From PIV to MIV® - Positive Input Ventilation has Evolved27/10/2010

Nick Heaton, Managing Director of EnviroVent discusses how positive input ventilation (PIV) systems work and explains the benefits for the council and social housing sectors.

In the last 25 years, the number of new asthma cases in the UK has increased six fold among children and three to four fold in adults. Asthma now affects more than five million people in the UK and kills 1,500 a year. Poor ventilation causes high levels of humidity which in turn increases the levels of dust mites - a known trigger for asthma. As we build tighter homes and continue to ‘seal up’ existing ones the requirement for good ventilation is becoming paramount.

A recent government report states that 50% of the world’s illnesses are caused or aggravated by poor indoor air.  Building our homes to be more energy efficient using improved building features such as cavity wall insulation, double glazing and draught proofing means that ‘natural ventilation’ is prohibited, leaving trapped air with high levels of humidity, mould, dust mites, tobacco smoke and contaminated gases in the home.

Finding a solution

To combat this major health issue, many local authority building professionals are turning to positive input ventilation systems (PIV). Sophisticated whole home ventilation and condensation control units that are designed to gently ventilate the home from a central position on the landing or in a central hallway, PIV delivers fresh, filtered and clean air into a property at a continuous rate. Moisture laden air is diluted, displaced and replaced to control humidity levels at around 55%.

This significantly reduces or eliminates surface condensation, the main cause for mould growth. And, with lower humidity levels, dust mite populations are also substantially reduced to provide improvements in the health of asthma sufferers and general indoor air quality.

Scientific support

New scientific research from Nottingham University’s School of the Built Environment supports the effectiveness of PIV systems. The research, using computational fluid dynamics (CFD), explains what happens in a property when a PIV system is installed by creating a simulated house with extreme moisture conditions of 100% RH. After just six hours the study showed that the unit reduced internal relative humidity levels to below 60%.

Introducing Multiple Input Ventilation (MIV®)

Leading the field in this area, sustainable ventilation manufacturer EnviroVent has developed the MIV® Air Source which supplies fresh, filtered air via multiple inputs into areas with a greater requirement for ventilation such as kitchens and bathrooms. Fresh air inputs can also be placed in living spaces or bedrooms where bad condensation occurs, or in the bedroom of an asthma sufferer to maintain constant humidity levels and keep the dust mite population to a minimum. The system also achieves multi zone destratification where the warm air at ceiling level is redistributed evenly around the property.

Going beyond traditional input ventilation, the MIV® Air Source has the facility to source cooler air from outside the building either automatically or on demand through a multiple of wireless control switches.  After detecting a rise in temperature the unit starts to draw air from atmosphere via a temperature controlled diverter mechanism, providing efficient perception cooling into the property during warmer weather. This feature also maintains the required level of ventilation continuously throughout the year and is beneficial for homes affected by high levels of radon and other indoor contaminants.

With numerous benefits for residents, the EnviroVent PIV and MIV systems are designed to last the lifecycle of the dwelling, easy to maintain and cost effective to enable local authority specifiers to really make a difference.

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