Orbit Housing Group: PAS 2035 retrofit assessment and coordination across SHDF Wave 1 and Wave 2

Greener Solutions Group worked with Orbit Housing Group across its Social Housing Decarbonisation Fund (SHDF) Wave 1 and Wave 2 programmes, providing specialist retrofit assessment, coordination, testing and technical support across Orbit's housing stock. Orbit is one of the UK's largest housing associations. Our role centred on producing the technical information and PAS 2035 oversight needed to take properties from initial assessment through design, installation and completion, combining retrofit assessment and coordination with thermal imaging, air pressure testing and fRsi analysis.

Project at a glance

• Client: Orbit Housing Group

• Programme: Social Housing Decarbonisation Fund (SHDF) Wave 1 and Wave 2

• Sector: social housing decarbonisation

• Standard applied: PAS 2035

• Services: Retrofit Assessment, Retrofit Coordination, RdSAP, IOE and MTIP, thermal imaging, air pressure testing, fRsi calculations, ventilation assessment, design support, post-works EPCs

What services did Greener Solutions Group provide to Orbit Housing Group?

Greener Solutions Group delivered a comprehensive range of retrofit services across both waves of the programme:

• PAS 2035 Retrofit Assessments

• Retrofit Coordination

• RdSAP assessments and energy modelling

• Improvement Option Evaluations (IOEs)

• Medium-Term Improvement Plans (MTIPs)

• Thermal imaging surveys

• fRsi calculations and thermal-bridge risk assessment

• Air pressure and air permeability testing

• Ventilation assessments

• Property condition and building fabric assessments

• Technical support to the Retrofit Designer

• PAS 2035 compliance and quality assurance

• Post-works assessments and EPC support

"Orbit have worked with Greener Solutions Group throughout the various waves of Social Housing Decarbonisation Fund Projects and Warmer Homes Social Housing Fund."

"Greener Solutions Group offer not only an efficient service but strive to deliver a pragmatic approach to delivering PAS assessment and retrofit works."

"The teams knowledge of SAP, PAS and general retrofit (inclusive of mechanical and electrical) help to offer a service you can not only trust but rely on."

"In addition, we have worked with the team across our EPC programme where they have helped us achieve our annual targets through great access rates, comprehensive surveys and an audit process to ensure the data coming into our business is robust and accurate."

Gemma Brookes -Head of asset optimisation Orbit Housing Group.

How were properties assessed and tested?

Our assessors and coordinators carried out detailed property-level assessments to establish the existing condition, construction, ventilation provision and energy performance of each home.

Where required, thermal imaging surveys identified heat loss, thermal bridging and potential defects within the building envelope. fRsi calculations then provided further analysis of surface temperature and condensation risk at vulnerable junctions.

Greener Solutions Group also carried out air pressure testing, producing measured data on the airtightness and air permeability of properties. That information supported the assessment of building performance and informed ventilation, airtightness and wider retrofit design decisions.

Combining on-site assessment with building performance testing and technical calculations gave the design and delivery teams a far clearer understanding of how each property performed before and after retrofit.

Why does air pressure testing matter in retrofit?

Air pressure testing measures how much uncontrolled air leaks through a building envelope, expressed as air permeability. It matters in retrofit because improving insulation and airtightness changes how a home ventilates. Measured data allows ventilation provision to be specified against the actual performance of the property rather than an assumed figure, reducing the risk of condensation, damp and poor indoor air quality once works are complete.

How did coordination support better retrofit design?

Our Retrofit Coordinators worked alongside the wider project and design teams to confirm that proposed measures suited each property and that the interactions between insulation, airtightness, ventilation and other energy-efficiency improvements were properly considered.

This allowed potential risks to be identified before installation. It supported better detailing, reduced the likelihood of unintended consequences and helped ensure that completed works delivered the improvements they were designed to deliver.

The outcome

Across Wave 1 and Wave 2, Greener Solutions Group gave Orbit and its delivery partners an integrated assessment, coordination and building-performance service capable of supporting retrofit delivery at scale.

The combination of Retrofit Assessment, Retrofit Coordination, thermal imaging, air pressure testing, fRsi calculations and technical design support provided the evidence and technical oversight required for robust, compliant and effective retrofit solutions.

The programme demonstrates our ability to support major social housing providers with the specialist technical services needed to deliver PAS 2035-compliant decarbonisation at scale.

Frequently asked questions

What is the Social Housing Decarbonisation Fund?

The Social Housing Decarbonisation Fund is a UK government programme providing grant funding to social housing landlords to improve the energy performance of their least efficient homes. It has been delivered in successive waves, with Orbit's programme spanning Wave 1 and Wave 2.

What is an Improvement Option Evaluation?

An Improvement Option Evaluation, or IOE, is a PAS 2035 requirement that considers the range of energy-efficiency measures suitable for a dwelling and evaluates them against factors including the condition of the property, occupancy, cost and expected performance. It informs which measures are taken forward.

What is a Medium-Term Improvement Plan?

A Medium-Term Improvement Plan, or MTIP, sets out the sequence of retrofit measures recommended for a dwelling over time where all measures cannot be installed in a single phase. It ensures that works carried out now do not prevent or compromise improvements planned later.

What is RdSAP?

RdSAP, the Reduced Data Standard Assessment Procedure, is the methodology used to assess the energy performance of existing dwellings in the UK and to produce Energy Performance Certificates. In retrofit it provides the baseline energy modelling against which improvements are measured.

Why are fRsi calculations used in retrofit?

fRsi is the temperature factor at the internal surface of a construction detail. Calculating it identifies whether internal surface temperatures at junctions and thermal bridges are likely to fall low enough to cause condensation and mould growth once retrofit measures alter the performance of the building envelope. Doing this at design stage allows risks to be designed out rather than discovered after installation.

Talk to us about your decarbonisation programme

Greener Solutions Group provides Retrofit Assessment, Retrofit Coordination, thermal imaging, air pressure testing and fRsi analysis for social housing decarbonisation programmes across the UK. Get in touch to discuss your project.