By
Andrew Nash, Divisional Manager – Residential, Nuaire
Permitted Development Rights (PDR) were introduced to accelerate housing delivery by allowing offices and other commercial buildings to be converted into homes without full planning permission. Since their introduction in 2013, more than 100,000 dwellings in England have been created through these change-of-use schemes. While this has helped boost housing supply, it has also introduced a number of technical challenges for the built environment sector, not least the growing issue of overheating.
One of the defining characteristics of PDR conversions is that they are not subject to the full scope of Building Regulations. Crucially, they are exempt from Part O, which was introduced to address overheating in residential buildings. Instead, developers are typically only required to comply with Part F ventilation requirements. While Part F ensures a basic level of fresh air is delivered, it does not consider solar gains, internal heat build-up, or the wider factors that contribute to high indoor temperatures.
This regulatory gap means that many converted apartments are technically compliant but still struggle to maintain comfortable conditions during warmer periods. In practice, overheating complaints are becoming increasingly common in PDR developments, particularly once properties are occupied.
A key reason for this is that buildings originally designed as offices were never intended for residential occupation. Commercial buildings often feature large glazed façades, minimal external shading and limited natural ventilation. In dense urban locations, where many of these developments are situated, opening windows may not be possible due to noise, pollution or security concerns. As a result, passive cooling strategies that would normally be considered in residential design can become impractical.
Under Part O guidance for new-build housing, designers must consider glazing ratios, façade orientation, solar shading and openable window areas to reduce overheating risk. However, because PDR schemes are not required to follow these principles, developers often retain the original façade and glazing configuration, which can exacerbate overheating problems.
Mechanical ventilation can help improve conditions in these situations. Mechanical Ventilation with Heat Recovery (MVHR) systems not only precondition air and filter out pollutants but also provide summer bypass functions which can be used in combination with elevated airflows to provide free cooling when external temperatures are favourable.
However, there are cases where MVHR alone may not be enough. Here, a Nuaire Hybrid Cooling unit which works in tandem with our MRXBOX MVHR could potentially assist in mitigating overheating. Such systems activate when indoor temperatures exceed a threshold – typically 23°C – and introduce pre-cooled fresh air to help maintain occupant comfort.
The built environment community must confront the reality that current practices in PDR conversions are insufficient. Whilst there is no requirement to carry out overheating analysis on a change of use, is it ethical to completely ignore the risks to future occupants?
Nuaire is a UK based ventilation solutions manufacturer.
