Energy Saving Devices

Archive for June, 2009

When installing a slab foundation and insulating it, it’s also important to consider moisture and air leakage control, as well as termite control.

Termites can tunnel undetected through exterior slab insulation to gain access to the wood framing in a home’s walls. As a result, some insurance companies won’t guarantee homes with slab insulation against termites. Building codes in several southern U.S. states prohibit installing foam insulation in contact with the ground.

“Floating” slab foundations with interior insulation provide more termite resistance. However, some builders in the southeastern United States have reported termite infestations through foam insulation on contained slabs.

To help offset termite problems, follow these guidelines:

* Provide effective moisture control systems.
* Remove all wood from around the foundation before backfilling.
* Install termite shields continuously under the sill plate of the building. The shield should project beyond the sill plate and all other portions of the exterior wall. While not 100% effective, the termite shield may deter or delay widespread infestation. It may also force termites into an exposed area where they can be detected. A continuous layer of a membrane—such as rubberized roofing material used in commercial buildings—may be used as an alternative to the termite shield.
* Use a foam insulation treated with a termiticide. Usually a derivative of boric acid, the termiticide should pose no more threat to homeowners than traditional termite treatments.

You’ll also want to regularly inspect for termites. If you use a pest control company, obtain a good warranty for its work.

Source: EERE, U.S. Department of Energy

Slab insulation can be installed using one of two basic techniques:

• Installing rigid insulation, typically foam board, directly against the exterior of the slab and footing
• Building a “contained” or “floating” slab with interior rigid insulation, typically foam board.

If insulation is installed on the exterior of the slab:

• Install it from the top of the slab to the bottom of the frost line unless a termite inspection gap is required.
• Encapsulate or cover the exterior face of the insulation with a protective membrane to serve as a capillary break and to protect the insulation from termites.
• Cover the above-grade portion of the insulation exposed to the outside air using a stucco coating, pressure-treated wood, brick, or aluminum flashing. When covering insulation, be conscious of how to detect termites in areas prone to termite infestation. Some states in termite-prone areas address this issue by requiring a termite inspection gap near the top of the slab insulation.

Source: EERE, U.S. Department of Energy

The International Energy Conservation Code Council (IECC) specifies both the R-value and minimum distance for the insulation from the top of the slab downward based on a locality’s Heating Degree Days (HDDs). Consult your local weather bureau for your area’s actual Heating Degree Days. Then use the table below to find the IECC’s recommended depth and R-value based on your Heating Degree Days.

Select and install insulation using these recommendations. Be sure to use only insulation approved for below-grade use.

Source: EERE, U.S. Department of Energy

Properly insulating your slab-on-grade floors not only will help you save on energy bills, but also will improve your home’s comfort. Cold concrete slabs can be a source of discomfort in a home. An insulated slab reduces heat loss, making it easier to heat. This reduction in heat loss helps moderate indoor temperatures.

Annual Energy Savings and Payback

Slabs lose energy primarily as a result of heat conducted outward and through the perimeter of the slab. Therefore, in most parts of the United States, insulating the exterior edge of the slab can reduce heating bills by 10%–20%. In climates with mild winters, slab insulation in a typical 1,800 square-foot home would save $50–$60 annually. Slab insulation with an R-value of R-10 for an 1,800 square-foot home typically could cost $300–$600 to install. Thus, the insulation would pay for itself in 5 to 10 years.

The investment in slab insulation is also economical as part of a mortgage. An insulation cost of $450 would add about $38 to the annual mortgage. However, the insulation would save over $50 annually in energy bills. Therefore, the savings exceed the additional mortgage cost from the beginning, resulting in an immediate payback.

