BUILDING PERFORMANCE IMPROVEMENTS FROM NCC2019

Transcription

1 BUILDING PERFORMANCE IMPROVEMENTS FROM NCC2019 DR PAUL BANNISTER, F.AIRAH FIEAUST Director, Innovation and Sustainability Energy Action (Australia) Pty Ltd PO Box 546 Belconnen ACT 2617 HONGSEN ZHANG, M.AIRAH Senior Consultant Energy Action (Australia) Pty Ltd PO Box 546 Belconnen ACT 2617 Hongsen ABOUT THE AUTHOR Dr Paul Bannister is an international authority on energy efficiency in the built environment and is a Board Member of AIRAH, IBPSA and EMANZ. Over a 25-year career in the sector he has undertaken hundreds of energy audits, been involved in scores of upgrade projects many of which have achieved energy savings in excess of 50%. Paul is also well known for his role as the primary technical author of the NABERS Energy and Water ratings for offices, hotels, shopping centres and data centres. Most recently he has led a major project to upgrade the National Construction Code, reported in this and other papers at this conference. Paul is currently working on projects in Australia, New Zealand and the UK. He has over 100 publications in the field of energy use and the built environment. ABSTRACT The National Construction Code of Australia Section J (Energy Efficiency) provisions for commercial buildings are being updated to include new stringency levels. This paper provides an overview of proposed new stringencies and uses simulation to predict the overall performance improvement in buildings based on the new provisions. The first step of the work was to establish a set of NCC 2016 compliant models across a range of building archetypes and use classes. These were then used in stringency analyses covering glazing, insulation, fans, pumps, chillers and boilers. Each of these measures was subjected to benefit cost analysis on an individual basis. Using the recommended updated stringencies, the base models were revised to a new set of models compliant with the proposed new levels of stringency. The performance of these models was then compared to the original models in order to determine the impact on total building performance and integrated benefit cost ratio. The revised models show a significant reduction in greenhouse emissions across all climate zones and building types, validating the savings potential from the proposed measures. Furthermore, most of the scenarios are predicted to be lower cost to build than the equivalent NCC2016 compliant scenarios; and where costs have increased the benefit cost ratio is acceptable in almost all cases. 1

2 INTRODUCTION Energy Action were contracted to review the current NCC Section J stringency provisions by the Australian Building Codes Board (ABCB). As a result of the review, numerous recommendations to the stringency of the future code have been proposed covering glazing, insulation, HVAC, lighting, and lifts. This paper presents an overview of major measures proposed for the NCC2019 revision of Section J, and reports on studies undertaken to ensure the sum of the individual recommendations provides a stringency that can deliver lower annual energy outcomes. IES <VE> dynamic thermal simulations are used to provide the means to qualitatively assess the energy performance for buildings compliant to NCC2016 and NCC2019 (proposed) stringencies. PROPOSED DTS MEASURES FOR NCC2019 The proposed Deemed to Satisfy measures for NCC 2019 cover all aspects of building energy consumption. The derivation of measures is described elsewhere, but in general was based on a benefit cost analysis with a target BCR of It is noted that this paper documents an intermediate stage of a 2-year code development process, and the final code requirements may differ from those presented. A number of areas where changes are already known to have occurred are identified in the footnotes. Readers are referred to the Australian Building Codes Board for the official version of any proposed code measures, which will be put through a full consultation process through The proposed measures are identified in the following sections. GLAZING NCC2016 specifies façade construction provisions on a separate wall construction and window construction basis. The wall construction must satisfy a minimum total R-Value, and the window construction must separately be assessed using the NCC glazing calculator. For NCC 2019, it is proposed to drop the glazing calculator approach in favour of an approach that specifies a maximum figure for the total solar admittance (which is the product of solar heat gain coefficient and window wall ratio, i,e., SHGC*WWR) and a maximum figure for the total U-value of the wall and window combination [Johnston et al 2017a]. This is closer to general international practice and enables the required performance to be summarised in a simple table, as shown in Table 1. 2

