by Sylvain Comeau

Speakers at scientific conferences normally discuss the same topic, but they are not always on the same page. Last week, Concordia invited speakers involved in an international hybrid ventilation project to compare notes with their collaborators.

Experts from 15 countries came to talk about their part in the research. Fariborz Haghighat, a professor in Concordia’s Department of Building, Civil and Environmental Engineering, organized the conference, and is the Canadian representative on the project. In an interview following the two-day event, Haghighat and two of the speakers from overseas explained the merits of hybrid ventilation.

“The project was launched four years ago, with the purpose of improving energy efficiency in buildings,” Haghighat said. “This is an increasingly important issue because of global warming and the creation of greenhouse gases like carbon dioxide. Buildings account for nearly 30 per cent of our total energy consumption, so minimizing this consumption in any way has a direct impact on the environment. Hybrid ventilation does this by minimizing the reliance on mechanical ventilation systems.” Haghighat’s part in the research is to develop computer simulations to model the system’s performance.

“It is a new concept in ventilation, which combines mechanical and natural ventilation [wind],” said Per Heiselberg, a professor in the Hybrid Ventilation Centre in Aalborg University, Denmark. “The idea is that there are two possibilities, the natural driving forces of wind, or mechanical ventilation and cooling. Hybrid ventilation chooses the optimal mode that results in the best energy efficiency, while ensuring good indoor climate and air quality.”

Better indoor air should mean fewer cases of sick building syndrome, which is a growing concern for occupants and building owners. “This ventilation system addresses sick building syndrome by removing contaminants from the indoor environment, and maintaining a flow of fresh air.”

In one of the product’s case studies, a school was renovated with hybrid ventilation, and the number of asthma cases at the school dropped sharply.

W.F. de Gids, a researcher at TNO Building and Construction Research in the Netherlands, explained that the key to the system is in the intelligent computerized controls.

“One of the keys to optimization is determining the correct amount of time you should rely on natural versus mechanical ventilation, and to switch effectively between the two, you need a very intelligent control algorithm. There are natural and mechanical systems already in place in most buildings; what is lacking is the computer brain to balance the two.”

The project, called Annex 35, includes a number of case studies, buildings around the world which are designed or renovated to showcase the ventilation system’s advantages.

“These are first-generation buildings with hybrid ventilation,” said Heiselberg, “The buildings have achieved a reduction in cooling energy by 25 to 50 per cent and the fan energy by 10 to 20 per cent. They have proven the potential of this system, that it is possible both to build for greater energy efficiency and a better indoor environment.”

While the case studies were developed overseas, Haghighat said that last week’s conference brings that knowledge to our shores.

“These researchers are working together to develop a methodology for hybrid ventilation, and this conference was intended to transfer this information to Canadian architects and engineers.”

The conference was sponsored by Natural Resources Canada, the National Research Council of Canada, Concordia, University and the Air Infiltration Ventilation Centre (AIVC).

The international project is sponsored by the International Energy Agency. Haghighat’s part of the research is supported by Natural Resources Canada.