Energy Saving Devices

Archive for April, 2009

The maximum performance of foam board insulation depends heavily on proper installation. Therefore, it’s best to have a certified insulation installer do it. If you’d like to have it installed professionally, you should do the following:

* Obtain written cost estimates from several contractors for the R-value you need. Don’t be surprised to find quoted prices for a given R-value installation to vary by more than a factor of two.
* Ask contractors about their air-sealing services and costs as well, if needed.

To evaluate batt installation, you can measure batt thickness and check for gaps between batts.

If you want to install it yourself, you should try to obtain instructions and safety precautions from the manufacturer. Carefully follow these instructions. You should also check your local building and fire codes.
Avoiding Direct Sunlight Damage

Protect all types of foam insulation from direct sunlight. Over time, the sun’s ultraviolet rays can damage the insulation. For roofs, this is generally done by applying a coating such as tar, acrylic, silicone, or rubberized paint. You can also cover the foam with a rubber or plastic membrane, or a layer of asphalt and roofing felt. Make certain you are using compatible products. The solvents in some coatings dissolve certain plastics.
Avoiding Potential Moisture Problems

In cold weather, warm inside air containing water vapor can get past the wall finish and insulation, condensing inside the colder wall cavity. In hot, humid climates the same thing can happen, just in the reverse direction. Humid outdoor air in the summer can condense inside cool, air conditioned wall cavities. If enough of this happens and the water cannot escape, wood rot, mold, and other moisture-related problems can occur. For this reason, building codes often require installing a vapor diffusion retarder on the warmest side of the wall cavity.

Foam board insulation is commonly placed between the exterior finish (i.e., siding, brick) and the studs of exterior walls. To prevent air infiltration, you should place rigid insulation boards tightly together and seal the seams with tape or caulk. However, this practice may worry some builders in cold climates since the foam board may act as a second vapor diffusion retarder. Studies have shown, however, that condensation rarely occurs in these areas unless something else is seriously wrong with the wall assembly (i.e., massive uncontrolled air leakage into the walls from the house). If the assembly is constructed correctly, the inside surface of the foam board stays warm enough to keep water vapor in its gaseous state long enough for it to escape.
Avoiding Potential Insect Problems

When insulating a foundation you need to consider that, although insects don’t eat foam board, they can easily tunnel through it. Insect burrows reduce the R-value and structural integrity of the insulation. For these reasons, some manufacturers treat their foam products with an insecticide, usually a borate compound. Many building jurisdictions also mandate treating the earth around the building with insecticides. These jurisdictions may also want an inspection area several inches wide and all around the foundation of a house kept bare of insulation board.

A better solution for below-grade walls in need of insulation is to install the foam board over the interior of the basement walls rather than on the exterior, which is more common. Interior applications prevent ground-dwelling insects from finding the foam board at all, and they eliminate the need for the bare inspection area. Insulating interior walls, however, requires careful attention to moisture control.

Most jurisdictions also require installing a fire barrier over the interior foam board. While this adds extra cost, the thermal performance of this method is superior in most cases to the more common exterior foam board application. This equates with a dollar savings in energy that can repay you many times over for the additional cost of an interior application. If you plan to convert a basement into a living space, there is almost no additional cost.
Ensuring Fire Protection

Foam insulation is relatively hard to ignite, but when it is ignited, it burns readily and emits a dense smoke containing many toxic gases. The combustion characteristics of foam insulation products vary with the combustion temperatures, chemical formulation, and available air.

Because of these characteristics, foams used for construction require a covering as a fire barrier. One half-inch thick (1.27 cm) gypsum wallboard is one of the most common fire barriers. Some building codes, however, do not require an additional fire barrier for certain metal-faced, laminated foam products. Check with your local building code/fire officials and insurers for specific information on what is permitted in your area.

Source:  EERE, U.S. Department of Energy

Foam boards—rigid panels of insulation—can be used to insulate almost any part of your home, from the roof down to the foundation. They provide good thermal resistance and often add structural strength to your home. Foam board insulation sheathing reduces heat conduction through structural elements, like wood and steel studs.

Source: EERE, U.S. Department of Energy

Concrete block insulation is typically installed for new home construction or in homes undergoing major renovation. Since installation involves masonry skills, it’s best to have a certified cement mason do it.

When using masonry blocks for a foundation wall, filling the block cores with high-pressure foam works better than most poured-in insulations, like polystyrene beads or vermiculite or perlite pellets.

Note that even though filling the block cavities and special block designs improve a block wall’s thermal characteristics, it doesn’t reduce heat movement very much when compared to insulation installed over the surface of the blocks either on the exterior or interior of the foundation walls. Field studies and computer simulations have shown that core-filling of any type offers little fuel savings since the majority of heat is conducted through the solid parts of the walls such as block webs and mortar joints.

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

Insulated concrete blocks can accommodate many walls in a home. Their cores are filled with insulation (except for those cells requiring structural steel reinforcing and concrete infill), which raises the average wall R-value. The better concrete masonry units reduce the area of connecting webs as much as possible.

