This guide is intended to help house builders and designers understand what the October 2010 changes to Approved Document F (Ventilation) (ADF) mean.  The latest ADF has been updated to take account of the recent increase in the as-built airtightness of buildings.  With Approved Document L1A (ADL1A) 2010 of the building regulations pushing for even lower levels of air permeability, it is important that correct provision is made to allow for controlled ventilation of our living spaces.  The changes have also placed a responsibility on the house builder to ensure that mechanical ventilation systems are installed correctly, and where they can be, they are tested and commissioned, and sufficient information on their operation and maintenance is given to occupiers.

As in the previous versions of ADF, its focus is the provision of ventilation for providing fresh air for health and well being, control of odour, airborne pollutants and excess humidity.  It does not cover the additional ventilation which may be required to control overheating in homes, this is addressed in ADL1A of the Building Regulations.

This guide gives examples of some typical homes, outlining a combination of measures needed to comply with ADF 2010.  The intention is to give a broad understanding of the approaches available for complying with the revised regulations and the practical changes this will entail.

The examples used are based on typical homes on typical developments, from information gathered by NHBC about the homes being built today.  The examples are similar to those used in the Part L 2010 - where to start guide with the addition of a single aspect apartment which has its own specific requirements for compliance.

This is only a general guide and there is no obligation to adopt any of the specific solutions detailed. You should always check with the Building Control Body (BCB) that your proposals comply with the requirements of the Building Regulations. You will also need to comply with Domestic Ventilation Compliance Guide (DVCG) 2010, NHBC Standards and planning requirements etc.
 

Key changes from ADF 2006 are:

• Air flow rates need to be measured on site and submitted to BCB
• Higher ventilation rate requirements introduced for dwellings with a
• fabric air permeability less than 5 m3/(h.m2) @ 50 Pa
• Passive stack diameter increased to 125 mm for all wet rooms
• All fixed mechanical systems need to be commissioned
• Commissioning notice needs to be given to BCB for each installation addressed
• Operation and maintenance manual needs to be provided
• Domestic Ventilation Compliance Guide has been produced to support ADF 2010, which includes guidance on design, installation, inspection and testing of natural and mechanical ventilation systems

ADF 2010 also offers additional guidance on the following issues:

• Fire and noise control
• Requirements for purge ventilation in habitable and wet rooms
• Background ventilation requirements for single storey dwellings on lower floors (ground to fourth)
• Design criteria for adequate cross-ventilation
• Requirements for air transfer between rooms
• Minimum efficiencies for mechanical systems as given in DVCG
• Routes for obtaining guidance for specific mechanical supply and extract systems
   

Ventilation is essential for our health and comfort.  We are all aware of the consequences of inadequate ventilation: dampness and mould growth on walls, drowsiness, ill-health and intolerance of allergens for occupiers.  In the past ventilation has been provided by a combination of purpose designed devices such as fans, trickle vents and windows and by the invisible but significant quantities of air infiltrating the dwelling through the building fabric.

In older homes the open chimney, sliding sash windows and gaps between floor boards all contributed to the amount of air entering and leaving the dwelling.  Openable windows and natural cross-ventilation would also help ensure that a high number of air changes could be achieved without any special ventilation devices.  Over time there have been more reasons to introduce specific measures, for instance to avoid condensation or to dilute and remove the combustion gases from heating appliances and boilers.  With increased focus on minimising energy losses from buildings especially due to infiltration, strategies for adequate ventilation need to take into account more airtight construction.

The building regulations identify specific ventilation mechanisms that apply to different requirements. There can be a short-term need to remove fumes and smells, from burning toast or painting and decorating.  This is generally described as ‘purge’ ventilation.  For certain rooms and activities it is desirable to remove the pollutants or water vapour at source - from the bathroom or kitchen for instance, this may be done by either natural or mechanical means.

A constant amount of ‘background’ ventilation is also required for each room throughout the day to ensure good air quality and prevent the build up of pollutants and water vapour from everyday activities such as clothes drying and of course human respiration.  In airtight homes this background ventilation has to be controlled: a specific amount of air has to be provided in a secure and draught-free way.  It is very important that the background ventilation is not overridden by the occupier, either in the belief that it is causing draughts and wasting money or because the system itself is perceived as being ineffective or too noisy and is turned off as a result.