This guide supports the industry ambition to build as designed and commission with care. It recognises that regulatory compliance is the baseline, but quality delivery requires attention to process as well as specification. It is non-statutory industry guidance intended to support more reliable ventilation outcomes in practice. 

The principles set out here are relevant across different delivery models, including: 

• Low-rise and taller residential buildings 
• Private sale, affordable housing and build-to-rent developments 
• Large national homebuilders and smaller regional or SME developers 
• Different organisations deliver 

Different organisations deliver projects in different ways, from smaller developments where responsibilities may sit with a single contractor to larger organisations where design, procurement and site delivery are managed by separate teams. Regardless of structure, the underlying requirement is the same: ventilation must be designed, procured, installed, commissioned and verified as an integrated system. 

The guidance is applicable to developments of all sizes, from individual plots to large multi-unit schemes. It supports both delivery models by clarifying roles, expectations and quality checks at each stage. It also recognises that improved outcomes require not only better design and installation, but also a credible likelihood that performance will be checked and verified.

Delivering successful ventilation in new homes requires individuals, from design, installation, commissioning and verification to be appropriately trained, skilled and competent. You can find more details on how these roles individual responsibilities, and how they should interact, in the guide.  

Competence of the responsible ventilation designer 

A ventilation design should be undertaken by a competent individual, supported by an organisation with appropriate quality management and accountability.  

Depending on the system type and procurement route, the responsible designer may be:  

• A specialist building services engineer  
• A specialist ventilation contractor providing a design-and-install service  
• An in-house design team with appropriate technical competence  
• A ventilation equipment manufacturer offering a fully coordinated design service 

Where manufacturers provide indicative layouts, these should be clearly identified as preliminary or quotation-stage information unless they are explicitly taking responsibility for the ventilation design and coordination. 

Where the ventilation design is undertaken by the installer or contractor, this function should be carried out by a competent individual with demonstrable ventilation design capability. Installation training alone does not constitute ventilation design competence. 

The responsible ventilation designer should be supported by appropriate organisational accountability and, where appropriate to the procurement route and project risk, professional indemnity or equivalent design liability arrangements. 

Membership of a recognised competent person scheme may provide additional assurance where design competence is included within its scope. Other routes to demonstrating competence may be appropriate, provided equivalent assurance can be evidenced. 

Competence from design to procurement 

The procurement route determines who holds design responsibility in practice. 

Where ventilation design is being undertaken by: 

• An installer 
• A specialist subcontractor 
• A manufacturer 
• An in-house team 

Homebuilders should confirm that the individual or organisation responsible for design has appropriate competence and that this responsibility is clearly defined in contractual documentation. 

Ventilation design responsibility is often assumed rather than explicitly defined and documented. In smaller schemes, the installer may effectively “design on the day”, based on experience rather than documented calculations. 

Where the installer is undertaking the design, procurement should require evidence of competence in ventilation design, not just installation. Where design is retained by the homebuilder or a specialist, responsibility should be clearly named and recorded, including on the ventilation checklist. 

Competent installation and commissioning 

Installation and commissioning should be undertaken by suitably competent individuals operating within a recognised competent person framework. As Part F requirements tighten around system resistance and measured performance, competence becomes increasingly important. 

Commissioning should not be treated as an administrative exercise. Measured airflows should be used to confirm that the whole dwelling ventilation rate has been achieved, not simply that individual wet room extract targets have been met. 

Procurement documentation should therefore: 

• Require commissioning against defined design airflow rates 
• Require production of a valid ventilation commissioning checklist 
• Ensure that ventilation-specific design information is made available to the installer on site 

A representative sample of completed dwellings, randomly selected, should be subject to independent third-party verification. The sample size should relate to the training and competence level of the installer and commissioner. Verification rates should therefore reflect: 

Installers or commissioners operating within a recognised competent person scheme. 

Where auditing and competency oversight arrangements are already in place, an indicative verification rate of around 10% of installations may be appropriate. 

Installers or commissioners operating outside a competent person scheme. 

Where no equivalent oversight exists, a higher verification rate, for example greater than 30% of installations, reflects the increased risk and provides a meaningful likelihood of review. 

These rates are indicative and may be adapted to reflect system type, dwelling complexity and project-specific risk. This approach recognises existing quality assurance mechanisms while ensuring that all systems 

Coming soon.....

Membership of a recognised competent person scheme may provide additional assurance where design competence is included within its scope. Other routes to demonstrating competence may be appropriate, provided equivalent assurance can be evidenced. 

There are a selection of Competent Persons Scheme already in operation, each covering different stages of the ventilation delivery process. You can find out more by clicking the links below. 

Coming soon....