Insulate Your Home For Maximal Energy Efficiency
Part 1 of 3... The Basics
That sudden slap-in-the-face... imported oil supplies were not as secure as had been thought... led to various mandatory and voluntary efforts to lessen our national dependence on imported oil. In the construction industry, changes occurred rapidly to increase the energy efficiency of both new and old buildings. Recommendations for attic insulation were increased, wall insulation (which before the '70's was considered a luxury) became commonplace, and the manufacturers of windows and doors struggled to market a product providing greater energy savings. The government issued guidelines and regulations to reinforce and protect the national interests.
This migration from relaxed enjoyment of nature's bounty to controlled consumption may have brought a smile to the lips of some conservationists but the sudden changes were not without negative consequences. Indoor pollution, once hardly noticeable, became a serious problem. Lack of ventilation caused mold and mildew growth and increased the danger from insecticides, household chemicals and carbon monoxide in the living space. The label "sick building" became a metaphor for overly air-tight, tomblike office buildings without even one operable window! (I bet you never thought you would have to monitor the diet of the person in the next cubicle, did you? Phew!)
Let's further examine the role of insulation in our homes... and our lives.
How insulation works... it keeps the heat where it belongs!
If you want your home to be warm in the winter and save on your heating bills, your insulation has one task... to keep the heat in! But if you want your home to stay cool on the warmest summer days, insulation's job is different... it must keep the heat out. How can one product do both? It's easy to understand once you grasp the simple concept of heat transfer.
There are three ways that heat can be transferred: conduction, radiation, and convection.
Conduction occurs when heat is transferred within an object or from one object to another by actual physical contact. Think of hand holding as a representation of conduction... warmth is transferred directly from one hand to the other, producing warmth. Very nice. Of course, conduction can be unpleasant... such as an icy toilet seat at the campground!
Materials differ is their ability to conduct heat. Metals and glass, for example, let heat pass through them very quickly, so they have little resistance to convection and are not considered to be good insulators. On the other hand, a lined glove used in the kitchen to handle hot pots and pans does not allow heat to pass through quickly... otherwise you would get a nasty burn. Therefore, the kitchen mitt resists convection... and is a good insulator.
The thickness of the insulator also affects conduction. A new kitchen mitt is thick and fluffy, giving you the most insulating value. After a number of washings the mitt, now somewhat matted and flatter, has lost much of its insulating value as it lost its thickness. Make a mental note of these other factors... we will return to them when we discuss the proper installation of insulation.
Convection is the transfer of heat between objects that are not touching each other. Instead, the heat is transferred by means of a fluid, such as water or air. The fluid is heated and the heat is transferred within it to the other object. Movement in the fluid is called a convective current. Have you even felt the air movement when you put your hand over a heated radiator. The air around the radiator is heated and rises, causing a detectable movement in the air. In fact, the weather itself is nothing more than convective currents moving water vapor and causing temperature changes. Get the umbrella... here comes a convective current!
Speaking about kitchen mitts... did you ever try to pick up something hot after getting the mitt wet? OUCH! It sure did burn, didn't it? That's because the insulating value of an object can change depending on other factors. Moisture is the most notorious. If an insulator becomes damp, it can lose much if not all of its insulating value. Why? The answer is convection... water as a fluid allows much quicker heat transfer than the insulating glove. If you ever touched a hot plate with a wet oven mitt, you know what I mean!
Radiation is the third way heat is transferred. You can relate this to the feeling of warmth felt when a rather attractive member of the opposite sex enters a room. Their warmth "radiates" outward from one "body" to another, right across open space. Heat transfer is good! Then again, fried hair and toasted eyeballs from sitting too close to a campfire are not my idea of fun, either. Radiation differs from convection in that it can occur in a vacuum... this is how the energy of the sun reaches the earth.
The value of R-Value... Promises, promises
Because of rampant fraud and misrepresentation in the insulation industry during the energy crisis of the '70's, we desperately needed a standard unit of measurement to compare different types of insulation. The US Department of Energy (DOE) established a method of gauging the effectiveness of insulating products, called the R-value.
The R-value is the ability of an insulator to resist heat transfer through it.
