Changing models

This Issue This is a part of the Commercial buildings feature

By and - , Build 145

Prototype models developed from bees data are helping to make energy modelling of commercial buildings easier, allowing building designers to concentrate more on the building’s design parameters.

Figure 1: Energy end-use consumption from office (left) and retail (right) prototypical energy models.

ENERGY MODELLING was used though the Building Energy End-use Study (BEES) to explore current buildings, opportunities for improved energy-efficiency and the impact of future change.

Dashboard developed

One output from the modelling work is a tool to look at the impact of a range of energy-efficiency strategies across non-residential building stock – the New Zealand Building Stock Energy Consumption Dashboard.

Fourty-eight buildings were modelled across seven different climate zones to build up representative data for the dashboard. Users are able to select different BEES building types in different regions, then select a range of energy saving strategies to determine the savings across the selected building stock.

Prototype models help with design

Another key goal of the BEES research was to take the findings of BEES and create prototypical models using base information from real monitored data. This appears to be a world first.

Currently, the New Zealand building design industry assumes various building model inputs for what lights and appliances consume and when they are turned on. With the BEES data, industry energy modellers can be better informed as to how typical commercial buildings actually operate.

Started with five simplified buildings

Initially, five BEES Template EnergyPlus models were developed representing different simplified building forms of typical office and retail buildings found in New Zealand’s non-residential building stock.

While they allow the user to quickly build models, they do not contain usage patterns or equipment loads based on how real New Zealand buildings are used.

New models have data from 100 buildings

The new prototypical models are informed by BEES data from approximately 100 buildings. Prototypical models represent an average building in the commercial building stock and include office and retail buildings. Each is populated with:

● measured data from BEES to inform typical lighting, appliance and hot water load densities and patterns of use

● New Zealand-relevant HVAC systems with associated efficiencies

● representative building sizes, window area and construction types.

Different scenarios can be examined

The biggest advantage of the prototypical models is that they allow building design teams to examine the building performance under different load density scenarios with additional low and high building load options.

This lets them understand whether the predicted building performance is dependent on the assumptions about people, lighting and equipment used within the design modelling and to assess the associated risks.

This is particularly useful for high-performance designs where a quick test using a range of design scenarios can establish the robustness of the design concept. Internationally, there have been criticisms of high-performance designs that only perform well in a very narrow band of scenarios based on assumed parameters.

EnergyPlus models updated

Along with new prototypical models, the initial five BEES Template EnergyPlus models have also been updated.

While they still have a library of New Zealand-relevant materials and constructions, they now include the different building load and usage pattern scenarios established for the prototypical models as well as the New Zealand-relevant HVAC systems.

Old presumptions overturned

Interestingly, the profiles and use patterns produced from the BEES data are significantly different than the required and assumed installed loads and patterns of use presented in the New Zealand Building Code.

This has led to a recommendation that the modelling section of NZS 4243:2007 Energy efficiency – Large buildings should be updated to incorporate the building templates and schedules developed through BEES.

Figure 1: Energy end-use consumption from office (left) and retail (right) prototypical energy models.

For more

Visit www.branz.co.nz/bees.

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Articles are correct at the time of publication but may have since become outdated.

Figure 1: Energy end-use consumption from office (left) and retail (right) prototypical energy models.

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