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Building Regulations - Approved Document F (Ventilation)

Confused about the changes to the Building Regulations that have just come into effect, as of June 2022? Don't worry, we have created a hub that includes our building regulations bitesize webinar recordings, our next upcoming webinars and free resources to easily understand the changesClick Here

 

Here, we have outlined the updates to ADF:Volume 1 Dwellings.

Approved Document F: Ventilation, Volume 1: Dwellings provides guidance on meeting building regulations that specifically apply to ventilation. ADF states that:

 “There shall be adequate ventilation provided for people in the building”. 

It is also important to ensure adequate ventilation to protect the structure of the building.

From June 2022, Approved Document F: Ventilation will be published in two volumes:

-           Volume 1: Dwellings

-           Volume 2: Buildings Other Than Dwellings

When building a new property it is important to comply with requirements in building regulations for installation, inspection, testing, commissioning and provision of information when installing fixed ventilations systems in your new and existing property. Approved Documents provide guidance on how to meet these building regulations.

For an existing dwelling, any building work (adding a room, replacing parts of a ventilation system) should meet the relevant standards of ADF. Where any energy efficiency standards are to be carried out in a dwelling, PAS 2035 is considered an adequate means of demonstrating compliance for meeting the F1 requirement for existing dwellings: There shall be adequate means of ventilation provided for people in the building.

When inserting a new internal wall care should be taken not to make any other matters, such as ventilation, worse. If a new room is being created as a result of the addition of an internal wall then care should also be taken to ensure that the existing room is ventilated adequately. The general rules for ventilating a room are:

Purge

This is achieved by opening the window. A system for purge should be provided for each habitable room and should be capable of achieving 4 ACH directly to outside.

If a wet room (kitchen/utility/bathroom/WC/ensuite) has no external walls and an intermittent extract fan is being used, the fan should extract at 4ACH (Air Changes per Hour) to provide purge ventilation. (In order to demonstrate compliance with Part O of the building regulations it is likely that a higher purge rate than 4ACH may be required).

Whole building - this is also known as trickle ventilation which can be incorporated in to the head of the window framework, or by some other means. The area varies on the type of room:

 Minimum Equivalent Area of Background Ventilators

Both of these forms of ventilation are normally required, however alternative approaches to ventilation may also be acceptable, subject to agreement with the building control body.

Due to the increasing complexity of the Regulations, ventilation strategies and system design must be considered at the earliest stages of building design.

Any new kitchen, bathroom (or shower room), utility room or toilet should be provided with a means of extract ventilation to reduce condensation and remove smells.

As an alternative for sanitary accommodation, the purge ventilation guidance may be used - Table 1.1 Note 3 of Approved Document F Any extract ventilation system you install should meet the requirements specified in ‘Approved Document F - Ventilation’.

In England and Wales, requirements for ventilation are contained in Approved Document F and can be downloaded from www.planningportal.gov.uk. The Building Regulations Approved Document F: Volume 1 dwellings considers ventilation through a combination of infiltration and purpose-provided ventilation. Regulations are constantly being reviewed, with the aim to improve building standards, so it is worth checking the Planning Portal website for any updates to Building Regulations.

Infiltration

An uncontrollable air exchange between the inside and outside of a building.

Purpose-Provided Ventilation

A controllable air exchange between the inside and outside of a building.

Approved Document F: Volume 1 Dwellings looks at different strategies for ventilation. The performance rates for each of the  ventilation approaches set out in Approved Document F are the minimum requirements needed to ensure that adequate air quality is provided for people indoors. The occupant's health could be at risk if these ventilation rates are compromised.

The following systems are outlined which satisfy the performance standard. From June 2022 the former numbering of Systems 1-4 will cease

Natural Ventilation – Background ventilation and intermittent extract fans

Background ventilation is a whole house ventilation system that allows the introduction of fresh outside air into a habitable room without opening a window. The purpose: To remove stale indoor air and replace it with fresh outside air.

A common approach to meeting the Building Regulations Approved Document F is intermittent extract fans with background vents (i.e. trickle vents in the windows). Extractor fans are located in the bathroom, ensuite, kitchen and utility room. They must comply with providing the following ventilation airflow rates for intermittent extract minimum rates.

Minimum Extract Ventilation Rates for Intermittent Extract Systems

In addition, background ventilators (trickle ventilators) must comply with the total ventilator area (mm²) as shown in table 1.1 above. 

 From June 2022 natural ventilation is only recommended for use in less airtight dwellings with a design air permeability of greater than 5m3/(h.m2)@50Pa

Ventilation System Types

Intermittent extractor fans can be operated with a number of different control functions: fan operates in conjunction with a light switch, remote switch, pull cord, humidistat, PIR (presence detector) or timer. Intermittent fans are not the most energy efficient way due to the heat loss incurred.

In addition, if they are not switched on, the property is not being adequately ventilated. The fans must be regularly maintained in order to work effectively and minimise sound levels.

