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Use the thermal storage potential of building components and mass to reduce heating and cooling loads. Fabric Energy Storage (FES) relies on thermal mass, or the ability of a building material to absorb and release heat. Thermal mass reduces thermal loads by absorbing heat and slowly reducing it into the building, reducing peak temperatures.

Exposed concrete ceilings, walls and columns. Thermal storage walls (Trombe walls). Volumetric Heat Capacity (VHC) is one property of materials used to quantify thermal mass. Typical values: 4,186 (water); 2,060 (concrete); 1,360 (brickwork) [KJ/m³ K] (Source: Underfloor air supply in conjunction with hollow core slabs or hydronic piping in slabs can be used to charge/discharge thermal energy at specific times, allowing for greater temperature control.

FES works by reducing the peak temperature within a building and also by delaying its onset by virtue of the slow thermal response of a structure. The client and design team establish minimum and maximum acceptable indoor temperature values as a baseline for design and engineering.

Comparison of FES systems (cooling capacity [W/m²]): Natural ventilation with exposed soffits (15-25); Underfloor ventilation with exposed soffits (20-35); Exposed hollow core slabs with mechanical ventilation (40-60, i.e. Termodeck by Tarmac); Chilled slabs (64-80); Chilled beams (100-160)

The benefits of traditional FES systems are primarily in the shifting of peak load conditions or in an actual reduction in overall heat gain or loss. These benefits are highly dependant on local climate, use and operation. Chilled systems have moderate to high cooling capacity. Chilled systems can receive free cooling from bore holes when used in conjunction with ground or water source cooling. Minimal to low maintenance.

Cores of hollow core slabs require periodic cleaning through access points. Water temperature must be controlled to avoid condensation. Hollow core slabs transmit structure-born sound from walking and require carpeting. Dark colors absorb heat most effectively.

1.4.7 Passive House Standards
1.6.3 Ground and Water Source
1.7.6 Night Time Cooling
1.7.8 Passive Solar Heating