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How Will New NHBC Guideline Affect My MVHR Installations

Dear Wendy,

By Wendy Thomas, Residential Product Manager, June 2014

I have recently read that the NHBC are bringing out new guidelines with regards to MVHR installations. I am responsible for new build for social housing and we have used MVHR several times. Please can you explain the implication for providers building new homes wanting to use MVHR.

Wendy Thomas, Residential Product Manager - The update to the NHBC Standards has been made as a result of a sharp increase in the number of MVHR systems being installed in new homes. There have been many trial sites to understand the issues and what is becoming increasingly apparent is the link between poorly installed systems and poor indoor air quality. The NHBC has worked with ventilation manufacturers of MVHR systems to identify common issues and make improvements in the design of MVHR systems.

The NHBC’s aim is simply to encourage best practice in installation as part of a wider aim to raise the standards of building for new homes. The new Standards became effective from January 2014 so you now need to make yourself familiar with the changes so that your future MVHR installations follow the best practice approach.

The NHBC has identified that the in-service performance of an MVHR system can be sensitive to installation defects, such as condensation forming in the ductwork. They advise house builders to consider MVHR at the design stage so that the MVHR and the ducting ancillaries are chosen based on the size and layout of the property, and so that issues such as the location of the fan unit, the routing of the ductwork, the type and position of the air valves and terminals, are all taken into account and form the basis of the ventilation design.

Step 1 - Choose the right MVHR - Choosing the correct MVHR system for the size and layout of your building is the first step. Nuaire designs MVHR systems to meet current building regulations, considering the ventilation rates that need to be achieved and the Specific Fan Power (energy) that the MVHR unit will use. The design of the ducted system and layout does have an impact on both the air changes and the Specific Fan Power (SFPs), so any changes to the design made at the installation stage without consultation with your fan manufacturer can result in several implications: failure to comply with building regulations, an increase in noise as the unit works harder to achieve the airflow, and poor indoor air quality resulting in condensation and mould.

Step 2 - Get support from your MVHR manufacturer - The NHBC guidelines are put in place to help best practice design and installation. You can also work with a trusted ventilation manufacturer that offers a drawing service to accompany its MVHR sales. Nuaire, for example, promotes MVHR installation best practice, not only through free NICEIC installer training, but through a highly detailed design service. As well as designing your MVHR system based on your property, Nuaire provides information on ventilation rates and SFPs, with full REVIT layout designs. With all components, ducting parts and ancillaries listed alongside the MVHR, the installation is much easier to carry out. If installed as per the design the unit will be efficient, quiet and fully compliant to building regulations.

Step 3 - Ensure your ducting is up to scratch - Correct duct work is another critical part of best practice installation. The NHBC advise using a single manufacturer for all the components required to make up a ductwork system. 'Ductmaster Thermal' from Nuaire is a new thermal duct designed for unheated spaces that is fully compliant is the ducting and insulation in one piece which reduces installation time by half.

Step 4 - Location, Location, Location - Location of the fan unit is also a focus of the new guidelines. The MVHR system should be located where it can be easily accessed by the occupants who will be required to regularly maintain the system to ensure smooth operation.

Step 5 - Get help early on! - My advice is to involve your manufacturer early on. It is the best way of preventing problems at installation stage, when time is money. By considering your ventilation when your building is being designed, rather than when joists, heating and plumbing pipes, and ceilings are installed will allow your MVHR design to work with your layout and services plan.

Nuaire uses the latest 3D AutoCAD Revit software, which enables it to provide designs that are guaranteed to replicate the installed system performance, and that detects clashes with other systems early on to provide costly on-site remedies.

If you'd like further support  speak to a member of our Design Team to create a guaranteed design for your MVHR installation. Call 02920 858500 or email:

These new guidelines aim to raise the standards of MVHR installation, and by following them with advice and support from a responsible manufacturer, the outcome should be that you avoid costly and time-consuming problems on-site, and that your MVHR systems perform efficiently creating a healthy indoor environment for occupants.

If you have a domestic ventilation question that I can help with I'd love to hear from you. Contact me by email: