FAQ

TermoDeck is used in buildings constructed using pre-stressed Hollowcore floor slabs. It is preferable to bring in TermoDeck at the initial stage of the design process. Since the system needs to be integrated with the structure it is obviously simpler and cheaper for the original Client’s design to be based on TermoDeck since this avoids abortive work. We have however frequently re-designed buildings successfully to produce a lower cost solution despite the need to recover the additional design costs.

One substantial advantage with TermoDeck is the layout flexibility. Since there is neither any duct work nor any false ceilings (normally) in the rooms, partition walls can be moved around easily. TermoDeck is very favourable for open landscape since the system is built in modules (every slab has one diffuser). To change the interior layout is easy with TermoDeck as you just need to put up the walls in new locations. Often the internal heat gains are changed which leads to a re-balancing of the air flows. For a conventional system, they need to supply each room with new ductwork and remove and put back the false ceilings again, a major operation. In TermoDeck, the ductwork is already there in form of the slabs. We strongly recommend a visit by a trained TermoDeck engineer to ensure that the system is properly balanced before occupation.

TermoDeck makes the drilling drawings. In some cases TermoDeck can also take the role as the mechanical consultant, then the TermoDeck team will do all the mechanical design.

In a hollow core slab, there are normally five cores, sometimes four or six cores. Three are used for TermoDeck. So there are 1-3 cores which can be used for electricity cables and other pipes such as sprinklers. Cables are often placed in the top screed on top of the slab (A screed of 50mm site-cast concrete is typically used in most markets to finish the top surface. This is done in the same way as for all buildings using hollow core slabs. Sprinklers can be placed under the slabs. If the architect doesn’t want them to be exposed they can be hidden above a false ceiling (See item 1 about false ceiling requirements) or in the wall facing the corridor.

Yes, TermoDeck can be used for sky scrapers. In Sweden, there is the Infra City hotel & office complex, over 30 floors high. TermoDeck was one of the proposed designs for a building more than 500 meters high in Dubai, called the Lighthouse.

TermoDeck has not been used so much in apartments since the internal loads are smaller and the benefits will be more limited than for commercial buildings, schools, hotels, theatres, etc. From 2008, the new building regulations within EU require heavily reduced energy consumption in new buildings. There has been interest from several clients to use TermoDeck in residential buildings, such as passive houses, as they now need to use more energy-efficient ventilation systems to meet the new standards.

To achieve a high ventilation and cooling effectiveness when the floor-to-ceiling height is high it is often better to let the supply air enter the room at low level (so called displacement ventilation). TermoDeck works very effectively when combined with Displacement Ventilation. The cooled supply air is getting warmer when passing the hollow cores in the slab, ensuring that the air entering a room at floor level will be only 1-3°C different from the room temperature. Conventional systems have experienced problems with draughts when using displacement ventilation because of the high supply air flow needed (as the supply air shouldn’t be below 17-18oC to avoid discomfort). There are several buildings with TermoDeck used together with displacement ventilation. In UK, for instance, there are over ten buildings, for example some theatres.

The benefits of TermoDeck will be limited in buildings with a lot of glazing due to the very high heating and cooling load needed. However, there are TermoDeck buildings equipped with one fully glazed facade and they all have a comfortable indoor climate.

Yes: There are measured data from Sweden, UK and Middle East

• Swedish buildings from the late 1980s have an energy consumption of between 30-50 kWh/m2 and year for heating. New building regulations will improve this value in new buildings. (In Stockholm, the degree days are 3570, 239 days of heating season and average outdoor temperature = 6.7oC)
• UK; Elizabeth Fry Building is one of the most energy efficient buildings in UK. The heating consumption has been measured for over ten years and it is around 25-30 kWh/m2 and year. See also Table 1.
• Middle East: A report carried out in 2005 by ASA Consulting[2] showed that TermoDeck would save around 40% in running costs compared to conventional HVAC systems. The installed cooling capacity would be reduced by around 50%. See table 1 above:

Yes. The fan is smaller in TermoDeck but it runs for a longer time. The total running cost for the fan might be similar compared to conventional air-cooled HVAC systems but the fans will be using off-peak electricity for much of the time. Since the installed cooling load and electrical power needed is around 50% smaller, the fan will also be reduced by 50% making the capital cost lower for the fan. When local cooling devices are used, such as chilled beams and fan coils, the fans are often smaller as the supply air is only used for ventilation purposes and the cooling is achieved via chilled water. The fans can therefore consume more energy than water-cooled HVAC systems. In both cases, the total energy consumption will still be smaller for TermoDeck as the free night air is used to cool the building and the stored heat in the slabs is keeping the building warm during winter.

The supply air flow for all individual rooms will be balanced when commissioning the system according to the thermal modelling carried out by TermoDeck. There are some ways to control air flow for every room or zone:

• Zone Control: Dampers and/or heating coils in the supply air ducts can be used for a number of rooms forming a zone, for example a southern façade of an office. Such zones can then be controlled individually.
• Individual Room Control, Cooling: The airflow can be regulated by using dampers in rooms with temporary higher internal heat gains such as large lecture theatres, conference rooms and seminar rooms. To achieve instant cooling we have developed a system called Switch Flow. By pushing a button (or driven via thermostat) the cooled air will only pass through one core and therefore it will enter the room at low temperature. Switch Flow doesn’t increase the energy consumption as the cooling is just delivered directly to the room rather than via the slab. Another alternative is to use direct airflow not passing through the slab.
• Individual Room Control, Heating: The temperature can be controlled in each room by using small electric heaters (150-200W) (often placed under the windows).

