Thermal Active Concrete

Nowadays everybody within the industry is talking about thermal comfort. There are various ways we can achieve the required level of comfort. These include: radiators, floor heating and wall heating. In the last few years comfort cooling has also become more popular. Now that new buildings require additional insulation in order to meet with current building regulations, the need for heating in a building is diminishing and the need for comfort cooling is increasing.

To achieve comfort cooling there are a number of systems available such as air conditioning, chilled beams, floor and wall cooling. One disadvantage of air conditioning is that if you want the cooling capacity to be great enough, you require a very low water temperature of around 6°C. Thereafter a large amount of air is blow into the room which could cause complaints of coldness and drafts. Floor heating and cooling is based on radiant heat; there is no moving air, therefore there are no complaints of drafts. This system has been proven effective for a number of years in The Netherlands. A new system has been in development recently: Thermal Active Concrete.

TAC takes a huge stride forward in floor heating and cooling. The system uses the thermal characteristics of the building construction. Using TAC the water is continuously pumped through the system, resulting in the entire construction being heated or cooled, thereby storing energy within the concrete mass. The floor temperature will remain constant and with only a slight difference to the room temperature.

The TAC system will often be used in combination with ground source heat pumps and. These ground sources can be of various types: closed source, open source, dual source or mono source. Each option will exchange energy between the ground and the water system.

An additional advantage of TAC is the self regulating effect. This effect will work only when the temperature difference between the floor and the room is 3°C or less. If the temperature differs by more than 3°C the self regulating effect is negated. This self-regulating effect automatically adjusts the heating or cooling capacity of the system when the internal heat load is altered, for example when additional people enter a room or additional computers are switched on. Itis possible that a particular room could be cooled whilst the primary energy source is set on low temp heating or the other way around when the primary energy source is set on high temp cooling.

When designing TAC, it must be taken into consideration that the floor temperature must be close to the room temperature. To achieve this you need relatively very low water temperatures for heating and relatively very high water temperature for cooling. For example: 24 - 28°C for heating and 18 - 22°C for cooling.

Because of these low water temperatures for heating, the boilers or heat pumps required will be smaller than with traditional systems. This means that the system will be more energy efficient, lowering the cost of the consumer’s energy consumption. It’s even possible to use free cooling. With free cooling the heat from the ground source can be directly mixed with the cold water return. This will result in a flow temperature of approximately 18 degrees.

Also the method of building is different from traditional systems. Firstly, the system has to be installed at a very earl stage of building, because the system must be installed in the middle of the concrete mass. Secondly, the system uses radiated heat from the floors and the ceilings, so lowered or suspended ceilings cannot be used. This means that the ceilings must be acoustically coated or other acoustic solutions must be used, without increasing the insulation-value between the room and the tubes.

With the regulation strategy there are a couple of differences between floor heating and radiators. Compared with other traditional systems, it is not possible to regulate individual room temperatures. Therefore the system often does not get the trust of people that it actually deserves. Actually it is not necessary to regulate the temperatures manually, because TAC regulates its own capacity when the room temperature changes. Because the water temperature is close to the room temperature, the system is very slow and gives a lower capacity than other systems. This can be solved by using a preheated or pre-cooled air ventilation system. The air ventilation system can also be used to make small changes in room temperatures.

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