While standard HVAC systems enjoy the edge when it comes to improving indoor air quality and achieving rapid reductions in indoor temperatures, mounting evidence shows that radiant cooling is the best option for buildings in terms of efficiency and cost.
Radiant cooling involves the use of temperature-controlled surfaces to reduce indoor building temperatures via the process of radiant exchange.
The cooler surfaces absorb the heat harboured by any physical objects within their direct line of light, while can also reducing indoor air temperatures by means of convective transfer.
Radiant cooling or heating systems generally consist of pipes installed beneath or behind the floors, walls or ceilings of a building. These pipes regulate their surface temperatures via the channelling cooled or heated water using pumps and control valves.
Forced air systems, more commonly known as HVAC systems, make direct use of air flow as their chief medium of heat transfer. This distinguishes it sharply from radiant cooling systems, which have a negligible influence on air temperature except by means of convective transfer via building surfaces.
Forced air systems first channel warmer air to a central processing unit by means vents and ducts, where it is cooled down before being circulated back to those parts of the building slated for temperature adjustment.
Given the sharp distinction between the physical mechanisms they employ, these two indoor cooling methods also differ significantly when it comes to efficiency, performance, and ancillary benefits.
Radiant cooling systems allow for more nuanced control of thermal comfort because they reduce the temperature of physical objects via radiant exchange and do not require direct interference in air circulation. This means room occupants can cool themselves without the need for increased air flow that some may consider undesirable or disruptive at times.
While forced air cooling systems involve manipulation of circulating air by definition, they possess a number of distinct advantages compared to radiant cooling systems.
Forced air systems are capable of creating changes in air temperature extremely quickly, with cooled air flow having a near-immediate effect upon the thermal comfort of occupants that enter its direct vicinity.
They also have the added advantage of helping to enhance the indoor air quality of a built asset as their operation involves the circulation of air through ducts systems that can be fitted with filters.
A single HVAC system can cycle through all of the air contained within a building several times a day. When ducts are fitted with filters capable of removing any airborne particles or pollutants, forced air systems can achieve dramatic improvements to the IAQ of a built asset.
When it comes to the critical issue of energy efficiency, however, multiple studies indicate that radiant cooling systems significantly outperform forced air or HVAC solutions.
Indian software giant Infosys conducted the world’s largest side-by-side comparison of radiant cooling and forced air systems at its Hyderabad development facilities in 2011.
Infosys equipped half of its SDB-1 facility with a radiant cooling system combined with a dedicated outdoor air system (DOAS) for ventilation purposes, while the other half was equipped with a variable air volume (VAV) system.
After two years of operation, the radiant system proved more efficient by a sizeable margin, consuming 34 per cent less energy compared to the VAV system despite requiring the installation of the ancillary DOAS for ventilation purposes and involving less initial outlay.
Another study undertaken by the University of California Berkeley’s Moore T. Center for the Built Environment concluded that radiant cooling used in combination with DOAS could achieved even greater energy savings compared to VAV systems.
According to their study undertaken during the months from May to September in Colorado, radiant cooling in tandem with DOAS can achieve energy savings of between 58 to 66 per cent compared to HVAC systems, or a reduction in the cooling load of between five and 10.6 megawatt hours.