How a Hidden Slot Diffuser Works: The Flowbar Air Path Explained
A hidden slot diffuser such as the Goodwind Flowbar supplies air through a narrow opening built into a ceiling shadow gap or reveal. How the air path works and how it differs from trimless and visible slot diffusers.
A hidden slot diffuser, such as Goodwind's Flowbar (model GT-H-SLT), supplies air through a narrow linear opening built into a ceiling shadow gap or reveal, so the ceiling shows a clean architectural line instead of a visible diffuser face. As with linear slot diffusers generally, the supply air reaches the slot from a duct or plenum behind it.
Flowbar at a Glance
| Item | Detail |
|---|---|
| Product | Flowbar (hidden type slot diffuser) |
| Model | GT-H-SLT |
| Manufacturer | Goodwind Technologies Private Limited, Coimbatore, Tamil Nadu, India |
| Material | Aluminum |
| Finish | Powder coated, anodized, or custom colors |
| Mounting | Integrated into a ceiling shadow gap or reveal detail |
| Typical use | High-end architectural ceilings where the diffuser must stay visually concealed |
What Is a Hidden Slot Diffuser?
A hidden slot diffuser is a linear air supply terminal designed to blend into an existing ceiling detail. The Flowbar is the hidden type: instead of presenting its own visible face, it works with a shadow gap or reveal line already in the ceiling design, so the supply air reads as part of the architecture rather than as a separate fixture.
How Does Air Move Through a Flowbar?
The steps below describe how linear slot diffusers work in general. Confirm the connection and plenum arrangement for the Flowbar with Goodwind.
- Conditioned supply air arrives through a duct connection behind the slot.
- A plenum, the chamber behind the slot, is normally used so the air spreads along the full length of the opening instead of rushing out at the connection point.
- The air passes through the narrow slot, where its speed is higher than in the plenum behind it.
- The shadow gap or reveal hides the opening, so the room sees a line and not a fixture.
- The supply air mixes with the room air and conditions the space.
Goodwind also makes plenum boxes, covered in our ductwork accessories guide. For the airflow arithmetic, see how to size a Flowbar diffuser.
Why Does the Shadow Gap Matter?
The Flowbar's position is dictated by the architectural line, not the other way around. The design team fixes the shadow gap or reveal first, and the diffuser sits within it. Because the product is built to integrate with a specific detail rather than a standard ceiling grid module, the exact reveal dimensions need to be confirmed before ordering. Our Flowbar installation and coordination guide covers who agrees what, and when.
How Is a Flowbar Different From a Trimless or Standard Slot Diffuser?
| Feature | Standard slot diffuser | Flowbar | Trimless slot diffuser |
|---|---|---|---|
| Model | G-SLT | GT-H-SLT | GT-T-SLT |
| Visible metal at the ceiling | A visible linear face | Almost none; it hides in a shadow gap or reveal | None; the plaster finish runs up to the opening |
| Installation detail | Visible linear element | Integrated into an existing reveal detail | Built into the ceiling structure before the final plaster coat |
| Best fit | A visible linear look is wanted | The ceiling design already has a shadow gap or reveal | A completely seamless plastered ceiling is wanted |
What Should You Check Before Specifying a Flowbar?
For MEP Consultants at the Design Stage
Fix the Reveal Detail First
Agree the shadow gap or reveal on the architectural drawings before placing any Flowbar, since the diffuser follows that line.
Ask for the Plenum and Connection Arrangement
Confirm with Goodwind how supply air connects behind the slot, and show the connection points on the MEP drawings.
For Contractors at Procurement Stage
Confirm Reveal Dimensions and Finish
Check the exact reveal dimensions and the finish against the architectural drawings before ordering.
Plan Access Before the Ceiling Closes
A concealed diffuser is harder to reach once the ceiling is built, so mark access points on the drawings while the ceiling is still open.
FAQ
What is a hidden slot diffuser?
A hidden slot diffuser is a linear supply air terminal that integrates into a ceiling shadow gap or reveal so that almost no fixture is visible. Goodwind's version is the Flowbar, model GT-H-SLT.
How does a Flowbar diffuser work?
Supply air reaches the slot from a duct or plenum behind it, passes through a narrow linear opening hidden in the ceiling detail, and mixes with the room air. Confirm the connection arrangement for the Flowbar with Goodwind.
What is the difference between a Flowbar and a slot diffuser?
A standard slot diffuser has a visible linear face as part of the design. A Flowbar is built to disappear into a shadow gap or reveal, so the supply reads as part of the ceiling detail.
What is a Flowbar made from?
Goodwind makes the Flowbar from aluminum, finished in powder coat, anodized, or custom colors to match the project.
Does a Flowbar need a plenum?
Linear slot diffusers are normally fed from a plenum or duct connection behind the slot so the air spreads evenly along the opening. Confirm the arrangement for the Flowbar with Goodwind.
About Goodwind
Goodwind Technologies Private Limited is an HVAC air distribution products manufacturer based in Coimbatore, Tamil Nadu, India. Its range includes grilles, diffusers, louvers, dampers and ductwork accessories. Contact Goodwind for project enquiries.
Last reviewed: October 2026.