Directorate for the Built Environment Building Standards Division

Transcription

1 Directorate for the Built Environment Building Standards Division Energy Management Solutions Ltd Investigation of measures to improve the energy performance of a existing building: Retail JUNE 2009

2 Report prepared by: Energy Management Solutions Ltd 19 Albany Street Edinburgh EH1 3QN Tel: Fax: The opinions expressed in this report are those of the author. Report commissioned by: Building Standards Division Directorate for the Built Environment Scottish Government Denholm House Almondvale Business Park Livingston EH54 6GA Tel: Fax: web: Crown Copyright 2009 Applications for reproduction of any part of this publication should be addressed to: Building Standards Division, Directorate for the Built Environment, Denholm House, Almondvale Business Park, Livingston, EH54 6GA This report is published electronically to limit the use of paper, but photocopies will be provided on request to Building Standards Division.

3 Contents Contents Executive Summary Introduction Research Methodology EPC Recommendations Review of Findings Appendix 1 Energy Output Ratio Pie Charts Appendix 2 Building Models (Designbuilder 3D) Appendix 3 Wind Speed Analysis for Wind Turbine Recommendation For the 1km grid square (NT0566)... 20

4 1 Executive Summary Energy Management Solutions Ltd (EMS) has been requested to carry out building energy usage and CO 2 emission modeling/calculation for a Boots Store in Livingston which has recently had a significant building extension added. The research study is to be undertaken using SBEM calculations and EPCs for the building prior to extension, as extended and with an increased level of insulation of up to 50% compared with 2007 Non-domestic requirements set out by the Scottish building standards. Prior to extension as built with extension up to 50% improvement in U-values EPC G F F If built to current standards F F+ F+ Area m CO 2 kg/m kwh/m Table 1 - Designbuilder SBEM and EPC Output The results in table 1 show that only a relatively minor improvement in energy usage is possible with the improvement in insulation for the building with extension and there is no Building Energy Asset Rating (BER) reduction in CO 2 emissions CO 2 kg/m 2 when applying a calculated 50% improvement in U-Values. The EPC recommendations for the building prior to extension and as extended are to be evaluated in terms of their impact on capital costs, costs in use, lifecycle costs, CO 2 emissions and energy usage. A total of 5 recommendations have been assessed including lighting, DHW, heat recovery and renewable generation and the results are highlighted below in table 2. 3

5 Prior to extension As built with extension Recommendation T5 retro fit Secondary DHW loop timer Plate heat recovery Solar thermal Wind turbine EPC before G F F F F EPC after G F F+ F F kg CO 2 9,020 1,600 8,000 3,200 3,200 reduction/yr kwh reduction or generation/yr 20,500 4,800 36,800 8,000 8,000 Costs Capital Cost 5,500 1,000 6,800 13,000 23,600 O & M - 1, ,472 5,769 10,713 Revenue or Avoided cost Energy 57,135 10,533 32,463 28,039 21,153 Disposal / Salvage ,269 Lifecycle cost NPV 53,144 9,533 23,445 9,947-11,891 Table 2 EPC recommendations improvements All values above are shown in present value for the whole 25 year lifecycle costs using a discount rate of 3.5% and an energy cost inflation of 2.5% per year. Other key findings: In the case of this building which is situated in a shopping centre with heated spaces around three of the sides, there is no economic justification for improving the insulation levels. This is due to the high cost of cooling (electricity). A large number of the recommendations produced by the SBEM EPC software are for un-obtained data (Seasonal efficiency etc) and therefore if implemented they are likely to improve the simulation results without actually reducing energy savings. Heating control recommendations by the SBEM EPC software have no effect on SBEM EPC results if implemented, even though in reality they are highly likely to reduce operational energy consumption. 4

6 2 Introduction Energy Management Solutions Ltd (EMS) has been requested to carry out building energy usage and CO 2 emission modeling/calculation for the Boots Store in Livingston which has recently had a significant building extension added. The research study is to undertake SBEM calculations and EPCs for the building prior to extension and as extended and with an increased level of performance/insulation of up to 50% compared with 2007 Non-domestic requirements set out by the Scottish building standards. The EPC recommendations for the building prior to extension and as extended are to be evaluated in terms of their impact on capital costs, costs in use, lifecycle costs, CO 2 emissions and energy usage. 5

