The Core Tools
The core tools of the Zebra suite are Zebra OC (operational carbon) and Zebra EC (embodied carbon). With Zebra OC you can model the energy and carbon used while the building is occupied. With Zebra EC you can model the carbon used while the building is being constructed and then subsequently demolished at the end of its life.
These are fully-fledged tools for use by professionals or students and are built around various standards. For example, Zebra OC is largely built around the same standard as PHPP, the popular tool used for designing certified Passivhaus buildings.
These tools are intended for early stage design, where many details are not yet available and options need to be evaluated quickly and cheaply. It can produce approximate results quickly, sufficient for initial design. It also aims to be usable by any designer, requiring no specialist expertise or software.
As such, they are powerful tools for developing efficient design concepts, before they are carried forward to detailed design and modelling.
Zebra OC (operational carbon) is an excel-based tool for modelling the energy and carbon of a building when it’s occupied.
Zebra EC (embodied carbon) is an excel-based tool for modelling the carbon of a building during construction and demolition
Zebra OC Online is an web-based version of Zebra OC. Is is similar, but slightly simplified in functionality
Zebra OC
Zebra OC (operational carbon) is an excel spreadsheet. With as few as 20 inputs, it can provide a prediction of the carbon and energy performance of a proposed building.
You start by defining the design requirements for your building. You can then either define the weather data for your site, or select a nearby site from a database. Lastly, you define details of the proposed building construction and dimensions.
Zebra allows for design at several complexity levels. This allows you to start at a low level of complexity, allowing the tool to make more assumptions. As you hone in on your final design you can increase the level of complexity that you want the tool to model
Documentation
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This document hosts ZEBRA’s internal documentation, which is then loaded into the spreadsheet automatically as the purple areas. We have placed all the commentary in a single document in part because some readers may find it easier than reading it within Excel, but also because it is easier for us to edit in Word than in Excel. At the end of the document you will find some notes for these needing to edit this document. You can download it here.
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Research paper that discusses the accuracy of the Zebra model, and compares it with more advanced modelling technologies. The paper is available here.
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We have made some notes for users who are running Zebra side by side with dynamic simulations to compare the outputs. The notes are available here
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We have written a guide on the best approach to take to iterate your designs for carbon and energy performance. This includes information on how to interpret the model and identify areas for improvement. It is available here.
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We have written some thoughts on things students may wish to consider when designing buildings to be efficient in terms of carbon and energy. You get get the notes here
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This essay explains the concept of energy and power in low energy building design. It is available here.
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The heating and cooling demand bar charts are in important part of the Zebra model, but they require some understanding of how the model works to interpret them effectively. We have written a guide on this which is available here.
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The definition of windows is one or the more complicated aspects of the Zebra model. You can download guidance on defining windows here.
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The Zebra model contains a built-in database of weather stations. However, sometimes you may have access to an EPW weather file that represents the weather at your project location better that the stations in the database. You can use this Excel-based tool to convert the hourly data in the EPW file into monthly directional averages required in the Zebra model. Download the tool here
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Choosing your heating and cooling setpoints is an important decision with energy modelling. We have written a guide on this in relation to Zebra, including a discussion of Adaptive Thermal Conform levels. The guide is available here. The spreadsheet to calculate Adaptive Thermal Comfort Levels which is mentioned in this guide is available here.
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This note is about how to account for changes to the heating and cooling of a building brought by sheltering structures, e.g. conservatories, external staircases (circulation space), via introduction of a temperature reduction factor. This note is available here.
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We have written an introduction to the concept of form factor and its relationship with heat loss of a building. This introduction is available here.
Videos
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We have some videos describing the background to the development of Zebra-OC. You can view these here.
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We have created detailed tutorial videos for each part of Zebra-OC, covering all the major inputs and outputs. You can watch these videos here.
Studio report
We produced a report to show how the ZEBRA tools (core and additional tools) might be used in a real studio project created by a group of students in the Department of Architecture and Civil Engineering at the University of Bath. ZEBRA was not used in their original project, so we have re-imagined the project by inserting a variety of results into their project report, based on calculations using ZEBRA. The ZEBRA sections can be easily found in the pages with a red border.
You can access the report using the following link:
Zebra EC
Zebra EC (embodied carbon) is an excel spreadsheet. It allows you to define some basic details about the building, before going on to specify the make-up of the building’s construction.
You define the make-up by selecting materials from inbuilt data for which carbon factors have been collected. For some aspects, such as transportation of construction materials, these factors will be calculated based on parameters you specify.
The output of Zebra EC is the embodied carbon for the buildings construction and demolition, broken down by building element and by lifecycle stage. This information allows the design to be evaluated for it’s carbon efficiency, and for the design to be iterated and re-assessed.
Documentation
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Zebra-EC contains a database of common construction materials and products. For many early-stage calculations, or to look at the gross impact of design choices, this database might well be enough. However, once you have a particular product in mind from a known manufacturer, better estimates of the embodied carbon (EC) can be calculated by using the Environment Product Declaration (EPD) from the manufacturer. This manual presents the procedure of importing indicators from EPD into the ZEBRA EC database. This manual is available here.
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A primer on embodied carbon in buildings, describing the background to EC in building, mitigation strategies to reduce it. This primer is available here.
Video tutorials
Studio report
We produced a report to show how the ZEBRA tools (core and additional tools) might be used in a real studio project created by a group of students in the Department of Architecture and Civil Engineering at the University of Bath. ZEBRA was not used in their original project, so we have re-imagined the project by inserting a variety of results into their project report, based on calculations using ZEBRA. The ZEBRA sections can be easily found in the pages with a red border.
You can access the report using the following link:
Zebra OC Online
Zebra OC (operational carbon) online is a web version of Zebra OC.
It is somewhat simplified, making more assumptions and presenting less-detailed summaries as the excel version, but it uses the same algorithms for calculating energy and carbon.
Documentation
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We have written a tutorial on how to get started with Zebra OC online, using a large commercial building as an example. This tutorial is available here