April 30, 2021

Approved Document X Tackling Residential Overheating - Coming Soon

Written by Rebecca Clayton

Glazing for self builds shown on Sand Dunes - a luxury new build in Cornwall on the coast.

Approved document X will only apply to new build homes and residential properties, leaving commercial spaces and pre-existing buildings unaffected. Solar control methods will be recommended where they are deemed appropriate, such as large elevations of south-facing glazing. The proposed document does not enforce any limitations on size or façade design, instead insisting glass façade designs and oversized glazing systems take extra precautions with shading solutions. There will be two routes to compliance, similarly to how building regulations part L1A currently offers multiple ways to show compliance for thermal performance requirements.

The route that offers architects and specifiers the most freedom involves using the ‘Dynamic Thermal Analysis’ method. This flexible approach allows an adaptedwater end house slim framed sliding glass doors version of the CIBSE's TM56 methodology for predicting the risk of overheating, to be used in conjunction with other strategies to reduce the risk of overheating. When architects choose to take this route, they have greater control over the overall design and can design the building to suit their client's preferences, as well as maintaining a safe and comfortable living temperature that is suitable for year-round use.

The second and slightly simpler route involves taking a look at the glazed area vs the floor area, restricting any glass elevations to between 13% and 21%, depending on the project type and geographical location. Each building will fall into a category-defining its ‘group’, which is determined based on the number of fabric elements and whether there are opening elements on opposite elevations. The glazing should be evenly distributed across all elevations or concentrated on North and East facing elevations. Subject to the proposed document, buildings in the Greater London area will be required to incorporate additional shading methods. There will be requirements surrounding the size of opening elements to ensure a decent amount of heat can escape the greater building envelope.

slim framed sliding glass doors large gable end windowThe solar gain will always be more of an issue during the summer months, particularly now we are now seeing higher temperatures across the country which are only set to increase with time. There are many solutions that can be used to reduce solar gain, including specifying glass with a high g-value. Another option would be to include an overhang in the exterior design, providing some shading to the glass beneath the structure. The new approved document is set to change the way highly glazed houses are designed, however, the focus on reducing overheating spaces will create more energy-efficient homes that are better equipped to deal with increasing temperatures.

Approved document X is not yet in effect, but the team at IQ is on hand to discuss any concerns or specification questions. You can get in touch with us on 01494722880.