FAQ – What is Positive Input Ventilation and why is it needed?

All new builds since the early 1990’s require passive ventilation and the easiest and simplest form of achieving this is by using trickle vents in windows and doors.

Ventilation is important because without it the air in your home would become stale, damp and unpleasant. It is important that properties have controlled ventilation for good indoor air quality. For health and well-being and to protect the fabric of the building from the harmful effects of moisture and mould.

In the past ventilation hasn’t been an issue due to houses being naturally draughtier as a result of the way they had been built. But with improved insulation and sealed windows and doors to help retain the heat, these draughts are no longer present. Which has resulted in an increase in condensation, mould and stale air. Which is why the regulations have been introduced.

Trickle vents are the simplest option for ventilation, however many people don’t like them because:

  • Sound – They affect the acoustic performance of windows, as they allow airborne sound to travel through the frame.
  • Looks – Some people can find trickle vents look unsightly
  • Heat loss – Many homeowners will keep their trickle vents closed to prevent heat loss in their home, instead opening a window for ventilation when needed.

Therefore if you are looking for low u-values and thermal performance it might be worth investigating other options, one of which is a Positive Input Ventilation system, or PIV system.

What is Positive Input Ventilation?

A Positive Input Ventilation system can provide a property with a basic form of mechanical heat recovery and also filter the air coming in.

The units use the tiles/slates and/or the loft space in your property to warm the incoming air before delivering it into the home. Solar air collectors can also be used for even greater pre-heating of the ventilation air. Therefore as well as providing ventilation it also helps to heat the home which can result in lower fuel bills and reduce carbon emissions.

South East to South West facing roof tiles or slates absorb energy from the sun. The loft space is a substantial source of energy. During winter months when the heating is on, it will almost always be warmer than outside because of solar gain and conduction and convection losses from the home.

How does a Positive Input Ventilation system work?

Unlike extract systems which draw in unheated, unfiltered air, even a basic positive input ventilation unit gently supplies tempered, filtered air into a home using otherwise unused heat within a roof.

This offers enormous benefits:

  • A significant proportion of external pollutants are prevented from entering the home.
  • The use of the otherwise unused heat in the roof results in the ventilation unit providing a significant net energy gain to the home.
  • There is no better way to ventilate a home than from the inside out via a single, centrally located, supply air diffuser. A good quality unit, fitted in your loft, will operate at an almost imperceptible noise level. You will hardly know it’s there.
  • A properly designed and installed unit will ensure that old, contaminated air in your home is continuously diluted, displaced and replaced with good quality air.

Features and Benefits

  • Cures condensation dampness – Positive input ventilation removes humidity from the air, preventing mould growth and controlling dust-mite allergens
  • Improves indoor air quality – indoor pollutants from cooking and cleaning are removed while outdoor pollutants including traffic fumes, pollen and Radon gas are kept out
  • Meets regulations – meets Part F & L of Building Regulations as a low-energy ventilation strategy
  • Extremely low power consumption – costs around 1p per day
  • Easy installation and very low maintenance – filter clean or replacement every five years
  • Fixed heat recovery – minimises loss of heat in the loft by recirculating the air, saving energy
  • System standby in summer months – when the loft temperature exceeds 23°C
  • Health benefits – clinically proven to help allergy and asthma sufferers
  • Many systems will offer a 5 year warranty for peace of mind

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