Continuous Mechanical Extract Ventilation

Continuous mechanical extract ventilation (MEV)can be either a whole house centralised MEV system, or localised decentralised MEV fan.

The centralised continuous MEV system is typically located in a loft space or hallway cupboard. Multiple ducts run from the unit to the kitchen, bathroom, ensuites and other wet rooms of a property to simultaneously draw moisture laden air from these wet rooms to control humidity levels.

Decentralised continuous MEV (dMEV) are individual room fans which operate continuously to draw moisture from either the bathroom, kitchen, utility room or other wet room. Continuous mechanical systems should include either manual or automatic controls (i.e. humidity sensors) to operate on between trickle and boost modes.

The minimum extract rates for continuous extract systems are shown here in Table 1.2 (Boost rate). The minimum whole dwelling ventilation rates by the number of bedrooms are shown in Table 1.3 (trickle rate for the whole dwelling).

Minimum Extract Ventilation Rates for Continuous Extract Systems

Minimum Whole Dwelling Ventilation Rates by the Number of Bedrooms

 Background ventilators are required for Continuous Mechanical Extract Ventilation. These should not be in wet rooms and should provide a minimum equivalent area of 4000mm2 for each habitable room. The minimum total number of background ventilators must equal the number of bedrooms plus two additional background ventilators.

Mechanical Extract Ventilation with Heat Recovery

Mechanical Ventilation with Heat Recovery (MVHR) provides fresh, filtered air, and a comfortable all year round climate. Stale, moist air is extracted out of the wet rooms of a home.

These include the kitchen, bathrooms, utility and en-suite rooms. MVHR systems should always provide the minimum whole building ventilation rate, which can be seen in table 1.3 above.

Background ventilators are not required with an MVHR system

Other Methods That Meet The Requirement

The Building Regulations Approved Document F: Ventilation Volume 1 Dwellings includes other systems that meet the F1 requirement.

Positive Input Ventilation

The EnviroVent Range of Positive Input Ventilation systems are accredited with BBA certification: 03/4043. These are sophisticated whole house ventilation systems, which dilute, displace and replace high humidity levels to control condensation and mould growth.

Trickle vents may not be required, provided that the whole house ventilation rate is met in Table 1.3 of Part F. It is recommended that supplementary extract fans are installed. Positive Input Ventilation is an all year round system that is a cheaper option than heat recovery ventilation. Systems can also be extremely energy efficient, taking advantage of the benefit of solar gain from the loft space and providing heat distribution.

Single Room Heat Recovery

Single Room Heat Recovery is a localised form of whole house heat recovery. Installed through the wall in a wet room, they are designed to provide both extract and supply ventilation, whilst recovering some of the energy that would normally be lost through extraction.

Passive Stack Ventilation

Passive stack is a non-mechanical approach to ventilation, where air vents are located in various locations around the dwelling. Using the principle of convection, currents allow the movement of air through the ducts.

Passive ventilation is a natural ventilation system that makes use of natural forces, such as wind and thermal buoyancy, to circulate air to and from an indoor space.

This uses a combination of the air flowing over the roof and the natural buoyancy of warm moist air to lift the moist, stale air from the kitchen bathroom, cloakroom etc up ducting to the roof ridge level where it escapes into the atmosphere. Fresh air is drawn into the building through the trickle vents in the windows and doors etc.

Background vents must be installed.

Compliance and Commissioning

Within the updated Approved Document F: Volume 1, there is greater focus placed on compliance and commissioning. From June 22 the Domestic Ventilation Compliance Guide is amalgamated into ADF.

When commissioning new build properties, all properties must be fully commissioned and not just a set percentage. There is a new commissioning checklist located in Appendix C. This details the system declarations, inspection and commissioning.

There is now a checklist for existing properties and commissioning is also required.

Ventilation has become a controlled service. Building Control must be notified if the installer is not part of a competent persons scheme.

Performance-Based Ventilation

Within Appendix B of ADF: Volume 1 is a section on performance-based ventilation and the criteria to meet this standard. There is a further table showing guidance values for indoor air pollutants.

This section looks at the control of moisture levels, indoor pollutants (VOCs) and harmful chemicals. It provides infiltration levels dependant on the air permeability linked to the performance-based ventilation.

 

The Future Homes Standard

The Future Homes Standard (FHS) is an efficiency criteria that is coming into effect in the UK in 2025, which will enforce a 75% reduction in carbon emissions that new homes produce than those built to current regulations and no fossil fuel heating.

This mainly effects new dwellings, but there is also guidance for existing and retrofit properties.

The main areas will focus on:

 

Approved Document L: Volume 1 Dwellings

Conservation of Fuel & Power

 

Interim Changes as of June 22

The interim uplift to Part L standards will be seen as a stepping stone to the 2025 deadline to achieve zero-carbon homes. The Government describes the uplifts as a fabric + technology’ mix of insulation/energy efficiency and low-carbon heating technology.

Part L changes that effect ventilation:

For an MVHR system or single system comprising supply and extract ventilation:

Specific fan powers remain as per the Non-Domestic Building Services Guide:

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