New free tool for exploring climate files Very useful for Passive House design

5 January 2024 by Jason Quinn

I’ve discovered a climate file exploration tool that will be really useful for Passive House designers. Best, it’s open source, so free to use. This is particularly timely given the promised update to the climate files we currently use for Passive House design in Aotearoa. What we currently access contains 30 years of climate data—but NIWA compiled those files 20 years ago! NIWA has been funded to compile the immediate past 30 years of hourly climate files, giving us more accurate information to feed into our models.

New Zealand is somewhat unique on two counts when it comes to designing high-performance buildings. Our geography makes for very varied climates across the country. Second we’re small enough that most architects and Passive House designers work on projects spread around New Zealand, including in locales they are not necessarily familiar with (or at least they don’t have a year-round personal experience of the climate).

Passive House design necessarily has to respond to the local climate, so the better the data and understanding of it, the better the design. Fine-tuning that understanding could lead to cost-savings, because over-specification is a risk too.

The CBE Clima Tool allows you to plot the hourly data in many ways to better understand the climate for individual projects. Good design requires you to understand the climate and design your building to work with it!

My favourite is the psychrometric chart, which provides a beautiful and compact understanding of how temperatures and humidity change throughout the year. Upload your own file or use publicly available files from around the world.



“[The tool provides] easy access to over 30,000 publicly available weather files in EPW format and creates interactive visualisations of the climatic variables therein contained. Additionally, CBE Clima can also analyse any valid EPW file and calculate many additional parameters, like sun diagrams, indoor and outdoor thermal comfort indices and natural ventilation potential among others.”

Betti, G., Tartarini, F., Nguyen, C. et al. CBE Clima Tool: A free and open-source web application for climate analysis tailored to sustainable building design. Build. Simul. (2023).

Source code here:

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