Countries across the world have recently signed commitments to reducing energy usage in an effort to control global warming and climate change.

At the same time building users are requesting increasing levels of control over their environment and to be able to maintain consistent temperatures throughout the year.  Building regulations stipulate a requirement to improve air quality for a healthier building and in the case of education particularly, improved concentration levels.  Recent press has focused on the importance of air quality for student’s concentration and a more natural approach can significantly help with this.

Our recent CIBSE CPD module considers how natural cooling utilising Phase Change Materials (PCMs) can be used effectively to improve the health of building occupants and dramatically improve the building’s sustainability. This is particularly relevant in the UK and Northern Europe where temperatures rarely reach high levels and invariably have cool night time temperatures.

What PCM Natural cooling systems are commonly used?
Natural cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve indoor “thermal comfort” with either very low or zero energy consumption. 

An example of a very simple form of a static passive cooling application uses PCMs in ceiling or wall tiles to provide cooling in a non-domestic building. This would typically be used in the summer season and cool night air will be drawn into the building and used to both lower the room temperature and store cooling energy in the PCM to utilise the following day.

Whilst this is a straight-forward approach, there is no control for the building user. It is not possible to manage which areas are cooled and also when then the stored cooling energy is utilised. It also requires a separate ventilation strategy as the static approach only controls temperature and not the CO2 level.

Unlike these passive applications where thermal mass is simply added to a building, more advanced natural cooling systems with PCM are able to intelligently control how much energy is stored and released from the thermal store and control exactly where and when this energy is released for example at set times in afternoons when maximum indoor temperatures are likely to occur.

In cases where peak loads can be particularly problematic such as sudden or extended seasonal volume usage in an IT suite then the most advanced natural cooling PCM systems integrate with heat pumps to form hybrid cooling systems allowing greater capacity to be provided on specific seasonal demand whilst still minimising year round energy usage. Both of these systems would also provide full ventilation and provide building specific CO2 and temperature control.

How does natural cooling using PCM allow buildings to be more sustainable?
By using PCM in a natural or hybrid cooling system building owners and users can dramatically reduce their carbon footprint and meet carbon reduction commitments (CRC) and energy costs as they are able to harness the natural environment using night air to cool a room and the PCM built into natural cooling applications to maintain a thermal comfort for room users.  It also allows building owners to satisfy building regulations for ventilation and thermal comfort.
By removing the need to use an air conditioning system, the key benefits are two-fold;

  1. The building will have no need to use environmentally damaging refrigerants e.g. R410a or R134a.
  2.  It removes the energy demand it places on the building. 

By using PCM for natural or hybrid cooling, buildings can be cooled by harvesting energy from both the internal and external environments.  The energy is stored as latent heat in the PCM. No electrical battery or wiring is required for the energy storage.

In some instances, by using a natural or hybrid cooling system, it can support the building in applying for BREEAM certification by contributing credits for areas such as a reduction in energy usage and therefore carbon emissions and minimising sources of air pollution by ventilating the room using fresh air from the outside instead of using a “sealed” box approach as with a traditional air conditioning system.

There are also health & sustainability benefits for users of the building; by continuing to circulate fresh air at the same time as cooling the room, occupants are likely to feel more alert and concentration levels remain high.  During daytime, natural cooling systems can monitor indoor and outdoor temperatures, internal CO2 levels and humidity. As temperatures and CO2 levels rise in the room through the day the systems will automatically ventilate the space.  By improving air quality the natural cooling solution can improve productivity and attendance and help reduce the effects of “sick building syndrome”.  By using fresh air there is also less of a “drying effect” of the air on the occupants.  A recent study in the US also showed the schools which had been built using “green” credentials also led to their students being more eco-conscious themselves in their own everyday lives.

Whilst traditional air conditioning systems can typically offer more accurate temperature control for occupants, natural cooling and ventilation is beneficial to reduce energy consumption and also to improve ventilation rates in a building or room.  It can provide temperature control within thermal comfort levels for a more balanced temperature.  By using an inorganic PCM modular structure in the natural cooling system, a cost-effective and environmentally friendly solution is available.  Case studies have shown that energy costs can be extremely low, whilst CO2 and temperature levels are also kept within the thresholds specified. 

If you would like to learn more or complete the CIBSE CPD module then this can be accessed through the online issue of the journal Monodraught CIBSE CPD or the printed July issue.

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