The larger the R-value, the better the insulation value of the product. But to make the R-factor meaningful and useful to both the consumer and builder, it had to somehow be related to the real insulation needs of a building. So the DOE established recommended insulation values for various parts of buildings based on the local climate. Any local building supply store can give you the recommended R-values for your region.
Remember... R-values are additive. If you have too little insulation in your attic, you can just add more to achieve the proper thickness.
Types of Insulation...
We have come a long way since the ancient Egyptians stuffed wads of papyrus into their shorts to keep warm! Today, there is a wide array of insulating products available. They all can offer superior insulating value... provided they are installed correctly in the appropriate location. Here is an overview of today's common insulation options, including each type's approximate R-value per inch of thickness.
Fiberglass: R-value 3.2 per inch
The most commonly used insulation in modern homes is fiberglass. A fluffy-looking stuff resembling cotton candy, it is used in walls, ceilings and as a wrap for air ducting and pipes. Fiberglass is chemically stable, will not rot and is nonflammable. It does melt with enough heat, so it offers no fire retardant properties to the home. It is also not water resistant and will readily absorb moisture, making it a poor choice in damp or wet locations. For you animal lovers, you'll be happy to know that rodents love fiberglass, and eagerly make their little nests in it when they can!
Fiberglass insulation is manufactured in a number of useful forms. Fiberglass rolls are available in various widths and lengths for use between the framing members of walls, ceilings and on attic floors. Fiberglass batts are the really the same as rolls, except that they are bundled in precut lengths to make installation in standard 8' walls easier. Both have an attached vapor barrier facing to protect them from moisture. This facing is designed to be stapled onto framing studs to keep the insulation in place prior to the installation of the wallboard or plaster. Paper is the most common facing, but there is also an aluminum facing which adds additional heat reflective properties to the insulation.
Fiberglass blankets are similar to batts in that they are sold in precut lengths, but do not have a vapor barrier facing. They are designed to be installed over the top of existing insulation in attic floors to increase the R-value, not as the primary insulation layer.
Loose fill fiberglass can be poured or mechanically blown onto attic floors, making this the fiberglass product of choice for quick retrofitting of insulation into older buildings or into areas with limited access for the installation of batts. Installation of a vapor barrier is essential with fiberglass insulation, which is why blowing loose-fill fiberglass insulation into existing walls is not advisable. This is because fiberglass insulation soaks up water like a sponge, causing a pronounced drop in its insulating ability.
Anyone who has ever worked with fiberglass has found it to be a scratchy, irritating product on all body parts. Contact with skin should be avoided by use of protective clothing and gloves. Eye protection and a quality dust mask or respirator should be worn whenever working with fiberglass.
There is some concern that fiberglass may be a source of potential lung problems similar to asbestos due to the small size of some of the fibers when airborne. Studies done in the '80s at an Owens Corning fiberglass manufacturing facility indicated increased levels of cancer and other lung diseases among the workers. The Occupational Safety and Health Administration (OSHA) has indicated that there have been epidemiological studies linking synthetic mineral fibers (fiberglass and mineral wool) to increased lung disease. Even now there are lawsuits regarding disease caused by improper installation of fiberglass and exposure to fiberglass dust. The next asbestos? We will have to wait and see as information accumulates, but if fiberglass is definitively shown to be even partially as dangerous as asbestos and the government takes regulatory action... hold onto your wallets!
Cellulose: R-value 3.2 per inch
Cellulose insulation is a byproduct of the paper industry, using up to 75% recycled newsprint! A known insulator for many decades, it grew in popularity during the energy crisis of the 70's as a way to increase home energy efficiency while being environmentally responsible. Aiding in cellulose's growth was the shortage of fiberglass due to the intense short-term demand for insulating products which outpaced production.
Indeed, like the second gold rush, every Tom, Dick and Jane jumped on the energy-saving bandwagon causing cellulose insulation to become an overnight hit. Because manufacturing costs were much lower than fiberglass, the product was more reasonably priced. Manufacturing and installation companies sprung up like weeds, renting do-it-yourself cellulose spray equipment and promising the world to consumers. As the energy crisis became a memory, the cellulose industry settled back into a minority status to fiberglass' majority, with only a few companies selling cellulose insulation today.
