© Building Performance Explained

Building performance in practice.

Building Performance Explained

Guides, tools and examples covering building performance, energy, comfort and sustainability.

What is building performance?

Building performance is about how a building works in practice. It includes how much energy it uses, how comfortable it is, how heat and air move through it, and how its fabric and systems work together.

BPEX looks at those individual parts, from the basic concepts through to the assessments, standards and tools used on real projects.

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IECC Climate Zone Map

See how the USA is divided into IECC climate zones, from hot and humid Zone 1 to subarctic Zone 8, and what the letters A, B and C mean.

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  • Part L U-Value Constructions for IES VE: Free Python Scripts

    Creating construction build-ups in IES VE can be time-consuming, particularly when working with multiple walls, roofs and floors with different U-values. To make this easier, BPEX has developed two Python scripts that automatically create Part L 2026 construction build-ups in your IES VE project. The scripts are provided as .txt (Text Document) files. Before using…

  • 7 of London’s Highest-Scoring BREEAM Outstanding Buildings

    BREEAM Outstanding is the highest BREEAM rating a building can achieve. A building normally needs to score at least 85%, as well as meet minimum requirements in key areas. Points are earned across areas such as energy, water, materials, waste, transport, health and wellbeing, ecology and management. An Outstanding rating therefore means the building has…

  • What G-value Should I Use for My Windows?

    There is no single G-value that is right for every window. The useful question is not “what is the best G-value?” but “how much solar gain does this particular space need, and how much can it cope with?” The right choice depends on the building around the glazing. Start with the problem, not the number…

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New guides, tools and building-performance explainers as they are published.