Your Home - Fall 2010 - Energy Saving Tips
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Fall 2010
 
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Spotlight On
Insulation

In colder states, heating can account for up to two-thirds of your annual energy bills, according to the U.S. Energy Information Administration (EIA). Heating and cooling account for 50 to 70% of the energy used in the average American home. Inadequate insulation and air leakage are leading causes of energy waste in most homes.

Insulation saves money and our nation's limited energy resources, makes your house more comfortable by helping to maintain a uniform temperature throughout, and makes walls, ceilings, and floors warmer in the winter and cooler in the summer.

The amount of energy conserved depends on several factors such as local climate, the size, shape, and construction of the home; living habits of your family; the type and efficiency of the heating and cooling systems; and the type of fuel used to heat the home. Once the energy savings have paid for the installation cost, energy conserved is money saved - and saving energy will be even more important as utility rates go up.

How Insulation Works
Heat flows naturally from a warmer to a cooler space. In winter, the heat moves directly from all heated living spaces to the outdoors and to adjacent unheated attics, garages, and basements - wherever there is a difference in temperature. During the summer, heat moves from outdoors to the house interior.

To maintain comfort, the heat lost in winter must be replaced by your heating system and the heat gained in summer must be removed by your air conditioner. Insulating ceilings, walls, and floors decreases the heating or cooling needed by providing an effective resistance to the flow of heat. This resistance to heat flow is referred to as an R-value; the higher the R-value, the greater the insulating effectiveness.

Insulation Product Types
Batts, blankets, loose fill, and low-density foams (These products may be more familiarly called fiberglass, cellulose, polyicynene, and expanded polystyrene) are all different product types of insulation.

Reflective insulation works by reducing the amount of energy that travels in the form of radiation. Some forms of reflective insulation also divide a space up into small regions to reduce air movement, or convection, but not to the same extent as batts, blankets, loose-fill, and foam.

Insulation is available in a variety of forms, including: Batts and Rolls, Loose-Fill (blown-in), Spray Applied Foam Insulation, Rigid Insulation and Reflective Insulation. Each of these types is described in more detail below. Each type works by limiting air movement.

Batt and Roll Insulation
Batt and roll insulation are comprised of fiber glass, rock and slag, wool or cotton/denim. They are commonly installed in sidewalls, attics, floors, crawl spaces, cathedral ceilings or basements.  Availability and advantages of batt and roll are that continuous rolls can be purchased and cut to fit, or pre-cut lengths are available in bundles. They come with or without vapor retarder facings. Several batts with a special flame-resistant facing are available in various widths for basement walls and the areas where the insulation will be left exposed.

Fiber glass is spun from molten glass and sand into fibers and is an extremely effective insulating material because tiny pockets of air resist the flow of heat and cold. Fiber glass batts are the most common form of insulation in American homes. They are easy to install and generally among the least expensive forms of insulation. Rock and slag wool is similar to fiber glass except that it is spun from slag and other rock-like materials instead of molten glass. It is sometimes called mineral wool. Mineral wool insulation was among the earliest commercial insulation types.

Little independent testing has been done on products made from cotton or recycled scrap denim  for fire performance or moisture absorption. Similar to cellulose insulation, these materials require the addition of fire retardant chemicals because they are combustible. Some fire retardants used in these products are known to cause corrosion of pipes and wiring.

Loose-fill or Blown-in Insulation
Loose-fill (or blown-in) insulation is an extremely effective insulating material because it prevents air movement and resulting heat loss resisting the flow of heat and cold. Installed in attics and walls and designed for use in hard-to-reach locations such as corners, nooks and crannies. It is common practice to have blown-in insulation installed by a professional.

Rock wool (or slag wool) loose-fill insulation is similar to fiberglass except that it is spun from blast furnace slag (the layer of impurities that forms on the surface of molten metal) and other rock-like materials. The production of rock wool uses by-products that would otherwise be put in a landfill. 

