Part O (Overheating).

Part O of the Building Regulations in the UK deals with mitigating the risk of overheating in residential buildings. Introduced to ensure that homes remain comfortable and safe during hot weather, Part O aims to address the increasing frequency of heatwaves due to climate change. Here’s an overview of its key aspects:

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Purpose

Health and Comfort: The main goal is to ensure that buildings do not become uncomfortably or dangerously hot in the summer, protecting occupants' health and well-being.

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Scope

Residential Buildings: Part O applies to new residential buildings, including houses, flats, and any buildings where people sleep, such as student accommodation and care homes.​

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Key Requirements

1. Limiting Solar Gains:

   • Orientation and Shading: Buildings should be designed to limit solar gains through appropriate orientation, window sizing, shading devices (like shutters or external blinds), and reflective glazing.

   • Ventilation: Effective use of natural ventilation (such as cross-ventilation) or mechanical ventilation to remove excess heat.

2. Assessment Methods:

   • Simplified Method: For typical houses and flats, a set of prescriptive measures can be followed to ensure compliance.

   • Dynamic Thermal Modelling: For more complex buildings or where the simplified method is not applicable, detailed thermal modelling can be used to predict overheating risk and demonstrate compliance.

3. Design Considerations:

   • Building Layout: Encourages layouts that promote natural ventilation.

   • Thermal Mass: Utilizes materials that absorb and slowly release heat to help moderate indoor temperatures.

   • External Shading: Incorporates external features like awnings or pergolas to reduce direct solar gain.

   • Glazing: Specifies types and placements of windows and other glazed areas to minimize unwanted heat.

4. Operational Aspects:

   • Night Cooling: Designs that facilitate night cooling by allowing cooler nighttime air to ventilate the building.

   • User Instructions: Providing building occupants with clear instructions on how to operate shading devices and ventilation to minimize overheating.

 

Compliance and Enforcement

• Building Control: Compliance with Part O is assessed by building control bodies during the design and construction phases.

• Documentation: Proper documentation and calculations must be provided to demonstrate how the building design meets the overheating criteria.

 

Summary

Part O is a crucial regulation to ensure that new residential buildings in the UK are designed to cope with high temperatures, prioritizing the health and comfort of occupants. By incorporating thoughtful design, appropriate materials, and effective ventilation strategies, Part O aims to mitigate the risks associated with overheating in buildings. Compliance with Part O can also affect SAP extension calculations. To learn more about SAP calculations - read our dedicated page.