The heat is on

Jon Crohill
Jon Crohill

New regulations for Part O, designed to prevent overheating in buildings, came into effect on June 15, 2022. Jon Crohill, Sheerline’s roofing and lantern specialist, looks at the most frequently asked questions surrounding Part O, while putting forward workable solutions.

What is Part O? Put simply, the role of Part O is to consider how overheating in new residential dwellings can be managed and reduced.

The Approved Document highlights the fact that certain areas within England are more at risk than others of overheating, particularly buildings in and around London, and other major cities where it is expected that temperatures will remain high throughout the night.

The purpose of the regulation is to help developers balance the need for thermal efficiency to ensure homes remain warm during the winter and reduce carbon emissions, while also ensuring homes do not overheat during the summer months.

For instance, during the planning stage for new builds, consideration must be given to the direction windows are facing and ways to limit solar gains.

June 15, 2022, was the date the legislation came into effect. It only applies to new residential dwellings in England and does not apply to extensions or conservatories that have been added to existing properties.

While the legislation did not apply to building notices or full planning applications submitted before the date, any works started after June 15, 2023, are subject to the new regulations.

Part O only affects new residential dwellings, which includes houses and flats. However, this also extends to institutional residential buildings or properties.

For example, this could include schools where pupils stay overnight, care homes, university halls of residence, a residential college, or other similar properties.

What does Part O mean for the fenestration industry? House builders and designers are required to consider a multitude of factors in relation to Part O. This includes the size of a glazed area, which way the windows, doors or glazed area are facing, whether there is any shade (curtains within the properties and trees outside cannot be included), summer ventilation, and other external factors such as noise or security concerns.

While Part O isn’t specifically focused on comfort, it does look at the health and wellbeing of residents.

And while the amended legislation doesn’t explicitly mention the fenestration industry, there are potential issues that need to be negotiated. For instance, reducing the size of glazing in high to moderate risk areas is one suggestion. However, the industry may offer practical solutions to overcome this issue without needing to reduce the size of glazing.

Ventilation is a key factor, and something that forward thinking companies within the fenestration industry are looking at in detail. This is partly because there is a need to balance Part O with Part L legislation, which focuses on fuel conservation and keeping homes warm, particularly during winter.

What solutions are available? Part O provides a two-pronged approach to dealing with overheating. It looks at prevention, which involves reducing the amount of sunlight through glazed windows and doors, and solutions for when too much sunlight has entered a space, for example, through adequate ventilation.

Preventative measures as specified in the amendment include shading options, such as shutters, external blinds, overhangs, and awnings. Other options are focused on the glazing design, such as the size, orientation, g-value, or depth of the window reveal.

Another option is the use of solar control glass, which is specifically designed to reduce the amount of heat entering a building or property.

Aside from preventing too much heat from entering the home, there are several ways homeowners can remove excess heat. This includes opening windows, ventilation louvres in external walls, a mechanical ventilation system, or a mechanical cooling system such as a dehumidifier or air conditioning.

An intelligent ventilation system that has recently been launched is SheerVent, from Sheerline, which is both Part L and Part O compliant.

One of the biggest advantages of this intelligent system is that it sits flush with the S1 roof lantern’s rafter bars.

Homeowners can choose between manual or automated options. The latter offering extra peace of mind as it features powered actuators that can be operated by discreet weather sensors that detect rain, or rain, wind, and light.

SheerVent offers reliable ventilation without the risk of leaks, which has been problematic within the industry in the past.

Another key advantage is that SheerVent can be retroactively fitted to existing S1 roof lanterns.

The fenestration industry can take several approaches in line with Part O. It can look at different window accessories that could be potentially in-built or add-ons, or work with glass suppliers who provide solar control glass. The other route involves focusing on ventilation that can be easily in built or retrofitted to existing properties.

The great thing about both approaches is that they can be viewed as standalone options, or they can work together collaboratively.