7 3 Research Methodology 3.1 Methods & Input data The SBEM interface software used for the creation and modeling of the buildings is Designbuilder. U-values 1991 Technical Standards Extension as built 2007 Non-domestic Technical Handbook: Maximum Extensions U-values to the building envelope: Maximum U- values Up to 50% Improvement in U-values (based on best material availability) Wall Floor Roof Flat Roof Pitched Table 3 - Construction U-values 3.2 Prior to extension Limited information was available for the building prior to extension regarding construction and HVAC systems. The building is 16 years old which gives it a year of construction of 1992/1993. As construction details are limited inference values for 1991 Scottish building regulations have been used. All U-values used or referred to in the specification of the building models are detailed in table 3. Lighting has been specified as T8 main frequency throughout for the existing building with the addition of display lighting in the sales areas with a lighting efficiency of 15 lumens/w. The HVAC systems for the existing building have been split between the floors with the first floor employee areas supplied by a central heating system using radiators and the ground floor having a split or multi-split heat pump system. All are using default efficiency values as no information has been supplied. Hot water is assumed to have been supplied by a stand-alone electric heater. This resulted in a G rating in the EPC calculations for the building prior to extension (Refer to Table 4 below). 6

8 3.3 Building as extended More information was to hand for the building as extended but some HVAC details such as seasonal efficiencies and heat recovery information on the air handling unit could not be obtained. The air handling unit is specified as a single duct Variable Air Volume (VAV) system and has been given an estimated seasonal heating efficiency of 82% from details found on the name plate. The default cooling efficiency for a unit of this type installed after 1998 has been selected form the SBEM software. Split/multi-split AC systems supply the offices/consultation, training and staff rooms. The system on the ground floor has been specified with a heating Seasonal Energy Efficiency Ratio (SEER) of 3.68 and a Cooling Energy Efficiency Ratio (EER) of The system on the first floor has been specified with a heating Seasonal Energy Efficiency Ratio (SEER) of 3.5 and a Cooling Energy Efficiency Ratio (EER) of The U-values in the Extension as built column in table 3 have been used for construction details. These have been arrived at by checking the specified U-values in the extension drawings with insulation manufacturers values for similar constructions and values obtain by Designbuilder layer model calculations using the surface construction details in the drawings. Most of the windows have been specified as metal framed double glazing units with a 12mm gap, apart from the window in the stairwell which is a PVC framed double glazing unit with a 20mm gap. The lighting is PLL type (55W) luminaries in recessed fittings in the sales areas with a 900 lux lighting level. Using the DIALux lighting software package and the lighting layout detail obtained on site this produced a design lighting energy usage of 25W/m 2. Display lighting has been selected with an efficiency of 15 lumens/w within the sales areas. Lighting in offices is also supplied by PLL luminaries with manual switching and a reduced illumination level of 600 lux. Again using the DIALux lighting software package and this time the specified lux level a design lighting energy usage of 12W/m 2. The training room has the same lighting details as the offices except there is passive infrared (PIR) movement detection switching control. The stock room, corridors and stairs are supplied by T5 lighting with PIR control and the toilets have PIR controlled 2D compact fluorescent lights (CFLs). The staffroom has manual switching high frequency T8 lighting. 3.4 Up to 50% insulation improvements The most significant observation regarding the result outputs is the fact that improvement of U-values by up to 50% is having no impact on the building asset energy rating and only marginal improvement on the kwh/m 2 energy output. The U-values used are the minimum specified by the insulation manufacturers in their documentation for the insulation material and construction composition currently being used. The increases in insulation depth are: from 50 to 65mm rigid phenolic insulation for the walls, 100 to 150mm rigid phenolic insulation for the roof and 40 to 100mm rigid phenolic insulation for the floor. The reason for this is the consequential increase in cooling demand as the building insulation is improved. This is simply because both heating and cooling transmittance rates are reducing as the building insulation is enhanced and the impact of this is the need to provide increased cooling to disperse internal heat produced from heat gains associated with people, lighting and other equipment. This suggests that the need for more passive cooling and ventilation design is paramount when considering 7

