New homes are built to be warmer, tighter and more energy efficient. That’s good news in winter, but in summer, it can cause a big problem.
Without the right ventilation, modern homes can quickly become hot, uncomfortable and difficult to live in. For property developers, landlords and facility managers, that can mean tenant complaints, poor indoor air quality and buildings that don’t perform as they should.
That’s why Approved Document O matters.
What is Approved Document O?
Approved Document O, also known as Part O, is part of the Building Regulations in England and was introduced to help reduce overheating in new residential buildings. It came into force on 15 June 2022, with full effect from June 2023, and applies to new homes, flats, care homes, dormitories and student accommodation, but not to extensions or existing buildings.
In simple terms, Approved Document O requires new residential buildings to be designed in a way that limits unwanted heat from the sun and provides a practical way to remove excess heat from inside the building. This means developers and design teams should first consider passive measures, such as building orientation, shading, thermal mass and ventilation, before relying on mechanical cooling such as air conditioning. Just as importantly, the overheating strategy must work in the real world, taking account of noise, air quality, security and safety.
The message is clear: new homes must be designed to stay comfortable, safe and usable during warmer weather. Overheating can’t be ignored.
Why overheating is becoming a bigger issue
Many modern homes are designed to keep heat in. They often include better insulation, improved airtightness and larger areas of glazing. While these features can help reduce energy use, they can also trap heat indoors during warmer months.
This is especially common in:
- New-build flats
- High-rise residential buildings
- Student accommodation
- Care homes
- Urban developments
- Homes with large windows
- Properties close to busy roads or railways
- Buildings where windows can’t be left open safely
In these situations, simply opening a window may not be enough. Noise, pollution, safety and security all affect whether occupants can use windows properly. That’s why a clear ventilation strategy is so important.
Why this matters for landlords and property managers
Overheating isn’t just a comfort issue - It can affect tenant wellbeing, sleep, indoor air quality and long-term satisfaction with the property.
For landlords, housing providers and facility managers, poor ventilation can also increase the risk of:
- Tenant complaints
- Condensation
- Damp and mould
- Poor air quality
- Expensive remedial works
- Compliance concerns
- Higher maintenance pressure
A well-planned ventilation system helps protect both the building and the people living in it.
Ventilation is key to tackling overheating
Approved Document O focuses on overheating. Approved Document F focuses on ventilation. In practice, the 2 go hand in hand. A home needs enough fresh air for everyday health and comfort. But it also needs a way to remove warm, stale air when temperatures rise. That’s where the right ventilation products can make a real difference.
What ventilation options are available?
There isn’t one solution for every building. The right choice depends on the property type, layout, budget and how the building will be used.
Here are some of the most common options:
Mechanical ventilation
Mechanical ventilation uses fans, ductwork and controls to move air through a building. It gives more control than relying on open windows alone.
This can be useful in flats, high-rise buildings, urban developments and properties where consistent airflow is needed. Mechanical ventilation can help remove warm, stale or moist air and support better comfort throughout the year.
MVHR systems
MVHR stands for Mechanical Ventilation with Heat Recovery. These systems remove stale air and bring fresh air into the building. They also recover heat from the outgoing air, helping to improve energy efficiency.
MVHR is often used in modern airtight homes, where controlled ventilation is essential. For developers, it can be a strong option for new-build properties where comfort, air quality and energy performance all matter.
Positive Input Ventilation
Positive Input Ventilation, or PIV, introduces filtered air into a property. This helps push stale, moisture-laden air out through existing vents and natural gaps.
PIV is often used to help reduce condensation and improve indoor air quality. It can be a practical option for landlords, housing providers and property managers looking to improve airflow in existing homes.
Decentralised fans
Decentralised fans are useful where a full ducted system isn’t practical. They provide ventilation on a room-by-room basis and are often used in bathrooms, kitchens, flats and retrofit projects.
They can help remove moisture, odours and warm air at source. For properties with limited space, they offer a simple and effective way to improve ventilation without major building work.
Bathroom and kitchen extract fans
Bathrooms and kitchens are major sources of heat and moisture. Cooking, showering and drying clothes all add warm, damp air into the home. Without proper extract ventilation, that air can spread through the property and lead to condensation, discomfort and mould risk. A good extractor fan helps remove this air before it becomes a bigger issue.
Roof windows and roof vents
Hot air rises. That’s why roof windows, rooflights and roof vents can play a useful role in helping warm air escape. They can support natural ventilation, improve airflow and bring more daylight into a space. For the right property, they can form part of a wider overheating strategy.
Don’t wait until tenants complain
The worst time to think about overheating is after the building is occupied - by then, the problem is harder and more expensive to fix.
Developers should consider overheating and ventilation early in the design process. Landlords and facility managers should review ventilation if tenants are reporting heat, condensation, poor airflow or mould.
A simple upgrade can often make a major difference to comfort and building performance.
What should you consider before choosing a system?
Before selecting a ventilation product, ask:
- Is the property a new build or retrofit?
- Is overheating already a problem?
- Can windows be safely opened?
- Is the building affected by noise or pollution?
- Are there problems with condensation or mould?
- Is there space for ductwork?
- Does the system need to serve one room or the whole property?
- How easy will it be to maintain?
Answering these questions can help you choose a solution that works in the real world, not just on paper.
Overheating is becoming a bigger issue in UK homes. For developers, landlords and facility managers, it’s no longer something to overlook.
The right ventilation strategy can help reduce heat, improve air quality and create better living conditions for occupants.
It can also help protect your property, reduce complaints and support long-term building performance.
Need help choosing the right ventilation product?
Explore Inbuild UK’s range of ventilation solutions, including mechanical ventilation, MVHR, PIV, decentralised fans, bathroom extract fans and roof ventilation products.
Keep buildings cooler. Improve airflow. Support healthier homes.
