What are some recommended strategies for ensuring that system leakage is below 10%?
To the extent possible, design the system to have as few connections as possible. Make sure that the duct liner is sealed to takeoffs and supple boots. Seal all corners of the plenums and connections between the plenum(s) and air handler with 181 tape and/or mastic. Use air-tight or duct board supply boots; if using crimped boots, the seams must be sealed. Exercise care in handling duct board assemblies – even small holes in the outer surface can leak air. Seal all penetrations in the air handler and coil housing. Some air handlers are built to tighter tolerances than others, so seek out models that are known to be less prone to leakage.
