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While new buildings can be designed and built to be energy efficient, the options to reduce energy consumption of existing buildings are much more limited, with practicality depending on constraints arising from the specific building design and cost, among other considerations. AGC had developed the retrofitting solution "ATTOCH Inner Window" (AIW) that adds a secondary layer of glass to the building's existing glass façade to reduce the amount of heat transmitted through the glass into the building interior, and hence the energy consumed by the building's air conditioning system.  While the AIW technology is highly compact and very easy and quick to install without the need for scaffolding, AGC Asia Pacific did not have the expertise to quickly quantify the performance of AIW in different tropical cities without experimentally testing AIW in each city.

AGC Asia Pacific approached the A*STAR team to carry out the performance evaluation of AIW as the A*STAR team had previously collaborated with AGC Asia Pacific to successfully develop a new methodology to evaluate the effectiveness of green building products in tropical climates, which was necessary as then-existing methods were more suitable for temperate climates; this evaluation method was subsequently used by AGC Asia Pacific to support their submission to qualify ATTOCH as a certified green glazing system by the òòò½ÍøGreen Building Council. 

IHPC customised the previously proposed method, and calibrated the resultant model against EPGC's experimental measurements for AIW.  Results from the calibrated model suggests that AIW could result in 41% annual energy savings from decreased cooling requirements compared to monolithic clear glass (i.e. a single layer of glass without glazing) when used in the following four Southeast Asian cities – Singapore, Kuala Lumpur, Manila and Bangkok; this savings could be substantial as Heating, Ventilation & Air Conditioning (HVAC) systems can consume more than 50% of the total building energy load for buildings in warm and humid climates.  The A*STAR team also advised AGC Asia Pacific that the AIW configuration with the highest (41%) energy savings also drastically reduced the amount of natural sunlight, and helped AGC Asia Pacific to quantify to their customers the pros and cons of deploying different AIW configurations through a trade-off of heat and natural light reduction that could differ for different customers with different interior conditions.  

This work is one of the many prior pieces of research supporting IHPC's current "Environmental & Food Sustainability" initiative that develops technologies contributing to food or environmental sustainability, such as the Integrated Environmental Modeller (IEM) that is capable of accounting for how multiple factors, e.g. air flow velocity and solar irradiance, moderate the microclimate experienced by individual buildings within a wider urban area – a capability that commercial building energy consultants do not have. 

In the next phase of IEM development ("IEM Phase 2") to be funded by the 'Cities of Tomorrow' programme, IHPC will extend our prior work in building energy modelling to create tools within IEM to estimate the impact of outdoor microclimate on the building's energy consumption for air-conditioning/ventilation.  This enhanced resolution in energy modelling is a significant step-up over the current offerings of commercial building energy consultants, and is a critical capability to enable buildings/precincts to be designed to have inherently-lower requirements for air-conditioning/ventilation.  Given IHPC's successes in IEM Phase 1 and energy modelling work with industry, HDB has expressed interest in such building energy tools to further bolster Singapore's push towards sustainability.