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Tips for designing a ventilation system to meet the requirements of the homes of the future

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Tips for designing a ventilation system to meet the requirements of the homes of the future

By EnviroVent Jun 21, 2022

Ruth MacEachern, Product Manager at EnviroVent, guides you through designing a ventilation system for new or renovated homes.

“For many years EnviroVent has been supporting architects and developers to help them develop sustainable ventilation designs, in line with best practice, which optimise the efficiency of the system and minimise energy usage.

So what are the basic design considerations for ventilation systems?

To design the most efficient ventilation system, this starts with our team having comprehensive information about the project.

This is the reason why in the first instance, we send the architect/developer a standardised list of questions to be able to develop EnviroVent’s Design Request Sheet.  These explore issues such as warm vs cold roof construction, whether windows open or not, if there is air conditioning in the property, if it’s a Passivhaus build, whether it’s an NHBC project, whether ceilings are vaulted and what height they are, plus many more.

It really helps if we are given access to a set of architects’ drawings – preferably AutoCAD Revit files.  These are then looked at by our account managers, and a budget quotation is often provided depending on customer requirements. Our design team and can then progress this and overlay our ventilation system design, which will be in line with current Building Regulations.

From this initial design, we can make the necessary calculations to determine the ventilation rates, propose a particular product, create a design with airflow calculations and prepare a quotation and recommendations.

With the Building Regulations changes being introduced in June 2022, the system needs to be designed and commissioned correctly to work out the airflow per room and to ensure the system balances.

There is great value in a well-designed system.  Often our clients will submit our ventilation system design to the Building Control Officer to meet their requirements.

In addition, we can provide 3D plans of a ventilation system, showing the ventilation unit, where the ducting goes into the riser, plus other useful information such as where any vaulted ceilings may be located.

What are the different designs of the ventilation system?

There are a number of different ventilation system designs, however since the Building Regulations have been tightened there are fewer systems which will be compliant.

The main systems to consider are:

  1. MVHR: Mechanical Ventilation with Heat Recovery.
  2. MEV: Mechanical Extract Ventilation.

The most effective in meeting the new regulations is undoubtedly MVHR, which is becoming an increasingly popular choice.   These whole house ventilation systems supply fresh air from outside into a property, as well as extracting air throughout the property.  MVHR also includes a heat cell which recovers between 70–95% of the heat from the exhaust air and greatly improves the energy efficiency of buildings – energy efficiency requirements in the updated Building Regulations Approved Document L have been increased from 70% to 73%.

MVHR systems are highly effective at keeping humidity low and indoor air quality high throughout the home. To prevent overheating in warmer weather our energiSava® MVHR units have an automatic bypass function which means air is no longer passed over a heat cell and room temperature air is supplied back into the property. When MVHR is specified, we always recommend click and connect fast track ducting, as it is more airtight, effective and results in a longer term better running system.

Mechanical Extract Ventilation (MEV) systems are another popular option for new builds and refurbishments.  These centralised systems help to reduce excess moisture by using multiple points in which to extract air. MEV systems provide year-round good indoor air quality, protecting a home from condensation, damp, and mould.  The MEV unit is usually located in the loft or hallway cupboard in an apartment to provide ventilation to the whole property.

Another option for new and refurbished homes is d-MEV, which is a decentralised version of the MEV, with individual fans located in wet rooms, such as bathrooms, kitchens and en-suites.  These provide continuous ventilation or it can be boosted automatically either by pull cords or light switches.

Compliance is becoming much more important and there are commissioning and compliance checklists at the back of the Building Regulations documents which need to be submitted to building control, within 5 days of the ventilation system being commissioned.  However, if the installer is NICEIC-qualified in the installation of ventilation systems, then this does not need to be submitted.

The important regulations you should know

There are two updates to Building Regulations coming into effect in June 2022: Approved Document F- Means of ventilation (ADF), and Approved Document L- Conservation of fuel and power (L1A/L1B) (ADL) in England. Approved Document O: Overheating Mitigation has also been introduced as a new regulation.

The proposed updates to Building Regulations will pave the way towards the Future Homes Standard, which is due to be introduced in 2025. This brings with it a greater focus on thermal efficiency, increased air tightness and indoor air quality.

Approved Document F has many proposed changes that will affect how ventilation is specified for new homes.  One of the most fundamental is that whole house ventilation rates will be increased from 13l/s to 19l/s for a one-bedroom property and up to 43l/s for a five bedroomed property. This increase will make it more challenging to meet ventilation rates, particularly in smaller properties, such as one-bedroom apartments, where, in the past, intermittent fans would have been used in ‘wet rooms’ rather than systems like MEV (Mechanical Extract Ventilation) for cost reasons. However, in a dwelling in which there is a single habitable space such as a bedsit or in student accommodation, 13l/s is still deemed to be an acceptable ventilation rate under the new changes.  The updated building regulations also mean that intermittent fans are now no longer suitable for very airtight dwellings, meaning a ‘systems approach’ is the natural choice.  Unsurprising, Scotland, with its increased airtightness and ventilation requirements has already moved away from allowing trickle vents and intermittent fans.

Some of the guidance on ventilation can sound quite complex, but this has been made easier to understand as there is now only one document: The Compliance Guide has been integrated into Approved Document F. To simplify things further, the updated Approved Document F contains separate guidance for dwellings and non-dwellings.

For the first time, Approved Document F also includes upgrades to existing homes.  When major refurbishment work is being carried out such as new windows or doors, insulation, loft conversions, then PAS2035 is the official document that complies.

Best practices to improve your ventilation design

In an ideal world, our ventilation system design would be followed verbatim but in the real world, we know that project plans can be changed at the last minute, so unforeseen amends have to be made.  However, it is important to be aware that these changes affect the ventilation design, therefore we ask that the design be re-submitted so the drawings can be amended and updated to ensure the system operates as efficiently as possible.  Otherwise it could lead to inaccurate sizing of the system.

In line with Best Practice, it is important that we are made aware of factors such as:

  • Are there any conservation considerations on the project?
  • Is it a Natural Trust property?
  • Are there any pollution or acoustic issues?
  • Is it close to a railway station or airport?
  • Is there a large amount of glass in the building which could cause an overheating issue?

If overheating is likely to be an issue this is covered in Approved Document O of Building Regulations for mitigating overheating in England.  Requirement O1 states that ‘reasonable provision’ needs to be made in residential buildings to be able to reduce the occurrence of high indoor air temperatures.

An MVHR system like the energiSava® range will switch to summer bypass and will drop the temperature slightly, in cases where overheating arises.

When designing a ventilation system, it is important to consider its sustainability:

This means being aware of where the company sources its components from,

  • Is it from the UK or from overseas? Which adds to the carbon footprint.
  • Do the ventilation systems offer low level electricity consumption?
  • Are used parts recycled from site to minimise waste and embodied carbon?
  • Does the manufacturer minimise packaging?
  • Does the company offer good sustainable practices and are they working towards zero carbon?

EnviroVent has a strong track record on sustainability and is working on a clear roadmap to achieve zero carbon by 2030.

An important point to bear in mind is that the Future Homes Standards are not static and even though the plans are to reduce carbon by around 75%, this figure could go higher.   It is therefore essential that architects and ventilation manufacturers work even more closely together to ensure that homes are future proofed to meet and achieve these standards.”

For more information about ventilation products and services from EnviroVent, call 0345 27 27 810.