2011-june guide building energy nabers · whole building commitment agreements. in addition, for...

Version 2011-June

NSW Office of Environment and Heritage

59-61 Goulburn Street Sydney PO Box A290 Sydney South NSW 1232

Phone: 02 9995 6334 Email: [email protected] Web: www.nabers.com.au

NABERS Energy Guide to Building Energy Estimation

1 Introduction

This document is to be used as a guide whenever a computer simulation is used to estimate base building or whole building energy use under NABERS Energy.

A separate document, being the NABERS Guide to Tenancy Energy Estimation is available that deals specifically with the modelling of energy use of tenancies. This latter document is also to be used when the tenancy for the building is known.

This document supersedes the ABGR Validation Protocol for Computer Simulations. It has been renamed to avoid confusion with the Validation Protocol for Performance Ratings.

1.1 ABGR and NABERS ABGR is a world first initiative, developed for Australian conditions, that provides accredited assessments of the greenhouse intensity of office buildings by awarding a star rating on a scale of one to five. ABGR now forms the basis of the National Australian Built Environment Rating System (NABERS). NABERS uses the ABGR methodology to provide star ratings for the broad environmental impacts of buildings – energy, water, waste, indoor environment and site impacts. ABGR has now been renamed NABERS Energy. For more information see www.nabers.com.au.

1.2 The Role of Simulation in the NABERS Energy Commitment Agreement Developers of new and refurbished office premises can use NABERS Energy by signing an NABERS Energy Commitment Agreement that commits their building to achieving a 4, 4.5, 5, 5.5 or 6 star NABERS Energy Performance Rating in operation. They are then permitted to use the relevant NABERS Energy trademark in publicity for the building prior to completing an accredited rating of the building’s actual operational performance. Persons or organisations quoting NABERS Energy ratings that are not substantiated by an accredited NABERS Energy Performance Rating or an NABERS Energy Commitment Agreement are in breach of trademark and may be subject to legal proceedings.

Under the NABERS Energy Commitment Agreement, simulation is recommended for buildings aiming to achieve NABERS Energy 4 stars for base or whole building ratings and is compulsory for 4.5, 5, 5.5 or 6 star NABERS Energy ratings. Compliance with this document is required for all simulations submitted for base building and whole building Commitment Agreements. In addition, for whole building Commitment Agreements, the modelling of the operation of the tenancy must comply with the NABERS Energy Guide to Tenancy Energy Estimation.

The use of a simulation as one part of determining energy performance is secondary in importance and authority to the recommendations of the NABERS Energy Independent Energy Efficiency Design Review. This is because any realistic determination of energy performance involves a substantial amount of professional judgement about factors that are either impractical or impossible to simulate.

Those using this document who are not engaged in a Commitment Agreement are advised to use the NABERS Energy Independent Energy Efficiency Design Review process to provide a more complete understanding of the likely performance of their building.

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1.3 The Role of Simulation in Design This document has been written for use in all applications where simulation is estimating the potential for a building design to reach the nominated NABERS Energy score (4, 4.5, 5, 5.5 and 6 stars).

Simulation is not a definitive indicator of the performance of a building, and indeed the relationship between the average performance of buildings and their simulations is very weak. Real buildings rarely reach the performance potential indicated by simulation and the gap between theroretical and actual performance is often very substantial.

As a consequence, simulation should not be advanced to clients as a sole and uncaveated means of estimating building performance in operation.

1.4 The role of this document This document is aimed at ensuring that simulations provide useful and realistic assistance to the design process.

This document assists in: The production of a building energy use estimate that can help inform the design, commissioning

and operation of a new building; and The conversion of a simulated energy use estimate, together with other energy calculations, into

an NABERS Energy Whole Building or Base Building Rating. This document is structured to allow its use in a prescriptive manner. A compliance checklist is provided to ensure that the building energy estimate complies with key elements. It is the responsibility of the simulator to comply with such requirements in as far as possible in any given project. Where an issue of technical interpretation cannot be resolved between the simulator and any body requiring compliance, the NABERS National Administrator may be approached to resolve the issue.

However, in all cases, simulators must satisfy themselves that any choice they make in the simulation of the building is a realistic assessment of what will happen once the building is built. In some cases this will be guided by this document and in others it must be guided by the simulator's professional judgement. It is strongly advised that simulators be conservative in their assumptions, include appropriate margins, and subject their own results to vigorous internal assessment rather than run the risk of producing an optimistic assessment of a building that subsequently rates lower.

No party associated in any way with the production or distribution of this document accepts any liability for any loss, financial or otherwise, caused directly or indirectly in association with the use of this document. In all cases, the sole responsibility for the simulation lies with the simulator.

1.5 The role of the simulator The role of the simulator in the assessment of building energy performance is to:

1. Use the simulation to assess and advise the building design to achieve a more efficient outcome, particularly with respect (but not limited) to: window shading and glazing options; HVAC performance and alternative design, sizing and system scenarios; and building envelope design and insulation performance.

2. Ensure that any interpretation of simulation results in terms of actual energy performance is balanced by a realistic assessment of the real-life factors that would or could degrade performance from that predicted by the simulation;

3. Utilise the simulation to identify and investigate performance risks and problems in the energy performance of the building, particularly in common areas of risk such as reheat operation; VSD



operation of fans; out-of-hours operation of small loads; impact of internal load variations and control of central plant; etc.

