Impact/Purpose:

In various parts of the world, humans have successfully increased the energy efficiency of buildings by installing a rooftop of vegetation known as a green roof. Nevertheless, there have been limited studies concerning green roofs used in the most hot and arid parts of the southwestern United States, where their energy saving potential would be most valuable. Therefore, a design plan which incorporates green roof technology into an area of the United States where its feasibility has been inadequately researched is an important and necessary innovation.

It is the intent of this UC Davis engineering team to develop a method to determine the efficacy of green roofs in arid conditions through usage of scaled model buildings in a controlled environment chamber. This method will quantify the energy savings of a green roof in arid conditions. This will provide a novel small-scale approach to screen the suitability of environmental conditions for full-scale green roof establishment.

Description:

We successfully designed and fabricated accurately scaled prototypes of a green roof and a conventional white roof and began testing in simulated conditions of 115-70°F with relative humidity of 13%. The design parameters were based on analytical models created through verified equations programmed into MATLAB (The MathWorks, Natick, MA). These equations were based on composite thermal resistance and evapotranspiration by the plants. Our green roof model resulted in a 14°C (25.45°F) difference in temperature for the air below the green roof compared to the air below the white roof. This is a heat gain reduction of 25% by the green roof compared to a 4% reduction in heat gain by the white roof. We also achieved moisture retention of 1.1 pounds of water per square foot of roof. This water will potentially be lost through evapotranspiration by the plants. The total weight of the green roof is 40 pounds per square foot due to our multiple layers, the water being retained, and the volume of growing medium. The green roof was effective under short term testing in reducing heat transfer through the roof while also surviving the harsh arid climate suggesting this green roof model is both energy efficient and durable.

URLs/Downloads:

Final Progress Report

Record Details:

Record Type:PROJECT( ABSTRACT )

Start Date:08/15/2008

Completion Date:08/14/2009

Record ID: 200851

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Related Organizations:

Role :OWNER

Organization Name :UNIVERSITY OF CALIFORNIA - DAVIS

Citation :Davis

State :CA

Zip Code :95616

Project Information:

Approach :

Results will be obtained through an experimental process using two accurately scaled-down models of single-story commercial buildings. Both model buildings will be housed in a controlled environment chamber set to conditions matching the diurnal cycles of Phoenix, Arizona. Each model building will be subjected to two roof treatments: simulated green roof (Hydro-Mat) and control. The results from the green roof treatment will be compared with results from the corresponding control treatment. A cost-benefit economic analysis will be conducted for the green-roof and traditional roof using the experimental data. The monetary savings from energy reduction will be determined using PG&E energy rates.

Cost :$8,915.00

Research Component :Pollution Prevention/Sustainable Development

Approach :

Results will be obtained through an experimental process using two accurately scaled-down models of single-story commercial buildings. Both model buildings will be housed in a controlled environment chamber set to conditions matching the diurnal cycles of Phoenix, Arizona. Each model building will be subjected to two roof treatments: simulated green roof (Hydro-Mat) and control. The results from the green roof treatment will be compared with results from the corresponding control treatment. A cost-benefit economic analysis will be conducted for the green-roof and traditional roof using the experimental data. The monetary savings from energy reduction will be determined using PG&E energy rates.

Cost :$8,915.00

Research Component :P3 Challenge Area - Energy

Approach :

Results will be obtained through an experimental process using two accurately scaled-down models of single-story commercial buildings. Both model buildings will be housed in a controlled environment chamber set to conditions matching the diurnal cycles of Phoenix, Arizona. Each model building will be subjected to two roof treatments: simulated green roof (Hydro-Mat) and control. The results from the green roof treatment will be compared with results from the corresponding control treatment. A cost-benefit economic analysis will be conducted for the green-roof and traditional roof using the experimental data. The monetary savings from energy reduction will be determined using PG&E energy rates.

Cost :$8,915.00

Research Component :P3 Challenge Area - Built Environment

Project IDs:

ID Code :SU833951

Project type :EPA Grant