By Sophie Neaves on Mon 20 November 2023
Compliance with The Future Homes Standard on Airtightness & Ventilation
Governments around the world are scrambling to reduce their nations’ carbon footprints – and the UK government is no different.
In June 2019, the UK passed a net zero emissions target into law. As a result, the UK must bring all greenhouse gas emissions to net zero by 2050. This went further than the previous target of an 80% plus reduction on 1990 levels.
According to the National Housing Federation, England’s homes are responsible for more carbon emissions each year than England’s cars. In the wider UK, households produce 20% of total emissions.
The Future Homes Standards aims to address this huge problem.
What is the Future Homes Standard?
Coming into force in 2025, the Future Homes Standard introduced changes to UK building regulations that will lead to new homes producing less carbon. Through low-carbon heating and ‘world-leading’ levels of energy efficiency, homes built from 2025 should produce 75-80% less carbon than homes built under current building regulations.
As well as reducing carbon output and driving greater energy efficiency, the Future Homes Standard is also focused on future-proofing the UK’s homes. One way to achieve all three aims is through Passivhaus design, which is the practice of creating buildings that have a negligible effect on the environment around them. Read this guide on Passivhaus for more details on the eco credentials of Passivhaus principles.
Airtightness standards
A key method for reducing the need for heating and increasing energy efficiency is raising the level of airtightness in a house. A more airtight house loses less heat to natural leakage, with less energy escaping through windows, roofs, walls and gaps in the building fabric. Airtightness also prevents less cold air coming in.
The Future Homes Standard sets out new minimum standards for fabric performance, updating Part L of building regulations. Measured using a U-value, these minimum standards are:
| External walls | 0.26 W/m2.K |
| Party walls | 0.20 W/m2.K |
| Floor | 0.18 W/m2.K |
| Roof | 0.16 W/m2.K |
| Windows | 1.6 W/m2.K |
| Door | 1.6 W/m2.K |
| Roof-lights | 2.2 W/m2.K |
Ventilation standards
As beneficial to energy efficiency as high levels of airtightness are, they naturally lead to a ventilation issue. When most of the air is kept within a building, stale air cannot escape so easily. This can create a whole host of problems.
During the Covid-19 pandemic, the role of poor ventilation in virus transmission came to the fore, but it can also lead to health conditions like asthma, fatigue and even cardiovascular problems.
Then there are the effects of poor ventilation on a building’s structural integrity. When the level of humidity in the air is allowed to grow unchecked, the inevitable result will be condensation and mould. In addition to the health risks mould and damp present, they will also damage the very fabric of a building over time.
So, when the Future Homes Standard regulations demanded greater levels of airtightness, they also highlighted the need for better ventilation, covered under Part F of the building regulations.
New requirements include a ventilation supply rate of six litres per second per bedroom. Unlike the previous regulations, this requirement is the same regardless of how many occupants there are, simplifying the regulations.
In addition, the Future Homes Standard dictates a minimum equivalent area of 5,000 mm2 for background ventilators in each habitable room.
Who needs to comply with the standards?
Anybody building a new home – of any size – under the new regulations must comply with the standards. In England, the standards came into force on 15 June 2022.
However, if a building notice, initial notice or full plans for building work were submitted before then and the work is started within a year, the new standards won’t apply.
Otherwise, all new homes built in the UK will be subject to the changed regulations.
What other measures can be taken to comply with the Future Homes Standard on airtightness and ventilation?
Fortunately, improved building practices, materials and systems now mean homes can be extremely energy efficient and enjoy constant ventilation.
Complying with air tightness standards
Insulation is one of the primary weapons in the fight against heat loss. It’s particularly vital where cold spots might form, such as around windows, doors and places where walls meet the floor or roof. At the top end of the scale, ‘super-insulation’ creates an envelope around the whole house, trapping warm air in.
Super-insulation also results in thermal breaks, which mean thermal bridges can’t form. A thermal bridge is a component within an object that possesses greater thermal conductivity than the surrounding materials, giving heat an easy way out. Super insulation shuts down these heat loss routes.
As well as insulation like warm-edge spacers around windows, the windows themselves must be double-glazed at a minimum. Passivhaus homes often go beyond this to include high-quality, triple-glazed windows, with sealed panes containing gases that don’t conduct heat.
Complying with ventilation standards
Since ventilation is central to the energy efficiency of a building, the Future Homes Standard pays close attention to it.
Whilst Natural ventilation, which includes the use of mechanical intermittent extract fans, remains an option for some homes, they are likely to be less airtight than those that have continuous mechanical extract ventilation in place
In terms of background ventilation, the minimum size of systems such as trickle vents and air bricks will be determined on a room-by-room basis. The minimum equivalent area of background ventilators in each habitable room should be 5000 mm2 – whether natural ventilation or a form of mechanical extract ventilation (MEV) is used.
However, mechanical ventilation with heat recovery (MVHR) is by far the best way to satisfy the airtightness, ventilation and energy efficiency requirements of the Future Homes Standard. Because it provides continuous ventilation, MVHR supports greater levels of airtightness, making sure there is adequate ventilation, even if the building is almost perfectly airtight. Plus, MVHR retains up to 95% of the heat from outgoing stale air, reusing it and minimising the energy needed to create new heat.
While it could take developers and builders a little while to fully understand the Future Homes Standard, it will soon become the norm as it applies to all new-build homes. And as more and more compliant homes fill the UK’s streets, the benefits – for the environment and householders – will quickly become clear.