📏 Required Panel Area
🌡 Condensation Margin
Sizing Breakdown
Full Calculation Table
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How to Use the Radiant Ceiling Calculator
Choose cooling or heating mode for the panel calculation. Most radiant ceiling systems in Canadian offices operate primarily in cooling mode, with perimeter heat handled by a separate system.
Enter the zone sensible load the panels need to offset and the ceiling area available for panel coverage, accounting for lighting, sprinklers, and diffusers that reduce usable panel space.
Enter the room dry-bulb temperature, the room dew point maintained by the DOAS, and the panel water supply and return temperatures.
Click Calculate Radiant Ceiling Sizing to see required panel area, panel surface temperature, and condensation risk margin.
Understanding Radiant Ceiling Panel Sizing
Radiant ceiling panels cool or heat a space by exchanging radiant energy with room surfaces and occupants directly, rather than blowing conditioned air through ductwork. Chilled water circulates through tubing bonded to a metal ceiling panel, and the cool panel surface absorbs radiant heat from the room. This approach handles sensible load only, which means every radiant ceiling installation needs a dedicated outdoor air system to manage humidity and ventilation, and it changes the comfort calculation in ways ASHRAE Standard 55 accounts for through its radiant temperature asymmetry provisions.
Why Panel Capacity Is Lower Than a Conventional Coil
A chilled ceiling panel typically delivers 40 to 65 watts per square metre of sensible cooling within condensation-safe operating limits, well below what a conventional air-side coil achieves in the same floor area. The trade-off is comfort: radiant cooling avoids the drafts and noise of high-velocity air distribution, an advantage worth confirming against the NC curve calculator for spaces with a strict acoustic target, and many occupants perceive radiant-cooled spaces as more comfortable at a slightly higher room temperature. The office HVAC calculator compares radiant systems against all-air alternatives at the whole-building level.
Condensation Risk Is the Central Design Constraint
Because the panel surface sits below room air temperature, it can drop below the room's dew point and collect condensation, the single biggest risk in radiant ceiling design. Most designers keep panel surface temperature at least 1 to 2 degrees Celsius above the expected dew point, worked out with the dew point calculator from the room's actual temperature and humidity, and many systems tie panel water supply temperature to a dew point sensor that raises water temperature automatically if humidity climbs. Getting the DOAS latent capacity right, covered by the DOAS calculator, matters as much as the panel sizing itself.
Water Supply Temperature Trade-offs
Radiant ceiling cooling commonly uses water supply temperatures between 14 and 18 degrees Celsius, well above the 6 to 7 degrees Celsius typical of conventional chilled water coils, a comparison the ASHRAE Handbook, HVAC Systems and Equipment volume covers in its panel heating and cooling chapter. This warmer water reduces condensation risk and allows more efficient chiller operation, sometimes even direct free cooling from a cooling tower on mild days, but it also means panels need more surface area to deliver the same total capacity. The chiller plant calculator covers central plant sizing for a radiant ceiling water loop.
Ceiling Coverage and Layout Constraints
Available ceiling area rarely equals total floor area once lighting fixtures, sprinkler heads, diffusers, and access panels are accounted for. Most projects achieve 50 to 70% panel coverage of the ceiling plane, so confirming the required panel area fits within the realistic coverage limit is an essential early design check before committing to a radiant ceiling approach for a given space.
Frequently Asked Questions
A typical chilled ceiling panel provides roughly 40 to 65 watts per square metre of sensible cooling within condensation-safe operating limits, depending on the water supply temperature and the difference between the room air temperature and the panel surface temperature. Higher water temperatures reduce capacity per panel but also reduce condensation risk, so most designs balance the two rather than maximizing capacity alone.
Radiant panels handle sensible heat only and do not remove moisture from the space, so a parallel dedicated outdoor air system with its own cooling coil must handle all latent load and ventilation air. Without this pairing, indoor humidity climbs uncontrolled and the risk of condensation on the cool panel surface increases significantly. See the DOAS calculator to size this companion system.
Condensation forms whenever the panel surface temperature drops to or below the room air's dew point temperature. Most radiant ceiling designs keep the panel surface at least 1 to 2 degrees Celsius above the expected dew point as a safety margin, since local humidity spikes or sensor lag can otherwise trigger surface condensation even when the design point looks safe.
Radiant ceiling cooling typically uses a water supply temperature between 14 and 18 degrees Celsius, noticeably warmer than the 6 to 7 degrees Celsius used for conventional chilled water coils. This warmer water reduces the risk of the panel surface dropping below the room dew point and allows higher-efficiency cooling equipment, but it also means panels need more surface area to deliver the same total capacity as a conventional coil. See the chiller plant calculator for central plant sizing.
Related HVAC Tools
Required latent capacity pairing
Central plant serving the panel loop
Whole-building system comparison
Alternative perimeter terminal
Alternative low-velocity system
Room dew point reference
Central air handling alternative
Zone load inputs for this tool