3 East North South West U total SHGC*WWR U total SHGC*WWR U total SHGC*WWR U total SHGC*WWR CZ CZ CZ CZ CZ CZ CZ CZ Table 1. Proposed stringency for NCC2019 showing maximum U-Value and SHGC*WWR 1 for daytime operating buildings. OPAQUE STRUCTURES No changes in stringency have been proposed for roof, wall or floor insulation, although it is noted that the wall R-values are affected significantly by the Utotal approach for the glazing in a manner that is still being resolved at the time of writing [Johnston et al 2017b]. However, it is proposed to remove many of the provisions for minor alterations to required R-values based on shading, solar absorptance, etc in order to simplify the code. It is also proposed to require that roof structures in Climate Zones 1-7 have a solar absorptance of 0.4 or less. No solar absorptance requirement is proposed for Climate Zone 8. CHILLERS, BOILERS AND PAC UNITS The NCC only makes requirements for chillers below 350kW and PAC units above 65kW because outside these side ranges the minimum efficiency of chillers is covered under MEPS. In the proposed revisions, incremental improvements have been made to the stated minimum efficiencies as shown in Table 2. Equipment Item Minimum COP 2019 (2016) Minimum IPLV 2019 (2016) Air-cooled Chillers <350kW 3.0 (2.5) 4.1 (3.4) Water cooled chillers <350kW (4.2) 6.7 (5.2) Air-cooled PAC Units >65kW 2.9 ( ) n/a Water-cooled PAC units >65kW 4.0 ( ) n/a Table 2. Proposed changes in equipment stringency for NCC2019. For boilers, the proposed NCC2019 stringency is a minimum gross thermal efficiency of 90%, which necessitates the use of a condensing boiler. Not that this only applies to space heating applications. 1 Since this paper was prepared, the U total requirements have been relaxed to 2.5W/m 2 K. 2 Since this paper was prepared, the requirements for water cooled chillers have been modified to a COP/IPLV of 4.5/6 for chillers below 200kW and 5/7.9 for chillers kW. 3

4 FAN AND PUMP SYSTEMS Under NCC2019, it is proposed to replace the current W/m 2 requirements with specific requirements as below. Minimum fan efficiencies based on ISO12759:2013 and set based on EU 2015 standards as listed in Table 3 and Table 4 [Department of Environment and Energy 2017] 3. Fan size Axial Centrifugal forward Centrifugal backward no housing Centrifugal backward with housing >125W and <0.75kW 31.4% 35.4% 47.7% 46.7% 0.75kW and <4kW 34.8% 38.8% 53.3% 52.3% 4kW and <10kW 38.5% 42.3% 59.3% 58.3% 10kW and <30kW 40.2% 44.2% 62.4% 61.4% 30kW and <185kW 41.2% 45.2% 63.7% 62.7% 185kW and <500kW 42.3% 46.3% 65.3% 64.3% Table 3. Recommended minimum wire-to-air efficiencies (%) for fans on static pressure basis. Fan size Axial Centrifugal forward Centrifugal backward no housing Centrifugal backward with housing >125W and <0.75kW 49.4% 40.4% n/a 49.7% 0.75kW and <4kW 52.8% 43.8% n/a 55.3% 4kW and <10kW 56.3% 47.3% n/a 61.3% 10kW and <30kW 58.2% 49.2% n/a 64.4% 30kW and <185kW 59.2% 50.2% n/a 65.7% 185kW and <500kW 60.3% 51.3% n/a 67.3% Table 4. Recommended minimum wire-to-air efficiencies (%) for fans on a total pressure basis. Use of turning vanes in bends. Maximum straight duct pressure drop as shown in Table 5 Maximum AHU coil and filter velocities shown in Table 6 and Table 7. Maximum Straight Duct Pressure Drop (Pa/m) Constant Speed System Maximum Straight Duct Pressure Drop (Pa/m) Variable Speed System <2000 hours hours >5000 hours <2000 hours hours >5000 hours Table 5. Proposed maximum pressure drop per metre length of straight duct. 3 Since this paper was prepared, it has been proposed to increase fan efficiency requirements to match the high efficiency requirements of the Emissions Reduction Fund. 4