9 high insulation building element design with aspects such as night purging, thermal mass calculation and stack effect cooling. The impacts of such measures would require careful review. This resulted in an F rating in the EPC calculations for the building as built with extension (Refer to table 4 below). 3.5 Results Prior to extension as built with extension up to 50% improvement in U-values EPC G F F If built to current standards F F+ F+ Area m CO 2 kg/m kwh/m Elec (kgco 2 /m 2 ) Fuel/Gas (kgco 2 /m 2 ) Heating (kwh/m 2 ) Cooling (kwh/m 2 ) Auxiliary (kwh/m 2 ) 3* Hot water (kwh/m 2 ) Lighting (kwh/m 2 ) Equipment (kwh/m 2 ) Table 4 - Designbuilder Full SBEM & EPC Output *The notable increase in the auxiliary energy values before and after the extension is due to the additional energy for the pump and fan to deliver the extra air flow required in a variable air volume air handling unit (after), compared with a split or multi split system (before). Further energy is also required for new extraction in some areas 8

10 4 EPC Recommendations We have also evaluated the EPC recommendations for improvement to both the original building and the building as extended. A lot of the recommendations produced by the EPC SBEM software are produced to cover information that has been left as default such as HVAC and DHW efficiencies or controls. The heating control recommendations have no real impact in terms of the SBEM calculations and therefore produce no change in energy usage even though they are likely to provide some actual heating energy reductions in terms of real time consumption, which is why they are recommended. Some lighting recommendations are also automatically produced by the software because design lighting energy levels have been specified instead of a lamp type being entered. Recommendations which are implementable and that produced a positive SBEM Building Energy Rating improvement included T5 retro fitting of T8 lighting in the original building. This could be done in the building as extended but the small area of application and the use of high frequency T8 lights produced no change in EPC rating or energy usage. The only recommendation that did have a positive effect on the rating of the building as extended was the plate heat recovery in the air handling unit. The timer control for the secondary DHW circulation loop reduced CO 2 output and energy use but not enough to improve the EPC rating. In addition, renewable technology recommendations were evaluated: a solar thermal system and a wind turbine. At this stage a passive cooling design was not evaluated as this would require detailed modeling of the building using Dynamic Simulation Software (DSM), such as EnergyPlus or IES. A summary of the result outputs using SBEM for the various improvement recommendations are summarized in Table 5 below. Prior to extension As built with extension Plate Recommendation T5 retro fit Secondary DHW loop timer heat recovery Solar thermal Wind turbine EPC before G F F F F CO 2 kg/m 2 before CO 2 kg before 93, , , , ,000 EPC after G F F+ F F CO 2 kg/m 2 after CO 2 kg after 84, , , , ,800 kg CO 2 reduction/yr kwh reduction or generation/yr 9,020 1,600 8,000 3,200 3,200 20,500 4,800 36,800 8,000 8,000 Costs 9

11 Capital Cost 5,500 1,000 6,800 13,000 23,600 O & M - 1, ,472 5,769 10,713 Revenue or Avoided cost Energy 57,135 10,533 32,463 28,039 21,153 Disposal / Salvage ,269 Lifecycle cost NPV 53,144 9,533 23,445 9,947-11,891 Table 5 - Recommendation Results All values above are shown in present value for the whole 25 year lifecycle costs using a discount rate of 3.5% and an energy cost inflation of 2.5% per year. Net Present Value (NPV) = Energy + Disposal/Salvage - Capital Cost O&M Salvage has been taken as a 20% return on initial cost. This does not apply to the T5 lighting for which disposal has to be paid for. Note that the cost in use is based on the change in gas and electricity usage at a rate of 3.5p/kWh and 12p/kWh respectively. 4.1 T5 Retrofit Recommendation The T5 retro fit kit can be easily installed and are reasonably cost effective at 25 per kit which includes the T5 fluorescent tube. It has been estimated that 164 tubes would need to be replaced giving a purchase cost of 4,100. The period over which the life cycle costs have been taken for all recommendations is twenty five years. Disposal costs are applicable for fluorescent tubes because of the mercury they contain. Disposal costs occur both during initial implementation and from replacement due to failure during the twenty five year life cycle cost period. The T5 lights are estimated to have a six year lifetime which is twice as long as for T8. This means the T8s are replaced eight times to the T5s four during the 25 year period, therefore the T5s cost less to maintain and dispose of during for the whole life cycle. Elements Costs In house time 200 planning 200 consultancy costs 0 Health & safety 200 Purchase 4,100 Installation 800 Total 5,500 Table 6 - T5 recommendation initial cost breakdown Energy 2,647 Table 7 T5 recommendation first year energy saving 10

