Factsheet: Building Performance Surveys

Building condition survey

A building fabric condition survey is a visual inspection of a building's condition.

Purpose: to assess the condition of the fabric and identify any issues, defects, or maintenance needs.

For the purposes of a Decarbonisation Plan, the survey should focus on the condition of the external envelope of the building (walls, roofs, windows and doors) as well as the supporting structure. It should also identify internal defects such as damp and mould.

The scope should include an assessment of external wall build ups, to inform estimated existing u-values. 

The survey should be carried out by a Chartered Building Surveyor registered with an appropriate professional body such as RICS.

Building pathology survey

A pathology survey is a more detailed investigation and diagnosis of the condition and performance of a building.

Purpose: to assess condition, identify defects and their causes, and propose remediation and management measures.

A pathology survey is a more comprehensive form of condition survey, that focuses on understanding the causes of material degradation, moisture ingress, condensation and structural movement, and how these affect the building’s performance and longevity.

It may include material testing and intrusive investigations, such as fabric moisture content and fungal testing and analysis.

Building structural survey

A structural survey is a comprehensive inspection of a property’s structural integrity.

Purpose: to assess the condition of a building’s load-bearing elements, and the causes and remediation measures of any existing damage.

For the purposes of a Decarbonisation Plan, the survey may be targeted to focus on areas where options for new interventions have been identified eg. loadbearing capacity of existing roof structure to accommodate new plant, to confirm feasibility.

The survey should be carried out by a Chartered Structural Engineer registered with an appropriate professional body such as IStructE.

Building services condition survey

A building services condition survey is a visual inspection of a building's mechanical, electrical and power systems.

Purpose: to understand how the existing building is currently serviced; to ascertain the capacity of the existing infrastructure, and to help establish a base point for energy reduction measures as part of a decarbonisation strategy.

The scope of the survey should include the life expectancy for each component alongside its current installation age and general condition.

The survey should be carried out by a Chartered Mechanical and Electrical Engineer registered with an appropriate professional body such as Engineering Council.

Thermographic survey

A Thermographic survey uses infrared cameras to inspect building elements and electrical systems for heat variations.

Purpose: to identify anomalies by detecting areas with abnormally high or low temperatures, which may indicate thermal bridges, missing insulation, fabric defects or air leakage.

Qualitative thermographic analysis involves the visual interpretation of thermal images, identifying patterns and anomalies to provide a quick assessment of thermal conditions.

Quantitative thermographic analysis involves the measurement and analysis of temperature data alongside the use of thermographic images to provide more detailed evaluation of performance. This survey is more costly and time-consuming to undertake but can provide accurate data on fabric performance and U-values.

Quantitative thermographic surveys have logistical considerations:

To ensure an accurate survey output, the thermal imaging will need to be carried out during ideal weather conditions – no precipitation, low wind speed, no direct sunlight and a stable external temperature.

The building will need to be consistently heated for 24hrs to ensure a minimum temperature difference between inside and outside. All doors and windows will need to stay closed.

Air tightness testing

Air tightness testing measures the volume of air lost through the building fabric. It quantifies m³ of air leakage per hour per m² of external area.

Two main methods include:

- Fan pressurisation method (‘blower door’ test method)

- Low-pressure pulse method (‘pulse’ method)

Purpose: to quantify heat loss through air leakage in the existing building. This informs assumptions as part of the estimated calculated energy baseline as well as proposed measures.

If on-site air tightness testing is not feasible as part of the decarbonisation plan, industry benchmarks can be used based on an understanding of the construction of the building and any uncontrolled ventilation systems.

Air tightness testing requires a high degree of preparation. This includes sealing windows and doors, closing ventilation systems, filling water traps, and potentially sealing temporary openings. This may need to be undertaken out of hours.

U-value calculations

U-value calculations determine how well a building component (e.g. wall, roof, or window) prevents heat transfer between internal and external environments.

A lower U-value indicates better insulation, meaning less heat escapes or enters.

Purpose: to measure how well the existing building construction resists heat loss, and to help set clear targets for improving insulation and increasing energy efficiency.

U-values are calculated by dividing the rate of transfer of heat through a structure by the difference in temperature across that structure. The units of measurement are W/m2K.

For the purposes of a Decarbonisation Plan,  U-values should be calculated for walls, floors, roof, windows and doors using information gathered from visual inspection, conditions survey and thermal imaging (if available).

U-value calculations should be carried out as part of the preparation of the decarbonisation plan, by a Chartered Mechanical and Electrical Engineer registered with an appropriate professional body such as Engineering Council.

Temperature, humidity, and CO₂ readings

Information about the internal conditions of the building, which may be available from building management systems or local sensors.

Purpose: evidence of daily and seasonal fluctuations of temperature, humidity and CO₂ levels within the building can help to understand the indoor environmental quality and performance of the existing building and service systems.

Data can be provided by the client, if available, or the services engineer may propose installation of monitors to gather information over a period of time to inform future design development or systems management.

Hygrothermal assessment modelling and analysis

This assesses hygrothermal performance of the fabric, which refers to the dynamic interaction of heat, air and moisture penetration in and across built fabric.

Poor hygrothermal performance can lead to condensation, mould, degradation of materials and reduced energy efficiency as well as negative impacts on occupant health and comfort.

Hygrothermal performance can be assessed through:

- physical testing of materials and assemblies to evaluate performance

- steady-state analysis of heat and moisture transfer through building components using the Glaser Method; or

- dynamic hygrothermal modelling using computer software such as WUFI to simulate heat, air and moisture transfer over time.