Building Services FEATURE

Engineers Australia | December 2013 57

Air we breathe taken for grantedby Patrick Durrant

The president of the American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE), William Bahnfleth, sees “a critical shift

in thinking from a goal of indoor environments that are ‘acceptable’ to occupants, to a fundamental obligation to provide indoor environments that are truly healthy and productive, while conserving resources”.

Compliance with building ratings schemes generally means that the air breathed by the majority of building occupants is of an “acceptable” standard; however, this less than optimum air quality has a significant effect on performance and long-term health. Outdoor air is the only source of ventilation supply air. This “fresh air” is generally contaminated with motor vehicle emissions, including diesel particulates from trucks and buses. Building filtration systems are generally designed to remove the larger particulates but not the gases, and so our lungs become the final filter.

Dr Ronald Wood, director of Innovative Plant Technology, stresses that the non negotiable goal for sustainable buildings must be to provide healthy, pollution free air to building occupants. The drive for energy efficiency without sufficient regard for building occupants can have significant adverse economic consequences for both building owner and tenant.

Although it looks like a green wall, active botanical air filtration is a high efficiency system with no leaks, no bypass and no filter changes. Its closed loop system is self-regulating, self-repairing, with no toxic residues and operates 24/7 in the dark as well as the light. Contaminated air is drawn through the planted wall, transferred from the gas phase to the plant root biofilm and metabolised by the associated micro-organisms before returning as clean, uncontaminated air back to the breathing zone. It has excess capacity to supply clean, unpolluted air equivalent to 80% of the required outdoor air supply for an office space, resulting in reduced energy costs from lower ventilation rates, reduced maintenance and replacement of fans and filters.

According to Wood, direct source control with air filtering is the only method to capture contaminants at or

near the source. AS 1668 – 1.2.2012 “The use of ventilation and air-conditioning in buildings” Part 2 Appendix D, allows “cleaning recirculated air to provide equivalent dilution effect”, ie equivalent outdoor air, but this still delivers less than optimum indoor air quality.

The three critical components of indoor air quality (IAQ) management are: source control, dilution and air cleaning.Source controlLow VOC construction materials are important; however, there are no regulations of chemical emissions from commonly used building materials. Some industry associations have developed environmental certification schemes but their legal standing is in doubt.DilutionWood says the conventional approach to diluting the toxicity of the air by increasing ventilation rates is only treating the symptoms, not the cause, and it substantially increases capital, operation and maintenance costs. In addition, this approach results in little appreciable improvement in “breathable” air quality, as some indoor chemical reactions occur faster than the ventilation rate.

A living green wall in Umow Lai’s Melbourne office. Photo: Ronald Wood

FEATURE Building Services

58 Engineers Australia | December 2013

System security unclassifiedGovernance of Security Systems by William MacCallumBook review by Patrick Durrant

William MacCallum is an engineer, technical writer and security manager with many years experience working mainly in defence, and has

been instrumental in developing Australian Department of

Defence computer security policy. While most of his work has resulted in many classified manuals and documents, he perceived a need for an unclassified document that would cover all aspects of system security. As such, Governance of Security Systems is a handbook for designing and implementing a security program that will protect businesses.

Aimed at security managers with the responsibility for drafting policy, standards and procedures, the book provides a broad introduction to the governance of security systems and the development of a supporting security program. Split into two parts, the first deals with security structure and policy, and introduces the three core elements: infrastructure, information and personnel as well as security intelligence. The second part deals with operational security – the implementation of policy and standards in an operational environment.

The book is neatly structured and makes for easy reading. At the end of the book there are useful tips on education for security personnel and how a security system should be maintained once established. A detailed glossary will help those who are unfamiliar with some of the terminology.

A must read for system security managers, Governance of Security Systems would also serve as a useful background for chief executive officers and associated executive directors who need to understand the principles of system security and their application in the public and private sectors.

Air cleaningMost building filtration systems don’t remove gaseous pollutants or ultrafine particles and upgrading existing HVAC systems to HEPA (high efficiency particulate air) filtration usually requires a complete refit of the air handling system due to potential leakage from mismatch of filter frames and increased energy consumption from the higher pressure drop (>250Pa). Complementing the HVAC filter system, active botanical air filtration reduces unwanted gaseous pollutant and particle re-circulation. This results in typical system pressure drops of less than

75Pa with the reduction in high ventilation rates leading to a potential 20% energy saving.

Biofiltration of the air circulating within the building envelope provides unpolluted, clean, cool air, reducing the need for 20-30% outside air to be conditioned. This provides savings on energy costs and contributes to thermal comfort by, on average, a 0.5°C temperature decrease: an effective way of achieving ASHRAE’s goal of a healthy and productive indoor environment while conserving resources.

CAPTION & IMAGE TO COME

Engineers Australia has a number of technical guidelines/practice notes to assist members in the practice of their profession. They include:u Practice Note for Design Fires (2012), published by the Fire Safety Society (a Technical Society of Engineers Australia)u Practice Note for Fire and Life Safety in Existing Buildings During Construction (2012), published by the Fire Safety

Society (a Technical Society of Engineers Australia)

The guidelines can be accessed through EA Books, a department of Engineers Media, a wholly owned subsidiary of Engineers Australia.

Go to www.eabooks.com.au and click on Guidelines/Notes.

EA TEchnicAl GuidElinEs/prAcTicE noTEs