Design for Performance (NABERS UK)
Design for Performance (DfP), particularly NABERS UK certification, is a methodology that can benefit the built environment and create value for asset owners, developers or building operators.
What kind of value can be extracted from a DfP project:
More reliable conversion from theoretical design to real life performance providing more certainty of operating costs over the lifecycle of a building.
Typically lower operating costs for buildings that have been designed with real life performance as a focus.
Performance gaps are mitigated causing less problem assets and therefore less capital expenditure for future improvement projects.
Asset value can benefit from the DfP certification as the asset has more operational certainty and verified real life operational performance.
In the future the DfP approach is likely to replace energy and carbon compliance targets within the building regulations. Early adopters will find themselves with stronger portfolios.
What do we mean by Design for Performance (DfP)?
In the UK there are concerns that a “Design for Compliance” culture has taken root. Meaning that building developments are only concerned with meeting the theoretical targets set out in energy compliance regulations such as Part L or Section 6 of the UK building regulations.
This culture has led to a “performance gap” where the building performance in operation is inferior to its theoretical design – this leads to a number of issues including increased operational costs and lacklustre energy performance. The Better Buildings Partnership (BBP) created a very illuminating visual back in 2019 with regards to the lack of correlation between compliance rating and real life performance, highlighting the importance of not only design for performance but also more robust compliance practices!
In an attempt to alleviate these issues a move towards a “Design for Performance” culture is being pushed by building related institutions in the UK. The approach includes measuring and verifying the building’s performance during operation – project teams have more responsibility for delivering a building that not only meets the theoretical compliance targets but also meets the real-life performance expectations of its operational target rating.
At Meadows and Ross we are firm advocates of using the Design for Performance approach when appropriate. By understanding our buildings better during the design stage we can have more certainty and better predictive knowledge of the building’s performance throughout its lifecycle. This is especially important with complex or high value assets such as commercial offices, schools and hospitals. In the UK, currently the most prevalent Design for Performance certification scheme is NABERS UK, Meadows and Ross are helping clients navigate the NABERS process and also assist with the integral building simulation modelling.
NABERS UK
The NABERS UK Design for Performance (DfP) scheme is a performance-based approach that shifts the focus from theoretical design predictions to actual operational outcomes. Originating from Australia, where it has seen significant success, NABERS (National Australian Built Environment Rating System) is now accessible for the UK market, where it is hoped the Australian success can be emulated.
The major contributions required for the NABERS process are:
Setting of a Target Rating
Building Performance Simulation Model
Independent Design Review
Verification of the Rating for the Operational Building
Multiple scenarios for testing the resilience of the design against changing conditions.
The rating system is connected to the energy consumption of the building and represents a measurement of the building’s efficiency and useful benchmark against similar assets. When selecting a rating it is important to be realistic as the top ratings require systems and occupant behaviours above and beyond the typical design approaches that target energy compliance like Part L and Section 6.
The building simulation model is a vital part of the NABERS process and beyond the design itself represents the largest piece of effort contributing to the process. A NABERS DfP simulation model endevaours to be as realistic as possible. The model should include very specific system parameters and occupant behaviours that are likely to be seen once the building is operational.
In order to achieve this level of detail and realism a very collaborative approach is required between the designer, the simulator and the intended occupants / stake holders. Free flowing and plentiful information specific to the operation of the building is vital if a realistic estimate of the future operational building is to be achieved.
The simulation must include hourly changes in thermal conditions, weather, internal gains and the impact of the thermal masses of the building construction. The output from the model must include energy consumption, internal temperatures, equipment loads and plant loads. The simulator should produce a Base Case Model which represents the office space as it is expected to operate. This allows the delineation between the base building energy performance and any energy usage by tenants. The modelling is performed prior to construction and operation therefore it is prudent to build in an appropriate margin for the energy consumption that will protect the project from risks to its energy performance during operation.
There are a number of “off-axis” models required to be produced by the simulator, these models should be variations of the Base Case Model and test the building’s resilience to performance risks. For example, a simulation may be performed based on future weather data and this would give an idea of the impact of climate change on the operation of the building. All these aspects of the simulation model are then collated into a simulation report which is then scrutinised in the Independent Design Review.
The Independent Design Review (IDR) typically occurs just before construction begins. This review is carried out by NABERS accredited assessors and its purpose is to judge whether the design is suitable for the target rating and whether the simulation model is truly representative of both the design and the expected behaviours of the incoming occupants.
The Verification of the Rating is the final step in achieving a NABERS rating. The verification can only begin after 12 months of occupation above a particular threshold. The verification uses real data to assess the performance of the building. For this reason it is important that the energy metering systems within the building are designed in a way that the NABERS energy rating can be measured. This may require additional metering compared to a typical design.
How Can Building Performance Consultants Assist?
As a voluntary certification scheme which is still in its early adoption stage it can be quite a challenge for new users to get to grips with the Design for Performance process and the rules pertaining to NABERS UK.
At Meadows and Ross we have experience of delivering NABERS projects and are able to assist clients with their DfP projects, including:
Identifying an appropriate Target Rating. By combining the experience of both building performance and the NABERS process a suitable and achievable Target Rating can be set.
Simulation of the operational building at the design stage. Using an appropriate software solution combined with MEP design experience allows consultants to create lifelike simulations.
Creating the simulation report containing all the aspects of building simulation for review in the IDR.
A Building Performance Consultant can perform the Independent Design Review. However, the Independent Design Review must be performed by someone who did not participate in the simulation stage so they can be an objective observer.
Verification of the rating by extracting the required evidence from the operational building in order to verify the NABERS Target Rating.
If you are interested in using the Design for Performance approach for your building please get in touch.
