Kevan Woolf of Velfac questions whether the introduction of Part O to mitigate overheating means inward opening windows are the only solution.
The recent introduction of Part O of the Building Regulations has prompted designers to seek effective solutions to meet ventilation requirements, with many turning to inward opening windows as a primary option. But is this the only solution? Not necessarily. While inward opening windows address the key requirement that “window handles on windows that open outwards are not more than 650 mm from the inside face of the wall,” they also present several considerations that housebuilders and developers must account for.
One of the most significant factors is the impact on internal space. Inward opening windows require sufficient clearance to swing open, restricting where furniture can be placed and limiting design flexibility. Unlike outward opening windows, which allow for clear, unobstructed use of internal space, inward-opening designs can interfere with room layouts, particularly in compact or high-density developments where every square metre counts.
Additionally, window cill boards – often used for decorative items, storage, or plants – become less functional, as they must remain clear to allow the window to open fully.
These practical limitations mean housebuilders must rethink internal layouts, potentially increasing design complexity and reducing usable space.
Another key consideration is cost. Inward opening windows often require more complex tilt-and-turn ironmongery, making them more expensive than traditional outward-opening alternatives. This additional cost, when applied across an entire development, can significantly impact budgets – something developers must factor in when specifying window solutions.
Beyond ventilation, another crucial aspect of Part O is the control of solar gain. Excessive heat from facade glazing can lead to overheating in modern homes, making it essential for architects and developers to carefully design window configurations that balance ventilation with thermal comfort. A key strategy is to minimise large fixed glazing elements and increase the proportion of openable windows to encourage natural airflow while limiting solar heat build-up. This means developers must be more strategic in their window selections, ensuring they meet both regulatory requirements and occupant comfort needs.
There are also additional design and usability factors to consider when choosing between inward and outward opening windows. Flexibility in ventilation is essential, and outward opening windows often provide a greater range of options, including lockable night vent positions, opening restrictors, and free opening on friction guides.
For developers working on accessible homes, it’s important to ensure that handle heights remain below 1400 mm from the floor, in line with the requirements of Part M4(2) for accessibility.
Furthermore, inward opening windows allow for easier internal cleaning, which can be a key advantage in high-rise developments, but this must be weighed against the potential loss of usable internal space.
For housebuilders and developers, understanding the full impact of Part O is crucial – not just in selecting compliant window solutions, but also in considering how these choices affect cost, space, and the long-term usability of homes. Finding the right balance between ventilation, solar gain control, cost-effectiveness, and spatial efficiency will be key in ensuring developments remain both practical and desirable for future homeowners.
Marine Place, a striking development by Acorn Property Group in Clevedon, consists of nine three and four-bedroom townhouses overlooking the Bristol Channel. Designed as ‘light-filled modern townhouses,’ each home features aluminium/timber triple-glazed windows, patio doors, and bi-parting doors, enhancing stunning seaside views.
The system specified also provides the exceptional weather protection required for this exposed cliff-top location, ensuring durability against salt-laden winds and driving rain.
Dave Gittins, head of construction for Acorn Property Group’s Bristol Region, highlights us as a quality choice, previously used in another development. Given Marine Place’s exposure to severe weather conditions, the system was selected for its tested performance and ability to withstand strong winds and loads.
Large windows on all four floors maximize the views, with bi-parting glazed doors opening onto sea-facing balconies and striking roof-level triangular gable windows. Internally, a white timber frame finish blends seamlessly with the interiors, while externally, dark grey aluminium frames complement the sandstone, white render, glass balustrades, and slate roofs, ensuring both aesthetic appeal and lasting performance.
Kevan Woolf is commercial internal sales manager UK at Velfac