MVHR Installer

In March 2016 a group of researchers from the The Mackintosh Environmental Architecture Research Unit (MEARU), Oxford Institute for Sustainable Development (OISD) and Fourwalls Consultants released the results of their meta study on MVHR systems in the UK.

The study revealed that most MVHR systems don’t perform as they were intended. It also flagged up a difference between standard systems and those designed and specified to Passivhaus standards, as their real performance reflected more their design values.

Here some excerpts of their findings:

Well designed, installed, maintained and used MVHR systems are able to make useful contributions to energy reduction and good ventilation. However, in practice achieving all these conditions is a challenge for the industry and many of the projects in the studies had a number of problems that would undermine these benefits.

Common problems included:

• Insufficient system air flow and system imbalance;
• Lack of appropriate airtightness;
• Poorly designed and installed ductwork;
• Lack of occupant handover and understanding;
• Inadequate maintenance, in particular filter cleaning or replacement.

In airtight homes, the importance of maintaining the ventilation provision is imperative and the consequences of failure may be more significant, and may have detrimental health implications for the occupants.

Read the full report here.

Our evaluation of the data:

From our experience in the industry, we see following issues as the underlying cause of these problems:

• The installation quality of MVHR systems is still an ongoing issue, as major mistakes and short-cuts are not the exception. We recommend to use trusted partners in the industry.
• A number of house house MVHR systems were never commissioned. Unless the system is fully demand controlled, a professional commissioning service should be a mandatory part of the system installation. Beware of companies that offer this as an optional extra.
• Cheaper MVHR systems are not volume-flow constant. With degrading filters the air flow rates will decrease and the system will probably go out of balance. This can be clearly seen in the measured data. We strongly recommend to use systems which are volume-flow or mass-flow constant.
• User operation of MVHR systems can make a big difference in how effective such system is.

Your wouldn’t let your joiner do your electrical installations, nor would you let your plumber check the foundations of your house? They should have some level of competence in that particular trade, so that their installations do not end in tears. When it comes to domestic ventilation the reality is different.

Whilst in England and Wales installers of MVHR systems need to have some basic training (BPEC or NICEIC courses for Domestic Ventilation Installers), in Scotland there is no training mandatory. As you can imagine this leaves the door wide open for a variety of quality levels and approaches.

Although we often mention that Domestic Ventilation is not rocket science, some level of competence and experience is needed, as it is in all trades.

Please find below the most critical points to watch out for when installing MVHR.