Field studies have found that foundation insulation for new houses (in the United States) has good economic outlooks, except for the warmest climates.

Source: U.S. Department of Energy

In the United States, the most common types of foundations include the following:

* Basements
* Crawl spaces
* Slab-on-grade floors.

Some construction techniques lend themselves to both foundation structure and insulation, including these:

* Insulating concrete forms
* Insulating concrete blocks.

When insulating any type of foundation, it’s also important to take into account moisture control and air sealing.

Source: U.S. Department of Energy, Energy Efficiency and Renewable Energy

Air ducts supply conditioned air from your space heating and cooling equipment to your living spaces. They also return an equal volume of air back to the equipment to be conditioned again.

Ducts are typically made out of thin metal materials that easily conduct heat. Therefore, uninsulated or poorly insulated ducts in unconditioned spaces can lose through conduction 10%–30% of the energy used to heat and cool your home. The heating and cooling equipment then has to compensate for the heat loss and gain by conditioning additional air. This added conditioning raises a homeowner’s energy bills. In addition, when ducts lose heat through conduction, rooms served by long duct runs can experience “cold blow” during the winter because they usually have lower heating-supply temperatures.

Ducts in conditioned spaces experience minimal conductive losses and gains since they are exposed to indoor air temperatures. However, these ducts may also require some insulation to prevent condensation on duct walls and to ensure that conditioned air is delivered at the desired temperature.

Source: Department of Energy

Use construction adhesive and screws to attach rigid foam insulation to the attic side of the door. Pay special attention to the clearance between the insulation and the door frame and air sealing details. Adjust insulation levels or R-values to meet those recommended for your area and climate. Also, insulate and air seal the knee walls themselves for maximum energy efficiency.

Source: Energy Efficiency and Renewable Energy, U.S. Department of Energy

To ensure a tight fit between the stairs’ flat panel and the frame, weatherstripping or gasket material should be added either to the frame or panel. Latch bolts may be installed to help ensure a tighter seal.

To insulate attic stairs access, you can construct a lightweight, moveable box from rigid foam or fibrous ductboard to fit over the stairs from the attic side. Insulating kits are also available from weatherization suppliers or local hardware stores.

A home’s attic access, which could be an attic hatch, pull-down stairs, or a knee-wall door, often goes uninsulated. This gap in the attic insulation increases heat loss in the winter and heat gain in the summer.

These accesses also often aren’t sealed properly. A 1/4-inch gap around the perimeter of an attic access can potentially leak the same amount of air supplied by a typical bedroom heating duct.

Before insulating your attic access, you should first determine the recommended insulation R-value for your area and climate.
Attic Access Location

If you are constructing a new home or remodeling an existing home, carefully consider the location of an attic access. The location will affect how or whether the attic access should be insulated. If possible, locate the access in an unconditioned part of the house, such as a garage, covered patio, or porch. A garage location, where the vented attic is uninsulated, can eliminate the need for air sealing and insulation.

Before insulating or deciding whether to add insulation to your attic, first see our information about adding insulation to an existing house or selecting insulation for new home construction if you haven’t already.

Warning: if you think you have vermiculite insulation in your attic, there’s a chance it could contain asbestos. Don’t disturb it. Only insulation contractors certified to handle and remove asbestos should deal with vermiculite insulation.
Attic Insulation Techniques

Loose-fill or batt insulation is typically installed in an attic. Although installation costs may vary, loose-fill insulation is usually less expensive to install than batt insulation. When installed properly, loose-fill insulation also usually provides better coverage.

Before installing any type of insulation in your attic, follow these steps:

* Seal all attic-to-home air leaks. Most insulation does not stop airflow.
o Duct exhaust fans to the outside. Use a tightly constructed box to cover fan housing on attic side. Seal around the duct where it exits the box. Seal the perimeter of the box to the drywall on attic side.
o Cover openings—such as dropped ceilings, soffits, and bulkheads—into attic area with plywood and seal to the attic side of the ceiling.
o Seal around chimney and framing with a high-temperature caulk or furnace cement.
o At the tops of interior walls, use long-life caulk to seal the smaller gaps and holes. Use expanding foam or strips of rigid foam board insulation for the larger gaps.

* Install blocking (metal flashing) to maintain fire-safety clearance requirements (usually 3 inches) for heat-producing equipment found in an attic, such as flues, chimneys, exhaust fans, and light housings/fixtures unless the light fixtures are IC (insulation contact) rated. IC-rated lights are airtight and can be covered with insulation.

* Make sure insulation doesn’t block soffit vents to allow for attic ventilation.

* Check the attic ceiling for water stains or marks. They indicate roof leaks or lack of ventilation. Make repairs before you insulate. Wet insulation is ineffective and can damage your home.

Also insulate and air seal your attic access if it’s located in a conditioned part of the house.

You’ll want to properly insulate and air seal any knee walls—vertical walls with attic space directly behind them—in your home as well.

Finally, if you’re constructing a new home or remodeling, make sure any attic decking, which provides additional storage space or a platform for an HVAC unit or hot water tank, is raised above the ceiling joists to ensure proper insulation depth. The decking then should be installed securely to the top of the raised lumber after the insulation has been installed.
Other Considerations

If you live in a hot or warm climate, you might consider installing a radiant barrier in your attic along with the insulation.

Source: U.S. Department of Energy

* Attic spaces
o Attic access doors to unfinished attics
o Knee walls in finished attics
* Ducts in unconditioned spaces
* Cathedral ceilings
* Exterior walls
* Floors above unheated garages
* Foundations
o Basements
o Crawl spaces
o Slab-on-grade floor

Source: U.S. Department of Energy

To properly insulate a new home, you first need to know where you need to insulate and the recommended R-values for each of those areas. Use the U.S. Department of Energy’s Zip-Code Insulation Program to determine where you need to insulate and the recommended R-values based on your climate and type of heating and cooling system, etc. The program also will provide cost estimates and a rate of return.

Once you know where you need to insulate and the recommended R-values, review our information on the types of insulation available to help you decide what type to use and where.

Before you insulate a new home, you also need to properly air seal it and consider moisture control.

Source: U.S. Department of Energy

It is unwise to rely on air leakage for ventilation because it can’t be controlled. During cold or windy weather, too much air may enter the house. When it’s warmer and less windy, not enough air may enter. Air infiltration also can contribute to problems with moisture control. Moldy and dusty air can enter a leaky house through such areas as attics or foundations. This air in the house could cause health problems.

The recommended strategy in both new and old homes is to reduce air leakage as much as possible and to provide controlled ventilation as needed.

Source: U.S. Department of Energy