1.6 Specific Application Requirements The following applications of this document make specific compulsory requirements.

1.6.1 NABERS ENERGY Commitment Agreement The purpose of simulation under the NABERS Energy Commitment Agreement is to provide a quantitative basis upon which the risks of the building’s performance can be assessed. This requires that the simulation is, as far as possible, a good representation of how the potential range of modes in which building will or may operate over time.

All the requirements of this document must be met for an NABERS Energy Commitment Agreement. In particular:

The building is to be modelled as it is expected to operate. If this is unknown, default figures may be used.

No specific restrictions on the simulation package are made. However, it is strongly recommended that packages meeting the requirements identified for the Green Star Office Design tool are considered.

Weather data shall be for a reference year data set for a local weather station representative of the building. Weather data shall use actual recorded solar radiation, temperature and humidity data from the local weather station and either be the ACADS-BSG/CSIRO Nominated Test Reference Year for the nearest available climatic weather station, a Typical Meteorological Year (TMY) for the location or other standard weather year. TRY formats are preferred where available. Additional analysis is recommended to quantify the potential effect of ‘non average’ weather conditions and climate change on future ratings.

1.6.2 Green Star Office Design Tool The Green Star Office Design tool (“Green Star”) uses this document to endeavour to create a simulation model that can be compared on an equitable basis against an absolute scale under standardised conditions. As a result, the following specific compulsory requirements are made under Green Star when using this document:

1. The default figures nominated in Section 5 of this document for occupant density, equipment density, and operating schedules must be used.

2. Lighting density shall be modelled as per the design for base building lighting provided to NLA and house areas with an extra allowance of 1 W/m² for tenants lighting to office floors. Lighting shall be schedules as per the figures nominated in Section 5 for Lighting (limited control)

3. The building must be modelled with all lettable spaces fully occupied with diversity of occupation as nominated in Section 5.

4. The simulation package must either:

o Have passed the BESTEST validation test; or



o Be certified in accordance with ANSI/ASHRAE Standard 140-2001: “Standard Method of Test for Evaluation of Building Energy Analysis Computer Programs”; or

o European Union draft standard EN13791 July 2000

5. Weather data must use ACADS-BSG/CSIRO Nominated Test Reference Year for the nearest available climatic weather station.

These requirements override any contrary requirements within this document when conducting a simulation for Green Star rating purposes.



2 Guidelines for simulation input parameters

In this section, guidelines are provided as to how the simulator should set up the simulation.

In all cases, the key imperative is to ensure that the simulation is as accurate as possible a model of how the building will be working when it is rated in operation. This operational rating will be the sole means by which the success of the building design - and by implication, the simulation - will be judged.

Simulators are strongly advised to avoid idealization of operating parameters as this generally leads to under-prediction of energy use. Suitable margins should be applied to simulation results to take account of the difference between idealised performance and the real world systems. These include a significant control errors, hysteresis, performance deterioration over time, fitout errors and ‘random’ activity of building occupants. Performance optimism in manufacturers catalogue data and the differences between factory/lab test rigs and real world installations need to be considered.

2.1 Preparatory information for the client All simulation packages have limitations. The simulator is to provide the client with a full briefing with respect to the ability of the proposed simulation package to model the building. This briefing must include the following as a minimum:

The simulation package: Is the simulation a full dynamic energy simulation? Has it passed any external validations standards such as BESTEST? Does it model building performance on an hourly basis for a full year?

Model limitations: How accurately can the simulation model represent:

The air conditioning system. Can the model be configured to represent the proposed air-conditioning system?

The air-conditioning controls actually to be used in the building. Note that most models make compromises in this area that can have quite a significant impact on the actual energy use of the building.

Glazing. Does the model represent glazing as a U-value and shading coefficient, or is a more complete model used?

Plant performance: Can performance curves and sizes for actual plant items be fed into the simulation?

Daylighting: Can the model calculate daylighting effects and model the operation of the type of daylight control proposed for light fittings (if applicable).

The building as modelled: are there any aspects of the building that have not been modelled accurately or where compromises have been made.

It is critical that the client and the simulator understand the limitations of the simulations and any models developed, in order to adequately interpret the validity of the final results. See Guidelines for the use of Simulation in Commitment Agreements.

2.2 Weather data The weather data used should comply with the following parameters:



To be from a weather station with a climate representative of the climate local to the building. Caution is required in some cities, and particularly Sydney, which exhibit a range of quite distinct weather patterns across the urban area.

The weather file must comply with the rules set out in section 1.6.

2.3 The Building Environment

External shading. Account to be taken of external shade from buildings and trees. Deciduous trees to be modelled as having time-varying transmissivity.

Horizon. In locations where hills cause the horizon to be substantially higher than a flat plane, additional shading or horizon modelling to be included to represent the impact of this on building performance.

2.4 The building envelope – Thermal Simulation The simulation model is to be a good representation of the building's physical shape, and should be modelled in zones that are sympathetic to the operational and thermal characteristics of the building. Form. The building form is to be modelled completely, with all floors represented (use of identical

floor multipliers to be restricted to cases where individual floors cannot be modelled because of restrictions of the simulation model). Simplification of envelope shapes to be limited and to pay heed to the potential impact of shading effects.

Glazing. Glazing must be modelled using a detailed glazing model rather than a simple shading coefficient and U-value model. This is particularly important when the window wall ratio exceeds 25%. Better models take account of differences in optical and heat transmission, variation of transmission with solar angle, and other such effects. If the standard simulation model does not take account of such effects, the simulator is to be prepared to demonstrate to the client why representation of glazing in detail is not important for the particular building. Impact of frame U-values shall be considered if projected frame area is greater than 5% of the glazing system area, or if high performance, low-E, double glazing is being used.

