The argument for MVHR has never been stronger - October 2012

This article appeared in H&V News, October 2012

Titon’s Ventilation Systems Operations Manager, Paul Rainbird, explains how to best utilise ventilation to help prevent homes from overheating.

The recently published report by the NHBC Foundation entitled ‘Understanding overheating – where to start’, identified a number of factors which are responsible for rises in indoor temperature, leading to overheating inside new build homes. As a result, the case for whole house mechanical ventilation with heat recovery (MVHR) should now be stronger than ever before.

Stringent legislation, including Part L of the Building Regulations, dictates that modern, newly built houses and apartments are airtight, fitted with highly efficient double glazing and copious amounts of insulation. Now, this is all well and good when the temperature outside is low, but it can result in overheating during the summer months, especially if there is little or no natural ventilation available.

One way to promote adequate circulation of fresh, clean air is by installing MVHR units, which have been specifically designed for buildings that have been constructed in a very air tight manner. MVHR units also remove stale air from wet areas, such as kitchens and bathrooms.

In order to help reduce these overheating issues, MVHR appliances may help to manage indoor temperatures and keep them at a comfortable level. Products utilising the latest features, such as a ‘Summer Mode’ (which turns off the supply air on demand or via a remote thermostat) or our own ‘SUMMERboost®’ (automatically increasing both the supply and extract ventilation rates) in conjunction with summer bypass can help reduce susceptibility to the overheating factor in dwellings during the warmer months of the year. These particular settings may assist in keeping internal temperatures under, what is considered to be, the ‘danger’ level of 35°C, as outlined in the NHBC report.

It is important that homeowners are taught how to operate their MVHR systems so that they perform at optimum levels of efficiency and, more importantly, help to prevent buildings from overheating where these additional features are employed. While there is generally a good understanding of the systems among designers and specifiers, the end user still needs to be aware how its controls work, otherwise they may still end up suffering from preventable high levels of indoor heat - after all, what is the point in having additional functions if they aren’t used correctly?

Utilising MVHR also provides continuous indoor air movement – the lack of which is identified in the NHBC report as one of the contributing factors to overheating and the residents’ discomfort – resulting in a healthier indoor environment. Preventing ‘stale’ air from lingering also has added health benefits for occupants, as it reduces the potential of condensation and mould growth.

Common sense preventative measures such as the proper use of daytime shading and the insulation of any heating distribution pipework will also help ensure that overheating is not a problem. These issues, as well as ventilation measures, should all be considered at the building design stage – anticipating any issues early on can go a long way to preventing any long term problems.

There needs to be an equal balance in keeping homes warm during the winter months and cool during the summertime; it is only by utilising MVHR that homeowners will be able to benefit from the best of both worlds.

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