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Article # 1 -

Room conditioning with conventional HVAC systems in combination with the capillary tubing system

written by : the author of this page Dipl.-Ing. Frank Schleifenbaum

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Article # 2

written by : Prof. Dr.-Ing. Helmut E. Feustel VDI, ASHRAE,

To cool or heat rooms, cold or warm water flows through the tubes of the capillary mats. The room surfaces equipped with these mats are evenly cooled or heated and heat is quickly carried off or is quickly delivered.

When cooling, the surface temperature is approximately 19°C (66°F) at a water flow temperature of 16°C (61°F). Depending on the installation, a cooling capacity of up to e.g. 95 W/m² (30,1 BTU / ft²) can be achieved depending on the correspondent room temperature of  26°C (79°F) and relative air humidity of 48%.
Taking away the cooling load this way the former necessary hourly air change is dropped from 4 or 5 times per hour (or higher)  to an air change of 2 or 2 1/2 times per hour. The HVAC never more carries the cooling load, it only guarantees (A) the hygenical air change and (B) the percentage of air humidity - which (A + B) is a must.

For heating, water at 26°C (79°F) to 28°C (82°F) flows through the same system. The surface temperature of the ceiling in this case is approximately 25°C (77°F) . Therefore, the energy radiated from the surface of the human skin (temperature 32°C / 90°F) is conveyed to the ceiling even when heating. Investigations have shown that up to a capacity of about 40 W/m²  (12,7 BTU / ft²) no loss in comfort needs to be feared when rooms are heated via the ceiling. If higher performance is required, additional capillary mats can be installed in walls or floors, or the flow temperature can be increased during the times when the rooms are not in use.

In commercial and industrial buildings, capillary tubing systems are usually used in combination with a supporting ventilation which carries off material and delivers fresh air. With the aid of such ventilation, the ambient air humidity can be adjusted to 40-50% relative humidity, which people find very comfortable.

For cooling and heating of houses and renovation of old buildings we recommend to preferably equip ceilings and external walls with capillary mats. Using this method there are no restrictions in connection with wooden floors, carpets, etc.

Of course, capillary tubing systems are very well suited for floor heating as well. The mat usually is installed just millimeters below the surface of the floor pavement. Consequently, the heat can be felt just a few minutes (usually less than 30 min) after switching on the floor heating. Capillary floor heating systems are extraordinarily thin. If a special film is put on top of the insulating layer, the installation height is only 15 mm  = ca. 9/16".
The function of the possibly necessary HVAC is the same like before when cooling - the only difference is that it never more carries the heating load.

Resume:
Thanks to the large exchanging surfaces, large amounts of energy can be transmitted between the active room surfaces and the room air even at small differences in temperature.

In modern commercial and industrial buildings, capillary mats are preferably installed in the ceiling.