Paul Croughan of EnviroVent looks at how the new build sector is meeting ventilation requirements and improving the air quality in new home construction
Requirements for increased levels of air tightness and energy efficiency mean that around 25 per cent of new homes are now being specified with MVHR (Mechanical Ventilation with Heat Recovery) systems, according to research by the NHBC (National Housebuilding Council).
MVHR is proving to be the most effective way of achieving acceptable levels of indoor air quality and ventilation, while reducing the amount of energy used to heat a property.
These MVHR systems, which are situated in a central location, usually in the loft space of a house or a utility room in an apartment, provide both supply and extract ventilation, extracting warm and moisture-laden air from the bathroom, kitchen, WC and/or utility room of a property. Air is drawn into the main system and passes over a heat exchange cell, before being ducted outside to the atmosphere.
At the same time, fresh air is drawn from outside into the system, the heat from the extract air is then transferred to the supply air through the heat exchanger. MVHR units can transfer over 90 per cent of the heat from the extracted air to the supply air as it passes through the heat exchange cell. This helps to reduce the overall energy requirement of the building, as well as its carbon footprint. This fresh, filtered and tempered air is then supplied into the living areas of the home, providing a good level of indoor air quality and preventing humidity which can lead to condensation and mould growth.
Higher levels of air tightness
Where higher levels of air tightness (levels of 3 m3/h/m2@50Pa or below) are required, MVHR is often specified to secure a larger percentage reduction between the DER (Dwelling Emission Rate) and TER (Target Emission Rate). A high performing MVHR system through SAP (Standard Assessment Procedure) may lower the DER.
For new homes, MVHR is helping to cost effectively contribute towards the improvements in CO2 emissions required by Building Regulations. With MVHR, the incoming air is filtered, improving internal air quality and it also negates the need for window trickle vents. In addition, MVHR is an attractive option for properties requiring acoustic measures as there is no requirement to open windows. For example, for homes located near busy roads or airports.
One of the main requirements with a ventilation system is to ensure it is correctly sized. If it is undersized, it could lead to under-performance of the unit and noise issues. This is the reason why we work closely with specifiers at design stage to ensure that new homes can meet the requirements for both ventilation and
air tightness. Correct installation is also essential with MVHR systems to ensure their effectiveness.
Since 2010, revisions to Building Regulations Part F meant domestic ventilation became ‘notifiable’ work, requiring ventilation provision to be installed by a competent and qualified person. It is vital that the installation of any domestic ventilation system is correct and meets the minimum requirements set out in regulations and standards. Over 90 per cent of faults with ventilation systems are down to poor installation. More installers are therefore becoming NICEIC (The National Council for Electrical Installation Contracting) trained which means they can work with the latest types of domestic ventilation products efficiently, receiving technical information and advice plus practical support.
Building Regulations updates made in 2010 placed greater importance on the effective design, installation and operation of ventilation systems, along with the introduction of the Domestic Ventilation Compliance Guide and BPEC Accreditation. These revisions to Part L and Part F have paved the way towards ventilation becoming more of a ‘controlled’ service, which focuses on energy efficiency and correct installation to ensure that what is specified is fitted and works correctly. The aim of these updates was to maximise carbon reduction through correctly specified systems that are installed by competent engineers, therefore minimising energy losses.
The guidance also stated that instruction must be given to the homeowner as to how a ventilation system should be operated effectively. This is part of the NICEIC training we provide to installers.
Smart technology is also making MVHR units appeal more to homeowners and buyers. Apps such as myenvirovent offer greater control for the homeowner, as well as speeding up commissioning for the installer. It allows them to connect directly to the unit through the app without the need for a wireless internet connection. They can then access the dedicated installer mode to commission the airflow rates and select additional options in the unit’s ventilation settings page. This makes the whole process much simpler and more efficient.
Conclusion
The latest generation of MVHR systems are highly efficient and can recover over 90 per cent of the heat that would normally be lost to the outside via trickle vents or extract fans. This energy is then supplied back into the house as warmed, fresh air, ensuring that developers are able to reduce the overall energy requirement of the building. There are obvious benefits to homeowners who are looking to reduce their energy bills.
Installing mechanical ventilation systems is the most effective way that the new build sector can meet Part F requirements and improve SAP ratings. The trend towards fitting MVHR systems in new homes therefore looks set to continue as part of improving indoor air quality and achieving compliance.
Paul Croughan is head of sales – new build at EnviroVent