To obtain a copy of a specific publication, users should contact the publication's publisher directly.
Abstract
While much research already has analyzed the thermal benefit of existing green roofs and modeled future performance based on experimental measurements, there exists a need for models that can evaluate the benefits of green roofs in a given microclimate before any experimentation is conducted. A quasi-steady-state model was created to compare roof temperatures on and heat flux through vegetative, reflective, and traditional roofs. All of the model’s calculations are based on first principles of heat transfer, along with plant and soil science. The model’s required inputs are basic climatic variables, including wind speed, hourly average temperatures, and average relative humidity, all of which are readily available for most global cities. The simplicity of the model will allow for evaluation of green roof sustainability in any city. The model has been used to evaluate fifteen global cities with different climatic characteristics, though only three global cities will be discussed in this work. Phoenix – US, Bamako – Mali, and Bangkok – Thailand were selected as they have high average temperatures, but different characteristics of wind speed, humidity, and daily and seasonal changes. Each city was evaluated for two dates in January and July, to demonstrate characteristics in both winder and summer. The results demonstrate that green roofing does offer the most stable roof temperatures and consistently low heat flux. While the model is a basic tool based on a generic green roof and generic building in a given climate, it can easily be adjusted to account for specific characteristics of buildings, roof types, or climatic variables. City planners and green roof researchers can use the model as it stands, or easily adjust it for a specific situation, to calculate green roof impact before any construction or experimentation is undertaken.
While much research already has analyzed the thermal benefit of existing green roofs and modeled future performance based on experimental measurements, there exists a need for models that can evaluate the benefits of green roofs in a given microclimate before any experimentation is conducted. A quasi-steady-state model was created to compare roof temperatures on and heat flux through vegetative, reflective, and traditional roofs. All of the model’s calculations are based on first principles of heat transfer, along with plant and soil science. The model’s required inputs are basic climatic variables, including wind speed, hourly average temperatures, and average relative humidity, all of which are readily available for most global cities. The simplicity of the model will allow for evaluation of green roof sustainability in any city. The model has been used to evaluate fifteen global cities with different climatic characteristics, though only three global cities will be discussed in this work. Phoenix – US, Bamako – Mali, and Bangkok – Thailand were selected as they have high average temperatures, but different characteristics of wind speed, humidity, and daily and seasonal changes. Each city was evaluated for two dates in January and July, to demonstrate characteristics in both winder and summer. The results demonstrate that green roofing does offer the most stable roof temperatures and consistently low heat flux. While the model is a basic tool based on a generic green roof and generic building in a given climate, it can easily be adjusted to account for specific characteristics of buildings, roof types, or climatic variables. City planners and green roof researchers can use the model as it stands, or easily adjust it for a specific situation, to calculate green roof impact before any construction or experimentation is undertaken.
Date
5/2008
5/2008
Author(s)
Caroline Howe
Caroline Howe
Page(s)
18
18
Keyword(s)
green roof; thermal analysis
green roof; thermal analysis