homeowners as they have now lived through the changing seasons in their newly raised structures. A few of the most common complaints have been:
- Lack of comfort.
- Increased heating system furnace/heater run times during the colder months and larger monthly energy costs [especially in homes with electric heating]
- Increased cooling season air-conditioning run times during hotter months to cool and dehumidify the additional vapor intrusion resulting in increased monthly energy costs.
- Condensation and moisture concerns and damaged flooring.
Once a slab home is elevated the old existing vapor barrier is greatly compromised. In such cases, the existing vapor barrier is partially destroyed, separating from the substrate, falling off and, in many cases, holding pockets of water against the slab. Basic laws of vapor migration dictate that the vapor under the slab is moving inward as we air-condition our homes and, without a properly-installed vapor barrier, this vapor is traveling right through the slab.
A consequence of this vapor trapped within the slab is increased conductivity resulting in additional heat-loss during the heating months. Many homeowners report feeling a “coldness on the floor that never existed before the home was raised.” As heating system run times increase to keep up with this discomfort and additional heat-loss monthly heating bills go up as well.
During summer months (cooling season) some homeowners have suffered from sweating floors, damp carpeting, and tiles detaching from the substrate.
Properly Insulating underneath an elevated slab home – the solutions
The same laws of vapor travel and solutions that apply to insulating raised pier and beam homes in our climate zone apply to slab homes as well. With most closed cell foam products, two inches will provide a perm rating of less than 1 which qualifies as a code-approved vapor retarder. Also, with a common R-value of 6.5 or higher two inches of closed cell foam will provide the sufficient insulation level supported by our local energy code of R-13.
Once our clients have had the closed cell polyurethane foam properly installed they have reported lower energy bills, greatly increased comfort and, in the more severe hot & humid seasonal cases, an elimination of all condensation problems and further floor damage.