Cellulose and fiberglass share similar R-values at normal temperatures, but cellulose has greater insulating properties at lower temperatures than fiberglass or mineral wool making it the better insulation choice in the colder climates. Cellulose is also less permeable to air movement than fiberglass and is less affected by packing and fluffing, making it a better insulation for blowing into uninsulated walls or other building cavities. Studies at the University of Colorado confirmed that cellulose is indeed the insulation of choice for walls and ceilings.
Because cellulose is a "loose-fill" product, installing it in walls in new construction was a dusty, difficult job until the development of a wet-spray method. A specially treated cellulose has a binder added to it which acts as an adhesive when moistened. The spray equipment mixes a small amount of water with the insulation, activating the binder to give it a "stickiness". This allows the filling of open wall cavities by means of low pressure spraying.
The installation is simple... a special spray tool pumps the thick cellulose "mush" into the space between the framing studs. When used as a soundproofing for interior walls, a screening similar to window screen is installed on one side of the wood framing to catch the insulation as it is sprayed. The small amount of moisture involved does not significantly affect construction schedules and the walls can generally be closed up within 24 hours of application. Spray application of this insulation gives the homeowner the full rated R-value for the wall cavity as opposed to batt fiberglass, which tends to have a more irregular R-value due to compression during installation.
Being a wood derivative (and inherently flammable), modern cellulose insulation is required to be treated chemically to be both fire resistant and fire retardant. This treatment makes it completely safe for all residential uses and gives it a quality that fiberglass does not have... it can actually slow down the movement of a fire in a building!
Cellulose has none of the irritating properties of fiberglass, and so far has not been shown to have any deleterious effects. Even so, for the safety of your lungs and eyes goggles and a protective mask or respirator should be worn when working with this or any other dusty product.
Mineral wool: R-value 3.1 per inch
Mineral wool, also known as rock wool, is an insulation product manufactured from steel slag. The slag, a byproduct of steel manufacturing consisting of dirt and limestone (yummy), is combined with other chemicals, heated and spun into a fibrous material that is an excellent insulator. It is permanent, will not rot, does not burn or melt, does not absorb moisture, and will not support mold or mildew. It is available in batts or as a loose-fill product that can be blown into walls and ceilings. It can also be installed between wall studs by using a mesh screen across one side of the studs, allowing floor to ceiling filling with a technique virtually the same as with blown-in cellulose (see above).
Because of its greater density and water resistant properties, mineral wool acts as a vapor barrier and, unlike fiberglass, does not need an additional vapor barrier to be effective. As mentioned earlier, fiberglass can lose much of its insulating ability when moist. Because of its fire resistant properties, it is the insulator of choice in applications where the maximum fire resistance is desired or required. Installation of mineral wool is not a do-it-yourself product, and is only professionally installed.
Mineral wool products and fiberglass share the same health concerns, since the type and size of the manufactured fibers are similar. Eye, skin, and lung protection are mandatory when working with this product.
Rigid insulation: R-value 4.0 to 6.5 per inch
There are various types of rigid board insulation, made from various materials such as polystyrene, polyisocyanurate, compressed mineral wool and rigid fiberglass. Used in a variety of applications both above and below ground, they are waterproof or water resistant and are available in a variety of sizes and thickness'. Some of the applications for rigid insulation are on exterior and below grade foundations, under basement slabs, as a backer for vinyl siding and as an insulator for basement walls.
Rigid insulation is often used to supplement the insulation in walls and ceilings. Adding a half inch of polystyrene foam board installed beneath the wallboard can give the homeowner the equivalent of 5 1/2" of fiberglass in a 3 1/2" thick standard stud wall. This is much more economical than using 2x6 studs instead of 2x4 studs for the framing. As an additional benefit, the rigid insulation stops the conduction of heat from the outside through the wall framing, eliminating "cold spots" on the wallboard at each stud. Of course, there are many other applications for rigid foam that are only limited by the homeowner's imagination.
