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Insulation


Around 50% to 70% of the energy used in the home is for heating and cooling the home. A well insulated home will help reduce your heating and cooling bills. Insulation also makes your home more comfortable by maintaining even temperatures and reducing exterior noise. Here is information on the types of insulation products available. We also explain how to understand insulation efficiency ratings.

R-Value

The ability of insulation to slow down heat flow is known as "R-value". Better insulation has a higher R-value. For example an R value of 20 is twice as good at slowing heat transfer compared to an R-value of 10.

Insulation works by storing pockets of air in a material such as fiberglass insulation. When installing insulation, you don't want to pack it too tightly because the air pockets are needed in the insulation. If insulation is packed too tightly then the R-value of the insulation will be reduced.

The ideal R-value for a home is based on your climate, your altitude, and the type of fuel used to heat your home. Also, local building codes my have minimum R-value requirements.

Perm Rating

The perm rating of insulation indicates how easy it is for water vapor to pass through the material. A lower perm rating indicates less moisture can pass through the material (a lower perm number is better)

Polyicynene Foam Insulation

Polyicynene foam is a type of insulation that is sprayed onto the walls and within a few seconds it expands to over 100 times it's original size and fills in the wall cavities. It sticks to the walls and tightly seals the wall. This foam has a similar R-Value to fiberglass insulation. However the foam seals the wall better and reduces air infiltration. With this foam you don't need a house wrap on the exterior of the home. Also, you don't need to do the additional caulking and foam sealing needed around outlets and other areas that you need to do with traditional insulation. This foam also makes the home more quiet and the foam can improve indoor air quality because the foam doesn't give off harmful gasses and helps keep outside dust and pollen from entering the home. Also, because the foam protects from moisture and air infiltration the inside of interior walls maintain a temperature closer to the room temperature and fewer drafts enter the home.

Cellulose Insulation

Cellulose insulation is made from recycled newspaper fibers. It is treated with flame-retardants but can still be flammable. Cellulose has less R-Value then fiberglass insulation and it also settles more over time (which can reduce it's insulation value). Also, cellulose insulation can have a reduction in R-value if it gets wet from a leak in the attic (fiberglass maintains it's R-Value if it gets wet).

Fiberglass Insulation - Batts versus Blown-In

For attic insulation, sometimes fiberglass is blown in instead of using the sheets (batts) of insulation. Either technique can provide good insulation. Batts mainly come in two standard widths and may be harder to fit in non-standard places or unusually shaped spaces.

With blown-in insulation it will need to be thicker (because blown-in has a lower R-Value per inch). Also there's a greater chance of not having consistent coverage with blown-in. However when done properly either style is fine. Blown in insulation is heavier and it is important the ceiling is properly installed using screws. To reduce the chance of a sagging ceiling when using blown-in insulation you may want to use 5/8 drywall for the ceiling. If you plan to finish the attic then you may want to use batts.

High Density Fiberglass Batts

You can buy fiberglass insulation that has more fiber and a higher R-value per inch. High-density fiberglass insulation can let you have higher R-value walls without having to increase the thickness of the wall. Insulation R value has increased over the years because of improvements made in manufacturing fiberglass insulation. For a 2x4 wall insulation an R-value of 15 is possible. For 2x6 walls the R-value of 21 is possible. In addition, adding 1 inch of polystyrene to the outside of the home can add 5 to the R-value.

Polystyrene

This material is usually sold in sheets that are 4’ x 8’ and it ranges in thickness of ½ inch to 2 inches. It has an R value of 5 per inch of thickness. This material is mainly used to add another layer of insulation to exterior walls or foundation walls. Sometimes it is used to insulate roofs if no attic space is available for insulation.

Adding Insulation to Attic

If you are putting an additional layer of batts in an attic and covering existing insulation batts, then put the new layer of batts at a 90 degree angle to the first layer. Changing the directions of each layer can help better seal the attic and reduce gaps in the insulation. Be careful you do not cover up any ventilation (such as ridge vents or soffits).