Insulation. Account to be made of thermal bridging effects for insulated walls and ceilings

Windows. The window wall ratio is to be accurately represented

Shading to be accurately represented, including modelling of overhangs and window insets.

Orientation. The building orientation is to be correctly modelled.

Car parks. Car parks intended for the sole use of tenants to be modelled, including both lighting and ventilation

2.5 The building envelope - Daylight Simulation The simulation model is to be a good representation of the building's physical shape and glazing/shading characteristics. Glazing. Glazing is to be modelled using a detailed glazing model rather than a simple shading

coefficient model.



Shading is to be modelled in detail. For Greenstar, moveable shading must be represented as movable or otherwise in the fixed position that is most disadvantageous to the building’s daylight performance.

2.6 Simulation of internal loads The key internal loads are lighting and office equipment. Overnight energy use of these systems can severely affect all rating types. It is essential to model this realistically rather than on the basis of idealized habits. Refer to Section 5 for default figures to be used if no information on the proposed internal loads is available and when simulating for the purposes of a Green Star rating. However, in all cases, consideration is to be given to the factors below:

2.6.1 Lighting Power Density The installed lighting power shall be assessed from the reverse ceiling plans for the tenancy. If the tenant fitout is unknown, allowance should be made for the possible increase in lighting power density caused by the fitout.

The power consumption used for individual fittings shall include the power consumption of the lamp plus any associated control gear and transformers. The total circuit watts of these components should be confirmed by manufacturers’ data or by in-situ measurement.

Toilets, lift lobbies, plant rooms and foyers are to be represented with different lighting power density levels (providing this is true in reality).

2.6.2 Lighting Hours of Use Overnight lighting energy use can severely impact upon the total energy use of a building. The lighting schedule should be chosen to represent the expected operating patterns for the tenancy. Such patterns may reasonably be derived by enquiry into the operating patterns of the tenants in their previous tenancy, if the switching technologies are similar. If such operating patterns are not known, then the default schedules provided with this document may be used and/or the defaults provided below used to assist in developing a probable pattern. Modellers are advised to give particular consideration of the after hours operation of lights.

Consideration of cleaner’s hours is recommended as these can have a strong effect on the lighting hours. Careful consideration should be given to the likely interaction of the operation of cleaners with the proposed lighting controls.

2.6.3 Lighting Controls Lighting controls are to be modelled realistically. Most simulation models have the ability to model daylighting controls; if this is not the case then either this function is not to be modelled, a different simulation model is to be chosen or a detailed and separate assessment of daylighting effects undertaken and incorporated into the model. Occupancy detector systems will require some judgement in their modelling. A conservative assessment would make little allowance for savings during the day but would still recognize the economies at the beginning and the end of the day. The default methodology provides some additional methodologies which may be used to assist in this process.

2.6.4 Equipment Loads If the tenant fitout is known, the loads should be modelled to represent the actual loads in the site. Suggested load figures are available under the default methodologies of the NABERS Guide to Tenant Energy Estimation. Loads based on tenant fitouts should be modelled on a zonal basis to ensure that the variability of loads passed through to the air-conditioning is captured in the modelling.



The design loadings must not be used as these are intended to be maximum loads rather than realistic operational loads.

2.6.5 Equipment Hours of Operation It is common for offices to leave over 50% of their equipment operating overnight. This represents a major problem for the achievement of a good rating in practice. If tenants are already known, it is worthwhile investigating what level of equipment turn-off they currently achieve, as this will probably be carried over to the new location. The default value of 50% overnight load is to be used unless demonstrable evidence to the contrary can be provided. Even in such a case, higher percentages of overnight equipment operation is to be considered as a potential energy performance risk for the building.

2.6.6 Occupancy The occupancy shall be modelled in a manner that reflects a realistic projection of the operating patterns of the site. This can viably be based on the operating patterns of the tenant at their previous site is this data is available. Occupant density can be based on the tenant fit-out if known; allowance should be made for less than one person per desk actually in attendance, as this is normal. Design occupant densities should not be used as these are normally overestimated, and are intended to be maximum loads rather than realistic operational loads.

The building should be modelled without vacant areas. If it is expected that the building may be only partially occupied at the time of the performance rating, then this should be investigated as an off-axis scenario.

If the tenant is unknown, then the default should be used.

2.6.7 Tenant Supplementary Air Conditioning Tenant condenser water loops can be significant energy uses within base buildings and supplementary air-conditioning, particular for 24 hour loads such as computer room air-conditioning, can be very substantial energy uses within tenancies and indeed may create significant loads for base buildings in terms of pumping and cooling tower energy.

The electrical input into the supplementary units should be determined on the basis of realistic loads, bearing in mind that computer rooms in particular tend to be considerably oversized relative to the actual cooling requirement. If metered data from a previous tenancy is available, this should be used to determine probably loads. If such data is not available, the default methodology should be used.

The impact on base building energy use should be assessed on the basis of the estimated incremental cooling tower energy arising from the calculated tenant loads plus the electrical input to the tenant supplementary conditioners plus the mechanical energy delivered to the condenser water by the pumps. Incremental cooling tower energy may be estimated on the basis of the average cooling tower energy use per unit heat rejection. In addition, the pumping energy must be counted.

2.7 Simulation of HVAC The simulation of HVAC energy use is an area with a high probability of producing misleading or inaccurate results. This likelihood will be reduced if the following factors are taken into account. System choice. The system modelled is to be a good representation of the system being installed in

each part of the building.

