Insulation is applied to ductwork to enhance thermal performance and prevent condensation and dripping. Duct thermal performance needs enhancement since air transported through a supply duct is at a temperature different than that of the surroundings. Insulation reduces the rate of thermal loss to those surroundings. Without insulation, the air would need extra heating or cooling in order to arrive at the design supply air temperature. Return air ducts only need to be insulated if they pass through environments that adversely affect the return air temperature. Exhaust air ducts normally do not need insulation. Supply air ducts may be left un-insulated if they run exposed through the space being conditioned; this arrangement also reduces system first cost.
Insulation prevents condensation and dripping from ducts. Un-insulated cold air ducts very often have surface temperatures below the local dew point. At this temperature, condensate will form and eventually drip off, causing an uncontrolled accumulation of moisture on the outside surface of the duct. Duct insulation eliminates the formation of condensate and consequently prevents rusting and staining.
Extra heating (or cooling) energy required to compensate for reduced thermal performance of un-insulated duct has a negative effect on the HVAC system’s life-cycle cost. Therefore, duct insulation always presents an optimization problem. Since insulated duct costs much more than un-insulated, the recommended air velocity becomes a key factor in optimization. For instance, a higher air velocity reduces duct surface area and thus insulation cost.
Because of the relatively small temperature differences between supply air ducts and the spaces through which they ductwork are routed, a one-inch-thick fiberglass blanket is almost always sufficient. Insulation should be wrapped around the duct’s exterior. A protective cover with a vapor barrier such as an aluminum foil, referred to as FKS, should be included in insulation specifications. Care must be exercised to protect exterior insulation integrity where insulation comes in contact with hangers, supports, and other structural members. Interior duct insulation (lining) should not be used in laboratory or cleanroom applications because the insulation tends to entrain microscopic particles into the airflow.
Special consideration must be given to ducts exposed to weather. Lagging materials or heavy metal covers over the insulation are commonly used to protect ductwork. A life-cycle cost analysis may be necessary to determine optimum insulation thickness when ducts encounter temperature extremes.
Ducts, Furnaces, & Air Handlers Belong Within Conditioned Space
Ducts, furnaces, and air handlers belong inside a house’s conditioned space. The best locations for ducts are insulated basements, sealed crawlspaces, or unvented conditioned attics. If placing ducts in these locations won’t work, they can also be installed in open-web floor trusses (in a two-story house with a centrally located mechanical room) or in some type of soffit, dropped ceiling, or chase. Continue reading
A whole-house fan is an attic-mounted fan that exhausts air from a home at night, when the heat of the day has passed and the outdoor temperature has dropped enough to feel comfortable. The main advantage of using a whole-house fan instead of an air conditioner is to save energy. A whole-house fan usually draws between 200w and 700w, in contrast to a central air conditioner, which draws 2000w to 5000w. Continue reading
Windows come in a number of different frame and glazing types. By combining an energy-efficient frame choice with a glazing type tailored to your climate and application, you can customize each of your home’s windows.
Types of Window Frames
Improving the thermal resistance of the frame can contribute to a window’s overall energy efficiency, particularly its U-factor. Continue reading
When To Vent Your Roof and When Not To
Much information has been devoted to the subject of roof venting. So much, that it’s easy to become confused and to lose focus. So let’s start with something that might sound controversial, but really isn’t: a vented attic, where insulation is placed on an air-sealed attic floor, is one of the most under-appreciated building assemblies in all of building science. A vented attic works in hot climates, mixed climates, and cold climates. It works in the polar arctic and in humid rain forests.
Executed properly it works absolutely everywhere, in every climate. Continue reading
There are plenty of excellent insulation materials on the market today. Many of these have been around for quite some time. Each of these insulations have their own ups and downs. As a result, when deciding which insulation material you should use, you should be sure to be aware of which material would work the best in your situation. Considering differences like R-value, price, environmental impact, flammability, sound insulation and other factors, here are the 5 most common types of insulation materials:
The 5 most common types of insulation on the market.
The 2016 Edition of Title 24, the California Building Standards has become effective as of January 1, 2017. The codes are revised every three years and are in conjunction primarily with the Code Change Cycle for the International Family of Codes and other Standards.