Duct Insulation
Ducts are the distribution arms of a building’s heat production system. They carry warmed air from the furnace to the farthest, coldest rooms in the living space, and deliver it through vents or registers in the walls or floors. Particularly when a duct has to convey heat over a long distance, or when it passes through a garage, basement, attic, or other unheated space, much heat may be lost through holes and cracks in the ducts, and simply through the duct walls, by conduction. When ducts run through walls and floors they are pretty well be yond your reach—carving your way through a wall to get at a heating duct is rarely worth the effort. But where the ducts emerge from the furnace to begin their journey through your house, a layer of 2-inch fiberglass blanket insulation can cut your heating bill by several additional percentage points and pay back its investment in just about two years.
Before you install insulation around your ducts, run air through them and check for leaks by passing your hands around the joints. Seal any leaks you may find with duct tape.
Ducts are insulated with blankets and batts, and ordinarily have no vapor barrier. However, if your ducts are used in air conditioning as well as in heating, you should make sure to use insulation with a vapor barrier, and install it with the barrier facing to the outside, away from the surface of the ducts.
Without crushing the insulation, wrap the blankets securely around the ducts.
Where the blankets meet, and at all the wrapping junctures, seal the insulation tightly with duct tape. Make sure you are not blocking any air intakes, and keep both tape and insulation out of contact with light fixtures, chimneys, and flue pipes.
If your ducts are located between joists—as, for example, at the ceiling of the basement—cut strips of batt or blanket insulation long enough to reach across not only the duct, but the adjacent joists as well. Cover the duct securely, and nail or staple the insulation to the outside edge of the joists.
• Pipe insulation: The same principles apply to pipe heating systems as to forced air systems. You will want to insulate those pipes that are exposed in unheated areas of your house.
Duct Insulation: 1. Run air through the ducts and check
for leaks by passing your hands around joists. If you find any leaks, seal
them with duct tape.
2. Without crushing the insulation, wrap the blankets around the ducts. Remember to keep the vapor barrier on the outside if the ducts are used for air conditioning in stead of or in addition to heating.
3. Where the blankets meet, and at the wrapping junctures, seal the insulation tightly with duct tape. Make sure you aren’t blocking any air intakes, and keep the tape and insulation out of contact with light fixtures, chimneys, and flue pipes.
4. Cut the insulation that reaches beyond the duct so that you have two parallel cuts, extending as far as the duct itself is high. Fold the flap of insulation you have just created over the end of the duct and tape it closed securely. Fold the two remaining ends of insulation over the first, and tape them. If you have more insulation on either flap than fits easily over the end of the duct, simply cut it off.
Cooling Systems
Logically, since insulation keeps heat in so effectively in cold weather, it ought to keep it out just as effectively in hot weather. In general it does—so to get the most significant savings possible in climates that get very hot during part of the year, it’s worthwhile insulating to keep the heat out and the cool in.
The whole purpose of insulation is to retard the flow of heat from a warm area to a cool one. So to be effective, insulation must have some heat flow to retard. In winter in most parts of the United States, there is a great deal of heat flow for the insulation to stop—temperatures are considerably lower out doors than indoors.
In summer, however, there is less heat flow to obstruct; the temperature difference between inside and outside is not as great, and sometimes (for in stance, at night) the outside temperature may even be lower than the inside one. As a result, in most parts of the United
States, insulation is more cost-effective when it retains heat in winter than when it retains coolness in summer (al though you will receive some benefit from both).
Unless otherwise noted, the following information applies to both insulated and uninsulated houses. However, for purposes of illustration, we are assuming that your house has been insulated to the recommended levels for your particular region.
• Circulation: Conditioned air is comfortable air. In warm weather, conditioning may involve dehumidifying and circulating the air.
Air that circulates evens out humidity, draws off body heat, balances temperatures even in a confined space, and freshens the surrounding air. Each of these processes makes you fee/ cooler, although none may actually reduce the ambient temperature.
Air flow in a room.
When the weather is hot, often you can condition indoor air more effectively by providing adequate ventilation than by turning on an energy-dependent air conditioner. Instead of automatically reaching for the air-conditioner switch, you might consider that a gentle movement of air through the open doors and windows of the house can go a long way toward providing indoor comfort. and this cooling air is free (as long as the air conditioner isn’t running at the same time, of course).
What Ventilation Does. SUMMER: In hot weather, proper
ventilation pre vents the attic from becoming a hot box that spills unwanted
heat down through the attic floor (even if the attic is insulated) into
the living area. WINTER: In cold weather, proper ventilation helps prevent
moisture from condensing in the insulation, structural timbers, shingles,
or on the roof.
Kinds of Ventilators: Turbine vent; Ridge vent; Roof
vent; Cupola vent; etc.
Next: Ventilation; Fans; Air Conditioners