Whole building assessment and benchmarking

Why it matters

Each dwelling will have its own combination of occupancy patterns, construction and site-specific issues (such as shading and access). Each will therefore need its own assessment. This will make sure that the right measures can be applied to each home without causing unintended consequences such as condensation, mould, overheating or drastically different energy consumption than predicted.

The dwelling assessment is also a key opportunity to engage with residents, understand how they use the property and bring them along on the retrofit journey.

If the project needs to comply with PAS 2035 then a whole dwelling assessment is a requirement of certification, and in most cases a suitably qualified retrofit assessor will need to be appointed.

Key steps to take

1. Collate all existing information on the property: Using existing information may save time and cost and act as a good starting point for the assessment. This could include an Energy Performance Certificate, boiler records, construction information, previous asbestos surveys, existing drawings/plans, fuel bills from the last 12 months etc. This will be a useful starting point and will allow you to understand what other information is needed.
   
   
2. Consider the level of assessment needed: The level of assessment needed will depend upon the retrofit measures you plan to carry out and the complexity of the building. For example, if the building is historic or of non-traditional construction, or if several measures are proposed, then a more detailed assessment may need to take place to include air tightness tests, thermal imaging or moisture assessments.
   
   
3. Appoint a retrofit assessor/domestic energy assessor (DEA): If you don’t have the skills in-house, then you should appoint a suitably qualified consultant to carry out the assessments for you. As a minimum, you should appoint a domestic energy assessor (DEA). If the project needs to comply with PAS 2035, you should appoint a Trustmark-registered retrofit assessor.
   
   
4. Engage with residents: The assessment will require access into people’s homes, therefore residents need to be informed and on board. You will need to make sure that access has been agreed, that residents know the time that the assessor will be arriving and what the assessment will entail, and that residents have the support they need during the visit.
   
   

Success factors

Engage with residents early: Gaining access into people’s homes is of the utmost importance for carrying out a thorough retrofit assessment. Residents should be notified well in advance of the surveys and should be informed what the survey is for and how long it will take. The assessor will likely need to carry out an occupancy assessment where they will speak with the occupants about how they use the home. It is important that residents are well-informed, and that vulnerable residents are given additional support if required. The retrofit assessor should also be made aware of any potential safety issues at the property.

Allow enough time and resources: You should allow around half a day to carry out a thorough assessment for each dwelling, so residents should be informed of this. You will need to set aside a budget for the assessment stage, particularly if you are appointing external consultants. Internal resources will also be needed to liaise with the consultants, collate existing information, engage with residents and arrange access to properties.

Deep dive

What should be included in the basic assessment?

All assessments should include the following as a minimum:

• Property condition: This will include a basic assessment of structural condition (noticing any cracks), presence of damp/mould and an assessment of the condition of components such as windows, brickwork, roof covering etc. Any defects should be highlighted, and a list of repairs should be compiled.
  
  
• Basic occupancy assessment: Residents will be invited to comment on property performance and their priorities for improvement.
  
  
• Heating and ventilation: The type of heating and ventilation systems including the distribution systems will be noted following a visual inspection and reviewing records.
  
  
• Site context: This will include any notes on the surrounding area, for example, trees, bus stops, parking spaces, party walls, potential access points, neighbouring properties, potential for flooding and if the building is in a conservation area.
  
  
• Photographs: Photographs should be taken both internally and externally.
  
  
• Measured floor plans and elevations: Internal and external dimensions so that floor plans and elevations of the property can be produced.
  
  
• Energy consumption: Meter readings may be taken on site or energy usage information compiled from bills if available.
  
  

What should be included in more detailed assessments?

• Structural survey: If there is any sign of cracking or structural disturbance, then a full structural survey may be needed. This would be carried out by a structural engineer. Any defects will need to be rectified prior to the retrofit installation.
  
  
• Ecology survey: If any protected species are suspected, then an ecology survey may be required. An example may be the presence of bats in an historic roof; if works to the roof are going to be carried out, mitigation measures may be required to ensure they are not harmed.
  
  
• Asbestos survey: If the building was built before 2000, it may contain asbestos. This will need to be highlighted and managed as part of the project. Asbestos surveys can be commissioned from specialist licensed consultants.
  
  
• Occupancy assessment: If you are proposing multiple retrofit measures, a more in-depth occupancy assessment may be required. This will look more closely at how many people live in the property and how they use it, e.g. how many hours they are typically in the property, how many baths/showers they have per day, etc.
  
  
• Moisture assessment: A moisture assessment would be particularly important in historic buildings or buildings of non-traditional construction; this is because the moisture balance is generally quite different in these buildings and this will affect which retrofit measures may be appropriate. Again, a suitably qualified professional - such as a RICS heritage building surveyor - should be appointed to do this.
  
  
• Thermal imaging: Thermal imaging can be useful in detecting key heat-loss points within a building and detecting hidden issues. It also acts as a good before-and-after comparison tool, particularly where insulation is being proposed.
  
  
• Ventilation assessment: This will be required if any fabric (insulation) improvement measures are being proposed. Your Retrofit Assessor will be able to carry out a calculation to see if the existing ventilation system is suitable for the proposed measures or whether further ventilation is required.
  
  

Modelling options for retrofit

Once all the data is gathered, the building should be modelled in an energy calculation software package. This will establish a baseline for energy consumption and also evaluate the options for different improvements to the building.

You can use either SAP (Standard Assessment Procedure) or PHPP (Passivhaus Planning Package) software for this process. PHPP is considered a more accurate modelling tool, but SAP can generally model more typical buildings and more types of building services. SAP tends to encourage low-carbon heating sources and renewables to reduce carbon emissions whereas PHPP encourages a fabric first approach. RDSAP should be avoided as this works on too many assumptions and does not consider site-specific factors or occupancy patterns.

Improvement Option Evaluation and Medium-Term Plan (PAS 2035)

Once the dwelling assessment has been carried out and the building has been modelled in an energy calculation software package, you will be able to explore options for the retrofit measures in further detail; this is known as the Improvement Option Evaluation in PAS 2035 and is a requirement for compliance.

This stage will involve the retrofit assessor and retrofit coordinator putting together different packages of retrofit measures and showing the benefits of each option in terms of payback period and carbon cost effectiveness. This will allow you to make informed choices about the retrofit options that are available.

If you aren’t planning on carrying out a whole house/deep retrofit, then the chances are that you are going to be phasing different retrofit measures over the next 20-30 years to reach net zero carbon. It is imperative that the measures are appropriately sequenced and that suitable combinations of measures are installed together. This can be set out as part of the Medium-Term Plan, which will be prepared by the retrofit coordinator.

Get in touch

If you would like to discuss monitoring and evaluation strategies for your retrofit project, please contact the RISE support team rise@turntown.co.uk

We would love to hear about your experiences. What has worked for your housing association? What lessons have you learned? What documents, reports or tools have you found most helpful? Please contact rise@turntown.co.uk if you would like to share your experiences.