Floor Register Covers Guide

Floor register vs floor return: the basic difference

A floor register (also called a supply register) is connected to a supply duct — it delivers conditioned air into the room. A floor return (or return air grille) is connected to a return duct — it draws air back to the HVAC unit.

Supply registers carry active airflow and are more sensitive to free open area restrictions. Returns carry passive airflow and can have a slightly lower free open area without causing system problems.

How to measure for a floor register cover

The critical measurement is the duct opening size — the clear opening in the floor — not the outside dimension of the current cover. Write down the length and width of the hole, measured inside the duct collar at floor level.

The register cover you order should have a face (outer) size larger than the duct opening to create an overlap. The standard overlap is 15–25 mm per side. So a 200 × 100 mm duct opening needs a register cover with a face size of at least 230 × 130 mm.

Free open area and why it matters

Free open area (FOA) is the percentage of the register face that is actually open for air to pass through. A register with 60% FOA lets air through 60% of its face area; the remaining 40% is bar or frame material.

For supply registers, FOA should be at least 60% to avoid restricting airflow and causing pressure drop. Below 55%, you may notice reduced room comfort and possible whistling noise at higher fan speeds.

• Standard parallel bar pattern: 65–72% FOA — good for supply registers.
• Square grid (3 mm bar): 60–68% FOA — versatile, supply and return.
• Diagonal pattern 45°: 55–65% FOA — decorative focus, suitable for return.
• Decorative laser-cut patterns: 35–55% FOA — return air or decorative use only.

Material selection by room

Installation types

• Surface (overlap): cover face overlaps the duct collar, sits on the floor surface. Easiest installation, slight raised edge visible.
• Flush drop-in: cover frame drops into a routed recess in the floor so the face is level with the floor surface. Cleanest look.
• Screwed: countersunk screws through the cover frame into the floor or duct collar.
• Magnetic hold-down: no visible screws, cover held by magnets, lifted with a tool for duct access.
• Tile-in frame: frame sized to replace a cut tile, cover drops into frame — fully integrated look.

Custom sizes and lead times

Standard residential register sizes (100×100 to 400×200 mm) are available in brass, stainless, and powder-coated steel. Non-standard sizes and custom patterns are made to order and take 10–14 business days.

To order, provide: duct opening dimensions (L × W in mm), floor finish type and thickness, preferred material and surface finish, installation type (surface, flush, or tile-in), and any pattern or customisation notes.