5 Maximum average face velocity (m/s) 1-2 Constant Speed System Variable Speed System Coil only Coil + 1 filter ( MERV 11) Coil + 1 filter ( MERV 12) Coil + 2 filters Table 6. Proposed maximum velocities for filters and coils in a fan system 4. Constant Speed System Variable Speed System Filter Class Maximum allowable velocity (m/s) <125Pa@2.5m/s 125Pa@2.5m/s <125Pa@2.5m/s 125Pa@2.5m/s ( MERV 13) ( MERV 14) ( MERV 13) ( MERV 14) 2.5m/s 2.0m/s 2.5m/s 2.5m/s For pumps: Table 7. Proposed maximum velocities for filters in a fan system without a coil 4. A minimum pump energy efficiency standard (still being defined at the time of writing) A maximum straight pipe pressure drop as shown in Table 8. Nominal Pipe Diameter Maximum Pressure Drop (Pa/m) Constant Speed System Maximum Pressure Drop (Pa/m) Variable Speed System <2000 hours hours >5000 hours <2000 hours hours >5000 hours 20mm >20mm, <65mm mm Table 8. Proposed maximum pressure drops for pipes. 4 Since this paper was prepared, updated recommendations have simplified this table somewhat. 5

6 COOLING TOWERS The proposed stringencies for cooling towers are shown in Table 9. The major changes are an increase in stringency and a move to a uniform W fan power per kw heat rejection metric. Tower Type Induced draft 2019 (2016) Forced draft 2019 (2016) Open circuit cooling tower 10.4 W/kW (12.4) 19.5 W/kW (23.5) Closed circuit cooling tower 16.9 W/kW (19.9) n/a 5 (26.7) Evaporative Condenser 11 W/kW (18) 11 W/kW (22) Table 9. Proposed stringencies for cooling towers and evaporative condensers ECONOMY CYCLE The proposed stringency for the requirement to provide an economy cycle is somewhat relaxed from NCC2016 as shown in Table 10. Climate Zone Economy cycle required above cooling capacity (kw) NCC2019 NCC n/a n/a 2 n/a 50 3 n/a Table 10. Proposed economy cycle requirements for NCC2019. OUTSIDE AIR MANAGEMENT The provisions relating to the management of outside air have been increased in stringency as shown in Table 11 below. 5 Forced draft closed circuit cooling towers are proposed to not be available under NCC2019 due to poor efficiency. Note that we were unable to find any such towers that actually comply with the associated NCC2016 requirements. 6

7 Region HX/CO 2 OA Flow CZ1 CO 2 >500 l/s CZ2 Not required n/a CZ3 CO 2 >1000 l/s CZ4 HX or CO 2 >500 l/s CZ5 HX or CO 2 >1000 l/s CZ6 HX or CO 2 >500 l/s CZ7 HX or CO 2 >250 l/s CZ8 HX or CO 2 >250 l/s Table 11. Proposed outside air management requirements for NCC2019. LIGHTING The proposed NCC2019 lighting measures are significantly more stringent that the NCC2016, reflecting the change from fluorescent technologies to LED. The full range of proposed changes is reported elsewhere [Jolley-Rogers et al. 2017], but for the purposes of this study the major changes are as reported in Table 12. NCC2016 NCC2019 Building Class/Form IPD (W/m 2 ) IPD (W/m 2 ) 3A A B aC Table 12. Sample lighting power density revisions for NCC2019 TESTING THE MEASURES: NCC2016 VS NCC2019 The methodology used to obtain comparative energy consumption between NCC2016 and the proposed NCC2019 is as follows: 1. NCC2016 baseline models were defined and dynamic thermal simulations were ran. 2. NCC2019 test models were created making sure the proposed stringencies were met. Further to this, a benefit-cost analysis was undertaken of the NCC2019 versus NCC2016 models to understand the holistic impacts of the proposed measures. TEST BUILDINGS The four-building class/form combinations used in for the analysis are given in Table 5 below. They include models 3A, 5A, 6B and 9aC which represent hotel, office, retail and health care (clinic) occupancies respectively. These models are selected to be representative rather than comprehensive; result for other building types may vary. 7