Rock wool insulation is well suited for locations where it is difficult to install other types of insulation, such as irregularly shaped areas, around obstructions (such as plumbing stacks), and in hard-to-reach places. Blown-in loose fill insulations are particularly useful for retrofit situations because, except for the holes that are sometimes drilled for installations, they are one of the few materials that can be installed without disturbing existing finishes. Rock wool is installed dry, and because it will not settle over time, maintains its full R-value over the life of the home.

Cellulose is made from ground-up newspapers.  It is treated with fire retardants, some of which have been known to cause corrosion of wiring and pipes.  The product settles significantly over time and must be over-installed to compensate for this settling.

All loose-fill insulations are required to detail their installed and settled thickness on the bag label to let consumers know the expected settled R-value. Cellulose is applied using a mechanical blowing machine. In an attic, cellulose is not typically installed above an R-30 because its weight can cause sagging of the drywall. Most energy codes now call for R-38 to R-49 in attics.

Special Note
Whenever water is added to a wall cavity, it is critical to make sure the right amount of water is used. Too much water can lower the R-value and cause problems with mold and moisture in a wall. A manufacturer should provide information on its label for proper drying time that includes consideration for humidity and temperatures. Spray applied fiber glass dries faster than wet spray cellulose.

Spray-Applied Foam
Foamed in-place polyurethane insulation can be applied by a professional applicator using special equipment to meter, mix, and spray into place. Polyurethane foam can also help to reduce air leaks. It is typically more expensive than batts or loose-fill insulation. In many cases, this insulation would be used in a few places throughout the home where air sealing is important and batt or loose-fill insulation would be used in the majority of the space.

Some foams, such as polyisocyanurate, polyurethane, and extruded polystyrene, are filled with special gases that provide additional resistance to heat flow. The still air is an effective insulator because it eliminates convection and has low conduction. The spray foams are ideal for hard to reach places such as plumbing chases, and penetrations such as electrical outlets and pipes. This type of insulation is always installed by a professional.

Rigid Insulation
This type of insulation contains hundreds of millions of densely packed air cells. It is pressed or extruded into board-like forms and molded pipe-coverings. These provide thermal and acoustical insulation, strength with low weight, and coverage with few heat loss paths. Boards may be faced with a reflective foil that reduces heat flow when next to an air space.

Rigid insulation product types include fibrous materials, plastic foams, extruded polystyrene, expanded polystyrene, polyurethane and polyisocyanurate. It is commonly installed in foundation walls, exterior walls, interior basement walls, under slab or around pipes.

Reflective Insulation
Since the resistance to heat flow depends on the heat flow direction, reflective insulation is most effective in reducing downward heat flow i.e. through the floor to a crawl space in the winter, or through the roof in the summer. It is typically used in warmer climates and should not be considered a replacement for typical insulation. Reflective insulation with a plastic core should never be left exposed in a building due to fire safety.

If a single reflective surface is used alone and faces an open space, such as an attic, it is called a radiant barrier. Radiant barriers are not insulation, and by definition, have no R-value. According to the North American Insulation Manufacturer’s Association (NAIMA), testing has shown that it is more cost effective to add insulation than a radiant barrier.

Additionally, the actual reduction in heat flow achieved through properly installed radiant barriers is substantially less than that claimed by some manufacturers. In cold weather, radiant barriers may reduce beneficial heat gains from the sun; because of this, they are mainly sold in areas with warmer climates.

Reflective insulation systems are fabricated from aluminum foils with a variety of backings such as kraft paper, plastic film, polyethylene bubbles or cardboard. It is commonly installed in roof rafters, floor joists, wall studs, crawl spaces, ceilings and basements.

Some nice green grass
Some nice green grass

From the Editor
Saving Energy

Saving energy is on everyone's mind this Fall. From worries over winter energy costs to concern for the environment, there are many ways you can reduce your home's energy output.

ARTICLES:

Preparing Your Home Heating System for Winter
Part 1 | Part 2
Cleaning out the furnace

Spotlight On
Insulation

Find out about what type of insulation you ahve in your home and how it works


Go Green
Energy Efficiency Audits
Professional energy audits expose problems that are invisible to the eye

Energy Saving Do’s and Don’ts

Switching to a timed thermostat can make a real difference in your energy usage

 

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