HEATING, VENTILATION & SERVICES: HEAT RECOVERY & VENTILATION
MVHR: sourcing the essential resource
EnviroVent’s Larry Soper gives his top tips on specifying the correct MVHR (Mechanical Ventilation with Heat Recovery) system to provide fresh air to your air-tight property
S
elf-builders are increasingly choosing MVHR as their preferred choice for ventilating a new home.
MVHR offers a sustainable long-term solution while generating good indoor air quality and energy savings.
WHAT IS MECHANICAL VENTILATION WITH HEAT RECOVERY ?
All new build properties require adequate ventilation, which means specifying a system which will remove any excess moisture and prevent condensation and mould growth. Extract fans and centralised extract ventilation systems can be inefficient and reduce the energy efficiency of a dwelling. However, MVHR addresses the issue by recovering the heat from the extracted stale, moist air within a property’s kitchen, bathrooms and ensuites. The energy from this extracted air is transferred through a high efficiency heat exchange cell to fresh filtered air and is re-supplied to the habitable areas of the home.
A typical MVHR system comprises a heat
recovery unit containing a high efficiency heat cell. This is typically installed in a utility room, cupboard or loft space and is connected to the habitable and wet rooms in the property via a network of ducts, which open into the rooms via extract or supply valves in the ceiling.
WHAT ARE THE BENEFITS OF MVHR? For many new properties, MVHR is the most efficient form of ventilation currently available. The right system, correctly installed, will take care of any condensation problems and will help reduce the cost of heating. MVHR naturally provides all-year-round fresh, filtered air. By maintaining an optimal indoor climate and removing condensation, MVHR not only saves energy but can also reduce wear and tear on paint, wallpaper and furnishings, reducing maintenance costs. Having good indoor air quality also helps to
april/may 2020
reduce symptoms of asthma and other respiratory illnesses, which can be triggered or worsened in humid, moist conditions where dust mites can be prevalent.
GET THE SIZING RIGHT
It is essential that the MVHR unit is sized correctly for your property. The type of MVHR unit selected depends on the size of the property, the number of rooms, ‘wet rooms’ and occupants. An oversized unit may be inefficient and use more power; an undersized unit will be noisy, inefficient and consume too much power. On a very large property the use of multiple units is recommended because it can provide a quieter and more energy efficient system with improved heat recovery. The sizing of the duct is also important. A duct that is too small for the airflow rate will result in high resistance and velocity of air creating noise issues. A reputable manufacturer will be able to advise on the optimum
It is therefore essential to get the installation of an MVHR system right, from the start, by working with a competent and certified ventilation installer
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