Passively Achieving Eco-Friendly Affordable Housing for Tomorrow

Published by Angela May for Passivent Ltd in Housing

Passivent’s innovative iPSV (intelligent Passive Stack Ventilation) is helping create  ‘the ideal affordable 21^st century house’ whilst delivering low running and lifetime costs and exceeding sustainability criteria.

 The system, which works solely using natural air movement, has been chosen for  homes being built for North Hertfordshire Homes to create Tomorrow’s Garden City, in Letchworth. The homes’ design is the result of a worldwide competition to generate housing solutions capable of delivering high quality, low cost, environmentally-friendly homes that achieved at least Level 3 of the Code for Sustainable Homes.

 “We are achieving Code Level 4,” observed North Hertfordshire Homes’ project manager Keeley Hale. “Passivent’s systems were felt to be the best system for the project in achieving the Code level and meeting the competition objectives.”

 To optimize efficiency, Passivent worked closely with builders SDC to deliver a ventilation strategy that was also easy to install in the 60 homes, a mix of apartments and houses. As a result, iPSV has been used in the houses, with Passivent’s iMEV in the apartments.

 Passivent iPSV harnesses natural air principles of convection and the venturi effect to function. Internal moisture-laden air rises, and air pressure increases with height, creating suction. Thus the internal air is drawn out through roof terminals, and fresh air drawn in through Passivent Energy Saver tricklevents. Humidity sensitive ceiling mounted extracts control the flow of air to the outside according to moisture content, allowing the stale air to ventilate through roof-mounted terminals while minimising the amount of heat loss through over-ventilation.

 As it responds to relative humidity levels within the room, Passivent iPSV ventilates only as, where and when required, optimising heat retention and cutting CO₂ emissions whilst eliminating the need for electrical wiring, fans, heat recovery units and switches. This not only reduces installation costs, but cuts lifetime maintenance expenses for both the system and the building, as there are no mechanical parts to be serviced or replaced.

 To minimize penetrations through the roof, and further helping reduce costs, the iPSV stacks are connected in groups of four to individual high capacity terminals. In the apartments, to ensure adequate ventilation through the longer ducting runs, Passivent iMEV was used, whereby a low wattage fan in the roofspace supplements extraction ensuring the ventilation still complies with Regulatory requirements and the specific project objectives.

 Observed Passivent Product Manager Dennis Bates, “Updated Approved Document F1 recognises the performance of PSV even in airtight (0m³/hr/m²) buildings. Further, studies by the Institute of Energy and Sustainable Development demonstrate that Passivent’s system provides sufficient ventilation under challenging or non-optimum conditions. Even in warmer summer months, when external temperatures are higher and thus the stack effect reduced, Passivent showed the lowest average levels of relative humidity against other ventilation strategies; in ‘wet’ rooms with no external wall or window, Passivent iPSV achieved the required airflow rates, even with an airtightness of 3m³/hr/m².”

 Passivent iPSV is just part of Passivent’s comprehensive range of natural and mechanical ventilation solutions for domestic environments for single person to multi-occupancy properties, plus a range of background window and through-wall ventilation solutions.