8 Building NLA (m 2 ) Storeys Occupancy Type Floor Length (m) Floor Depth (m) Floor to Floor Height (m) Ceiling Height (m) Model 3A Hotel Model 5A Office Model 6B Retail Model 9aC Health Care Table 13. Building geometry details Screenshots of the models used are given in Figure 1, Figure 2 and Figure 3. Note that model 3A and 5A share the same building geometry but differ in the external constructions and internal loads such as equipment, people and lighting densities. Operating schedules were identical between NCC2016 and NCC2019 models. Figure 1. Model 3A and 5A, NCC2019 compliant format. Figure 2. Model 6B, NCC2019 compliant format. Figure 3. Model 9aC, NCC2019 compliant format. 8

9 For the NCC2016 models, the glazing was selected based on the largest windows that could be accommodated while just meeting compliance using common glazing types. As a result of how the glazing calculator works, this led to divergent glazing types and WWRs on different facades. For the NCC2019 models a fixed WWR of 30% 6 was used and the nature of the proposed measures meant that the glazing selection could be kept consistent between facades in almost all cases. SHGC and U value were selected to just meet compliance. A minimum 5% daylight factor was required for all NCC2019 scenarios to ensure that a minimum level of functionality was guaranteed. HVAC EQUIPMENT AND CONTROL Water cooled, hermetic centrifugal chillers with variable speed drive controlled compressors were used in the IES <VE> modelling for each climate zone. The in-built water-cooled chiller curves in IES were adjusted to match the COP requirements of NCC 2016 and NCC Non-condensing boilers were modelled for the NCC2016 scenarios. Heating hot water supply/return temperature was modelled at 80/60 C (fixed) with a rated boiler efficiency of 80%. Condensing boilers were modelled for NCC2019 DTS simulations, with a heating hot water temperature reset was modelled to be 80 C when the outside dry bulb is 4 C above design heating temperature, 60 C when the outside dry bulb is 14 C above design heating temperature and linear in between, reflecting a new control requirement proposed for NCC2019. The rated gross boiler efficiency was modelled to be 90% 7. Open circuit, induced draft cooling towers were used in both NCC2016 and NCC2019 simulations. The capacity of the cooling towers changed between NCC2016 and NCC2019 as a result of different building loads, and fan power requirements were set to comply with the measures in the respective codes. AHUs were used in model 5A and 9aC buildings with 3A and 6B models using FCUs. The AHU and FCU fan power were set up as per the NCC standards. The 2019 fan power density (W/m²) was calculated by applying all proposed limiting pressure drops and face velocities through each system component (straight duct, filters, coils etc) to the 2016 base case system. After applying these limiting factors, a revised pressure drop for the system was calculated and the resultant W/m² determined. This asserted a 40% to 50% reduction fan power between NCC2016 and NCC2019 scenarios [Balme et al 2017]. Control parameters were identical for NCC2016 and NCC2019 models. The zone set point was modelled to be 22.5 C with 1 C dead band and 1 C proportional band either side. The cooling supply air temperature was reset from 12 C to 22.5 C when the average zone temperature changes from 24 C to 23 C. The heating supply air temperature was reset from 30 C to 22.5 C when the average zone temperature changes from 21 C to 22 C. An economy cycle was incorporated into the HVAC models where required by NCC2016 and the NCC2019 proposed stringency. A dry bulb economy cycle was modelled which mixes the return air and outside air to achieve the desired supply air set point. A dry bulb lockout of 24 C and dew point lockout of 14 C was used. AHU supply air was delivered to the zones via VAV boxes. The VAV turndown was modelled at 50% for centre zones and 30% for perimeter zones. The FCU was modelled as a constant volume system. 6 As 25% of the wall faces the plenum, a 30% WWR is equivalent to a 40% WWR to the occupied space. 7 The efficiency of condensing boilers ranges from about 90% up to 98% or greater. 9