Types of Concrete Block Insulation

There are several ways to incorporate foam insulation—such as polystyrene, polyisocyanurate or polyiso, and polyurethane—into concrete blocks. The hollow cores of concrete blocks can be filled by pouring and/or injecting loose foam beads or liquid foam. Some manufacturers make concrete blocks that accommodate rigid foam inserts.

Some block makers coat polystyrene beads with a thin film of concrete. The concrete serves to bond the polystyrene while providing limited structural integrity. The most common group of ingredients are expanded polystyrene mixed with Portland cement, sand, and chemical additives. These make surface-bonded wall assemblies with a wall R-value of R-1 per inch thickness. Polystyrene inserts placed in the block cores increase the unit thermal resistance to about R-2 per inch.

In the United States, two varieties of solid, precast autoclaved concrete masonry units are now available: autoclaved aerated concrete (AAC), and autoclaved cellular concrete (ACC). This class of material has been commonly used in European construction since the late 1940s. Air makes up 80% (by volume) of the material. Autoclaved concrete has ten times the insulating value of conventional concrete. The R-1.1 per inch blocks are large, light, and have a flat surface that looks like a hard, fine sponge. Mastic or a thin mortar is used to construct a wall, and the wall then often gets a layer of stucco as the finish. Autoclaved concrete is easily sawed, nailed, and shaped with ordinary tools. Since the material absorbs water readily, it requires protection from moisture.

Precast autoclaved cellular concrete uses fly ash instead of high-silica sand as its distinguishing component. Fly ash is a waste ash produced from burning coal in electric power plants. The fly ash is the material that differentiates ACC from AAC.

Hollow-core units made with a mix of concrete and wood chips are also available. They are installed by stacking the units without using mortar (dry-stacking). Structural stability comes from the concrete fill and appropriate rebar throughout for structural walls. One potential problem with this type of unit is that the wood is subject to the effects of moisture and insects.

Concrete blocks are also sometimes filled with vermiculite or perlite pellets.

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

Blanket insulation—the most common and widely available type of insulation—comes in the form of batts or rolls. It consists of flexible fibers, most commonly fiberglass. You also can find batts and rolls made from mineral (rock and slag) wool, plastic fibers, and natural fibers, such as cotton and sheep’s wool.

Batts and rolls are available in widths suited to standard spacing of wall studs, and attic or floor joists. Continuous rolls can be hand-cut and trimmed to fit. They are available with or without facings. Manufacturers often attach a facing (such as kraft paper, foil-kraft paper, or vinyl) to act as a vapor barrier and/or air barrier. Batts with a special flame-resistant facing are available in various widths for basement walls where the insulation will be left exposed. A facing also helps facilitate fastening during installation. However, it’s recommended that you use unfaced batts if you’re reinsulating over existing insulation.

Standard fiberglass blankets and batts have a thermal resistance or R-values between R-2.9 and R-3.8 per inch of thickness. High-performance (medium-density and high-density) fiberglass blankets and batts have R-values between R-3.7 and R-4.3 per inch of thickness. See the table below for an overview of these characteristics.

*This table is for comparison only. Determine actual thickness, R-value, and cost from manufacturer and/or local building supplier.

Installation

The maximum thermal performance or R-value of blanket and batt insulation depends heavily on proper installation. Therefore, it’s best to have a certified insulation installer do it. If you’d like to have it done professionally, you should do the following:

* Obtain written cost estimates from several contractors for the R-value you need. Don’t be surprised to find quoted prices for a given R-value installation to vary by more than a factor of two.
* Ask contractors about their air-sealing services and costs as well, if needed.

To evaluate batt installation, you can measure batt thickness and check for gaps between batts.

If you want to install the insulation yourself, carefully follow instructions and the necessary safety precautions. The insulation’s manufacturer may offer instructions. You should also check your local building and fire codes. Please see the Installation and Reading List resources on the right side of this page (or below if you’ve printed the page).
Cost

Blanket (batt or roll) insulation and installation usually costs less than other types of insulation.

Source: EERE, U.S. Department of Energy

To effectively insulate your basement for energy efficiency and to create a comfortable space, you need to properly control moisture in your basement.

Most basement water leakage results from either bulk moisture leaks or capillary action. Bulk moisture is the flow of water through holes, cracks, and other discontinuities into the home’s basement walls. Capillary action occurs when water wicks into the cracks and pores of porous building materials, such as masonry blocks, concrete, or wood. These tiny cracks and pores can absorb water in any direction—even upward.

