Balance Fresh Air, Moisture Control, and Efficiency
Healthy air in an attic conversion starts with a tight envelope and deliberate ventilation. After air sealing, choose a strategy that fits the assembly and use: a dedicated bathroom exhaust (sized by code and ducted outdoors), a continuously running low-sone fan on a timer, or a small energy recovery ventilator (ERV) to supply filtered outside air and exhaust stale air while conserving heating and cooling energy. In compact volumes where temperature swings are pronounced, pairing an ERV with a variable-speed heat pump delivers even comfort and consistent humidity.
Moisture-Smart Detailing
Terminate all exhausts at the exterior—never into soffits or the attic cavity. Use smooth, sealed ducts with short, straight runs, backdraft dampers, and insulated sections to prevent condensation. In bathrooms, add humidity-sensing controls to clear steam quickly, and specify a fully waterproofed shower with a sloped pan and continuous membrane to keep vapor where it belongs.
Filtration, Combustion Safety, and Monitoring
Choose MERV-11+ filtration on the HVAC zone serving the attic and schedule regular filter changes. If any combustion appliances remain nearby (in older homes), confirm they are sealed-combustion or properly vented, and perform a worst-case depressurization test. Add CO/smoke combo detectors, target 40–50% relative humidity, and monitor with a smart sensor to catch trends before they become problems. For planning steps and sizing tips, see our NYC attic remodeling service ventilation guide.