Source: EERE, U.S. Department of Energy

Here are some guidelines to follow for insulating a ventilated crawl space:

1. Carefully seal any and all holes in the floor above (”ceiling” of the crawl space) to prevent air from blowing up into the house.
2. Insulate between the floor joists with rolled fiberglass. Install it tight against the subfloor. Seal all of the seams carefully to keep wind from blowing into the insulation. Also, adequately support the insulation with mechanical fasteners so that it will not fall out of the joist spaces in the years to come. DO NOT just rely on the friction between the fiberglass and wood joists to secure it in place.
3. Cover the insulation with a house-wrap or face it with a vapor barrier. The orientation of the vapor barriers depends on the home’s location or climate. In most of the country, the vapor barrier should face upward. However, in certain regions of the Gulf states and other areas with mild winters and hot summers, it should face downward.
4. Install a polyethylene vapor retarder, or equivalent material, over the dirt floor. Tape and seal all seams carefully. You may also cover the polyethylene with a thin layer of sand or concrete to protect it from damage. Do not cover the plastic with anything that could make holes in it, such as crushed gravel. Be sure the headroom of the crawl space meets local code regulations if you are considering pouring a concrete slab.

Source: EERE, U.S. Department of Energy

1. During the early phases of construction, the builder should inform all subcontractors (plumbing, electrical, HVAC, etc.) that they need to keep the space between the floor joists as clear as possible. Run drain lines, electrical wiring, and ductwork below the bottom of the insulation so that a continuous layer of insulation can be installed. For freeze protection, supply plumbing may be located within the insulation. The best approach is to run supply plumbing together in a few joist spaces. The insulation can be split and run around the plumbing.
2. Seal all air leaks between the conditioned area of the home and the crawl space. High-priority leaks include holes around bathtub drains and other drain lines, plenums for ductwork, and penetrations for electrical wiring, plumbing, and ductwork (including duct boot connections at the floor).
3. Insulation batts with an attached vapor barrier are typically used to insulate framed floors. Obtain insulation with the proper width for the joist spacing of the floor being insulated. Complete coverage is essential. Leave no insulation voids. The batts should be installed flush against the subfloor to eliminate any gaps, which may serve as passageways for cold airflow between the insulation and subfloor. The batts also should be cut to the full length of the joist being insulated and slit to fit around wiring and plumbing.
4. Insulate the band joist area between the air ducts and the floor as space permits. Use insulation hangers (wire staves) spaced every 12-18 inches to hold the floor insulation in place without compressing the insulation more than 1 inch.
5. The orientation of the vapor barrier depends on the home’s location or climate. In most of the country, the vapor barrier should face upward. However, in certain regions of the Gulf states and other areas with mild winters and hot summers, it should face downward.
6. Insulate all ductwork in the crawl space.
7. Insulate all hot and cold water lines in the crawl space unless they are located within the insulation.
8. Close crawl space vents after ensuring that the crawl space and all the construction materials are dry.

For insulating truss floor systems, it’s better to install netting or foam board insulation to the underside of the floor trusses. Then, fill the space created between the netting or insulation and subfloor with loose-fill insulation.

Source: EERE, U.S. Department of Energy

1. Review plans for this method of foundation insulation with pest control and local building officials to ensure code compliance.

2. Eliminate or seal the foundation vents.

3. Ensure that combustion furnaces and water heaters located in the crawl space are sealed-combustion units equipped with a powered combustion system.

4. Seal all air leaks through the exterior wall during and after construction, including the band joist.

5. Locate the crawl space access inside the home or install an access through the perimeter that will remain airtight after repeated use.

6. Install rigid foam board or batt insulation—exterior foam, interior foam, or interior batt—to achieve complete insulation coverage. Insulate the band joist with batt insulation, as well as the crawl space access if it’s located in the wall.

7. Install a continuous termite shield between the band joist and masonry foundation wall that covers the wall insulation and extends completely outside (or leave a 2- to 4-inch insulation gap at the top for termite inspection).

8. Install a supply outlet in the crawl space, relying on the leakiness of the floor to provide the return air path.

Source: EERE, U.S. Department of Energy