The idea with TermoDeck is to even out the temperature differences between the rooms by using the thermal mass of the slabs and preferably also the internal walls. If individual control is required for all rooms, local heating/cooling systems might be necessary to implement. TermoDeck International engineers can advise.

This depends on factors such as the outdoor climatic conditions, the building envelope and the internal heat gains. With TermoDeck it is often possible to achieve a comfortable indoor climate even if no chiller is used in temperate and cold climates such as in UK and Northern Europe. Even during winter in cold climates, TermoDeck has shown that very little heating is needed due to its capacity to store the internal heat gains. For extended periods of un-occupancy, heating must always be installed. In warmer climates the supply has to be cooled.

For conventional systems there are often problems with noise and draughts. TermoDeck is silent (since the slabs act as very efficient silencers) and with no draughts.

There is no condensation on the slab surfaces since the temperature of the surfaces of the slab only differs from the room temperature by a few degrees and should never be less than 19-20oC. There is no big difference from a normal air-cooled HVAC system. It is more important to insulate the steel ductwork properly as the surface temperature of the duct will be around 16-17oC (if room temp is around 22-23oC). In some cases in humid climates, a dehumidifier is used separately. However, in a hot and humid climate, condensation can occur in any building if the doors and windows are kept open and the outdoor air is entering the building.
TermoDeck buildings are operating in hot and humid climates such as Dubai and Jeddah (Saudi Arabia) since many years without any condensation problems.

This will be handled in the same way as in conventional systems. Normally, a hole with a grill situated in or above the door is used. Either horizontal return air ducts are used or the area above the false ceiling in the corridor is used as a plenum.

TermoDeck works very well together with district cooling as the cooling load is spread out over 24 hours. The peak in cooling load can be avoided.

It is very favourable to use TermoDeck together with district heating as TermoDeck is a low-temperature heating system (the supply air temperature is not higher than 35-40 oC as the room is heated by the ceiling and floor surfaces acting as very large radiators). The return water flow can be used which otherwise is not used. This also increases the efficiency of the district heating system and it is therefore possible to achieve a lower price from the district heating supplier.

Yes. IDA ICE is one of the most powerful simulation programs in the world today. We have developed a TermoDeck application, called IDA ICE-TD which is based on theoretical and empirical data for the behaviour of the interaction between the slab, the supply air and the room.

Details of structural connections between support beams and Hollowcore slabs are usually little affected by the TermoDeck design but are rather a question for the structural Engineer.
We have available experienced structural engineers who are familiar with design of connections for pre-cast concrete buildings and who can assist with the development of suitable construction details for specific projects.

Use of pre-cast, pre-stressed, Hollowcore floor slabs are recommended for a TermoDeck building but a variety of frame or wall-panel support structures can be used, including: steel, site-cast concrete, Half PC, PC or brickwork.

Hollow core slabs are manufactured using steel moulds which should provide a high quality and smooth soffit (bottom) finish suitable for paint decoration at site.

Pre-stressed Hollowcore floors are manufactured using long-line steel production beds and an extrusion process. High strength 7-wire pre-stressing strand reinforcement is used.

This depends on the architect. Normally they leave it since the slabs sit tight to each other. Then the joints will be visible. If the architect wants to change this, there are several alternatives that can and have been used.

• Plastering: If the joints shall be plastered at the soffit it must be carefully done using the proper material and handling to avoid cracks in the plaster. See item 28.
• Painting: A stipple (textured) paint finish on the ceiling to avoid cracks to be visible
• Leave a gap between the slabs: For instance, the lighting has been placed between the slabs so the lights are flush with the slabs.

Longitudinal joints between Hollowcore slabs are to be filled with a sand-cement mortar from the top. This is needed for structural purposes.

No, not in the slabs. The slab has to be properly made and dried out before painting. This is normal practice everywhere where hollow core slabs are used.
Thermal movements may produce very fine cracking at longitudinal joints between slabs. These are of no structural significance and are not noticeable if the joints are left unfilled. For commercial projects, this is the normal procedure.
If the architect/developer choose to fill the joints (flush filled) it is advisable to use a stipple (textured) paint finish on the ceiling to avoid cracks to be visible.

Hollowcore slabs are manufactured using high strength concrete and are not damaged structurally by installation of suspension-straps and they can be shot-fired into the soffit of the hollowcore slab. We can offer advice with this in connection with specific projects.

[1] TES = Thermal Energy Storage
[2] Schultz T. ASA Consulting (2005) “Market Study: Thermal Energy Storage AC Systems in Saudi Arabia”, commissioned by British Offset. Address: PO Box 238 Cobham Surrey KT11 2WP England. Phone: +44 1372 844 317 . Email: asaconsult@btinternet.com