By  Payam Bahrami, Ph.D., A.AIA

As most of us know, placing climbing plants on building façades is an effective way to reduce building energy consumption, mitigate the urban heat island effect and create natural habitat areas in cities.  These green walls lower heat transfer by reducing the façade’s exposure to solar radiation and wind, cutting the façade  surface temperature and providing extra facade insulation.

Figure 1. Example of an ivy-covered façade in London.

A collaborative team of researchers from the Illinois Institute of Technology College of Architecture and the Council on Tall Buildings and Urban Habitat (CTBUH) is conducting a research project evaluating the effect of green walls on building façade thermal performance and building energy savings.  The research was funded by a seed grant from the Wanger Institute for Sustainable Energy Research (WISER).

This year-long project is focused on developing a model to predict the effective thermal resistance of a plant layer placed on the façade.  A sensitivity analysis will determine which plants have the highest effect on the façades’ thermal resistance in different weather parameters.  The study also examines the importance of facade orientation, façade material, and climate zone.

To confirm the model’s predictions, the team has conducted an experiment measuring the thermal performance of the ivy-covered façade of Siegel Hall building at the Illinois Institute of Technology ion Chicago, which was designed by famed modernist architect Mies van der Rohe.  Future steps include calculating the average annual thermal resistance of the plant layer based on a combination of the selected parameters and façade orientations.

Additionally, an annual energy simulation will be conducted for a building model with a plant-covered façade to define building energy savings.  The simulation results will be used to form recommendations for building designers to lower building energy consumption through the use of green walls.

We will keep you posted on our progress.

Payam Bahrami, Ph.D., A.AIA
CTBUH Research Associate
Council on Tall Buildings and Urban Habitat
S.R. Crown Hall, Illinois Institute of Technology
3360 South State Street, Chicago, IL 60616, USA
312.567.3287; pbahrami@ctbuh.org
www.ctbuh.org