Introduction
With rising energy prices and increased pressure for UK businesses to decarbonise, drone-based thermal surveying has rapidly become one of the most effective techniques for diagnosing heat loss and assessing retrofit potential. Using a DJI Mavic 3T equipped with a 640×512 radiometric thermal sensor, this survey produced high‑resolution data that reveals the true condition of the building’s external envelope.
Thermal surveying is performed in accordance with established guidance such as BS EN 13187 and BRE IP 1/06, ensuring that all images are captured in stable environmental conditions and interpreted against known material emissivity and thermal behaviour. Conducting the survey after sunset removed the influence of solar gain and allowed heat‑loss patterns to be detected with clarity.
Environmental Conditions & Methodology
To ensure accuracy, the survey was carried out after sundown when external temperatures were consistent and building surfaces had sufficiently cooled. Internal heating was operational, producing a temperature differential exceeding 10°C between interior and exterior surfaces—optimal for identifying heat loss.
The drone captured both nadir (downward) and oblique façade imagery. Radiometric R-JPEG files were used to allow precise temperature extraction. Emissivity was set at 0.92, suitable for most external building fabrics.
Roof Thermal Analysis
The building’s roof exhibited a number of concerning thermal anomalies. The three rooftop images captured during the survey clearly show extended red and yellow thermal zones, which indicate localised heat retention and elevated surface
temperature. These patterns are typically associated with water ingress beneath an aging roof membrane.
When moisture becomes trapped beneath a roof membrane, the affected areas behave very differently from surrounding dry insulation. As the sun warms the roof during the day, the water stores thermal energy and releases it more slowly overnight. This creates a persistent warm signature on the thermogram—precisely the phenomenon seen in the images below.
These red/yellow zones therefore signify not simply heat loss, but a significant loss of roof integrity. The extent and shape of the warm areas strongly suggest that the insulation has become saturated, reducing its thermal resistance and potentially leading to long‑term structural deterioration.
This type of water‑driven thermal anomaly is one of the most important indicators in flat‑roof diagnostics and typically justifies intrusive inspection, core sampling or full roof‑membrane replacement depending on severity.
Façade Heat-Loss Assessment
The façade thermal imagery shows heat loss concentrated around window frames, wall junctions and service penetrations. These elevated temperatures indicate thermal bridging, aged window seals, and likely air‑leakage paths. Variations in wall surface temperature also suggest uneven or degraded cavity insulation. Addressing these issues would significantly improve the building’s energy performance.
Retrofit Recommendations
Based on the thermal evidence collected, the following retrofit actions are recommended:
- Roof membrane replacement or refurbishment due to clear evidence of water ingress and insulation saturation.
- Full moisture survey using core samples or capacitance testing to map the extent of trapped water.
- Upgrade flat‑roof insulation, especially in saturated zones, to restore thermal resistance. Window and door seal replacement to address frame‑related thermal bridging.
- Cavity insulation assessment to identify voids or settlement. Air‑tightness improvements around penetrations, door frames, and service routes.
These measures would reduce heating demand, extend the lifespan of the roof structure, and support EPC improvement.
Budget Prioritisation Through Data Review
Beyond identifying technical defects, reviewing the factual thermal data is essential for determining where limited budgets should be allocated for maximum impact. By quantifying the severity and extent of heat-loss pathways, thermal surveys allow building owners to prioritise expenditure on the areas that will deliver the greatest reduction in energy waste. This evidence-led approach is especially valuable and ensures that every pound is invested where it will produce measurable efficiency gains.
Conclusion
The drone‑mounted thermal survey provided a comprehensive view of the building’s thermal performance. The rooftop findings are particularly significant: the presence of large warm zones indicates moisture trapped beneath the roof membrane, signalling a deterioration in roof integrity that requires attention.
By addressing both the roof and façade deficiencies identified in this survey, the building owner can significantly reduce heat loss, lower operational energy costs, and plan targeted retrofit interventions aligned with UK energy‑efficiency standards.
Ready to build your expertise in drone-based thermal imaging?
Join iRed’s Infrared Thermal Imaging for Drone Operators course, running 12th–16th January 2026 in Emsworth. This hands-on training is designed for UAV pilots looking to accurately capture and interpret radiometric thermal data.
For more information or to book your place, call 01243 370 296