#730: Septic Fix, Insulating a Cape, and Ducts in Plenum Trusses

Prioritize air sealing over excessive insulation levels in attic knee walls, as air leakage is often the primary cause of comfort and energy issues.

For Cape Cod-style homes with knee walls, consider removing the knee walls to extend the thermal boundary to the roof line for more effective air sealing and insulation.

When using spray foam insulation in attics, ensure proper ventilation and be aware of potential warranty limitations from shingle manufacturers if an unvented assembly is chosen.

Plenum trusses are a viable solution for running HVAC ducts in slab-on-grade homes or where attic conditioning is not desired, but require early coordination with HVAC, truss, and general contractors.

If using a smart vapor barrier with plenum trusses, plan for future air barrier connections and ensure adequate space for taping at corners to maintain airtightness.

For can lights in ceilings with air barriers, use recessed fixtures designed not to penetrate the ceiling plane, and ensure sufficient strapping depth for wiring clearance to meet code and electrician comfort.

When introducing innovative building techniques to a contractor, share relevant resources (e.g., podcasts, articles) and communicate your thought process clearly to foster collaboration and comfort with new methods.