India has many single-skin or lightly insulated metal clad commercial, retail and industrial buildings. It is predicted that, given the size of the population and warm climate, use of air conditioning will grow significantly but adjustments to building design and specification may mitigate some of the additional energy demand. The total number of potential ‘Cooling Degree Days’ in India has been calculated to be 3906, which compares to 279 in the USA. Absolute demand is therefore extremely high. If this load is met conventionally there are adverse environmental impacts (much of India’s power generation relies on coal fired power stations), and considerable stress will be placed on electricity generation and distribution infrastructures (as reflected in the power blackouts of 2012 attributed to a surge in power demand caused by air conditioning). The effective use of innovative advanced coatings for building envelopes could significantly reduce cooling needs, including in relation to industrial buildings. These coatings can increase solar reflectance on the outside of buildings (materially reducing ‘through fabric’ heat transfer), and reduce emissivity on the inside surfaces such that heat exchange between building and the occupants/internal spaces is reduced. Savings can be made by adjusting thermostat settings with no loss of thermal comfort. Critically, these coatings are economic, can be used in conjunction with other simple passive measures, and unlike many insulation techniques, have little or no adverse effect in terms of increasing the embodied energy of the building fabric. This paper examines the effects of solar reflective and low emissivity coatings on electricity use for air conditioning (and heating), peak cooling load, and roof surface temperatures for single skin or lightly insulated metal clad buildings in three Indian climates. A typical metal clad retail building has been modelled using dynamic thermal simulation software, to assess the effect that different roof cladding reflectance values have on cooling and heating loads. It has been found, for example, that air conditioning loads can be reduced by as much as 18% for single skin buildings in Mumbai when the solar reflectivity of the roof is increased to 65%, with similarly significant effects in other highly developed locations in India. Significantly, it has also been identified that peak cooling loads can also be reduced by over 25%. This reduction could play a significant role in reducing the potential risk of power outages associated with periods of high grid energy demand, and in reducing the imperative to continually increase grid capacity in relation to exponentially expanding demand.
Kendrick, Christopher C.Resalati, ShahaboddinOgden, RaymondInman, Paul
School of Architecture
Year of publication: 2017Date of RADAR deposit: 2021-03-26