A frameless ventilation valve has no visible rim: the body is plastered into the ceiling and the face finishes flush. Sizes, airflow rates, Part F duties and how to install one.

Eight free, browser-based HVAC tools worth bookmarking — cooling load, Part F ventilation and duct sizing calculators, refrigerant pre-charge, silencer selection, psychrometrics and more. No login needed.

Acoustic Box (GTG) or Thermo Box (VTBOX)? How Ventmann’s two plenum boxes differ — top entry vs side entry, noise reduction vs insulation — and which one your linear slot diffuser needs.