System design. The plant size, number of systems, airflows and zoning is to be as per the design. Default efficiency curves for boilers and chillers are to be replaced by the actual known efficiency



curves of the plant being installed. Note that chiller data must be specified under conditions that reflect the intended condenser water temperature controls. Most chiller data is by default specified under standard condenser water conditions which are not suitable for use in a simulation.

System control. This is the most problematic area. In particular, the simulator must consider how well the simulated control system actually models the design control system.

Some key issues in this respect are as follows: The economy cycle for an air-based system

Primary duct temperature control for air-based systems.

The control of airflow for variable speed fans systems.

In all cases, there are often differences between how these are commonly controlled in reality and how these are modelled. Extreme care is required in ensuring that there is good alignment between the two. In many cases, this will be an opportunity to improve the control system of the real building.

System loads. Simulation models tend to assume that loads are uniform throughout a building. In practice, loads are not evenly distributed. This immediately causes significant additional energy consumption. Consideration is to be given to running some scenarios with different internal loads in different zones of individual HVAC systems, to determine how robust results are to this factor. The default figures in Section 5 provide figures for use in this respect.

2.8 Energy Efficiency Risk Assessment A range of scenarios are to be modelled to identify the "weak points" in the simulation information. The particular scenarios required will vary between buildings but generally are to deal with the parameters that are least well defined for the building. Suggested parameters are: HVAC controls. As it is often extremely difficult to exactly align the simulation model with the real

control operation, it is worthwhile to model several HVAC control scenarios, covering the range from "worse than expected control" to "better than expected control". This will also provide valuable information into the controls design process. To achieve this, common flaws in control are to be identified and attempts made to simulate these. In general, this will require some compromise, as few if any HVAC models are able to represent the detail of real failure modes.

HVAC after-hours operation. It is particularly important to determine how efficiently the plant can respond to the low loads generated by an after-hours call. This should be tested well beyond the ‘base case’ after hours assumptions in this document.

Equipment hours of use. Given the unpredictability of overnight equipment loads, the sensitivity of the model to this parameter is to be tested.

Lighting hours of use. If there are no specific technologies in place to prevent overruns of lighting hours, the sensitivity of the model to this parameter are to also be tested.

HVAC loads. As noted earlier, it is a natural tendency in simulation modelling to assume uniform internal loads across different zones. In practice there will almost always be rogue zones that cause, for instance, cooling demand in the middle of winter. The effect of this on system performance is to be investigated.



Multiple failures. Buildings are highly interactive systems and as a result the effect of multiple minor failures can often vastly exceed the sum of the impacts of each failure taken individually. It is essential to consider building failure issues in an integrated manner to avoid a gross underestimate of the total potential impacts.

The purpose of modelling these scenarios is to assist in identifying the factors that pose a risk to building operation in the inevitable situation that the building does not work perfectly. Thus for instance, a common issue with air-based reheat systems is that they use too much reheat. This can be demonstrated and enumerated via simulation. A design team can then consider taking this information and using it to either reduce or eliminate reheat from the design, or specify means of monitoring and managing reheat operation.

It is recommended that design assessment and energy performance assessments are based on a number of non-idealised scenarios rather than on an idealised case. This is because the idealised case will in general over estimate the efficiency in the building.

2.8.1 Suggested Off-axis Factors for Common System Types The following list is not comprehensive but is provided to assist in the compilation of off-axis scenarios for particular projects. System type Off-axis factor All Increased overnight tenant equipment and lighting loads

Excessively tight control bands (e.g. no deadband and heating/cooling proportional bands only 0.5°C each) Increased running hours at no appreciable occupancy. Impact of changes in shading from other buildings and/or trees. Different operating schedules. Impact of a small tenancy running 24 hours per day Impact of the building operating at 75% occupancy

Variable air volume VAV turndown limited to half of design figure (e.g. a turndown to 50% becomes a turndown to 75%) Supply air temperature control constant at minimum supply temperature Linear fan energy turndown (representing poor fan speed control)

Air based systems No economy cycle Increased fan pressure (i.e. poor duct construction, dirty filters)

Baseboard or slab heating/cooling systems

Conflict with air based systems

Tenancies Increased overnight tenant equipment and lighting loads Changes in tenant equipment loads per person Changes in server consumption

A minimum of one off-axis scenario simulation investigating the simultaneous impact of not less than four key off-axis factors in combination is required for a compliant simulation. The simulator must select off axis factors which are likely to have the greatest impact, depending upon the design of the HVAC system, rather than selecting factors that are least likely to impact negatively on the results.



3 Estimating a whole building or base building rating under NABERS ENERGY

3.1 The NABERS ENERGY Base Building and Whole Building Ratings NABERS Energy awards stars based on the greenhouse performance of rated space, with a higher number of stars for better performance. The number of stars is determined from the normalised emissions figure in kgCO2/m

2, which is calculated from the type and quantity of energy consumed and the rated area, normalised for hours of use, equipment density and climate.

The NABERS Energy base building rating rates the greenhouse performance of the landlord operated services in an office building. The NABERS Energy whole building rating rates the greenhouse performance of the combination of landlord services and tenancies in an office building.

This section discusses the calculation of the NABERS Energy Whole Building and Base Building ratings only. Details on the NABERS Energy tenancy rating are provided in the NABERS Guide to Tenancy Energy Estimation.

The key items of data required are:

The net lettable area of the office space being rated, less exclusions for non-office or otherwise non-assessable items.

