The Change In Building Regulations – What Does It Mean For Me?

What are these approved documents, and what do they mean?

Part F – Ventilation

Part F details the ventilation requirements to ensure there is a constant level of background ventilation to limit the accumulation of moisture and pollutants, that would otherwise become a hazard to the health of the people living within the building – something which has become more prominent with the increase of air tightness in buildings.

Part L – Conservation of Fuel and Power

Part L refers to the conservation of fuel and power in dwellings, in essence, making all homes more energy efficient. This has been updated to help the government hit the target of net zero by 2050.

Do Part F and Part L not contradict one another?

When put side by side, the requirements of Part F and Part L do seem to contradict one another – when viewed in isolation.

Homes are responsible for around 14% of emissions, so it’s key for the government to improve energy efficiency in order to meet the net zero target, but without impacting the health and wellbeing of the people who live there.

New Build homes are designed to deliver both ventilation and energy efficiency, the problem arises in retrofit projects because it requires sealing up buildings, that aren’t designed to be sealed. While sealing these homes reduces emissions, and therefore meet the requirements required for Part L, they create a whole host of problems – mould, damp and the build up of pollutants – cue Part F…

The solution to this is either ‘continuous mechanical ventilation’, ‘mechanical ventilation with heat recovery and no background ventilators’ or ‘background ventilation’.

Part F, Ventilation

In our fenestration world, we can focus on ‘background ventilation’ - Trickle vents or head vents as they’re sometimes known as, provide just that.

First lets talk about EA or ‘Equivalent Area’, this is the measure of how much air passes through a vent as a measurement of airflow performance. There is a minimum EA requirement for habitable rooms, kitchens and bathrooms, within both single and multi storey properties.

Trickle vents provide a secure, draught free means of ventilation, which means more energy efficient windows and doors can be retrofitted to properties, therefore raising the general level of thermal performance, without compromising any health and wellbeing.

This requirement comes into effect as of the 15^th June, with no grace period, meaning all windows fitted after this date – even if replacing windows without trickle vents currently – must have them.

The only exemption, is if, for example, the sash is too small to accommodate trickle vents. Document F makes reference to ‘Technical Feasibility”, meaning is windows are too small, then you may fit what is achievable, despite not meeting requirements in full.

Part L, U-Values and Energy Efficiency

Simply put, the combination of trickle vents plus windows and doors with a maximum U-Value of 1.4W/m²K or a WER of B, satisfies the requirements of Part F and Part L and makes a happy home!

With new build homes, the maximum U-value of windows and doors with less than 60% glazing is 1.2W/m²K and all other doors 1.0W/m²K. There is however, some wriggle room.

For example, a new build home combines windows, doors, roof and wall insulation, which all work together to contribute to the overall energy efficiency of that house and satisfy (and more than likely exceed) the requirements of Part L. Therefore, you can decrease the notional U-Value of one of those elements, as long as the overall end result is still on target.

However, there is still a line that can’t be crossed, called the ‘limiting value’ – so no matter how energy efficient your new build home is, the windows and doors must be a minimum of 1.6W/m²K.

Are conservatories covered by these new requirements?

Glazed conservatories are only exempt from Part L, as long as the following apply:

The extension is at ground level
The floor area doesn’t exceed 30m2
Glazing compiles with Approved Document K – Protection from Falling, Collision & Impact
Walls, doors or windows separating the extension are retained or, if removed, are separated with a wall door or window

So, where does Part O come into this?

Part O – Over Heating

Part O is a new regulation, which has been introduced to prevent the overheating of homes, specifically via solar gain – it applies to new build and new residential buildings only as it falls within the broader topic of “Future Homes and Building Standards”.

To summarise, it sets limits on the allowable glazing area depending on the building’s orientation.