12 The value will increase by 2.5% each subsequent year. Elements Costs insurance 0 operation 0 cleaning 0 maintenance - 82 Total O&M - 82 Table 8 T5 recommendation yearly operation & maintenance cost 4.2 Timer for Secondary DHW Loop Recommendation Installing a timer for the Secondary DHW loop will help reduce the heat loss in the hot water pipes as well as reduce pump energy consumption. Elements Costs In house time 200 planning 200 consultancy costs 200 Health & safety 0 purchase 200 installation 200 Total 1,000 Table 9 Secondary DHW loop timer initial cost breakdown Energy Secondary DHW loop timer first year energy saving The value will increase by 2.5% each subsequent year. Elements Costs insurance 0 operation 0 cleaning 0 maintenance 0 Total O&M 0 Table 11 Secondary DHW loop timer yearly operation & maintenance cost 11

13 4.3 Plate Heat Exchanger Heat Recovery Recommendation Installing a plate heat recovery system into the air handling unit (AHU) will reduce the heating energy use as the heat exchanger pre-heats the cool intake air thus reducing the work done by the heater. The plate heat exchanger has a default recovery efficiency of 65% in the SBEM calculations. Installation costs are high for the heat recovery system because it would have to be retrofitted to the AHU. The plate heat exchanger would also require cleaning and some extra maintenance to ensure it remains working at maximum efficiency (Refer to Table 14 below). Elements Costs In house time 400 planning 400 consultancy costs 600 Health & safety 400 purchase 3,000 installation 2,000 Total 6,800 Table 12 Plate heat recovery initial cost breakdown Energy 1,504 Table 13 Plate heat recovery first year energy saving The value will increase by 2.5% each subsequent year. Elements Costs insurance 0 operation 0 cleaning 50 maintenance 100 Total O&M 150 Table 14 Plate heat recovery yearly operation & maintenance cost 4.4 Solar Thermal Recommendation The solar thermal energy is calculated according to the collector orientation and inclination and an annual efficiency conversion factor which is taken as 38% in SBEM. SBEM does not allow alteration to the conversion efficiency for different collectors, account for different preheating strategies or consider pump electrical consumption. The solar thermal system has been specified as south facing at a 30 o inclination with a 10m 2 collector surface area. The recommendation may be a good option for this building because hot water is currently supplied by electricity which is much more expensive than gas and has a higher CO 2 conversion factor. Solar thermal systems have few 12

14 moving parts which reduces maintenance costs but the effects of the extra pipe work and pumps still has to be considered. To help ensure the solar thermal collector is working at maximum efficiency, it should be cleaned regularly. Insurance will also be needed due to the potential for damage to the building and the solar thermal system itself from extreme weather events (refer to table 17 below). Elements Costs In house time 800 planning 800 consultancy costs 1,000 Health & safety 400 purchase 8,000 installation 2,000 Total 13,000 Table 15 Solar thermal system initial cost breakdown Energy 1,299 Table 16 Solar thermal system first year energy saving The value will increase by 2.5% each subsequent year. Elements Costs insurance 100 operation 100 cleaning 50 maintenance 100 Total O&M 350 Table 17 Solar thermal system yearly operation & maintenance cost 4.5 Building Mounted Wind Turbine Recommendation The wind turbine calculations are based on the Average Power Density Method. Wind speed is taken from the CIBSE test reference years for one of 18 sites around the country. This means variations in the local wind resource from those used in SBEM are very likely. A 6kW wind turbine has been specified as having a 5.5m rotor diameter giving a blade sweep area of 23.7m 2. The hub height has been set at 20m with a terrain type of Suburban or industrial area. Some allowance had been made within the installation costs for building mounting a wind turbine. A wind turbine of this size requires a yearly service which requires the wind turbine to be lowered to the ground. Planning for a wind turbine of any size to be placed on a building can be problematic especially in this case where a different landlord owns the shopping centre. Insurance may also be expensive due to potential for damage to the building from vibrations and to the wind turbine itself from extreme weather events. A detailed feasibility study would be required. 13