The energy consumed by the base building (Base Building rating) or the whole building (Whole Building rating)

Hours of occupancy; and

The number of computers (Whole Building rating only)

These are discussed in Section 0.

A simulation result does not constitute an accredited rating under NABERS Energy. This can only be provided by an accredited performance rating conducted by an Accredited Assessor. The NABERS National Administrator strongly recommends that an NABERS Accredited Assessor be used to advise on the application of the NABERS Energy methodology to new or refurbished buildings entering into a Commitment Agreement.

If there is any doubt as to application of the NABERS Energy methodology for the inclusion or exclusion of a particular item of information (eg the area of a particular space or the energy associated with another space), advice should be sought from the NABERS National Administrator or an NABERS Accredited Assessor



4 Identifying data to generate the rating

4.1 Floor area

4.1.1 Data required:

Base Building and Whole Building The Net Lettable Floor Area less deductions for non-office space. The primary data is the Net Lettable Area or NLA. This is defined as the net lettable area for the office tenancy based on the Property Council of Australia publication "Method of Measurement for Lettable Area" March 1997. The rating area is to be based on the NLA, excluding areas that are not offices or supporting the office, or not reasonably comparable to typical office spaces. Car parks are excluded from the area calculation.

4.1.2 Interpretation The simulation is to be based on full occupancy (i.e. no vacant areas), and thus the full rateable floor area with no reduction for vacant areas should be used. If it is likely that the building will not be fully occupied, a lower occupancy (with a correspondingly reduced floor area) is to be investigated as an off-axis factor. Note that energy calculations are treated separately to area calculations. Energy use associated with spaces that are excluded from the area calculation may be included in the energy calculation. Spaces to be INCLUDED in the rating area include:

- The “office space” in which business, clerical or professional activities are conducted.

- Other areas that are not technically considered “office” spaces but support the people carrying out those tasks. This includes meeting rooms, kitchenettes, storage spaces, computer rooms.

- Non-office spaces for the exclusive use of tenants, if the space may be reasonably compared with an office. To be included in the rating, non-office spaces must be included in the NLA, and fitted out for occupancy with air conditioning and lighting to suit. This would include:

o Gymnasiums, child minding centres, treatment rooms and similar (if for the exclusive use of tenants).

o Storage spaces within the office space (if for the exclusive use of tenants).

o Commercial cafeterias and cafés (if for the exclusive use of tenants).

- Spaces open to general public access, up to 10% of the total rating area. Where the public access is over 10% of the rated area, a maximum of 10% of the rated area is allowed to be included. The remainder must be excluded

Spaces to be EXCLUDED from the rating area include: - Non-office spaces not for the exclusive use of tenants. This would include gymnasiums, child-

minding facilities etc that are open to the public.

- All car parks

- All retail facilities



- Long term storage spaces, or temporary storage fitted out in non-office spaces

- Toilets, showers and change rooms (whether installed by the tenant or landlord) are not considered comparable to an office, and the area must be excluded.

It is common for simulation floor areas not to exactly reflect the actual building floor areas. In this situation, it is preferable to evaluate the simulation model areas in terms of the PCA guidelines to produce an estimate of the rated floor area, rather than working solely to the building plans. This is because the key output required for the rating is an accurate picture of the energy density of the building.

4.2 Hours of occupancy


Base Building Whole

Hours per week for which services are required by tenants, excluding start-up times.

Hours per week in which the building occupancy is 20% or more of normal peak occupancy.

4.2.2 Interpretation The hours of occupancy used in assessing the rating are to be assessed as per the table above. The NABERS Energy methodology has correction factors that normalise the actual occupancy hours to standardised occupancy hours. The rating hours are to be weighted by area:

For each space, determine the hours per week according to the rules above.

For each space, multiply its hours per week by its area.

Add all of these together and then divide by the total rated area.

This calculation is expressed in the equation below:

A

ahH

N

iii

1

Where: H = Rated Hours (hours/week) A = Rated Area (m2) i = each space within the rated area hi = hours allocated to each space (hours/week) ai = area of each space (m2)



4.3 Number of occupants and computers

4.3.1 Data required

Base Building Whole Not required Number of computers

4.3.2 Interpretation The number of occupants field of the NABERS Energy rating calculator is not used directly in the calculation unless it is required to assess the number of computers. Modelling of the number of computers is covered in Section �. The figure used in the NABERS Energy rating calculator should represent the number of computers normally switched on during the day.

4.4 Energy consumption details


Base Building Whole Energy consumed supplying building central services including; common area lighting,

lifts

air-conditioning and ventilation

exterior lighting

car park ventilation and lighting where car parks are for the exclusive use of tenants. Does not include energy use associated with car parks outside the building.

hydraulic systems and DHW systems to be modelled, or budgeted as appropriate (allowance for use and testing)

safety and emergency systems

miscellaneous fans (eg kitchens, toilets, refuse etc)

supplementary services provided for tenants, eg chilled water / condenser water / outside air.

on-site generators (allowance for use and testing)

in a representative calendar year.

Energy consumed in base building systems as listed opposite plus tenant lighting, power and supplementary air-conditioning units.



4.4.2 Interpretation The energy used in the building should include all sources of utility energy including electricity, natural gas, LPG, coal, and oil.

The correct interpretation of energy use is essential. The key principles are:

1. The energy use included within the rating is always at least the minimum coverage specified in the table above, but may include a number of items that are not properly part of the energy coverage of the rating but cannot practically be excluded.

