- Air seal ductwork using mastic/mastic tape:
- Plenum seals
- Collars to plenum
- Collars and boots to flex liner
- Seams in boots and wyes
- All flex liner to wye connections
- Air handler unit seams
- Insulate ductwork to standards set by EarthCraft:
- Unconditioned attic: R-8
- All unconditioned spaces other than attics: R-6
- HVAC ductwork installation meets EarthCraft standards (Details below):
- Fully duct all supply and return ducts
- No ducts in exterior walls or vaulted ceilings
- Install rigid ducts, or pull all flex ducts with no pinches and support at intervals ≤5'
- Ducts suspended above attic floor trusses to allow for full depth of attic floor insulation
- HVAC system and ductwork protected during construction (Details below):
- Protect all ceiling/floor registers until construction is complete
- Protect HVAC fan until construction is completed
- Pleated filter installed during construction
Poorly sealed ductwork allows conditioned air to leak both inside and outside the building envelope, reducing system efficiency. Ductwork insulation controls heat transfer and reducing the risk of condensation on ductwork by reducing the temperature difference between air within the ductwork and air surrounding the exterior.
By keeping construction dust and debris out of ductwork and the HVAC equipment throughout the duration of construction IAQ goals and system integrity are maintained.
Seal all seams, joints and connections in forced-air delivery systems using mastic paste or Butyl rubber backed foil tape (mastic tape), including but not limited to:
- Supply and return ducts
- Supply and return plenums
- Duct-to-plenum connection
- Y-splits, butt joints and boot connections
- Outdoor air intakes
- Air handler condensate and refrigerant line penetration, wire penetrations and unused holes in the air handler cabinet
- Duct tape is not a suitable sealant for ducts. Foil tape may only be used for sealing leaks at the air handler’s removable access panels and at filter access panels. Duct boots may be sealed to floor, wall, or ceiling using caulk, foam, mastic tape, or mastic paste.
- Wrap mastic tape at least two times around duct seam touching at least 1 1/2” of duct inner liner and metal collar or sleeve.
- Assemble duct board using code-approved foil tape and coat seams with layer of mastic paste covering seams by 1.5” on both sides and as thick as a nickel.
- The EarthCraft Technical Advisor will visually confirm compliance of criteria at midconstruction and final inspections.
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