The Importance of Air Conditioning and Ventilation Design when Working in HRBs

The Building Safety Act 2022 has introduced a fundamental shift in how higher-risk residential buildings (HRBs) are designed, constructed, and managed. Applicable to buildings 7 storeys or 18 metres tall and above, the legislation aims to ensure building safety is prioritised throughout the entire project, from initial concept through to completion and occupation.

From June 2024, the Building Safety Regulator (BSR) rigorously enforces a linear three-gateway process, to monitor and ensure compliance at every stage of the project. Each stage requires meticulous attention to detail to prevent post-approval deviations, which can delay or halt all progress on site.

Gateway One – Planning Approval

At Gateway One, application for planning permission takes place which includes the submission of a full fire statement, covering site layout, emergency access, and evacuation strategies.  

As external condensers or heat pumps require planning permission, if there are any required for the project these also need to be submitted with the Gateway One planning application to ensure no sub-applications are required at a later date, as these seriously delay the approval process.

Specialist input is therefore critical in this element of the design process – from specifying the exact model of the external unit required and determining its ideal location from a technical, visual and noise perspective, to taking a 24-hour sound survey and preparing an acoustic report to mitigate any sound concerns, to issuing all technical details, drawings, and details of any acoustic treatment required.  Getting one element of this wrong can lead to a planning refusal, resulting in costly redesigns and delays at Gateway One.

The Calibre planning application package covers all of these disciplines under one roof, saving a huge amount of cost, time, coordination and communication, with a 100% success rate to date across over 50 projects, minimising risk of application rejection and streamlining the process.  

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Gateway Two – Pre-Construction

Before any physical work begins on site, the Gateway Two application must be signed off by BSR. The application requires complete technical design on every aspect of the project, internal and external, along with documentation outlining how contracts will be administered. Both the Principal Designer and Principal Contractor must be appointed before the application is submitted, ensuring that safety risks throughout the construction process are being managed by competent duty holders.  

As full technical design is required prior to any work on site, there is far less scope for the specialist elements of the design (such as air conditioning and ventilation) to be changed or developed under CDP by the appointed subcontractor. The common issue with this is that a Stage 3 or even Stage 4 M&E design is rarely sufficiently developed to prevent variations occurring, and once the specialist trades and subcontractors commence on site and discover design errors and services coordination issues, this can create a major problem as it often presents a significant amendment to the BSR-approved design, resulting in a re-application.

Air conditioning and ventilation systems are two of the most important ones to get right for the Gateway 2 application as changes to ductwork routes and equipment selection can directly impact the fire strategy through positioning of fire dampers, fire alarm interfacing etc.

The Calibre approach to this is to firstly determine all client requirements and expectations including preferred noise levels for each room, the degree of cooling required, aesthetic considerations, listed building and conservation area implications etc at the inception of the project, and then work the design out from there.

In this way, systems can be correctly specified, not only to meet all of the clients requirements, but also to meet the BSR requirements, planning authority requirements and the interior aesthetic requirements. We work alongside the appointed M&E consultant to ensure our air conditioning and ventilation design is correctly coordinated with their other services.

Delivery Process – Design Changes

During the course of construction, the site progress is strictly monitored by BSR to ensure adherence to the approved designs, as well as safety on site. On-site variations are classified as either notifiable changes or major changes.  

Notifiable changes include minor modifications that still comply with the approved design intent, which must be reported to BSR but do not require formal approval. Major changes, on the other hand, are significant alterations affecting fire safety, structural integrity or compliance with building regulations.

Should one of these arise during the delivery stage of a project, the work must be halted and sent as a formal application to the BSR prior to continuation of work – and according to the government website, the change control application must be determined within 6 weeks of receipt, or ‘within such longer period as at any time the regulator and the applicant agree in writing’. This highlights the importance of a feasible technical design based on real-life use requirements at Gateway Two to prevent costly programme delays at delivery stage.  

Gateway Three – Pre-Occupation

Gateway Three represents the final inspection before occupation. Every aspect of the project must exactly match the approved designs, enforced by a BSR review, who also verify that all documentation—including as-built records and operation and maintenance (O&M) manuals—is in place. Any deviation triggers re-submission and review, making it essential to collaborate with specialists who can deliver what was promised at Gateway Two.

Our experienced in-house project management team collaborate closely with the wider construction team, as well as liaising with the designers, to deliver the signed-off technical design as agreed.

Key Considerations for Successful HRB Projects

To avoid project disruptions, technical design must be completed earlier than in traditional developments – and specialist elements of the project require specialist designers, who understand potential pitfalls, relevant legislation and fire-stopping requirements. Generic indicative designs provided by an M&E consultant will not have sufficient information for subcontractors to deliver a fully integrated and compliant installation under CDP.

For this reason, specialist design areas such as air conditioning must be developed in full by a specialist designer, from determining the initial scope of works to signing off the final design. This ensures clarity on the delivered result and minimises the likelihood of discrepancies at delivery stage by having a fully developed, feasible, and compliant system design, based on property-specific calculations and real-life use.  

The Calibre Climate Approach

At Calibre Climate, our turnkey solutions for luxury residential properties are designed as standard to comply with the stringent requirements of the Building Safety Act. All our designs are covered by £5m PI insurance, and undergo a Designer’s Risk Assessment [DRA] as standard, to design out lifetime risks involved with the systems installed, such as safe access, refrigerant leak detection and compliance with relevant building regulations.  

Through years of working in the industry, we have honed our approach to minimise on-site variations from initial design, providing certainty on both delivery programme and cost. Our ability to produce detailed technical designs early on allows us to coordinate with all relevant project parties to deliver a fully integrated result that exceeds client expectations.

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