last updated 13th October 05
by 4ecotips.com

Passive stack is proven solution

If you're thinking of building your own house, as thousands of people do these days, then you might seriously consider incorporating a passive stack ventilation (PSV) system. A special version can also be retrofitted in existing homes.

PSV costs you nothing to run and provides an effective, healthy environment in which to live and flourish.

Passive stacks are not new, they have been used in buildings for thousands of years- as chimneys! What is new, however, is the use of modern technology to further enhance the effectiveness and energy saving potential of the system by introducing automatic demand controlled operation.

One such system is the well tried and tested Passivent PSV. It's driven by natural stack, or convection effect, whereby moisture laden warm air rises. Extracts in the main moisture producing areas, so-called "wet" rooms of bathrooms and kitchens, extract the moisture at source to the outside, through ducting connected to a roof terminal.

Wind blowing across the roof provides additional suction through the venturi effect. PSV provides an energy free ventilation solution, which can be used to effectively ventilate the entire home.

INTELLIGENT NYLON BANDS
Within the extract grilles, 'intelligent' hygroscopic nylon bands respond to changes in relative humidity to open and close the extract louvers thereby controlling the amount of ventilation through Passive Stack. The grilles operate automatically without any electrical or occupant input 24 hours a day.

The PSV concept is taken a stage further when the 'wet' bathroom and kitchen extract systems are combined with the background ventilation provision to create a "Whole House" passive stack ventilation facility, operating between relative humidity of 40-70%.

Intelligent window or wall inlets are installed in the 'dry' rooms only to provide a flow of drier replacement fresh air into the home. This introduces planned air paths into the house with the direction of air movement being from 'dry' areas to 'wet', from where stale, moisture laden air is extracted to the outside.

The system ventilates the entire home creating a comfortable and healthy environment for the occupants.

The use of humidity sensitive extracts means ventilation is demand controlled, saving unnecessary ventilation and therefore heat loss. It also means there are no fans, reducing electrical consumption and eliminating operational noise.

As an alternative to Whole House PSV a single Passive Stack can be used to ventilate an individual or en-suite bathroom. An effective alternative to an intermittent mechanical extract fan, it operates when there is a need ie when humidity levels in the room rise, without electricity, and without noise- particularly useful when the room is used at night.

Usefully, PSV Single Stack can be easily retro-fitted in existing homes, providing an energy free, natural ventilation solution for refurbishment schemes.

Where building layout makes PSV impractical, an Assisted Ventilation (AV) system can be incorporated into the building design as an alternative ventilation solution. By using the same basic principles as PSV, Whole House AV embraces many of the same benefits.

CONTINUOUSLY RUNNING
A single low power continuously running central extract fan, usually located in the roof void, provides efficient extraction of low volumes of air along lenthgy ducts to ensure gentle, draught-free air movement throughout the building and to eliminate moisture and odours. No occupant involvement is required.

The latest development, designed to meet the aspirations of apartment owners, is a single system that links the kitchen extractor hood and bathroom and en-suite extracts to a single low power fan, ensuring all rooms are properly ventilated.

The whole apartment's ventilation system requires only a single wiring loop and, with a single wall terminal, penetrations through the façade are minimised. The central, continuously running fan operates at low level until the cooker hood is switched on. This simultaneously boosts the fan and opens a damper in the hood to extract cooking smells and moisture from the kitchen.

Shown here are photos of a bathroom with a PSV wall terminal and a house built incorporating passive ventilation system.

You can find out more about Passivent PSV at www.passivent.com