The best approaches for preventing these problems will depend on your local climate, type of insulation, and style of construction. However, the following general rules apply to most basement designs for creating a water-managed foundation system (see corresponding illustration):

1.Keep all untreated wood materials away from earth contact.
2.Provide drainage, such as gutters, to conduct rainwater away from the house.
3.Slope the earth away from all sides of the house for at least 5 feet at a minimum 5% grade (3 inches in 5 feet). Establish drainage swales to direct rainwater around.
4.Add a sill gasket to provide air sealing.
5.Install a protective membrane, such as caulked metal flashing or EPDM-type membrane, to serve as a capillary break that reduces wicking of water up from the masonry foundation wall. This membrane can also serve as a termite shield on top of foam board insulation.
6.Damp-proof all below-grade portions of the foundation wall and footing to prevent the wall from absorbing ground moisture by capillary action.
7.Place a continuous drainage plane over the damp-proofing or exterior insulation to channel water to the foundation drain and relieve hydrostatic pressure. Drainage plane materials include special drainage mats, high-density fiberglass insulation products, and washed gravel. All drainage planes should be protected with a filter fabric to prevent dirt from clogging the intentional gaps in the drainage material.
8.Install a foundation drain directly below the drainage plane and beside the footing, not on top of the footing. This prevents water from flowing against the seam between the footing and the foundation wall. Surround a perforated 4-inch plastic drainpipe with gravel and wrap both with filter fabric.
9.Underneath the basement’s slab floor, install a capillary break and vapor diffusion retarder, consisting of a layer of 6- to 10-mil polyethylene over at least 4 inches of gravel.

Consult a qualified builder, basement designer, and/or insulation contractor in your area for specific basement moisture control measures concerning your climate, type of insulation, and construction style.

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

Once you have determined the insulation R-value you’ll need for either adding insulation to an existing basement or new home construction, you can choose the type of insulation, including the following:

* Blanket (batt and roll) insulation
* Concrete block insulation (new construction)
* Foam board insulation
* Insulating concrete forms (new construction)
* Loose-fill insulation (good choice for finished basements)
* Sprayed foam insulation (good choice for finished basements)

The installation of insulation in your basement will depend on the type you choose and the best way to control moisture in your particular climate.

Source: U.S. Department of Energy

In most cases, a basement with insulation installed in the exterior basement walls should be considered a conditioned space. Even in a house with an unconditioned basement, the basement is more connected to other living spaces than to the outside. This connection makes basement wall insulation preferable to insulating the basement ceiling.

Compared to insulating the basement ceiling, insulating basement walls has the following advantages:

• Requires less insulation (1,350 square feet of wall insulation for a 36 x 48-foot basement with 8-foot walls, compared with 1,725 ceiling)
• More easily achieves continuous thermal and air leakage boundaries because basement ceilings typically include electrical wiring, plumbing, and ductwork.
• Requires little, if any, increase in the size of the heating and cooling equipment. The heat loss and air leakage through the basement ceiling is similar to that through the exterior walls of the basement.

These are some other advantages of insulation on exterior basement walls:

• Minimizes thermal bridging and reducing heat loss through the foundation
• Protects the damp-proof coating from damage during backfilling
• Serves as a capillary break to moisture intrusion
• Protects the foundation from the effects of the freeze-thaw cycle in extreme climates
• Reduces the potential for condensation on surfaces in the basement
• Conserves room area, relative to installing insulation on the interior.

The disadvantages of basement wall insulation include the following:

• Costs may exceed those for insulating the basement ceiling, depending on materials and approach selected
• Installation is expensive for an existing building unless a perimeter drainage system is also being installed
• Many exterior insulation materials are susceptible to insect infestation
• Some contractors are unfamiliar with proper detailing procedures that are critical to performance
• If surrounding soil contains radon gas, the house will require a mitigation system underneath the basement floor.

Adding insulation to the interior of the foundation is often more cost effective for an existing building. Interior insulation has the following advantages and disadvantages.

Advantages:

• Interior insulation is much less expensive to install than exterior insulation for existing buildings
• Almost any insulation type can be used, giving a wider selection of materials
• The threat of insect infestation is eliminated
• The space is isolated from the colder earth more effectively than when using exterior methods

Disadvantages:

• Many insulation types require a fire-rated covering since they release toxic gases when ignited
• Interior insulation reduces usable interior space by a few inches
• It doesn’t protect the damp-proof coating like the exterior insulation
• If the perimeter drainage is poor, the insulation may become saturated by moisture weeping through the foundation walls
• Superior air-sealing details and vapor diffusion retarders are important for adequate performance

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

A properly insulated basement can help reduce your energy costs. However, basement walls are one of the most controversial areas of a house to insulate and seal. You need to carefully consider the advantages and disadvantages, not to mention moisture control.

Annual Energy Savings

The energy cost savings of basement wall insulation vary depending on the local climate, type of heating system, fuel cost, and occupant lifestyle. Typical annual cost savings by R-value in a few U.S. cities are provided in the table to the right for a 1,500 square-foot home with a conditioned basement heated by natural gas ($0.72/therm).

Although you can achieve considerable savings in space conditioning costs by insulating the foundation, the installation costs can become relatively high, especially for retrofit projects. The type of materials used, the application method, and the extent of work all affect the overall cost. Simple payback is typically in the range of 6 months for a simple do-it-yourself installation to 20 years for professionally installed and more involved work. Adding foundation insulation during new construction is usually less expensive.

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