2. Whatever exclusions are made must be able to be replicated in the rating of the actual building once it is built. In general this means that there must be an intention to install and monitor sub-metering that would enable the excluded energy to be explicitly identified.

The following points are essential in this process: Coverage. It is essential to ensure that all relevant energy use is included in the rating. This implies

that energy use for items commonly not simulated, such as lifts and domestic hot water, plus often ignored items such as common area and exterior lighting, control systems, electrical losses and system losses must be included in the model where applicable. This can be achieved either by separate calculation or within the model itself. Energy figures must cover one complete and continuous year. ‘Miscellaneous’ energy usage is often underestimated (particularly systems which operate after hours) and must be carefully quantified based on a knowledge of actual data from existing buildings.

Metering. The simulator is to assess the intended metering of the building with some care. The actual performance rating will be based on the meter readings, and thus the interpretation of the simulation model is to mimic this as far as is possible. Any assumptions made about sub-metering are to be made clear to the in the reporting of the simulation.

Treatment of non-office occupancies. Energy use associated with non-office occupancies that are not for the exclusive use of tenants may be excluded from the rating. The most common situation here is that the base building servicing includes occupancies for retail functions on the ground floor. If any of the energy for the non-office area is intended to be separately metered then the metered energy of this non-office space can be excluded. Any component of the energy that is not intended to be separately metered is to be included within the scope of the rating. Note that non-office occupancies for the exclusive use of tenants are to be included in energy calculations.

Treatment of car parks. The energy use of lighting and ventilation for internal car parks provided for the exclusive use of tenants is automatically included within the scope of a base building or whole building rating, and must be included whether separately metered or not. If tenants have use of part but not all of the building's internal car park then the energy use associated with these car parks must be included, following the rules for proportioning as follows.

Proportioning is only permitted in the circumstance where there is a separate utility meter or sub-meter that covers the entirety of energy use associated with the car park and no other aspect of the building central services energy use that is required is to be included within the rating.

If the lease(s) assign a proportion of the relevant energy use, then this proportion shall be used in the assessment of the rating.



If no specific allocation of the energy use is identified in lease documentation, the relevant proportion shall be determined by the total number of tenant allocated spaces divided by the total number of available car parks. Where pass cards or keys are provided, the number of tenant allocated spaces is to be deemed to be the greater of the number of physically dedicated spaces and the number of pass cards or keys issued (to a limit of the total number of available car parks). Tenant car park, pass or key allocation information should be sourced from the lease documentation.

If there is no documentation describing carpark use by tenants then all of the energy use must be included.

The percentage of energy allocation must be documented as per the above; therefore the actual percentage rate can be used in the allocation, up to a maximum of 100% of the relevant utility bill.

Treatment of on-site generation. On-site generation that is connected to the building-side of the electricity meter can be counted against on-site energy use. No discount of on-site energy use is available against energy exported from the site under any circumstances. Fuels used to generate on-site energy must be included within the energy assessment.

Treatment of GreenPower. Any planned or future purchase of GreenPower, the accredited zero greenhouse emission renewable energy supply product provided by energy retailers, is to be treated as normal (i.e. non-GreenPower) electricity for the purposes of the assessment of a new building’s performance under this document. High greenhouse performance in the new building or tenancy is to be achieved through good design focussed on energy efficiency, and / or the application of renewable energy integrated into the building and used by the building to reduce its reliance on fossil fuel energy sources.

5 Default Figures

Where no information is available, the following default occupancy information is to be used: Occupant Density*: 1 per 15 m²

Equipment loads*: 11 W/m², built up by the random distribution into zones of the following loads figures: 5W/m²|7W/m²|11W/m²|15W/m²|19W/m² in the following proportions: 1:2:2:1:1 Simulators must check that the area-weighted average equipment load in their model is within 10% of 11W/m².

Lighting load in tenancies (for “shell and core” buildings)*: 12 W/m²

Lifts 8 kWh/m² based on NLA.

Domestic hot water demand*: 2 kWh/m² based on NLA, plus any system losses

Hourly profiles*: As per the default schedules below.

Base building energy for tenant condenser water loops (tenant unknown)*. The energy use shall be derived on the basis of cooling loads at 50% of the supplementary condenser water system capacity operating for 10 hours a day and at 20% of the supplementary condenser water loop capacity for the balance of time. A COP of 2.4 shall be used for the tenant units.



Base building energy for tenant condenser water loops (tenant known). The energy use of the tenant units shall be derived on the basis described in the NABERS Guide to Tenancy Energy Estimation. This shall be used as an input to reasonable modelling of the cooling tower and pump operation.

For whole building ratings where the tenancy is known, the tenancy defaults described in the NABERS Guide to Tenancy Energy Estimation shall be used.

Items marked * are compulsory when a simulation is being used for a Green Star Design rating. The default schedules are as listed in the schedules below. The “after-hours zones” schedule (which operates the HVAC from 9.00am –midday on Saturday) must be applied to a single after-hours zone of the building. The schedules correspond notionally to a 50 hour a week schedule. However, this is sensitive to the relative size of the after hours zones. When calculating the impact of the after hours zone on the hours for the rating, it is required that the floor area included with the additional hours is limited to the smaller of 10% of the building, 1 storey, or an individual and distinct tenancy with area greater than 5% of the total building.



