Assessing Energy Saving Potential in Existing Buildings in Abu Dhabi through Passive Retrofitting Strategies: Case Study –Office Buildings

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The British University in Dubai (BUiD)
The UAE as a leading country in the region has set goals to reduce CO2 emissions by 2020 in line with Copenhagen Accord. However, the challenge is considered great since the UAE has been identified as one of the highest ecological footprint in the World in 2007. The future plans in the country invest heavily on sustainability frameworks and future plans such as Abu Dhabi Plan 2030. While the sustainability codes and regulatory frameworks have been recently developed in the country, the regulations are only applicable to minor percentage of the overall building stock. In general the new buildings represent only 0.5% to 2% of the total building stock. Therefore, sustainability guidelines for existing building refurbishment are considered to be critical to reduce the energy consumption in the built environment and associated CO2 emissions. This research has studied the existing urban development in the Emirate of Abu Dhabi, and identified the commercial buildings as a major contributor to the energy consumption in the capital, with almost one third of the total energy consumption being accounted for commercial uses. An additional 25% for governmental usage has common elements with commercial buildings, yet needs to be further detailed for their sub-categories. The paper has identified two building prototypes as representation of the existing commercial building stock for the periods from 1980-1989 and 1990-1999 and prior to the implementation of the Estidama pearl building rating system for new construction. Computer modelling was used to assess the savings in electricity consumption, associated cooling loads, energy consumption, and CO2 emissions for the selected 1980s prototype, with an indication of the annual electricity savings for a typical floor layout for a 1990s prototype. The 1980s case study of 17 stories building was modeled in three simulation models; typical floor, roof floor, and ground and mezzanine floors. Building simulations for each of the models were conducted to assess savings due to individual elemental refurbishment and combined scenarios considering upgrades to 1 and 2pearl rating thermal properties. The potential reduction in cooling loads for the overall building varies dramatically depending on the refurbishment application. For the upgrades to 1 pearl rating standard, the savings ranged from 0.21% in the case of roof, to 5.13% and 11.90% in the case of the wall and fenestration upgrades respectively. However, for the upgrades to 2-5 pearls rating requirements, the savings were estimated at 0.22% for the roof upgrades, 5.61% and 14.67 for the wall and fenestration upgrades respectively. The study indicated that the savings achieved through refurbishment of the roof is negligible compared to that for the replacement of glazing due to the roof area being 6.4% of the building’s external envelope while the glazing forms 25.2% of the same. In this context, the glazing upgrades are considered the most efficient II | P a g e solution. The study also concluded that individual elements of the building, and individual floors could be looked at for prioritized refurbishment strategy depending on the individual savings that could be achieved, easement of implementation, and economic feasibility. Moreover, the study highlights that combined solutions achieve greater savings than when individual refurbishment applications are considered. The savings for the overall building are considered significant estimated at 18.90% and 22.12% for the 1 pearl and 2 pearls upgrades respectively. Solar gain and external conduction gain analysis indicated that the elements behavior and specifically the external conduction gain profile varies for the various applications. As an example, the 2 pearl combined scenario has 0.0727 MWh less annual conduction gain than the sum of the individual scenarios. The economic feasibility study indicated that the most feasible refurbishment solution for the building prototype of 1980s is for 2 pearls glazing upgrade, where 9 years payback period could achieve savings of 164.2157 MWhe of annual electricity consumption. However, it was noted that the highest savings for the combined solution in the case of 2 pearls upgrades would return its capital cost in around 16 years. The simple payback period calculations excludes the savings in government electricity cost subsidies, evaluation of building envelop performance upgrades such as humidity resistance, air tightness, aesthetical appearance, as well as future increases in the cost of electricity. It is expected that once all the benefits are quantified, the Simple Payback Period (SPP) analysis will result in reasonable timeframe for the owners to recoup their initial investment cost. Finally, the research is concluded by extrapolating the annual reduction in electricity consumption to represent the savings across Abu Dhabi. For the 1980s, the implementation of a combined retrofitting scenario to 2 pearls rating requirements; is estimated to achieve annual reduction in electricity consumption of 18,433 MWeh/yr. Whereas, the refurbishment of the most economically feasible solution to upgrade the building glazing to 2 pearl rating standards, can achieve an overall reduction of 12,214 MWeh/yr. CO2 emissions reduction for the combined solution of 2 pearls rating is estimated at 9,530,968 KgCO2/yr. Moreover, an indication of the typical building prototype upgrade for the period from 1990-1999 has indicated that the overall savings for Abu Dhabi for the 1990s buildings, when the glazing elements are upgraded, are 28,599 MWeH/yr and 20,152.MWeh/yr for the 2 pearls and 1 pearl rating respectively.
energy saving, Abu Dhabi, United Arab Emirates (UAE), passive retrofitting, office buildings, CO2 emissions, built environment, energy consumption