Advice Pack The PAS2035 stages - Stage two – Retrofit Assessment

What is Retrofit Assessment in the PAS2035 process?

The retrofit assessment is a comprehensive evaluation of property’s current condition to identify opportunities for enhancing its energy efficiency. It is necessary for all properties going through the retrofit PAS2035 process. The key components of a retrofit assessment are:

• Occupant assessment: evaluates the needs and behaviours of the building’s occupants to ensure that the retrofit measures will be suitable and beneficial for them.
• Condition survey: this involves a detailed inspection of the building’s existing structure, including its heating, ventilation, and insulation systems.
• Energy report: this report provides an analysis of the building’s current energy performance and areas where improvements can be made.

The Retrofit Assessment is carried out by a Retrofit Assessor. Retrofit assessment is crucial in understanding the current state of the building stock and it provides the data needed by a Retrofit Coordinator to create a detailed improvement plan. Six Stages of the PAS2035 Process: 

1. Preliminary work
2. Retrofit assessment
3. Pre-stage coordination
4. Planning permission
5. Construction coordination
6. Post-stage coordination

Significance Assessment 

For buildings designated as traditional or protected, an assessment of significance is required. This assessment, based on the ‘five key values of significance,’ evaluates the building’s appearance, form, and relationship with its surroundings and significant fabric. The results will guide the Retrofit Designer and Retrofit Coordinator in selecting and designing retrofit measures.

Five key values of significance:

1. Historical
2. Evidential
3. Architectural
4. Aesthetic
5. Communal

Air testing

For buildings where energy efficiency measures are constrained, the Retrofit Coordinator should consider an initial air leakage assessment. This test identifies overall air leakage and major leaks before retrofit work begins, forming a baseline for airtightness strategies. After major insulation work, a follow-up test should verify reduced air leakage through the building’s external envelope.

1. Preparation: All external doors, windows, and vents are closed, internal doors are left open. Any designed ventilation systems are temporarily sealed.
2. Equipment setup: A fan is installed in an external doorway to create pressure difference between inside and outside of the building.
3. Testing: The fan is used to either pressurise or depressurise the building to a standard reference pressure.
4. Measurement: The amount of air needed to maintain the pressure difference is measured, indicating the building's air permeability rate.
5. Analysis: The results highlight areas of significant air leakage, which can then be targeted for improvement.

Thermography

Thermography is the technique used to detect and measure variations in heat. It involves creating images based on infrared radiation, which can revel temperature differences on the surface or within buildings.

The Retrofit Coordinator might choose to carry out thermography in projects where there are concerns about insulation, thermal bridges, air leaks, moisture and damp, or to allow non-invasive inspection of traditional/historic buildings.

Measured Building Survey

All properties should be subject to a measured building survey, involving detailed measurement and documentation of a building’s physical dimensions and features. This survey is essential for accurately assessing the building’s current condition and planning effective measures. The key components of the measured building survey are:

• Overall Dimensions: measuring the entire building’s heat loss envelope, including basements and attics.
• Building Elements: documenting the dimensions of all exposed floors, external walls, roofs, and other structural elements.
• Openings: measuring all window and door openings to understand their impact on the building’s energy efficiency.

This detailed information helps in creating a precise retrofit design that addresses the specific needs of the building, ensuring that energy efficiency measures are appropriately tailored and effective.

In-depth Testing

In-depth testing involves physically examining a building’s structure to gather detailed information that isn’t viable through non-invasive measures. In-depth testing may be necessary during retrofit assessment in properties which have one or more of the following issues:

• Suspected structural issues: signs of structural damage or instability such as cracks or uneven floors.
• Hidden damp or moisture: where there are indications or dampness such as mould growth or musty odours.
• Uncertain insulation: to verify the presence and condition of insulation in walls, floors, or roofs.
• Thermal bridging: if thermal imaging reveals significant areas of heat loss, in- depth can help identify and address thermal bridges that are not externally visible.
• Material degradation: where there is need to address the condition of building materials, such as timber or masonry, for signs of decay.

In-depth testing can provide critical information that helps to design effective and targeted retrofit measures.

What happens next?

After the Retrofit Assessor completes the retrofit assessment, including the relevant tests above, the findings are presented to the Retrofit Coordinator, who then moves on to the next stage of the PAS2035 process: pre-stage coordination.

Useful links

You can download a free copy of PAS2035;2023 here.