Weekdays (All zones) Time Period Occupancy Lighting

(Automated time of use control)

Lighting (limited control)

Equipment HVAC Operation

0000-0100 0% 5% 15% 50% off 0100-0200 0% 5% 15% 50% off 0200-0300 0% 5% 15% 50% off 0300-0400 0% 5% 15% 50% off 0400-0500 0% 5% 15% 50% off 0500-0600 0% 5% 15% 50% off 0600-0700 0% 5% 15% 50% off 0700-0800 15% 30% 40% 65% on 0800-0900 60% 75% 90% 80% on 0900-1000 100% 100% 100% 100% on 1000-1100 100% 100% 100% 100% on 1100-1200 100% 100% 100% 100% on 1200-1300 100% 100% 100% 100% on 1300-1400 100% 100% 100% 100% on 1400-1500 100% 100% 100% 100% on 1500-1600 100% 100% 100% 100% on 1600-1700 100% 100% 100% 100% on 1700-1800 50% 75% 80% 80% on 1800-1900 15% 25% 60% 65% off 1900-2000 5% 15% 60% 55% off 2000-2100 5% 15% 50% 55% off 2100-2200 0% 5% 15% 50% off 2200-2300 0% 5% 15% 50% off

2300-2400 0% 5% 15% 50% off



Weekends and holidays (Non-after-hours zones) Sundays and Holidays (After hours zones) Time Period Occupancy Lighting




0000-0100 0% 5% 15% 50% off 0100-0200 0% 5% 15% 50% off 0200-0300 0% 5% 15% 50% off 0300-0400 0% 5% 15% 50% off 0400-0500 0% 5% 15% 50% off 0500-0600 0% 5% 15% 50% off 0600-0700 0% 5% 15% 50% off 0700-0800 0% 5% 15% 50% off 0800-0900 5% 15% 25% 55% off 0900-1000 5% 15% 25% 55% off 1000-1100 5% 15% 25% 55% off 1100-1200 5% 15% 25% 55% off 1200-1300 5% 15% 25% 55% off 1300-1400 5% 15% 25% 55% off 1400-1500 5% 15% 25% 55% off 1500-1600 5% 15% 25% 55% off 1600-1700 5% 15% 25% 55% off

1700-1800 0% 5% 15% 50% off 1800-1900 0% 5% 15% 50% off 1900-2000 0% 5% 15% 50% off 2000-2100 0% 5% 15% 50% off 2100-2200 0% 5% 15% 50% off 2200-2300 0% 5% 15% 50% off 2300-2400 0% 5% 15% 50% off



Saturdays (After-hours zones) Time Period Occupancy Lighting




0000-0100 0% 5% 15% 50% off 0100-0200 0% 5% 15% 50% off 0200-0300 0% 5% 15% 50% off 0300-0400 0% 5% 15% 50% off 0400-0500 0% 5% 15% 50% off 0500-0600 0% 5% 15% 50% off 0600-0700 0% 5% 15% 50% off 0700-0800 0% 5% 15% 50% off 0800-0900 5% 15% 25% 55% off 0900-1000 5% 15% 25% 55% on 1000-1100 5% 15% 25% 55% on 1100-1200 5% 15% 25% 55% on 1200-1300 5% 15% 25% 55% off 1300-1400 5% 15% 25% 55% off 1400-1500 5% 15% 25% 55% off 1500-1600 5% 15% 25% 55% off 1600-1700 5% 15% 25% 55% off

1700-1800 0% 5% 15% 50% off 1800-1900 0% 5% 15% 50% off 1900-2000 0% 5% 15% 50% off 2000-2100 0% 5% 15% 50% off 2100-2200 0% 5% 15% 50% off 2200-2300 0% 5% 15% 50% off 2300-2400 0% 5% 15% 50% off



6 Documentation Requirements

Where a simulation is being submitted in compliance with this document, it must be accompanied by the documentation listed in this section. Input data validation form;

Metering requirement description;

Simulation Results, including scenario listing, building operation summary, energy end use summary, floor area calculation and figures used in rating estimates;

Interpretation of the Results, including Estimated NABERS Energy Performance Based on the Simulations, Risk Assessment and Disclaimer;

Compliance Checklist

The format for each of these items is provided in the sections below. While exact use of the formats provided is not essential, the documentation is to cover the information requirements laid out within the formats in a clear and concise manner. The documentation requirements have been designed to provide a degree of error checking in the process. The forms also provide an opportunity to list all the potential issues with the simulation model and the associated results. Simulators are strongly advised to be full and frank in identifying problems and compromises in the simulation.

6.1 Input data validation form Descriptions provided in this form must describe the simulation treatment of each item and highlight any compromises and assumptions that have been made in putting together the simulation. Item Description Climate Data Type of data, weather station locations. Note: see section 1.6. Building Form Describe how this has been represented. Any simplifications

must be identified External Shade Describe how this has been represented Glazing Describe the type of glazing and how it has been represented in

the model Insulation Describe insulation levels modelled Car parks Describe what has been modelled for car parks Floor Area Describe the modelled floor area. This may not be the same as

the rated floor area. Lighting Power Density Identify different levels in different areas if applicable Lighting hours Provide a full description of the schedule. Include assumptions

about the operation of cleaners on site Lighting Controls Describe controls that have been modelled, including notes on

how control effects were modelled. Equipment Density Include assumptions made for equipment load per person. Equipment Hours Identify the pattern of equipment use assumed and the

consequent effective equipment operating hours.



Occupant density Identify the basis upon which this figure was derived. HVAC system type Describe the systems modelled and any differences between the

design and the modelled systems HVAC Hours Describe the hours of operation of the HVAC plant HVAC After hours Describe the representation of after-hours operation used. HVAC plant Describe the plant sizes used, and specifically note any areas

where the simulation was allowed to default rather than use data from the design. Describe chiller and boiler efficiencies.

