The principle of BATISO
The principle is as simple as it is effective; the solid concrete ceilings of the building are charged overnight to keep them at a controlled temperature by means of water flowing through the plastic pipe coils embedded in the concrete floor slab.
Control is achieved by regulating the temperature of the circulating water such that the rooms are heated by the ceilings in winter and cooled by them in the summer. Depending on the season and the specific conditions in the building, the required water supply temperatures lie between 16°C (summer) and 26°C (winter).
The better the thermal insulation of the building, the more evenly the temperature of the thermo-active ceiling can be maintained. 60% of the heat exchange between the tempered concrete ceiling and the interior of the room is by radiation. In this way, thermal conditions are provided throughout the year, which are perceived by the occupants as very comfortable.
BATISO Concrete Core Tempering system comprises a series of regularly spaced pipes formed into coils attached to a metal grid and integrated within the neutral zone of the concrete slab. Low temperature hot water for heating or high temperature chilled water for cooling is circulated through the slab in order to in order to add or remove heat from the concrete structure.
Heated or chilled water is provided to the zones either by conventional means such as hot water boilers and refrigeration machines, or alternatively the BATISO system is an ideal compliment to geothermal systems where, for example, cooling can be provided directly from the ground source utilising ‘free’ cooling and heating from a ground source coupled to a heat pump.
Control of the BATISO system so that the rooms can be heated in winter and cooled in summer, dependent of course upon the specific load profile, is achieved by varying the temperature of circulating water. This is typically between 18°C summer and 25°C winter in accordance with the design recommendations of THERMIE.
The concrete core activation system can be controlled to provide a specific working environment at the commencement of occupation but should the outdoor conditions for example in summer increase throughout the working period, then the space temperatures will, by maintaining a differential temperature, slowly increase according to the outdoor condition to maintain an acceptable differential.
Room environmental conditions are typically controlled with all air systems on the dry bulb temperature. Maintaining a specific dry bulb temperature does not necessarily result in acceptable comfort conditions, as comfort is also a function of the relative humidity and the mean radiant temperature of the surrounding surfaces.
The concrete core activation system varies the surface temperature of the exposed concrete thereby exchanging heating and cooling between the various room surfaces mainly by radiation (+/-60%), and hence controlling the mean radiant temperature of the occupied space and hence providing higher levels of comfort.
Relative Humidity can be controlled by the addition of an outdoor air ventilation system if desired.
ECON 19 suggests that for a typical standard office building the delivered energy for cooling, fans, pumps & controls, would be in the order of 90-100kWh/m2 per annum.. Experience in Continental Europe is providing typical figures in the order of 25-40kWh/m2 per annum.
Water based Concrete Core Tempering Systems can be typically applied to buildings having moderate heat gains typically up to 60 W/m2 and heat losses of up to 50 W/m2.
Such buildings will have a defined operating period generally not more than 9 hours per day to allow the cycling effects of the storage to take effect.
Concrete Core Tempering is not suitable for areas having a high continuous cooling load, for example in IT rooms.
The application of Concrete Core Tempering projects require from the outset a close team effort between the architect, mechanical consultant, structural engineer and installing contractors and of course the chosen manufacturer to realise a successful project.
Once it has been determined that a Concrete Core Tempering System is to be installed the basic engineering sequence associated with the system will be as follows:
- Determination of the zoning and associated heating and cooling loads
- Defining the available areas for the coils to suit the structural constraints
- Calculation of the cooling circuits to match the zoning requirements
- Laying out of the coils on the construction plans
- Design of the interconnecting pipe work between the coils and the chilling and heating plant.
Fully proven design software is important to ensure the selection and operation of the system.
Water based concrete core cooling systems have been installed successfully for many years. In the UK, we have successfully completed the following projects:
- Keeble College
- Latymer School