Canadian Consulting Engineer
International congress under way in TorontoEngineering
Building designers and researchers from around the world are in Toronto this week for the CIB World Building Congre...
Building designers and researchers from around the world are in Toronto this week for the CIB World Building Congress 2004. Over 470 people from 39 countries are registered for the event, which runs between 1-7 May.
Organized by the National Research Council of Canada’s Institute for Research in Construction, the CIB conference is now in its 50th year. Dr. Sherif Barakat, P.Eng., head of IRC is also currently president of CIB. Headquartered in Rotterdam, CIB stands for “Conseil International du Batiment pour la Recherche l’Etude et la Documentation/International Council for Building Research Studies and Documentation.”
The keynote presentation on Wednesday was addressed largely to practising mechanical and electrical engineers. Dr. Andrew Persily of the National Institute of Standards and Technology in Maryland spoke on the sometimes conflicting demands of energy and ventilation. Good ventilation demands high volumes of air, which must be heated or cooled to keep the occupants comfortable.
Persily outlined technologies that can help designers meet energy and air quality, listing both those that are available “off-the-shelf” today, and those that are more leading edge.
He mentioned heat recovery ventilation; demand controlled ventilation, economizer operation or “free cooling,” and enhanced particle filtration.
Newer strategies he finds promising are natural and hybrid ventilation where only fresh air is used to cool a building, sometimes with a fan to assist the movement. Natural ventilation is very effective for indoor air quality, producing far fewer complaints from building occupants, he says. However, he warned that its effectiveness depends on the quality of the outdoor door. When a building is located in a smog-laden and polluted environment, obviously it’s not a good idea. He also said some natural ventilation systems are more “aesthetics” than real. They need to be engineered.
Displacement ventilation by which cool air is drawn in at the lower level of a floor space and vented high after it has warmed up is another promising technology, as is “decoupled ventilation,” where the cooling or heating system is separate from the ventilation system and thus gives more flexibility for using equipment like radiant panels — “it makes a lot of sense to me,” said Persily.
He mentioned “task ventilation” where the air is brought in at the desktop location and can be controlled individually by the occupants. He also talked about gaseous air cleaning technologies for cleaning outdoor or recirculated air, but mentioned that no standards are available yet.
Security and HVAC systems was another topic Persily covered briefly. Whereas safety issues for HVAC engineers used to be primarily concerns about explosions in equipment, etc., he said, since 9/11 they have to contend with possible biological contamination, etc..
One strategy for engineers to mitigate against such risks is to isolate the air systems of vulnerable locations such as mailrooms through positive air pressure systems, and similarly to be able to positive pressure an entire building so that a harmful substance couldn’t infiltrate from outside. There are also automatic detection systems, he explained, but the technology is “not really there yet.”
For tomorrow, Persily said he hopes to see “loads-based indoor air quality design,” similar to the loads based HVAC systems now where heat, cool and ventilating supply is adjusted according to the fluctuating number of occupants. However, to implement loads-based air quality design he said we need more data on what are base leels for human comfort. Throughout the presentation he emphasized the need for a tight building envelope.
Hundreds of other papers were presented at the conference, many of a highly technical and specialized nature. However, keynote speakers and some practitioners who presented had a broader appeal. On Monday there were several papers on the evolution of the high-rise, for example, including one by Tibor Kokai of structural engineers Yolles. He spoke about the new demand here for highrise condominium buildings of around 50 storeys in Canada, and the challenges that brings for structural engineers because of the emphasis on keeping costs low in North America. Another practising engineer who spoke that day was Mark Brook of Brook Van Dalen & Associates. He also talked about highrise residential buildings, but about fire issues and their cladding systems.
The conference was held in conjunction with the 6th International Conference on Multipurpose Highrise Towers and Tall Buildings, and the 5th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings.