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Mechanical Ventilation with Heat Recovery (MVHR) systems are increasingly popular in new build and refurbished properties. But there are some misperceptions about the technology. Lee Stones, Category Manager at Xpelair, examines the myths around MVHR, what’s behind them and the root causes that really need tackling.
INDOOR AIR QUALITY BSEE
MVHR INSTALLATION: Just a load of hot air?
W ‘
ith increased awareness of the importance of Indoor Air Quality (IAQ), builders are having to
look more closely at ventilation. Where the choice of ventilation is concerned, it’s no secret that whole house ventilation wins out in the efficiency stakes, and certainly for new build properties it’s a no brainer for housebuilders to opt for whole house systems like MVHR.
MVHR is ideal for new builds because it is suited to smaller homes, flats or apartments where insulation levels are high. Available as a centralised, whole-house system or single room units, the proven technology extracts moist, stale air from inside the property and replaces it with fresh, incoming air. Crucially, it uses heat from the outgoing air to warm the incoming air, with high efficiency systems able to warm air up to more than 90 per cent of the internal air temperature. Yet despite its growing popularity, there’s a lingering misperception that MVHR systems can be unreliable in terms of performance, primarily due to lack of education, incorrect specification and substandard installation.
The specification game
As public knowledge of IAQ issues increases, alongside a growing new build market, there’s no doubt that MVHR is going to grow with it. Gaining independent certification to install the systems is a great way for installers to differentiate and promote themselves in this marketplace.
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Heat recovery is a system comprising two components – the heat exchange unit and the ducting. The design and quality of both is equally important in achieving maximum performance. Because the heat exchange unit is in an isolated space, equally important is how the device is connected to the critical areas of the house requiring ventilation (such as bathrooms and kitchens). Since the role of the system is to take stale air out and bring fresh air in, the suitability of the ducting that travels in and out of the unit is vital. The specification of the MVHR unit must be appropriate for the design of the house and demands of the associated ventilation. With today’s increasingly stringent building regulations, knowledge of MVHR systems is required to ensure the best specification and the most appropriate ventilation solution for each property. Slightly more complex is the correct specification of the supporting ducting to ensure an optimum flow of air around the system. If you specify a certain duct run, the MVHR unit needs to be able to be operate effectively alongside it. If excessively long ducting is used or the duct has too many bends or a completely inappropriate type of duct is fitted (for example flexi ducting) then an MVHR unit will not be able to perform to its best. It’s also important to know your duct in terms of performance as well as regulations. For example, certain parts of the house will need insulated duct. Appropriate specification of the MVHR unit and the ducting to operate alongside it requires an overall design
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view, in the context of the property it is destined for, to ensure the best heat exchange unit and optimum ducting is selected. Our dedicated in-house Xpelair System Design Service spend their time working with clients reviewing property design and ventilation requirements to help them get this right.
Dealing with duct
The ducting within an MVHR system affects the short and long-term indoor air quality, the overall system efficiency and airflow rates and the speed and ease of installation – so it’s vital to get it right. The installer then has to manage and install the duct correctly, which is where issues often arise.
With traditional ducting systems, installers need to make multiple connections manually, each of which has an impact on system integrity. This calls for on-site sealing, adding to installation time, and sealing every ducting connection point to mitigate the risk of air leakage. Modern ducting systems are more straightforward to manage but we still see a number of common installation mistakes which have an impact on performance. One issue we see a lot is ducting coming away from the heat recovery unit when it is not properly connected. Crucial to the connection of the ducting is ensuring that the seals are air tight, which can easily be achieved with the use of appropriate sealants or tape. Another common installation problem that we often see is when the condensation trap is not water tight, which more often than not will lead to leaking – leaving unsightly damp patches. All of these issues can easily be avoided with some training and system know-how.
Installation know‐how
Poor performance of MVHR systems is very rarely driven by an issue with the unit itself which is frustrating for manufacturers – but this isn’t about pointing the finger at installers. There’s a real requirement for manufacturers to educate the sector on improving the specification process as well as do more to work with installers to understand the systems and installation requirements, which is the key driver behind our training tools. Even when the right heat exchange unit has been specified and the correct ducting to accompany, we still see far too many failing MVHR systems because of misguided installation. I always say that ‘you can’t know what you don’t know’ therefore the key thing here is raising awareness with installers around the opportunity for training.
Xpelair offers two levels of learning around MVHR systems including a BPEC two day course and the industry-approved CPD one-hour seminar. Installers and contractors seeking to develop their skillset can now benefit from three different BPEC courses with Xpelair, all of which
conform to the new Summit Skills syllabus for ventilation and are certified by the independent training organisation (BPEC).
Through both theoretical and practical training, attendees can learn about the main types of domestic ventilation systems and how to install them safely and efficiently, then test them afterwards. On completion of the BPEC training, installers are certified to install all four ventilation systems for five years – including mechanical ventilation with heat recovery (MVHR).
Targeted more at specifiers, and those seeking to gain a basic understanding of the MVHR opportunity within a limited time frame, the free CPD seminar’s covers the principles of heat recovery, meeting Passive House standards and best practice for domestic heat recovery.
The opportunities for installers
The importance of IAQ should not be underestimated. Mould or condensation in the home can aggravate pre-existing health conditions such as asthma and eczema, whilst high levels of Volatile Organic Compounds (VOCs) from everyday household items such as polish or air fresheners can also lead to symptoms include fatigue, rhinitis, dizziness, headaches, coughing and sneezing.
As public knowledge of IAQ issues increases, alongside a growing new build market, there’s no doubt that MVHR is going to grow with it. Gaining independent certification to install the systems is a great way for installers to differentiate and promote themselves in this marketplace. MVHR systems such as Xpelair’s new Natural Air 180 can play a vital part in improving the IAQ in our homes, as well as driving a whole-house approach to energy saving and carbon reduction. With its compact design and suitability for whole-house ventilation, including wetrooms, the Xpelair Natural Air 180 delivers classic MVHR benefits for all builds large and small. The Natural Air 180 uses Intelligent Adaptiflow Sensing to deliver constant volume performance. Designed for easy installation and hassle-free handling, the Natural Air 180 is supplied in two lightweight section rather than one. As a result, it is a lot more portable than all-in-one units. With the Internet of Things changing the face of the heating and ventilation industry, we can expect to see some exciting add-ons and integrations to MVHR systems in the coming months. By working closely with leading manufacturers such as Xpelair, installers can stay ahead of the game and take advantage of the opportunities that this will provide for them.
www.xpelair.co.uk BUILDING SERVICES & ENVIRONMENTAL ENGINEER JULY 2017 27
uXpelair offers two levels of learning around MVHR systems.
uXpelair Natural Air 180 delivers classic MVHR benefits for large and small builds.
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