Air Barrier Interface
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  • Know the appropriate air-vapor barrier detailing for your climate zone.
  • Take the time to coordinate air and/or vapor barrier membrane interfaces with the responsible subcontractor and suppliers. This is a potential problem area.
  • While only a few codes now require air barriers, they will become nationwide in future code cycles.
  • Frame cavity insulation improves overall thermal performance, especially with retrofit panning, but must be placed to exterior of the vapor barrier membrane.
  • If wall cavity air is expected to be cold, isolate the window frame inboard of the thermal barrier. Non-permeable air barrier membranes should “tie into” window frame perimeters inboard of the thermal barrier
  • Don’t install windows if air barriers are damaged, torn, discontinuous, or otherwise ineffective. Have the air-vapor barrier installer mark the location of studs when critical for window anchorage.
  • Don’t forget that window frames and adjacent wall substrates usually move relative to one another. This must be accommodated in interface detailing. Keep window anchors clear of the membrane system.
  • Ensure that sequence of installation is workable, and ideally, does not depend on the window installer to complete the waterproofing contractor’s work.
  • Watch out for specifications disallowing sealant in weather-resistive elements. This stricture will require special interface detailing.
  • In general, standard Wausau window and curtainwall systems will not accept secondary water from others’ work into the frame head for drainage. The wall cavity drainage system should be kept independent of window frames.
  • All parties’ respective scope of work and warranty obligations need to be clearly defined in the bid documents, and the GC or CM must “buy” the project accordingly.