The Effects of Applying UCrb on CO 2 Emissions

Considering the huge area of UC buildings (505,845 m2_{) reducing the threshold of benchmark}

from 240 kWh/m2/yr (CIBSE TM46 UC) into 130 kWh/m2/yr (UCrb) has a large impact on the fossil energy consumption in UC buildings. According to the UCrb, 50% of analysed UC buildings are not energy efficient and they need to implement effective measurements to adjust with the new benchmark.

UCrb dramatically impacts on the fossil thermal energy reduction and accordingly CO2 emissions

if applied as an Irish UC benchmark. Based on comparison of TM46 UC benchmark with UCrb, if the revised benchmark applied, almost more than 55,000,000 kWh of fossil thermal energy consumption would be reduced annually. Likewise, more than 10,500 tonnes of CO2 emissions

could be prevented. Additionally, the financial aspect of the issue is important. The CIBSE TM46:2008 UC benchmark was approximately 1.85 times greater than the UCrb. Figure 4.28, presents the amount of improved energy consumption as well as CO2 emissions using UCrb.

Resample size 80 Resample size 160

Mean 132.125 Mean 131.0375 Median 129.562 Median 129.601 Mode 134 Mode 134 Minimum 117 Minimum 116 Maximum 145 Maximum 146.5 Sum 10330 Sum 20518 Count 80 Count 160

Upper bound 155.6224 Upper bound 148.1531 Lower bound 125.6276 Lower bound 127.9219

Resample size 320 Resample size 800

Mean 130.828125 Mean 129.949375 Median 129.751 Median 129.583 Mode 134 Mode 134 Minimum 101 Minimum 101.5 Maximum 150 Maximum 148 Sum 41225 Sum 103159.5 Count 320 Count 800 Upper bound 137.18 Upper bound 131.42 Lower bound 128.47 Lower bound 129.48

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Figure 4.28.Reduced fossil thermal demand and CO2 emissions using UCrb

In Table 4.12 the results of current studies that reviewed the accuracy of CIBSE TM46 in educational buildings is compared. According to the results, the minimum error of CIBSE TM46 thermal benchmarks was 10% belonging to primary schools in the UK. In this context, the error in Irish primary schools was 36%, which is a significant discrepancy compared with UK schools. In addition, the errors of CIBSE TM46 benchmark in university buildings were greater than schools. For example, in the UK the errors of 25% and 39% were observed. The error that was found in the current study was 46%.

Table 4.12.Comparing the results of UCrb with the results of similar studies

Scholars Country Building type

TM46:2008 Thermal benchmark kWh/m2_/yr % of Discrepancy Between TM46 and measurements Discovered performance kWh/m2_/yr Patxi Hernandez [45]

Ireland Primary schools 150 36 96 Sung-Min Hong [105] UK Primary schools 150 20 121 Daniel Godoy- Shimizu [16] UK Primary schools 150 10 136 Sung-Min Hong [105] UK Secondary schools 150 26 111 Daniel Godoy- Shimizu [16] UK Secondary schools 150 12 132 Xuefeng Gao [93] USA Non-residential

(a Group of buildings)

- - 167.3 Hawkins [23] UK UOB 240 25 180 Harry Bruhns [15] UK CIBSE dataset

Review; UC 240 39 --- Current PhD research Ireland University Campus 240 46 130

From 2008 that CIBSE TM46 published, the thermal demand reduced annually as indicated in 52 case study buildings. The reasons for this reduction were discussed comprehensively in this

Reduced fossil thermal energy

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chapter previously. Considering the difference (110 kWh/m2) between TM46 UC benchmark and UCrb, the gradual reduction of benchmark could be recommended as a goal toward zero fossil thermal energy by 2040 in existing buildings, and zero fossil thermal energy for all new buildings by 2030. Such goals can be defined based on the zero energy buildings standards.

4.4. Conclusion

The heat consumption of 52 UC buildings belonging to 4 major Irish universities in Dublin e.g., TCD, DIT, DCU, and UCD were analysed. Based on DEC measurements the heat consumption was compared with the CIBSE UC benchmark. The UC category consists of nearly 62% of buildings having DEC. According to the assessments, a significant discrepancy of 46% between DEC measurements and CIBSE TM46 was found. In addition, the relationship between the building area and heat demand was assessed and the linear regression value of 0.91 revealed a strong relationship.

Further analysis revealed that the mean annual heat consumption was 152 kWh/m2/yr. By comparing the mean heat consumption with the CIBSE benchmark of 240 kWh/m2_{/yr, it can be}

concluded that the difference between DEC consumption measurements with the CIBSE standard was 88 kWh/m2_{/yr. Theresult ofevaluation confirmed a significant gap between measured data}

and CIBSE prediction.

In this regard, the results of DS analyses showed that the performance of approximately 90% of UC buildings was lower than the benchmark. Accordingly, the annual heat consumption of 75% of the analysed buildings was between 65 and 160 kWh/m2/yr.

Moreover, among four analysed campuses DIT with a mean consumption of 119 kWh/m2/yr was the most energy efficient campus, in contrast, the lowest energy efficiency was found at UCD with a mean consumption of 172 kWh/m2_{/yr. In this context, the most energy efficient building}

was Aras an Phiarsaigh at TCD with annual heat consumption of 62 kWh per unit area, while the greatest heat consumption belonged to Science Centre Hub at UCD with an annual heat consumption of 623 kWh per unit area followed by Biochemistry building, Biotechnology Building, and CRANN & Sports Centre at TCD with 423, 299 and 294 kWh/m2_{/yr respectively.}

The mixed use activities was a factor which increased the heat demand in these buildings. The broad consumption range and significant difference between the greatest (623 kWh/m2_/yr)

heat consumption and lowest (62 kWh/m2/yr) shows the category of UC covers various building types.

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The percentage cumulative frequency distribution analyses showed that the median heat consumption of 52 college buildings was nearly 130 kWh/m2_{/yr which reflected the consumption}

of 50% of the analysed samples. Based on the definition of the energy benchmark, the median consumption was suggested as a UC revised benchmark (UCrb). UCrb decreases fossil fuel consumption and CO2 emissions in UC buildings. Using UCrb approximately 55 million kWh of

fossil thermal energy as well as more than 10,500 tonnes of CO2 can be saved annually.

Furthermore, the25th _{percentile of samples was 95 kWh/m}2

/yr which indicates the good practice index. It is suggested that this index is displayed on future Irish DECs as a motivator.

Since energy benchmarking in buildings underpins the DEC methodology and on the other hand DECs form the foundation of energy action plans at local as well as national scale, revising the current benchmark is crucial to provide accurate energy efficiency plans. The revised benchmark increases the energy efficiency of buildings comparing CIBSE TM46 benchmark and consequently, reduces the fossil thermal consumption and CO2 emission. Considering the large

size and number of college buildings the impact of revised benchmark (UCrb) on mitigation of global warming is significant. Other advantages such as reduction of fuel expenses are also important.

The revised UCrb benchmark will be used in the heat modelling methods (in chapter 5) in order to improve the accuracy of the thermal demand estimations. Finally, the energy assessment presented in this chapter highlighted three key parameters which affect heat demand in the typical college buildings including, building area, energy efficiency, and UCrb. These factors will be used to create the monthly heat models for typical college buildings.