Roofs inevitably need replacing during a building’s life. Retrofitting them effectively is essential to meet modern performance standards and ensure long-term resilience. The challenge lies in the unique conditions of each building; construction quality, exposure to weather, and occupant behaviour all affect roof durability and moisture risk.
Retrofit projects must be viewed holistically. Improving insulation and airtightness elsewhere in the building changes how moisture moves, which can affect the roof. For example, adding loft insulation lowers the roof-space temperature, increasing condensation risk.
Before upgrading insulation, assess the existing underlay. Traditional high-resistance membranes like bitumen felt may need replacement. More recent low-resistance (LR) membranes are vapour-permeable but typically airtight, meaning they may still require some roof-space ventilation. Care must also be taken not to block eaves vents when installing insulation.
- Proctor Group’s Proctor Air® membrane provides a retrofit-friendly solution. As an air-permeable LR underlay (APLR), it allows both air and vapour to pass through the roof without needing a separate vapour control layer or roof-space ventilation. This enables insulation to extend into the eaves without risking blocked vents, and mitigates condensation risk.
Proctor Air’s water resistance has been tested and meets the threshold of over 1m of water holdout recommended in the NFRC’s Technical Bulletin TB06. However, consideration should be given to protection of the roof during inclement weather.
Supported by a 15-year warranty and backed by BBA certification, Proctor Air provides a reliable, future-ready underlay for pitched roof retrofits.