15 Elements Costs In house time 800 Planning 1,000 consultancy costs 2,000 Health & safety 800 Purchase 15,000 Installation 4,000 Total 23,600 Table 18 Wind turbine initial cost breakdown Energy 980 Table 19 Wind turbine first year energy saving The value will increase by 2.5% each subsequent year. Elements Costs insurance 200 operation 100 cleaning 50 maintenance 300 Total O&M 650 Table 20 Wind turbine yearly operation & maintenance cost 14

16 5 Review of Findings No improvement in EPC Asset Rating KgCO 2 emissions results from the increase in performance of the building when using the up to 50% improvement U-values in table 1. These U-values are the minimum specified by the insulation manufacturers in their documentation for the insulation material and construction composition currently being used. The reason that there is no CO 2 reduction is because the cooling already accounts for a large part of the energy usage and CO 2 emissions, such that increasing the insulation whilst reducing heating, will also increase the amount of overheating and therefore the cooling demand. The overheating and therefore cooling demand can mainly be accounted for by high internal heat gains such as high lighting levels. The majority of the heating energy is supplied from gas which has a lower CO 2 conversion factor than electricity. This means that to meet this additional electricity based cooling demand, even though the overall energy building usage kwh/m 2 is slightly less, the CO 2 emissions are calculated to be at the same level (Refer to table 21 below). Assuming a cost of 3.5 p/kwh for Gas and 12 p/kwh for electricity, the energy costs for the up to 50% improved U- Value building are actually about the same /m as for the building as built with the extension as shown in table 9 below. In conclusion no economic or environmental justification can therefore be given recommending 50% U-value improvements for this type of building without designing the building to maximise the use of passive ventilation and cooling. Prior to extension as built with extension up to 50% improvements to U-values Elec kwh/m /m Gas kwh/m /m Total kwh/m Total /m2 30 Table 21 - Estimate kwh/m2 and cost /m2 comparison The EPC recommendation results show that the recommendations providing the biggest reduction in energy consumption or CO 2 emission are not necessarily the most financial sound investments. Lighting upgrade is generally one of the best ways to reduce energy usage where applicable and normally have a short payback period. Heat recovery in a large AHU should always be implemented where possible and applicable. If it is included during the initial installation much of the capital costs associated with this recommendation would have been reduced. 15

17 The renewable generation recommendations had mixed results. The solar thermal system and wind turbine system used in the recommendation produce the same amount of energy but the default electric DHW efficiency of 75% meant the solar thermal energy cost saving is greater. The electrical DHW system also substantially increases the CO 2 and cost savings that would be experienced by a natural gas DHW system with solar thermal implemented and also for the secondary DHW loop timer. The high initial cost of these systems means the NPV is low for the solar thermal and negative for the wind turbine system. The energy produced by the wind turbine is highly sensitive to the actual site wind speed and the quality of the wind (turbulence), this is not taken into account by the SBEM calculations. The energy produced by the wind turbine therefore could be substantially higher at a good wind site than that given by the calculations although it is believed to be representative for this site Prior to extension (6ms 25m hub height). As built with extension Plate Secondary heat DHW loop timer recovery Solar Wind Recommendation T5 retro fit thermal turbine EPC before G F F F F EPC after G F F+ F F kg CO 2 9,020 1,600 8,000 3,200 3,200 reduction/yr kwh reduction or generation/yr 20,500 4,800 36,800 8,000 8,000 NPV 53,144 9,533 23,445 9,947-11,891 Table 22 - Recommendation summary 16

18 Appendix 1 Energy Output Ratio Pie Charts Figure 1 - Prior to Extension energy usage percentage Figure 2 - As built post extension energy usage percentage 17

19 Figure 3 - Up to 50% improvement energy usage percentage 18

20 Appendix 2 Building Models (Designbuilder 3D) 19

21 Appendix 3 Wind Speed Analysis for Wind Turbine Recommendation For the 1km grid square (NT0566) Wind speed at 25m agl (in m/s)