10 Electricity cost (Real 2016 $/kwh) CO2 control was used in the building simulations where instructed by NCC2016 and NCC2019 proposed stringencies. The CO2 control proportionally varies the outside air supply based on CO2 readings for each floor of the building. CO2 levels are controlled between 700 and 900 ppm using 50% outside air as supply at the lower value and 100% outside air used as supply for the higher level. No differences in pump system efficiency were modelled as the measures in this area had not yet been finalised. COST BENEFIT MODELLING Incremental capital costs were modelled using the cost models used in the benefit-cost analyses for each individual measure 8. Energy costs were modelled using forward estimate gas and electricity prices derived from AEMO forward estimates [AEMO 2016a, AEMO 2016b]. The forward price curves are shown in Figure 4 and Figure 5. It is noted that there is considerable uncertainty in the forward projection of energy costs; the AEMO data was selected as being a most probable scenario. The benefit cost analyses did not formally include sensitivity analysis, but informal assessment showed that the fundamental results determined using the stated cost assumptions were robust. Similarly, a potential carbon price was considered but omitted from the analysis on the grounds that the impact on results was not significant. $0.25 $0.20 $0.15 $0.10 $0.05 $ Year Figure 4. Forward price for electricity used in the analyses 8 Requests for more complete reportage on these analyses should be directed to the Australian Building Codes Board. 10

11 Gas Cost (2016 Real $/GJ) $30.00 $25.00 $20.00 $15.00 $10.00 $5.00 $ Figure 5. Forward price for gas used in the analyses For benefit cost analyses, component lives of 15 years were assumed for lighting and air-cooled equipment; 25 years for HVAC generally and 40 years for façade elements. A 7% discount rate was used in line with Federal Government guidelines. For each individual measure, a target of achieving an outcome of a benefit cost ratio of was set by the ABCB. This was assessed individually for each measure in order to set stringency. RESULTS The results show a significant reduction in energy use across almost all scenarios as shown in Table 14. Change in Annual Energy Use (%) Location 3A 5A 6B 9aC Climate Zone 1-10% -32% -37% -41% Climate Zone 2-37% -45% -39% -45% Climate Zone 3-31% -38% -39% -49% Climate Zone 4-32% -37% -37% -37% Climate Zone 5-36% -43% -43% -43% Climate Zone 6-33% -40% -39% -37% Climate Zone 7-35% -44% -38% -18% Climate Zone 8 4% -13% -28% 4% Table 14. Change in annual energy use as a result of NCC2019 stringency. Expressing the annual energy use in terms of greenhouse gas emissions (kg CO2 equivalent), the reduction from implementing the proposed NCC2019 stringency is significant, as shown in Table

12 Change in GHG Emissions (%) Location 3A 5A 6B 9aC Climate Zone 1-10% -32% -37% -41% Climate Zone 2-37% -45% -40% -46% Climate Zone 3-33% -36% -41% -52% Climate Zone 4-39% -39% -41% -44% Climate Zone 5-38% -43% -46% -46% Climate Zone 6-43% -46% -46% -48% Climate Zone 7-44% -49% -38% -38% Climate Zone 8-34% -38% -31% -31% Table 15. Change in annual greenhouse gas emissions as a result of NCC2019 stringency The change in capital costs between NCC2016 and the proposed NCC2019 was evaluated separately for an NCC2019 compliant case with a 30% WWR case and an equivalent performance NCC2019 compliant 45% WWR case. Results are shown in Table 16. Note that the percentage change refers only to the capital costs of the elements affected by the measures, rather than the cost of the whole building. In terms of a benefit cost ratio, the NCC2019 stringency compares to the NCC2016 provisions as found in Table 17. Location Modelled WWR 3A 5A 6B 9aC Climate Zone 1 30% -41% -52% -27% -23% 45% -5% -20% 13% 25% Climate Zone 2 30% -35% -33% -28% -30% 45% 5% 10% 9% 14% Climate Zone 3 30% -43% -22% -33% -36% 45% -9% 26% 2% 2% Climate Zone 4 30% -48% -38% -25% -26% 45% -18% 2% 12% 18% Climate Zone 5 30% -49% -24% -32% -35% 45% -19% 25% 4% 4% Climate Zone 6 30% -43% -29% -17% -19% 45% -9% 18% 25% 28% Climate Zone 7 30% -46% -49% -32% -34% 45% -13% -19% 2% 2% Climate Zone 8 30% -49% -43% -34% -27% 45% -10% -1% 10% 22% Table 16. Change in capital costs for building elements affect by code compliance between NCC2016 and NCC

