Cape Town based architects KUBE recently completed a sustainable Protea packing facility in Riviersonderend. One of the methods employed towards greening the building is called TABS. Thermally Activated Building System (TABS) is a technique by which the concrete structure of a building is used for heating and cooling of spaces. Cooling through absorption of energy from the space, or heating by the release of stored energy into the space. The building’s concrete structure is thermally activated by pumping water through pipes embedded in the structure. Hot water circulates through the concrete structure resulting in heating of the space whereas cold water cools down the interior.
The thermal inertia of the concrete mass utilized also allows for “off peak” heating/cooling with advantageous electricity tariffs which has significant commercial impact. In Germany 3 out of every 10 new buildings designs incorporate this strategy from concept level. In South Africa the FynBloem Protea Packing Facility is one of only 6 commercial scale projects to have employed this system.
During winter FynBloem uses the heat generated by the refrigeration equipment of the cold store for heating the water which flows through the 540m2 floor and roof slab of the office component, thereby heating the space with virtually no help from Eskom. In summer when cooling of the occupied building space is required the refrigeration plant cools the water which circulates through the building’s concrete structure.
Due to the large exposed surface areas used when heating/cooling with TABS, the resultant cooling water temperatures are higher than conventional system requirements and the required heating water temperatures are also lower than with conventional systems, hence the terminology “low temperature heating and high temperature cooling” is commonly referred to when using TABS. This feature considerably improves refrigeration cycle efficiency (COP) and also aligns with passive system concepts of which the heat recovery concept in this particular project is a fitting example.
Free convection between the room air and heated/cooled concrete surface also means that no forced convection is required, eliminating the use of fans. The lowered temperatures of the wall, ceiling and floor surface in close proximity to occupants also allows for higher room temperatures in summer, not affecting occupant thermal comfort negatively, which reduces the Nett energy transfer requirement to and from the building space. TABS is predominantly a surface based climate conditioning system as opposed to Air Conditioning which is predominantly an air based conditioning system, thus the concept of natural ventilation perfectly combines with the greater TABS concept, enabling windows to be opened for fresh air ventilation as required by the building occupants.
You can read more about the sustainable measures which were implemented at the FynBloem Protea Packing Facility here, or you can take a look at the Cohen Residence where solar panels are used to heat the water circulating through the house.