Approved document o

[edit] National building standards

The first set of national building standards was introduced in 1965. The 'building regulations' establish standards that have to be achieved in the construction of buildings. They set out:

• What qualifies as ‘building work’ and so falls under the control of the regulations.
• What types of buildings are exempt.
• The notification procedures that must be followed when starting, carrying out, and completing building work.
• Requirements for specific aspects of building design and construction.

The 'approved documents' provide guidance for satisfying the requirements of the building regulations in common building situations.

[edit] Approved Document O

Approved Document O was published on 15 December 2021 as part of the government’s plans to deliver net zero. This approved document takes effect on 15 June 2022 for use in England. It does not apply to work subject to a building notice, full plans application or initial notice submitted before that date, provided the work for each building is started before 15 June 2023. Full detail of the transitional arrangements can be found in Circular Letter 01/2021 published on gov.uk.

[edit] The requirements.

The Requirements of O1 Overheating mitigation

1. 'Reasonable provision must be made in respect of a dwelling, institution or any other building containing one or more rooms for residential purposes, other than a room in a hotel (“residences”) to— (a) limit unwanted solar gains in summer; (b) provide an adequate means to remove heat from the indoor environment.
2. In meeting the obligations in paragraph (1)— (a) account must be taken of the safety of any occupant, and their reasonable enjoyment of the residence; and (b) mechanical cooling may only be used where insufficient heat is capable of being removed from the indoor environment without it.

[edit] The aims

The aims of the requirement is to protect the health and welfare of occupants of the building by reducing the occurrence of high indoor temperatures.

Compliance can be demonstrated by using one of the following methods:

• The simplified method for limiting solar gains and providing a means of removing excess heat, as set out in Section 1.
• The dynamic thermal modelling method, as set out in Section 2.

[edit] The simplified method

The categorisation of residential buildings will be made according to their location and the inclusion or not of cross-ventilation, this is to limit unwanted summer solar gain and remove excess heat. Limiting solar gains needs to be achieved in this model by setting maximum glazed areas of the buildings, and of the most glazed room as well as providing shading for high-risk locations, the acceptable strategies for doing this are listed in the regulations as:

1. Fixed shading devices, comprising any of the following: Shutters, external blinds, overhangs, awnings,
2. Glazing design, involving any of the following solutions: Size, orientation, g-value, depth of the window reveal.
3. Building design – for example, the placement of balconies.
4. Shading provided by adjacent permanent buildings, structures or landscaping.

NOTE: The guidance states that although internal blinds and curtains as well as foliage, such as tree cover, can provide some reduction in solar gains, they should not be taken into account when considering whether the requirement has been met.

The removal of excess heat is to be achieved through cross ventilation approaches, which rely on the correct calculation of minimum free areas for windows and vents which is given, this guidance varies depending on the level of risk for assessed though the building's location The regulation lists the following means for

1. Opening windows (the effectiveness of this method is improved by cross-ventilation).
2. Ventilation louvres in external walls.
3. A mechanical ventilation system.
4. A mechanical cooling system

NOTE: A passive means of removing excess heat must be demonstrated as far is reasonably possible before mechanical cooling, and all approaches must also comply with the other relevant regulations, such as Document F for noise and maintenance. When considering opening lights and an increase in purge ventilation.

[edit] The dynamic modelling method

To demonstrate compliance using the dynamic thermal modelling method, all of the following guidance should be followed.

• CIBSE’s TM59 methodology for predicting overheating risk.
• The limits on the use of CIBSE’s TM59 methodology set out in paragraphs 2.5 and 2.6.
• The acceptable strategies for reducing overheating risk in paragraphs 2.7 to 2.11.

Find out more at: https://www.gov.uk/government/publications/overheating-approved-document-o

[edit] Related articles on Designing Buildings

• Approved documents.
• Approved inspector.
• Building control bodies.
• Building Regulations exemptions.
• Building Regulations.
• Competent person schemes.
• Licensing.
• Overheating.
• Planning permission.
• Solar gain.
• Statutory approvals.
• Statutory authorities.
• The Building Act.