Yes when you bury ducts in attic insulation in a humid climate you increase the risk of water vapor condensation on the jacket of the duct insulation.
Ductwork buried in insuation attic.
Reduces thermal losses from ducts located in vented attics.
For buried ducts to be considered inside conditioned space the 2018 ir specifies a maximum duct leakage of 1 5 fm25 100sfcfa cubic feet per minute at a test pressure of 25 pascals per 100 square feet of conditioned floor area served by the duct system.
When hvac ducts are installed in a vented attic in any climate encapsulate the hvac ducts in attic insulation to protect them from temperature extremes in the unconditioned attic space.
But in my last article i also showed you some preliminary results from a research study on buried ducts in a hot humid climate.
Attic insulation covers buries the ducts.
If you bury attic ducts in cellulose or fiberglass insulation you need to think about summertime condensation.
Putting a furnace in an attic is not ideal but will happen.
In a hot humid climate moisture can condense on cool ducts and register boots when the air conditioning system is blowing cool air through the ducts.
Hvac ducts should be buried under insulation hard covered too.
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When hvac ducts are installed in a vented attic in a dry climate bury the ducts in attic insulation to protect them from temperature extremes in the unconditioned attic space.
Ducts buried under insulation in a vented attic is a viable builder practice option 20 ducts placed on the ceiling drywall or over the bottom truss chords.
If you re following the performance path your calculations can treat buried ductwork as being insulated to r 25 as long as it s covered by an r 19 layer of insulation in addition to the r 8 duct wrap.
Install ductwork so that it is in direct contact with i e laying on the ceiling and or truss lower cords.
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The added insulation shields the ducts from temperature extremes.
Data from doe s building america program shows buried ducts can save more energy than a home with vented attics and ccspf below the roof.
Hvac ducts buried within ceiling insulation in a vented attic buried ducts duct leakage.
Install ductwork so that it is in direct contact with i e laying on the ceiling and or truss lower cords.
They found r 8 duct insulation was sufficient to prevent condensation.
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