13 Model Information Benefit Cost Ratios Location Modelled WWR 3A 5A 6B 9aC Climate Zone 1 30% negative cost negative cost negative cost negative cost 45% negative cost negative cost Climate Zone 2 30% negative cost negative cost Negative cost negative cost 45% Climate Zone 3 30% negative cost negative cost negative cost negative cost 45% negative cost Climate Zone 4 30% negative cost negative cost negative cost negative cost 45% negative cost Climate Zone 5 30% negative cost negative cost negative cost negative cost 45% negative cost Climate Zone 6 30% negative cost negative cost negative cost negative cost 45% negative cost Climate Zone 7 30% negative cost negative cost negative cost negative cost 45% negative cost negative cost Climate Zone 8 30% negative cost negative cost negative cost negative cost 45% negative cost negative cost Table 17. Benefit cost ratio summary for models with WWRs of 30% and 45%. DISCUSSION ENERGY AND EMISSIONS IMPACTS The results in Table 14 show that the proposed measures have a significant impact on energy use across all models and most climate zones. The exception is climate zone 8, where energy use rises as a result of increased heating loads; this is caused partly by the generally higher façade stringency of NCC2016 in this climate zone, and partly by the reduction in internal gains arising from the reduction in lighting power. Underlying the NCC2016/NCC2019 façade stringency difference is the fact that the analysis for NCC2019 uses a greenhouse gas basis rather than an unweighted energy total as used for NCC2016 and earlier; this change reduces the prioritisation of heating in NCC2019 relative to NCC2016. The results for achieved greenhouse gas savings are consistently beneficial, as can be seen in Table 15. CAPITAL COSTS AND BENEFIT COST RATIOS The incremental capital costs associated with the proposed changes under NCC2019 are dominated the reduced capital costs associated with the use of smaller windows 9. The high cost of façade means that even a moderate reduction in glazed area dominates the cost increases associated with other measures. As a result, the majority of scenarios for NCC2019 are actually cheaper than those 9 Opaque insulated wall costs were estimated at $198-$239/m 2, compared to glazing system costs used in this study of $225-$1245/m 2 plus $625/kW for increases in plant capacity. In later work, the glazing costs were revised based on industry feedback to a range of $302-$597/m 2, reducing this difference but still maintaining a significant additional cost for glazing relative to opaque wall. 13

14 for NCC2016. Where costs are larger, the benefit cost ratio is typically larger than 1, indicating an acceptable outcome under the economic framework set for the code upgrade. CONCLUSIONS The proposed DTS measures for NCC2019 represent a significant upgrade relative to the current code. Measures include more stringent requirements for glazing, lighting, and most HVAC components, mostly unchanged requirements for insulation and some relaxation of requirements for economy cycle installation. Modelling of four case study buildings under NCC2016 and proposed NCC2019 compliance scenarios shows greenhouse gas emission reductions mainly in the region of 31-49%. Assessment of capital costs shows that incremental costs are dominated by decisions on window wall ratio, as windows are significantly more expensive than opaque wall to build. The generally smaller WWR proposed under NCC2019 therefore results in lower capital costs in most scenarios. Where costs are higher than NCC2016, the benefit cost ratio is generally above 1, indicating that the overall suite of measures is viable on a whole building basis. REFERENCES 1. AEMO 2016a National Electricity Forecasting Report, Australian Energy Market Operator AEMO 2016b. National Gas Forecasting Report for Eastern and South Eastern Australia, Australian Energy Market Operator, December Balme et al Proposed Fan Measures for NCC2019 T. Balme, P. Bannister, H. Zhang, J. Spears, D. Johnston, AIRAH Future of HVAC Conference, Sydney, August Department of Energy and Environment E3 Consultation RIS for Fans, March Johnston et al 2017a Glazing studies for NCC2019 D. Johnston, H. Zhang, G. Wang, P. Bannister. AIRAH and IBPSA s Australasian Building Simulation 2017 Conference, Melbourne, November Johnston et al 2017b Roof, Walls and Floor insulation Study for NCC2019 D. Johnston, G. Wang, H. Zhang, P. Bannister AIRAH and IBPSA s Australasian Building Simulation 2017 Conference, Melbourne, November Jolley-Rogers et al Modelling for Potential Increases in Lighting Power Density Stringency in Section J6 of the NCC C. Jolley-Rogers, L. Boland, P. Bannister. AIRAH and IBPSA s Australasian Building Simulation 2017 Conference, Melbourne, November