For all its benefits, one problem with rigid foam insulation is insect infestation. Carpenter ants have been known to nest within it, chewing their way to an easy comfortable abode. In warmer climates, pest control professionals frown on using below-grade foam insulation at all unless the foam stops well beneath the surface of the ground to allow for termite control. Termites seem to find foam insulation an ideal tunneling medium, and use it to reach above grade wood.
Sprayed foam insulation: R-value 4.5 to 6.5 per inch
Foam insulation can be sprayed into building cavities or directly onto surfaces. Plastic foams have higher R-values than fiberglass, cellulose or mineral wool. One type, polyurethane foam, has the highest R-value of any residential insulator... 6.2... almost twice the R-value of fiberglass!
Spray foam is an inert product that resists rot and mildew and, because of the strong bond it makes with structural members, actually adds strength to the building! The same insect infestation warnings apply to sprayed foam as to rigid insulation panels... using it within the hollows of cement block foundations and in any other below or near ground level applications can give termites a direct route into your home! (Photo left courtesy North Carolina Foam Industries, Copyright© NCFI)
Application of foam can vary by climate and can be mixed with other types of insulation, according to Roger Morrison of North Carolina Foam Industries. "Spray-applied polyurethane foam is commonly used in combination with glass fiber insulation in warmer climates. A nominal 1/2-inch of spray foam is applied to the inside of the exterior sheathing within an open stud wall cavity. A glass fiber batt is then installed over the spray foam. The purpose of the spray foam is primarily as an air barrier but it also supplements the insulation with an additional R-3 or so."
When I asked him why they didn't just fill the wall with foam, he continued, "Basically, different strokes for different folks. Generally, home builders will totally fill the wall cavity with foam in colder climate, where the higher insulating value of foam exceeds that of fiberglass. In warmer climates, though, using less expensive fiberglass is preferred."
Sorry, but this is a pro-only product and not available for
do-it-yourself installation. Cheer up... you can purchase smaller
quantities of spray foam at your local hardware or home store in easy-to-use
aerosol cans. One of the most familiar of these products is Great Stuff
from Flexible Products.
One important caution about using these expanding foam products... DON'T OVERDO IT!! I have rescued more than one homeowner who used this product in an "overzealous" fashion. One couple used it to seal the gaps around a door frame in their semi-finished garage. It stopped the air leaks alright, but also permanently sealed the door shut as it pinched the door tightly within the frame. It took over an hour to cut out enough foam to free the door. A little goes a long way. Fortunately, the companies have realized the problem and have modified their formulas so that the foam expands with a little less force!
Do not confuse modern spray foams with the controversial urea formaldehyde foam insulation (UFFI) that caused such a furor in the 70's. To make a long story short, along with the increased use of fiberglass, cellulose and mineral wool, UFFI foam was injected into the walls of thousands of homes, promising greater R-values for the dollar. However, an unanticipated side effect emerged... formaldehyde vapors released from the curing foam began to make people sick. This sickness, now called chemical sensitivity, made these homes essentially poisonous for their owners causing both short term and long term health damage. It was determined that the sometimes staggering levels of formaldehyde released were primarily related to poor mixing and installation techniques. This fact combined with the fact that different people have different tolerances to chemicals by nature led to some confusion... everyone using UFFI did not become ill.
After much consideration, the Consumer Product Safety Commission banned the use of UFFI in the early '80's. Though the ban was eventually overturned, the ruling was moot... the bad publicity all but crippled the UFFI industry. Many years have passed since the ban, and homes with this foam still in the walls no longer exude any discernable levels of formaldehyde. Even so the fear (and the legislation) persists and many states still require disclosure during sale of a house if it contains UFFI.
If you are thinking of purchasing a home with UFFI in the walls (or are curious about your own home), there are tests that can be done to determine whether there is any formaldehyde present in the house. Once source of formaldehyde testing monitors is Air Quality Research, at http://www.airqualityresearch.com. Their indoor area monitor, PF-1, is may be ordered directly by calling 1-800-818-5894.
Be aware that there are other sources of formaldehyde in your home... plywood and particle board, for example. So zero levels of formaldehyde are unlikely in any modern home, especially a new one!
Continue to Part 2 - How much insulation does your home need?