HVAC Zoning Describe the zoning of the HVAC systems and identify any differences between the design and the model.

HVAC Control Assess the differences between the known or likely control methodologies of the actual building and those modelled.

Energy Coverage Describe energy covered within the scope of the rating. Identify any exclusions or any items outside the scope of the NABERS Energy rating that have had to be included in the energy coverage because of lack of metering.

Document Referencing List drawing and specification versions and dates used to source information.

6.2 Metering requirements description This table must provide a full description of the metering arrangements required or assumed to allow the NABERS Energy rating to be conducted Metering Requirements Energy Coverage Meter Description and Location Describe the energy items covered by this meter. Repeat as necessary for additional meters. Include any sub-

metering required to exclude non-rated energy from the assessment.

6.3 Simulation Results This section must list each scenario, identifying: Any changes between this scenario and the reference case;

The purpose of the scenario

Results for the scenario in the format presented in the following subsections

An absolute minimum of two scenarios, being a reference scenario and one off-axis scenario representing a minimum of four off-axis factors is required for compliance with this document.

6.3.1 Building operation summary This section must identify any issues noted with the building design, including but not limited to the issues listed in the table below:



Issue Comments HVAC system performance Are any of the systems failing to meet peak demands? How

well are temperature control targets met? Plant performance Do boilers and chillers meet the demand? Conversely, do they

appear oversized? Are systems sized and staged to perform efficiently over the full range of loads?

Improvements – Building Envelope Are there any aspects of the building envelope performance that appear capable of being improved?

Improvements – HVAC Are there any aspects of the HVAC design and control that immediately appear capable of being improved?

It is required that the following information is provided for each simulation scenario.

A quantitative identification of the percentage of occupied hours that any conditioned spaces lie outside the nominated control range for the building.

A quantitative indication of the percentage of plant operation hours that the HVAC plant fails to meet the system load demands.

6.3.2 Energy End-use Summary The following information is to be provided for each of the nominated design and off-axis scenarios. Energy End Use Total Electricity

Use Total Fuel Use Fuel Type:________

Electricity included in Rating

Fuel included in Rating

Tenancy Lighting Common Area Lighting

Car Park Lighting Exterior Lighting Tenancy Equipment

Lifts/Escalators Domestic Hot Water

Miscellaneous Non-Tenant Loads

Space Heating Space Cooling Heat Rejection HVAC fans (Occupied areas)



Ventilation fans (toilets, plant rooms)

HVAC fans (Car parks)

Tenant condenser water loop energy use

Tenancy Supplementary Air-conditioning energy use

Total Energy Use

6.3.3 Floor Area Calculation The following information must be listed in description of the modelled floor area:

For each floor of the building as modelled: Gross floor area, net lettable area, and brief description of spaces.

Total net lettable area of the building as modelled.

Total net lettable area of the building in reality.

6.3.4 Figures for use in NABERS ENERGY ratings The following information must be listed for all scenarios for which an estimate of the performance under NABERS Energy has been completed. Item Figure for use in Rating Notes Post Code Rated Floor Area (as modelled) Describe rated area and any

exclusions made. Hours of Use Relate to input data Number of Computers Relate to input data Electricity Use Describe how this figure was derived

from the figures in the other tables. Fuel Use Describe how this figure was derived

from the figures in the other tables.



6.4 INTERPRETATION OF RESULTS

6.4.1 Estimated NABERS Energy Performance Based on the Simulations The estimated building performance must be discussed in the context of the Scenarios Results. It is not compulsory under this document to present a single result figure. However, where external requirements dictate that such a single figure is provided, it is compulsory to present the following:

The nominated performance level in MJ/m², kg/m², and NABERS Energy stars

The kg/m² figure for the nearest NABERS Energy half star performance level

The scenario(s) that represent the nominated performance

Any caveats on the interpretation of the performance level.

6.4.2 Risk Assessment In this table, the simulator must summarize the risk factors that might impinge upon the achievement of the nominated estimated performance, the potential impact of these risks as derived from the energy risk assessment simulations and suggestions as to how these risks might be abated. Risk Potential Impact Abatement approach Describe the area of risk. For instance "Equipment hours of use sensitivity"

Describe the potential impact. For instance "Changing equipment hours of use changed the rating from four stars to three stars."

Describe how the problem might be approached. For instance “Incorporate lease clauses to place obligations on tenants."

Repeat as necessary

6.4.3 Disclaimer It is required to include, as a minimum, the following disclaimer: Computer building simulation provides an estimate of building performance. This estimate is based on a necessarily simplified and idealised version of the building that does not and cannot fully represent all of the intricacies of the building once built. As a result, simulation results only represent an interpretation of the potential performance of the building. No guarantee or warrantee of building performance in practice can be based on simulation results alone.



6.5 COMPLIANCE CHECKLIST This table must be completed for a complying simulation. Item Included? Notes Input Data Validation Form Yes/no Metering Requirements Description

Yes/no

Scenarios Listing Yes/no Off-axis Scenarios Yes/no Building Operation Summary Yes/no Energy End-use Summary Yes/no Figures for use in NABERS Energy Rating

Yes/no

Risk Assessment Yes/no Interpretation of results Yes/no Disclaimer Yes/no A complying simulation must include all the items listed in the compliance table.

2011-june guide building energy nabers · whole building commitment agreements. in addition, for...

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