Westcoast Windows Building Regulation datasheets for guidance when specifying our Swedish composite windows and doors – Approved Document F – Ventilation

The UK Building Regulations Approved Document F covers Means of Ventilation for new dwellings, buildings other than dwellings and work on existing buildings. We’ve put together advisory notes for consideration when specifying our Swedish designed and manufactured composite windows and doors to meet the requirements of Approved Document F.

Approved Document F is published in one volume – F1 Means of Ventilation. The key aim of the requirement of Part F1 is that a ventilation system should be provided that, under normal conditions, is capable of limiting the accumulation of moisture and pollutants originating within a building which would otherwise become a hazard to the health of people within the building.

Requirement F1 does not apply to a building or space within a building:
A. Into which people do not normally go; or
B. Which is used solely for storage; or
C. Which is a garage used solely in connection with a single dwelling.

Ventilation is described as simply the removal of ‘stale’ indoor air from a building and its replacement with ‘fresh’ outside air. The document assumes that outside air is of reasonable quality and states that ventilation is required for the following purposes:

A. Provision of outside air for breathing;
B. Dilution and removal of airborne pollutants, including odours;
C. Control of excess humidity (arising from water vapour in indoor air);
D. Provision of air for fuel burning appliances (see Part J of building regulations).

Ventilation may also provide a means to control thermal comfort but this is not controlled under Building Regulations. Part L – Conservation of fuel and power addresses minimising energy use due to the effects of solar gain in summer.

Part F1 explains that buildings are ventilated through a combination of infiltration (uncontrollable air leakage) and purpose provided ventilation (controllable air exchange by natural or mechanical devices) and it states the importance of minimising uncontrollable air infiltration (see also Part L).

The air permeability limiting value in Part L is 10m³/hour/m² @ 50 Pa., but modern methods of construction can achieve significantly more airtight buildings of typically 5m³/hour/m² or lower. As a result, Part F (New Dwellings) sets out minimum guidance requirements for “all levels of design air permeability” (assumes zero air permeability and thus no infiltration),
or alternatively for buildings that are leakier than 5m³/hour/m².

In the case of new dwellings, minimum rates are set out for both Extract ventilation and Whole dwelling ventilation and describes 4 alternative Systems for achieving the requirements.

 

The ventilation strategy adopted in Approved Document F requires:

  • Extract ventilation – from rooms where most water vapour and/or pollutants are released, e.g. kitchens, bathrooms, utility rooms and sanitary accommodation in order to minimise spread to the rest of the building. The method of extract can be intermittent or continuous.
  • Whole building/dwelling ventilation – to provide nominally continuous fresh air exchange to the building and to dilute and disperse residual water vapour and pollutants not dealt with by extract ventilation.
  • Purge ventilation – throughout the building to aid removal of high concentrations of pollutants and water vapour released from occasional activities such as painting and accidental release of smoke from burnt food or water spillage. Purge ventilation is intermittent and required only when such activities occur.

This ventilation strategy can be delivered by either a natural ventilation system or a mechanical ventilation system or a combination of both.

For mainly naturally ventilated buildings, it is common to use a combination of ventilators to achieve this strategy; so for example:

  • Intermittent extract fans for extract ventilation.
  • Trickle ventilators for whole dwelling ventilation.
  • Opening windows for purge ventilation.

 

For mechanically ventilated or air-conditioned buildings, it is common for the same ventilators to provide both local extract and whole building/dwelling ventilation and for buildings other than dwellings, to provide purge ventilation as well.

In all cases, it is important that ventilation is controllable so that it can maintain reasonable air quality and at the same time avoid waste of energy. Controls can be either manual or automatic.

Manually controlled trickle ventilators should be positioned typically 1.7m above floor level to avoid discomfort due to cold draughts and are intended to be normally left open in occupied rooms in dwellings. The equivalent area of trickle vents should be marked, either permanently or temporarily on the product for inspection purposes.

Windows with a night vent facility are not recommended for the purpose of Part F because of the difficulty of measuring the equivalent area for background ventilation reasons.

 

Ventilation systems for dwellings

Building designers will select one of the following four ventilation systems illustrated in Diagram 2a.

System 1: Background ventilators and intermittent extract fans.

System 2: Passive stack ventilation (PSV).

System 3: Continuous mechanical extract ventilation (MEV).

System 4: Continuous mechanical supply and extract with heat recovery (MVHR).

Doc Part F image1 sml

Doc Part F image2 sml

Guidance on the minimum total equivalent area provisions for Whole dwelling ventilation (background ventilators) is set out in the document for each of the four Systems for both “dwellings with any design permeability” and “dwellings with a design permeability leakier than 5m³/hour/m² @ 50 Pa”.

The guidance is subject to the total floor area of the building, the number of bedrooms it contains and occupancy levels. Further rules apply for single aspect situations (limited opportunity for cross ventilation), where two habitable rooms are treated as a single room for ventilation purposes, where a habitable room is ventilated through a conservatory and for basement locations.

 

These systems are expanded upon in our Approved Document Part F Datasheet, along with Key Features, Appendices and technical drawings of Westcoast Windows Trickle Vents: WESTCOAST WINDOWS APPROVED DOCUMENT PART F GUIDANCE NOTES

 

For further information visit the Government Statutory guidance page for means of ventilation: Approved Document F:
https://www.gov.uk/government/publications/ventilation-approved-document-f

 

To find read our other Building Regulations advisory notes datasheets, visit our DOWNLOADS page (ADD LINK) or click on the following links:

Approved Document B – FIRE SAFETY
Approved Document K – PROTECTION FROM FALLING, COLLISION & IMPACT
Approved Document Q – SECURITY

If you have any queries regarding these notes or to discuss an upcoming project call our office on: 01359 241944 or email: info@westcoastwindows.com

Diagrams taken from the Approved Document F – F1 Means of Ventilation (2010 Edition) © Crown copyright 2010

Westcoast Windows Building Regulation datasheets for guidance when specifying our Swedish composite windows and doors  – Approved Document F – Ventilation