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INDOOR AIR QUALITY BSEE Energy efficiency and air quality in schools


A building might perform well ‘on paper’, but the moment it is occupied by people and electronic equipment, any addional heat that’s generated will impact on indoor air quality. Roy Jones, Technical Director, Gilberts


(Blackpool) Ltd, explains why a natural venlaon strategy could oer the ‘best of both worlds’.


N atural


ventilation has for


years been the


preference


within schools, but building design has inevitably meant that in some instances,


mechanical alternatives are also utilised.


Our climate is actually well suited to natural ventilation: with low extremes of temperature, it delivers benefits for everyone. For architects and M&E consultants, it is


comparatively easy to design in. For the contractor, it is generally simple to install and for the building owner it costs little to run. Plus, maintenance costs are less.


The ventilation strategy should avoid overheating, provide indoor air quality, and meet energy efficiency and environmental standards. Numerous measuring


standards exist for educational establishments – Building Bulletins 87, 93 and 101, Priority Schools Building Specification, CIBSE TM52, EN15251, and the Facilities Output Specification, which stipulate criteria of average concentration of CO2, airflow rates, prevention of draughts, noise levels, heat recovery, etc.


BB101 is currently being updated, with the latest version giving due


‘ The latest


‘hybrid’ is seeing a natural venlaon system with an integrated damper that mixes the warm exhaust air with the cooler incoming air. As a single sided strategy with quick installaon, it provides many cost and me benefits, and it is a recognised soluon by the Educaon Funding Agency.


’


consideration to indoor air quality. Whilst this is to an extent just bringing school guidelines into line with other criteria, it may still prompt the development of new elements within the ventilation strategies. The key performance objectives currently for ventilation in primary or secondary schools, are: uLimit daytime average concentrations of CO2 at seated head height to less than 1000ppm with a maximum of 1500ppm for no more than 20 minutes with mechanical systems and 1500ppm to 2000ppm for natural ventilation systems. uPrevent draughts and discomfort: air speed across occupants should be no more than 0.25m/s. uVentilation design should where possible recover heat gains from occupancy uNoise levels in a standard classroom should be at or below 35dbA uStaff over-ride of ventilation control should be provided


Within those criteria, air flow should be available at 8litres/second per person. But those parameters could be exceeded through external weather, occupant activity, etc. So an energy-efficient solution is required to maintain the comfort levels prescribed in the form of a “boost” condition within the


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ventilation system strategy. The ideal is a solution, offering ‘the best of both worlds’, would be a natural ventilation strategy that can still make use of the previously rejected warm air inside the classroom and meets all the required performance standards, without all the costs, time and coordination for a mechanical system, or the cost and high energy consumption of an MVHR (mechanical ventilation with heat recovery) option. The latest ‘hybrid’ is seeing a natural ventilation system with an integrated damper that mixes the warm exhaust air with the cooler incoming air. As a single sided strategy with quick installation, it provides many cost and time benefits, and it is a recognised solution by the Education Funding Agency. Comparison data from our latest thermal modelling of schools, relating to a referenced school design, show in a typical primary school all the ventilation performance criteria are met, and an improvement in the TER (Target Emission Rate) against alternative strategies. The results show that the “hybrid” type units can meet and exceed traditional systems and delivers improvements for Part L compliance, showing this is an efficient way to condition our schools.


Many schools now have a multi-functional purpose, so the type of system chosen for the school day must now also provide IAQ and comfort conditions to suit activities out of school hours.


Manufacturers of hybrid units are now looking at IAQ over and above the temperature and C0² requirements. Most areas do not require any specific form of outdoor air filtration, but some specific areas subject to high pollution will need it. Hybrid manufacturers are preparing for filtering the air, to ensure compliance in these highly polluted internal and external conditions. Providing a product where extensive filtration is required will be the next step in hybrid evolution.


The W.H.O. guidelines are detailed for the protection of public health from risks due to a number of chemicals commonly present in indoor air. The substances


considered as well as C0² are benzene, carbon monoxide, formaldehyde, naphthalene, nitrogen dioxide, polycyclic aromatic hydrocarbons (especially benzo[a]pyrene), radon, trichloroethylene and tetrachloroethylene, All of these are known in respect of their


hazardousness to health and are often found indoors in concentrations of health concern.


BUILDING SERVICES & ENVIRONMENTAL ENGINEER MAY 2018 35


u‘Hybrid’ type units can meet and exceed tradional systems and deliver improvements for Part L compliance, showing this is an ecient way to condion our schools.


Hybrid manufacturers have already evolved, providing the enhanced benefit of the units by introducing a heating feature. This removes the need for radiators, thus saving cost, time and space. It also frees up wall space and reduces the risk of damage or harm to occupants. As this market


evolves, it is proving to be a popular choice, for end- users, designers and contracting teams alike. When built to the latest guidance our new schools will be created to deliver an outstanding educational space with an excellent IAQ and an environment perfectly suited for learning.


uPapers detailing the thermal modelling analysis for the hybrid (Gilberts Mistrale Fusion) in both a 1,200 place secondary and 180 place primary school, are now available from Gilberts.


uCall 01253 766911 or email info@gilbertsblackpool.com


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