BB101 Overheating Assessments for Schools

Walker Energy Analysis carries out BB101 overheating assessments for new school buildings, using dynamic thermal modelling in IES Virtual Environment. BB101 sets the ventilation, thermal comfort and indoor air quality standards for education buildings, and compliance is a required part of DfE and local authority technical submissions, not an optional check.

Classrooms behave differently to offices or homes: occupancy is dense, internal gains from teaching equipment are high, and the building sits empty for large parts of the year. A BB101 assessment tests specifically against these conditions, rather than applying a general-purpose overheating check to a building type it wasn't built for.

How BB101 Assessments Work

BB101 draws on the same CIBSE TM52 methodology used for other non-domestic buildings, but with limits set specifically for schools. Three criteria apply, tested for occupied hours between 9am and 4pm, Monday to Friday, from May to September, including the summer holiday period as though the school were in normal use.

Criterion 1 is the minimum requirement and must be passed: the number of hours the operative temperature exceeds the comfort threshold by 1 degree or more must not exceed 40 hours across the assessment period.

Criterion 2 and Criterion 3 assess the severity and peak of any overheating that does occur. These are reported for information and considered alongside Criterion 1, and where a design doesn't meet them, we set out mitigation options for the project to consider.

Modelling is run using the CIBSE DSY1 2020 weather file appropriate to the school's location, in line with current BB101 guidance.

Dynamic thermal modelling in IES VE, using occupied school hours and realistic internal gains from pupils, lighting and teaching equipment
Assessment against BB101's three criteria, with Criterion 1 confirmed as a pass or fail
DSY1 2020 weather data appropriate to the school's location
Practical mitigation recommendations where Criterion 2 or 3 flag a risk
A report structured for DfE, ESFA or local authority technical review

Working at Any Design Stage

Concept design: early testing of glazing, orientation and ventilation strategy, so classroom layouts and window design reflect overheating risk from the outset.

Technical design: full BB101 assessment, ready for DfE, ESFA or local authority submission.

Design changes: fast re-runs when the ventilation strategy, glazing or classroom layout is revised.

Why Work With Us

We're a specialist energy consultancy. This is the core of what we do, not a sideline. Every assessment runs through IES VE as standard, we turn changes around quickly, and results come back in a format your team, DfE, or local authority reviewer can use immediately.

FAQs

Is BB101 the same as TM52?BB101 is based on the same CIBSE TM52 methodology used for other non-domestic buildings, but sets its own occupied hours, internal gains, and a school-specific limit of 40 hours for Criterion 1.

Does a school have to pass all three criteria?No, only Criterion 1 must be passed. Criteria 2 and 3 are reported for information, and where they flag a risk, we set out mitigation options for the design team to consider.

What weather data is used?The CIBSE DSY1 2020 weather file appropriate to the school's location, as required by current BB101 guidance.

Do you assess every classroom, or a sample?Generally speaking, all rooms are assessed. Where a sample is agreed, we test the highest-risk spaces, typically south or west-facing classrooms and rooms with limited ventilation.

Get Your BB101 Assessment in Place

Talk to Walker Energy Analysis at concept stage, before classroom layouts and glazing are fixed.

Talk to an engineer