Energy efficiency: New drywall building material can cut buildings' energy consumption by 40%

The boards, that are combined with passive strategies (sunlight, natural airing), can reduce energy consumption in building up to 40% what contributes to mitigate the problem of energy crisis, particularly in Spain that we import the 80% of energy.

The research carried out by the group Department of Building and Architectural Technology at the E.T.S. of Architecture of the UPM is based on the incorporation of phase change materials (PCMs) to the boards. This new constructive element is able to store in a 1.5 of thickness, five times the thermal energy of a conventional gypsum board with the same thickness. As a result, this research has achieved to keep local temperature where the board is installed within the comfort area (20-30ºC) without need of air conditioning systems. In addition, the repayment period is between one and two years.

PCMs are substances that store or release thermal energy by latent heat. Throughout the day, the "energy surplus" (they come from sunlight, electrical appliances, and users) encourages its liquefied, avoiding the local overheating. Throughout the night, when the outside temperature drops, they solidify by releasing the stored energy to the environment, avoiding subcooling. The effect is similar to a thick and heavy wall of high thermal inertia.

There are many applications of PCMs in diverse fields (medical, botanical, sports). Since the early 80's, the PCMs applied to buildings are studied to be integrated in building elements (concrete, plaster, ceramic, glass).

To develop this new material, researchers at the UPM chose plaster because of its availability, extensive use in building, low cost and ease integration of new additives. In addition, the position is always the inner side of the insulation what ensures a better use of its theoretical capacity of thermal storage between 90-95% (useful thermal capacity), compared to 10-15% that is achieved when it is placed in the outer side of the insulation. This is not a new thing, since the 90' the gypsum integration is studied; there is even a commercial product. However, the current percentage of PCMs incorporated in plasterboards is 26% compared to the 45% achieved with this new research. This difference is because these substances deplete the mechanical ability of the constructive element.

In order to avoid problems with gypsum during the liquid phase, they chose microencapsulated paraffin manufactured by BASF as PCMs. Besides, to achieve a high percentage of PCMs in boards and to ensure compliance of mechanical and physics benefits, they added other two additives to the mixture: fibers and fluidizing.

They combined the substances: gypsum, PCMs, fibers and fluidizing by varying the proportions to obtain different compounds. They tested combinations in order to know the physical properties (density, porosity, workability, and setting time) mechanical (hardness, strength, flexibility) and aesthetics. They selected the combination of higher percentage of PCMs, 45% with applicable regulations and thermally tested. In the 20-30 ºC temperature range, a gypsum board 1.5 cm thick containing this percentage of PCMs can store five times more thermal energy than conventional plasterboard of the same thickness, and the same amount of energy as half-foot hollow brick masonry.