Insulation Around Recessed Lighting or Fans

If you have recessed lighting fixtures or fan motors near the attic then you need to avoid covering the fixtures with insulation because this can trap heat and create a fire hazard. Typically a box needs to cover these types of fixtures to provide at least 12 inches of space between a fixture and insulation. Check with your electrical inspector for more details. If you have recessed lighting, you can buy more efficient recessed lights to reduce the air leakage.

Check For Missing Insulation

Before the drywall is installed, check the insulation and see if any places are missing insulation. Common places missed are small openings near windows or doors. Put insulation in any places that have been missed and fill in any gaps where more insulation may be needed.

Raised Heel Height Roof

Standard framed roofs have very little room to put insulation above where the wall meets the roof. Building a raised roof can help you provide more room to put more insulation.

Insulating Around Electrical Outlets

Electrical outlets on exterior walls are common sources of drafts. Using foam insulation around the outlets can reduce this problem. Also, rubber outlet gaskets are available to help reduce drafts.

Vapor Barrier

Most insulation has a vapor barrier. The barrier should face the heated space.

Continuous Vapor-Barrier

To better reduce drafts in a wood constructed home you can use a continuous vapor barrier. These barriers are plastic wraps that go on the inside of the walls between the drywall and the insulation. When using a vapor barrier over fiberglass insulation then unfaced insulation is used (insulation without an attached vapor barrier) is used.

Radiant Barriers

Radiant barriers are highly reflective materials that reflect radiant heat. These materials usually look like aluminum foil and is put on roofs or under roof rafters to reflect heat. Sometimes radiant barriers are also put on exterior walls. Radiant barriers help reflect heat and can reduce heat gain in the summer. Most materials have an "R-Value" that measures the ability of a material to slow down the transfer of heat. Therefore insulation is intended to slow down heat transfer. Radiant barriers are designed to reflect heat and can help prevent heat from reaching the insulation.

These barriers are mainly helpful in reducing cooling costs in hot climates (they may not be worth the cost in colder climates). Radiant barriers can also be helpful on houses that are not well insulated. However if a home is well insulated then a radiant barrier has less benefit. If you are building a new home it is probably better to invest money in better insulation. According to the Department of Energy a radiant barrier can reduce cooling costs around 2 to 10% . Some radiant barriers are reflective on both sides and can help reflect heat back into the home. This may help reduce heating costs but this benefit is minor and is hard to measure.

Sometimes radiant barriers are put on attic floors or on top of insulation. It is less beneficial to have radiant barriers on attic floors because dust can gather on the barrier and reduce it's ability to conduct heat. When a radiant barrier is covered with dust it can actually absorb heat (and defeat it's purpose) rather than reflect heat. You can get foil chips to help solve the dust problem. With foil chips, their is many layers of a radiant barrier and the dust only affects the top layer.

Also radiant barriers on attic floors or over insulation can help cause more heat build up and moisture condensation in the attic. The effectiveness of a radiant barrier is measured by its ability to reflect heat (this is called emmissivity). Emmissivity is measured on a scale of 0 to 1 and the lower the emmissivity is better. Most radiant barriers have an emmisivity of around .03 to .05 and the manufacturer's specifications will have that information.

 Basement Insulation

About 4 feet below grade level the ground temperature becomes more stable and insulation may not be needed. Check your building codes. Some states recognize this fact and don't require insulation lower than 4 feet below grade. You may be able to save money in the basement by only insulating 4 feet below grade.

Attic Insulation

The biggest source of heat loss in a home is the attic. The best way to save energy is to invest in a good amount of insulation in your attic. Try to have an insulation of R-38 or higher in your attic.

Insulating Floors

You should put insulation in any floors that are over unheated space. For example insulate the floor over a crawlspace and the floor of a room over a garage.

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