Modern Building Services

MODERN BUILDING SERVICES SEPTEMBER 2022 17 FEATURE ZERO CARBON BUILDINGS This is, after all, the oldest means of ventilation, so more than proven in practice. Simplistically, it uses naturally occurring pressure differentials in air movement, wind, and buoyancy to deliver a steady supply of fresh air for building ventilation and space cooling. Warm air rises. Nature abhors a vacuum, so draws cooler air in the replace the rising warmer air. In a building, the process delivers the best of both worlds- little/ no energy consumption with low capital costs as there is no requirement for plant and with reduced ductwork. The useable space inside is optimised as the area required for services is reduced. Passive natural ventilation (natvent) works best when designed into the building whilst still on the drawing board. Air paths can be effectively planned using external low-level air inlets, and internal transfer grilles to allow the fresh air through the diverse compartments, with the warmair rising up planned shafts or building structures for extraction through high-level exhausts such as roof terminals. Especially in our ever-larger commercial buildings, and all the Building Regulations with which we have to comply in terms of fire safety, access, etc, it is- or was- difficult to retro-fit, to achieve effective air paths through the numerous storeys and compartments. Our ability to optimise natvent- or hybrid solutions- in retrofit is fundamental to the drive towards carbon zero, when you bear in mind 80% of the buildings in use by the target date of 2050 are already constructed 3 . As the drive to reduce energy has risen in priority, so has technology in making natural ventilation- or versions of- a viable option in modern, multi-storey buildings. Hence the advent of hybrid or mixed mode ventilation, whereby a low energy fan supplements the air movement only when required i.e. when there is poor air movement: in effect, dynamic natvent. Hybrid can also be a stand-alone system, with one unit ventilating one zone or compartment within the building. Therefore it is an ideal solution for successfully integrating natvent/ low carbon ventilation strategies into both new build and refit scenarios. It is further a useful tool for areas of high loading- for example where there is a high occupancy level or higher than average heat loading (from computers, printers etc). It is proven in practice: Endeavour House, a three-storey office development in Plymouth, uses hybrid ventilation and has attained a BREEAM rating of Excellent. Latest versions of stand-alone hybrid products can be integrated with heat pumps, further optimising the low/zero carbon ambition. LPHWheat coils can be fitted, warming the internal environment and in the process eliminating the need for radiators, further reducing the energy loading and having the added advantage of optimising the floor plan. With a little thought, it is possible to achieve the perfect balancing act, of good ventilation, good air quality and low/no energy for ventilation within an airtight building. The trick for building services consultants going forward is to work with knowledgeablemanufacturers. Working with such complexities on a daily basis, they have the in-depth knowledge to help guide you. You can then be sure that the systems you specify are as energy-efficient and environmentally friendly in all aspects as possible, helping to deliver the desired aesthetics and with the appropriate quality of internal air and comfort. Sources: 1. Principle of HybridVentilation, IEA Energy Conservation in Buildings & Community Systems Programme Annex 35 hybrid ventilation in new and retrofitted office buildings 2. https://post.parliament.uk/ research-briefings/post-pb-0044/, https://www.aiavt.org/news- events/news-details/post/ embodied-carbon-in-building- materials-the-next-challenge-for- vermonts-net-zero-goals 3. https://www.ukgbc.org/climate- change-2/ More information can be found at www.gilbertsblackpool.com