Plenums & Air Returns — Design, Fabrication & Installation

Balanced airflow starts at the plenum and returns. We build and install tight, properly sized supply plenums, return plenums, and return drops so your furnace or air handler can move air quietly and efficiently.

Why it matters

• Even room temps: correct return sizing stops “starved” systems and hot/cold spots.
• Lower noise: smooth transitions and lined plenums cut grille hiss and vibration.
• Efficiency & equipment life: proper airflow keeps static pressure within the manufacturer’s spec and prevents overheating or icing.
• Cleaner air: sealed returns stop dusty attic or crawl air from being pulled into the system.

What we install

• Custom sheet-metal plenums matched to the unit outlet/inlet
• Return drops and trunks with smooth transitions, no abrupt “speed bumps”
• High-capacity filter cabinets (4–5″) for MERV 11–13 with low pressure drop
• Sealed connections using mastic and UL 181 tape; insulated exterior in unconditioned spaces
• Acoustic lining near the air handler to reduce blower noise where it helps
• Additional returns and larger grilles where airflow is limited

Installation process

1. On-site assessment: measure equipment airflow needs, check duct static, map existing returns.
2. Design & sizing: lay out supply/return geometry to hit target CFM with smooth transitions and correct filter area.
3. Fabrication: shop-built metal plenums and fittings sized to your equipment.
4. Professional install: set and seal plenums, fit filter cabinet, add/resize returns, strap and insulate as required.
5. Test & balance: verify static pressure and room airflow, adjust dampers, provide a simple report and filter sizes.

Signs you may need new plenums/returns

Whistling or roaring at grilles • Dusty home or musty return air • Rooms never reach setpoint • Burnt or collapsed filters • High blower speed with weak airflow • Visible leaks or tape peeling at the plenum.

Schedule a technician for an on-site assessment and a written installation plan: 510-400-6425.