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Posts Tagged ‘insulation’

If you have or will have an unventilated crawl space, then your best approach is to seal and insulate the foundation walls rather than the subfloor. The advantages of insulating the crawl space are as follows:

* You can avoid the problems associated with ventilating a crawl space.
* Less insulation is required (around 400 square feet for a 1,000-square-foot crawl space with 3-foot walls.)
* Piping and ductwork are within the conditioned volume of the house so they don’t require insulation for energy efficiency or protection against freezing.
* Air sealing between the house and the crawl space is less critical.

The disadvantages of insulating a crawl space include the following:

* The insulation may be damaged by rodents, pests, or water.
* A radon mitigation system will require ventilation of the crawl space to the exterior. Not planning for radon-resistant construction may necessitate air sealing the floor to mitigate the radon through ventilation.
* The crawl space must be built airtight, and the air barrier must be maintained.
* The access door to the crawl space must be located inside the home through the subfloor unless an airtight, insulated access door in the perimeter wall is built and maintained.

Source: EERE, U.S. Department of Energy

If you properly insulate your crawl space—in addition to air sealing and controlling moisture, you will save on energy costs and increase your home’s comfort.

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

How to insulate a crawl space depends on whether it’s ventilated or unventilated. Traditionally, crawl spaces have been vented to prevent problems with moisture; most building codes require vents to aid in removing moisture from the crawl space. However, many building professionals now recognize that building an unventilated crawl space (or closing vents after the crawl space dries out following construction) is the best option in homes using proper moisture control and exterior drainage techniques. There are two main reasons for this line of thinking:

* Ventilation in the winter makes it difficult to keep crawl spaces warm
* Warm, moist outdoor air brought into the crawl space through foundation vents in the summer is often unable to dehumidify a crawl space. In fact, this moist outdoor air can lead to increased moisture levels in the crawl space.

Source: EERE, U.S. Department of Energy

Insulating Concrete Forms

Homes built using an insulating concrete form (ICF) system literally have the insulation built into the walls as part of the structure. This system creates walls that have a high thermal resistance, with R-values typically above R-17. Even though ICF homes are constructed using concrete, they look just like traditional stick-built homes.

Types of ICF Systems

Insulating concrete forms (ICFs) are basically forms for poured concrete walls, which remain as part of the wall assembly. These forms also provide a backing for drywall on the inside of a home for stucco, lap siding, or brick on the outside.

ICF systems consist of interconnected foam boards or interlocking, hollow-core foam insulation blocks. Foam boards are fastened together using plastic ties. Along with the foam boards, steel rods (rebar) can be added for reinforcement before the concrete is poured. When using foam blocks, steel rods are often used inside the hollow-cores to strengthen the walls.

There are three basic types of ICF systems that use either foam board or foam blocks. A flat system yields a continuous thickness of concrete, like a conventionally poured wall. A grid system creates walls using a waffle pattern—the concrete is thicker at some points than others. A post-and-beam system consists of discrete horizontal and vertical columns of concrete, which are completely encapsulated in foam insulation.

Another ICF system uses foam board in the center of the concrete wall. This is often referred to as “tilt-wall” construction. The walls are poured in a form on a flat deck. After curing, the walls are “tilted” upright into position by a crane. Because the foam board is inside the wall, it reduces potential problems related to the foam’s fire resistance, insect infestation, and moisture.

The foam webbing around the concrete-filled cores of blocks can provide easy access for insects and groundwater. To help prevent these problems, some manufacturers make insecticide-treated foam blocks and promote methods for waterproofing them.

Installation

Installation or construction of an ICF system requires a contractor who has experience with this building technique.

Source: EERE, U.S. Department of Energy

The most common types of materials used in making foam board include polystyrene, polyisocyanurate or polyiso, and polyurethane.

Molded Expanded Polystyrene Foam Board

Molded expanded polystyrene (MEPS) is a closed-cell material that can be molded into many everyday items, such as coffee cups and shipping materials, or into large sheets of foam board insulation. MEPS foam board insulation is commonly known as beadboard.

To make beadboard, loose, unexpanded polystyrene beads containing liquid pentane are mixed with a blowing agent and poured into an enclosed container. The mixture is heated to expand the beads many times their original size. The beads are then injected into a mold. Under more heat and pressure, they expand to become foam blocks, which are shaped as needed.

The physical properties of MEPS foam board vary with the type of bead used. It’s manufactured at various densities, depending on the application. Beadboard for roofing materials has to be dense enough to walk on without damage; wall insulation foam boards are several times less dense than roof boards. R-values range from 3.8 to 4.4 per inch (2.54 cm) of thickness.

MEPS foam board is available with a variety of facings. Since spaces between the foam beads can absorb water, a vapor diffusion retarder is necessary if water transmission through the insulation might become a problem.

MEPS foam board also is often used as the insulation for structural insulated panels (SIPs) and insulating concrete forms (ICFs).

Extruded Expanded Polystyrene Foam Board

Extruded expanded polystyrene (XEPS) is a closed-cell foam insulation similar to MEPS. To make it, the polystyrene pellets are mixed with various chemicals to liquefy them. A blowing agent is then injected into the mixture, forming gas bubbles. The foaming, thick liquid is then forced through a shaping die. When cooled, the panel is cut as required. Foam densities are typically 1.5 pounds per cubic foot (0.21 kilograms per cubic meter).

XEPS is more expensive than MEPS. Like MEPS, the R-value depends upon the density of the material and is generally about R-5 per inch. It’s also much more consistent in density and has a higher compressive strength than MEPS, making it better suited for use on roofs or for wall panels. Extruded polystyrene also has excellent resistance to moisture absorption.

Like MEPS, XEPS is available with a variety of facings and is also often used as the insulation for SIPs and ICFs.

Polyisocyanurate and Polyurethane Foam Board

Polyisocyanurate or polyiso and polyurethane are very similar, closed-cell foam insulation materials. Because both materials offer high R-values (R 5.6 to R per inch of thickness, you can use a thinner foam board to achieve the required thermal resistance. This can be an advantage if you have space limitations.

Polyiso foam board insulation is available in a variety of compressive strengths. Compressive strength refers to the ability of a rigid foam board to resist deformation and maintain its shape when subjected to a force or load. Also, polyiso remains stable over a wide temperature range (-100ºF to +250ºF). This makes it good as roofing insulation. And when used with a laminated aluminum foil facing, polyiso foam board provides an effective moisture or vapor barrier.

These foam boards can also be used to make SIPs.

Source: EERE, U.S. Department of Energy

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

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

A properly insulated foundation can result in lower heating costs and more comfortable below-grade rooms, if you have any. It can also help prevent moisture problems, insect infestation, and radon infiltration in your home.

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

Insulating any floors above your unheated garage will help reduce the energy costs for the above conditioned space.

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

When insulating floors over unconditioned garages, use the following techniques:

* Seal the joint between the header or band joist and the subfloor
* Seal the joint between the top or sill plate and the header joist
* Seal all air leakage sites in the floor (e.g., electrical penetrations)
* Trim insulation to fit snugly with no gaps
* Staple the kraft paper to the floor joist from above instead of using wire mesh or stay wires to hold the insulation in place
* Install an air barrier to prevent cold air in the garage from “short circuiting” the insulation underneath the subfloor

Source: U.S. Department of Energy