Air principle · radiation and convection

Cooling without a jet.

A chilled ceiling is a cool surface above your head. It absorbs heat from people, walls and equipment by radiation, and cools the air flowing past its fins by convection. Nothing blows. Ventilation has its own, smaller task: fresh air.

What the air does

Heat goes to the cold surface.

Radiation

A cold surface exchanges heat with the people and surfaces in the room. What you feel is the operative temperature: roughly the average of the air temperature and the mean radiant temperature of the surrounding surfaces (TB 69 p. 3).

Convection

Warm air rises, cools along the fins or the panel and sinks again. In open fin registers such as the SKS-4/3, radiation and convection work together (DS 4094 E p. 2).

Static

A static chilled ceiling has no fan and no primary air. A multifunction chilled sail such as AVACS combines it with an induction unit for the air supply (DS 4170 E p. 2).

When to choose a chilled ceiling

High loads, strict comfort.

High cooling load in category A. Above 50 W/m², category A is only achievable with a chilled ceiling combined with an air distribution system for the hygienic air change (TB 69 p. 3).
Silent and draught-free. Water removes the heat, so little air needs to move.
High internal loads. Offices with high heat loads, TV studios, technical and industrial rooms (SKS-4/3-duo, DS 4143 E p. 2).
Refurbishment. The SKS-4/3 has a low installation height (DS 4094 E p. 2).

When not: If the room mainly needs heating, check carefully: a warm ceiling is felt as unpleasant much sooner than a cold one (TB 69 p. 3).

Design limits

The limits from TB 69.

radiant asymmetry, categories A and B

(TB 69 table 4)

cold ceiling < 14 K · warm ceiling < 5 K
cold wall < 10 K · warm wall < 23 K

In cooling mode the 14 K limit is never reached in practice: condensation would occur first (TB 69 p. 3).

heating with the chilled ceiling

(TB 69 p. 3–4)

Normally no comfort restriction as long as the heating capacity stays below 55–65 W/m² (fig. 4)
Together with displacement: at most 50 W/m² floor (A) and 70 W/m² (B), because of the gradient
Together with mixing from the ceiling or underfloor ventilation: up to 100 W/m²

With mixing ventilation and a chilled ceiling in cooling mode, the vertical gradient stays far below the limits (TB 69 p. 4).

Type	Kind	Cooling capacity (per m² element)	Source
SKS-4/3-duo	static, above an open ceiling	216 W/m² (without modular ceiling, DIN 4715)	DS 4143 E p. 2
SKS-4/3	static, concealed or exposed	175 W/m² standard, freely suspended	DS 4094 E p. 3
SKS-5/3	static, exposed chilled sail	160 W/m² as chilled sail	DS 4105 E p. 2
AVACS	chilled sail with induction unit	up to 165 W/m² at 10 K (EN 14240); up to 80 W/m² floor at approx. 85 % coverage	DS 4170 E p. 5, p. 8
KKS-5/LD-M	contact cooling, metal ceiling	95 W/m² at 8 K	DS 4181 p. 4
PKS	cooling meanders in plaster	up to 82 W/m² active surface	presentation p. 60
KKS-3/GK	contact cooling, plasterboard	up to 75 W/m²	EB 4132 E p. 2

water

Typically 16/18 °C for the SKS-4/3 (DS 4094 E p. 8); AVACS is designed for 17 °C flow and 19 °C return at 26 °C room temperature (DS 4170 E p. 8).

Typical mistakes

Where it goes wrong.

Counting element m² as floor m². Datasheet values apply per m² of cooling element. What you achieve per m² of floor depends on how much of the ceiling is covered. For AVACS: 165 W/m² element, up to 80 W/m² floor (DS 4170 E p. 5, p. 8).
Too little free area. Above an open modular ceiling, capacity depends on the free area and coverage. The SKS-4/3-duo gives correction factors for 20 to 75 % free area (DS 4143 E p. 2).
A ceiling that is too cold. Below the dew point of the room air, water condenses on the ceiling. Flow temperature and controls must be set up for this.
Heating beyond the limit. A warm ceiling beyond 5 K radiant asymmetry is unpleasant, and with displacement the gradient increases (TB 69 p. 3–4).
A chilled ceiling without ventilation. The ceiling cools but does not refresh the air. The hygienic air change always comes from a separate air system (TB 69 p. 3).

The types in the collection

Static chilled ceilings: SKS-4/3-duo · SKS-4/3 · SKS-5/3 · SKS Slimline · SKS Alcedo

Chilled sails and multifunction ceilings: AVACS · KrantzCool · Multifunction exposed ceiling

Contact cooling and integrated systems: KKS-4-GK · KKS-3/LD · KKS-5/LD-M · KKS-3/GK · PKS · WHK-GK

Convection: DK-F (passive chilled beam) · LUVAS-S

All chilled ceilings →

Where you’ll find it

At the Luchtverkeershaven Schiphol, SKS-4/3-duo radiant ceilings work alongside Krantz linear whirl outlets WL and nozzles DW-V2 (old Peek website).

All references →

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