Acoustic Design and Compliance Delivery – The Oakgate

Residential ‘Build-to-Rent’ | 214 Apartments with Amenity Space

Project Overview:

PDA Acoustics was appointed to provide acoustic consultancy for The Oakgate – a large-scale ‘build-to-rent’ (BTR) residential development comprising 214 apartments and amenity space. The scheme aimed to deliver high-quality residential accommodation with an emphasis on occupant wellbeing, sustainability, and long-term operational standards.

Chris Wright of PDA Acoustics, led the project from RIBA Stage 3 onwards, developing and implementing a robust acoustic design strategy to ensure compliance with The Building Regulations Approved Document E (ADE) and to secure enhanced acoustic performance credits under the Home Quality Mark (HQM) One Technical Manual.

Figure 1: The Oakgate

Technical Strategy:

PDA Acoustics led the development of a comprehensive acoustic strategy to support both regulatory compliance and HQM performance delivery. A coordinated design approach was employed from the outset supported by predictive modelling using BS EN ISO 12354, manufacturer data reviews, and coordination with architectural and M&E teams to integrate acoustic performance into the core design. The scope of works included:

• Assessment of the building envelope and façade elements to ensure that noise ingress from external sources, including transportation and environmental noise, was adequately controlled in line with BS 8233 and WHO guidelines.
• Specification of internal partitions within both residential units and shared amenity spaces to meet the performance requirements of Approved Document E while also aligning with enhanced performance targets under HQM.
• Review of critical junction details across the scheme to ensure that the sound insulation of separating elements was not compromised by flanking transmission paths.
• Specification of acoustic absorption within communal and amenity areas to control reverberation time and ensure acoustic comfort.
• Commissioning testing to validate acoustic performance including; pre-completion sound insulation and post installation plant noise measurements, demonstrating compliance with both regulatory and planning requirements targets.

The acoustic strategy also extended to the assessment and control of building services noise – a critical component for both planning compliance and HQM credit attainment. PDA Acoustics provided comprehensive evaluations of internal mechanical systems (e.g. MVHR units) and external plant (e.g. air source heat pumps, condensers) to ensure that operational noise levels did not compromise internal amenity or adversely impact nearby noise-sensitive receptors.

Figure 2: Results of Soundplan Noise Model

Key technical contributions included:

1. Partition Design Advice & Compliance with Approved Document E

• Specification and validation of wall and floor constructions to achieve minimum performance of:

– DnT,w + Ctr ≥ 45 dB (airborne sound insulation between dwellings)

– L’nT,w ≤ 62 dB (impact sound insulation of separating floors)

The sound insulation performance was verified via pre-completion testing, all of which met or exceeded targets.

2. Flanking Transmission Control

• PDA conducted in-depth junction reviews, focusing on weak points such as slab/wall junctions, SFS interfaces, and service penetrations. A variety of treatments were developed to minimise flanking paths ultimately ensuring that the acoustic performance of the separating partitions is not compromised.

3. Building Services Noise Assessments

• PDA undertook internal mechanical services noise assessments using octave-band analysis of manufacturer data and in-duct transmission modelling. Predictions were benchmarked against BS 8233 and HQM requirements, targeting:

≤ 30 dB L_Aeq,T in bedrooms

≤ 35 dB L_Aeq,T in living spaces

• External plant noise emissions were assessed in accordance with BS 4142:2014+A1:2019. PDA conducted environmental sound surveys to establish representative background sound levels and used source-specific data to predict rating levels at nearest sensitive receptors.
• SoundPLAN Noise Modelling software was utilised to calculate the propagation from source to receiver.
• Where necessary, PDA recommended acoustic mitigation measures such as low-noise plant selection, acoustic enclosures, anti-vibration mounts, and barrier screening to ensure compliance with both HQM targets and Local Authority Planning Conditions.

4. Construction Monitoring & On-site Support

PDA provided on-going technical support during RIBA Stage 5 including:

• Attendance at coordination workshops with the wider design team.
• Design reviews to assist with value engineering
• On-site inspections of slab edges, service routes, and wall junctions etc. to ensure compliance with the acoustic design strategy and identify potential issues at an early stage.
• Pre-completion testing, providing prompt feedback to the site team and ensuring that certification reports are issued in a timely manner.

 Figure 3: Flanking detail at junction of separating/corridor wall

Acoustic Challenges & Design Coordination:

One of the key acoustic challenges encountered during the design process involved the control of noise emissions from external air source heat pumps (ASHPs) proposed at roof level. The mechanical design included a cluster of ASHP units located within a designated rooftop plant compound, in proximity to both nearby noise-sensitive receptors and upper-level residential units within the development itself.

PDA Acoustics undertook a BS 4142:2014+A1:2019 assessment to evaluate the likely impact of operational noise from the plant on the surrounding acoustic environment. Following detailed modelling, it was determined that 300mm deep acoustic louvres would be required around the perimeter of the plant compound to achieve the necessary insertion loss and control breakout noise.

This introduced a complex design coordination issue: while the louvres offered the required acoustic attenuation (particularly in the mid-to-high frequency range critical to ASHP noise spectra), they also introduced a pressure drop that risked exceeding the tolerance envelope for efficient operation of the ASHPs.

PDA worked closely with the M&E design team to achieve a balanced solution. The process included:

• Iterative acoustic modelling of breakout noise levels using manufacturer spectral data, accounting for directivity and reflection paths off rooftop structures;
• Selection of high-performance acoustic louvre systems with reliable acoustic test data and known airflow characteristics;
• Consideration of pressure drop and its effect on ASHP performance, referencing manufacturer guidelines and engaging with equipment suppliers to validate tolerances;
• Review of louvre placement and free area to optimise performance, including consideration of louvre orientation, spacing, and integration into the architectural envelope.

This multi-disciplinary effort resulted in a final plant enclosure design that satisfied both acoustic and airflow requirements, ensuring compliance with the Local Authority Criteria, HQM credit eligibility, and reliable long-term operation of the mechanical systems.

 Figure 4: 3D model of roof top plant compound (produced by Tim Groom Architects)

Outcome

The development achieved full compliance with Approved Document E, with all separating elements passing on first test, and successfully securing the enhanced HQM ‘Level 3’ Certification.

PDA’s comprehensive approach to design ensured that acoustic comfort was embedded into the development. In particular, the early-stage assessments of internal and external building services noise, proved instrumental in discharging planning conditions and protecting future residential amenity.

PDA’s technical expertise and focus on delivering pragmatic solutions to acoustic challenges, helped deliver a development where acoustic performance was not only compliant with regulatory standards, but optimised to enhance residents’ quality of life, operational resilience, and contribute towards sustainability goals.