![]() Air leakage may return if your ducts shift and crack the mastic duct sealing, or you have to move them. Getting mastic into cracks and crevices can be challenging, if not impossible. It can be difficult to know if you’ve blocked all leakage after you’ve painted it on. Mastic, on the other hand, is a permanent solution that won’t degrade or lose adhesion. Tape is a popular and affordable choice, but its main drawback is that it breaks down and loses adhesion over time. You have a couple of options for air-sealing ducts in the attic: tape or mastic. That’s a lot of cooled air you’re missing out on that your HVAC system has to replace. ![]() Department of Energy estimates that the average home loses up to 30% of airflow because of leakage. A horizontal air handler keeps the supply ducts close to the floor where temperatures are lower. Vertical air handlers raise the supply ducts higher, where the air is warmer. Most air handlers are installed vertically, but horizontal installation can improve your air conditioner’s efficiency. Ducts located between floors, in dropped ceilings, or in a sealed and insulated basement, crawl spaces, or attic will be cooler and more efficient. Installing ducts in conditioned air spaces is one of the most efficient options if it’s reasonably possible. The hottest areas are up close to the roof deck, with the temperatures dropping the closer you get to the floor.Ī duct system in an attic can be insulated with the same insulation used for the attic floor to reduce heat transfer. On a typical summer’s day, the interior of an unconditioned attic can reach temperatures of around 120 degrees Fahrenheit or higher. Install your ductwork close to the floor to keep it separated from the warm air. It’s difficult to fathom why some construction companies run duct work by strapping it directly to the roof deck. If you want to understand how hot it can get up there, try holding your hand against it around midday. The underside of the roof is always the hottest part of the attic on a warm, sunny day. Heat is transferred across a greater volume of air to reduce the heat gain across each cubic foot. Increasing air flow velocity might be a reasonable trade-off. Unfortunately, the longer that HVAC-cooled air stays inside your ducts, the more radiant heat it will absorb. Slower moving cold air is preferred because it reduces airflow resistance. Check your work to make sure there aren’t any gaps that could allow moist air to penetrate the insulation and cause condensation. Use metallic foil duct tape recommended by attic insulation professionals to seal the insulation and hold it in place. Use a square and utility knife to cut the sheets to size so they fit around the duct without needing compression. You can wrap fiberglass insulation around your ductwork. In IECC climate zones 1A, 2A, and 3A, the building code allows you to bury your ducts in insulation. If you live in a dry climate, you can cover the ducts with blown attic insulation. Standard duct insulation is available, but only to R-8. While many people insulate their attics, the heating and cooling ductwork is often neglected. However, there’s no barrier to prevent heat transfer into the interior of your ductwork if it’s not insulated. Insulation prevents a lot of heat transfer into your home through the ceiling. Insulate the Air Ducts and Air HandlerĪs the sun heats up your roof, the roof cavity will reach temperatures much hotter than outside. Once installed, radiator barriers use no added energy or resources and are compatible with other duct improvement methods. Trapped heat will eventually radiate into your home and make your HVAC work harder.Ī radiant barrier is a reflective surface that bounces radiant heat out of your attic back out into the atmosphere. The stored heat is then released into an already warm interior, making it hotter than the outside ambient temperature. Radiant heat is heat absorbed by materials inside your attic, including insulation. So, what options do you have when you have HVAC ducts in a hot attic? The following strategies will improve your ductwork and increase your home’s energy efficiency. Leaky ducts waste cool air and will increase your energy bill.Īn obvious strategy would be to air condition the attic, but that isn’t always possible and can be expensive. Ducts traveling through an attic are inefficient and can add as much as 25% to the cooling load of your HVAC system.
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