The Problem of Over-glazing Buildings: Post Occupancy Evaluation from External Evidence
Authors: Byrd, Hugh
ABSTRACT: This paper will present the findings of research carried out on user-response, from external evidence, in highly glazed office buildings and will analyse the impact of this on predicting the environmental performance, productivity and energy consumption of office buildings.
Design tools such as the LT and LTV methods indicate that the optimum energy performance of a typical office building envelope is achieved when the proportion of glazing in a facade is in the order of 30 to 50% depending on many factors. However, there has been a trend in the design of commercial buildings to significantly exceed this proportion. For example, in New Zealand in 2010, the average proportion of glazing on buildings accredited with a ‘green’ design was approximately 80%.
With high proportions of glazing, there is a significant difference between the theory and actual performance of a building envelope in particular because of user preferences. Excessive glazing increases the probability of blinds being operated to reduce the impact of glare or direct sunlight. This significantly reduces the amount of daylight while only marginally reducing excessive heat gains.
In the case of the buildings in this research, it was found that blinds were extensively used and that artificially lighting was also used to supplement the loss of daylight, even on bright days. The additional energy used for both cooling and artificial lighting results in high proportions of glazing being responsible for significantly greater energy consumption than predicted and a potential loss in productivity.