Air Duct Systems
The air duct systems that branch through the ceiling, floors and walls are designed for around-the-clock control of the comfort level, freshness and humidity of the air in your home. Ducts provide energy efficiencies that lower your cooling and heating bills and significant comfort levels when they are properly insulated and connected. This short video provides an visual overview.
Air duct systems provide three types of venting. Exhaust air is removed and not returned; this type of venting keeps the air clean and prevents dust and moisture damage by removing cooking smoke and other airborne impurities and moisture from washing machines and bathrooms. Supply air is outside and/or recirculated air that is conditioned and delivered into the home. Return air is supply air that is either returned to the HVAC system for additional conditioning or released from the home. Venting effectiveness is dependent on duct insulation, sealant and sizes and on the the heating and air system materials.
The improvements in energy conservation, temperature control and condensation reduction in air duct systems are due to the advances in materials used in duct work. Flexible ducting connects supply outlets to rigid ductwork and works best in lengths up to fifteen feet and with minimized turns. It is round and covered with a thin layer of plastic over fiberglass insulation. Fiberglass insulating duct panels are sound-dampening and have built-in thermal insulation and can be cut into different shapes using special tools. Galvanized steel can be lined or wrapped with fiberglass insulation and can be bent and cut easily.
Insulated air duct systems reduce mildew and mold problems and increase energy efficiency. Supply ducts, if they run exposed through the conditioned space, do not need insulation. Exhaust ducts generally do not require insulation. Return air ducts should be insulated if they run through an environment that negatively impacts the temperature of the return air. The most commonly used insulation material is fiberglass. Other materials include spray foam, self-adhesive foam with aluminum foil backing, and tubular polyethylene foam.
The insulative effectiveness of air duct systems is measured in terms of R-value. R-value is a measure of heat flow resistance; the higher the R-vlaue, the higher the level of insulation. Applying duct insulation sheets can be a simple DIY project. Duct insulation thickness ranges from 1 ” to 2.5 ” and provides an R-value of approximately R-4 per inch of thickness. Recommended R-values for unconditioned areas range up to R-8 for warm and mixed climates and range from R-2 to R11 for cold climates.
