2004 Building Systems Technology Research Grant
Passive Ventilation Design Investigations

The following research endeavor summarizes the findings from a series of interviews conducted with architects and engineers at leading firms in the United Kingdom during the summer of 2004 regarding two issues relevant to designing multistory buildings employing passive ventilation strategies. The first topic attempts to optimize the dialogue between architects and engineers by defining the constraints and opportunities of building ventilation simulation methods. The second topic addresses the need for postoccupancy evaluation methods to be employed in passively ventilated buildings while examining the barriers and gathering suggestions on how this process might be facilitated. The scope of this project involves examining the design process itself, referencing specific buildings for the purpose of illustrating broader statements. The buildings discussed range from three to forty stories high and utilize a building management system to operate the passive ventilation systems during appropriate times of the year. This research is formatted not only to report how cutting-edge firms are operating today, but also how they evaluate the relevancy of their tools in terms of accuracy and preference in methodology. Although the paper discusses the design process, the scope does not include restating initial parameters for natural ventilation (including appropriate temperatures, humidity, wind speed, and building function), but instead focuses on the methods available to confidently test and compare designs for passive ventilation.

Proposed Study

Passive ventilation addresses several pertinent issues including the opportunity to decrease energy used on cooling loads, improve indoor air quality, and increase occupancy comfort. The design of large-scale passive ventilation requires careful coordination between the architect and engineer as well as the quantitative confirmation of comfort conditions through the use of building simulation tools. At the present, there is a suboptimal architect/engineer relationship in which the architect lacks simple tools for initial design analysis and usually lacks understanding of the constraints of the engineer’s analysis process. A productive dialogue between architect and engineer is necessary to facilitate the exchange of ideas and allow for iterations to optimize design. Few firms have achieved this ideal collaboration on a consistent basis, and my research focuses on dissecting how those firms use simulation tools and building monitoring to inform the design process for passive ventilation. The first topic discussed examines the role of building simulation tools in leading architecture and engineering firms relative to their purpose and influence in various stages of the design process. The second component of the research addresses the need for postoccupancy evaluation of passively ventilated buildings to determine if they are performing as expected and to apply those findings to future projects. Postoccupancy evaluations are often difficult to arrange or lack funding. The interviews offer the opportunity to evaluate current practice and reflect upon potential improvements to the data collection methods and building performance evaluation techniques.

Implications for Architecture Practice

These findings illuminate several principles and opportunities regarding natural ventilation design. First, these successful building examples demonstrate the necessity for an open dialogue and debate between the architect and engineer from a very early point in the design process. This is critical because while the architect may rely on “rules of thumb” to guide ventilation principles, the engineer has the analytical ability to run numerical calculations, useful in comparing one design scheme to another. In addition, it is likely that an experienced engineer’s intuition will allow him/her to suggest modifications to the building design. Even during schematic design, without the engineer’s input, the architect can only speculate on airflow predictions.

The architect lacks the ability to quickly conduct quantitative calculations to compare design schemes. This highlights an opportunity for the development of a tool geared toward architects facilitating the evaluation of ventilation potentials of different design schemes during the schematic design phase. For example, it would be very useful to have a graphic-oriented tool (not a spreadsheet) in which the architect could enter variables such as building envelope shapes, window opening sizes and configurations, or varied building orientations. A basic airflow prediction would utilize local site climate data to assist designers in determining the exterior and interior airflow patterns relative to the temperature and pressure data. The constraint in such a tool is the potential danger of a “garbage-in, garbage-out” process; in other words, if input information is too simplified, the results or data are irrelevant or not useful. Exploration in computer airflow analysis is being conducted at MIT’s Building Technology Department, making it an appropriate environment for further research into the development of an architect-oriented interface.

The future of postoccupancy evaluations can be influenced by a few factors. First, in order to acquire funding, the public must deem healthy, low-energy buildings a priority. Public demand has the potential to motivate appropriate legislation and financial support. Ecological building rating systems are one approach to encourage public awareness. In addition, changes to the fee structures of engineering services should reflect the environmental impact of a building’s design.