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Zero Energy Building Reduced Algorithm (ZEBRA) is a novel super-reduced, pedagogical tool for designing net zero buildings at early design stages.



Project status

In progress



We are moving towards a carbon neutral society. Within the industrialised world, the built environment is the sector with the largest carbon emissions (approx. 40%). So those involved in the building design process have a large responsibility to design zero or near-zero carbon buildings. Since early-stage decisions have the largest environmental impact, we need to use tools that estimate the energy and carbon performance of buildings at early design stages. However, most commercially available tools require a detailed description of buildings which is unknown at early stages. They may also look over-complicated to non-specialists due to their numerous inputs and lack of guidance.

In this context, we developed a super-reduced, pedagogical tool called ZEBRA. This provides a rough estimate as quickly and transparently as possible, showing which factors contribute the most to results. It is a spreadsheet software tool that requires 33 inputs and no training, considers embodied emissions and renewables, and leaves users upskilled on zero carbon design. It is sufficiently accurate compared to popular commercially available tools, such as the Passive House Planning Package (PHPP).

ZEBRA was developed as part of the Active Building Centre Research Programme at Bath. The programme brings together ten leading universities and several businesses to develop and test innovative ideas and technologies that will enable the construction industry to transform into a net zero emissions sector.

ZEBRA explained

ZEBRA is organised around topics (such as walls, ground floor, roof etc) with one per spreadsheet tab. Given its pedagogical focus, each tab includes information relevant to each topic that may be well known to experienced modellers, but unknown to beginners. Using ZEBRA for the first time takes about 45 minutes considering that you read all information and familiarise yourself with the interface. After that, it takes less than 20 minutes.

Users can state their requirements, such as designing a net zero energy building, at the beginning of the modelling process. After inserting all the required inputs, outputs, such as energy balances, can indicate whether such requirements have been met. If not, users can further adjust their model according to the information provided by ZEBRA on the major drivers of energy.

ZEBRA is released under an open license, so feel free to download it, edit it, and share it with others!


Download ZEBRA Current version is v21-07-12

Contact us

Please get in touch if you have any issues, suggestions or questions about ZEBRA.