ARRDHOR CRITT Horticole Green Roof R&D
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ARRDHOR CRITT Horticole Green Roof Research; A part of the 200 square meter green roof system for plant resistance tests. Photos Courtesy Maxime DarnisProject Name: ARRDHOR CRITT Horticole Green Roof R&D
Year: 2007
Owner: ARRDHOR (Association R?gionale de Recherche et de D?veloppement horticole)
Location: Rochefort sur mer, France
Building Type: Educational
Type: Extensive, Test/Research
System: Custom
Size: 3229 sq.ft.
Slope: 1%
Access: Accessible, Private
Submitted by: Maxime Darnis and Philippe Faucon

Designers/Manufacturers of Record:
Greenroof Research: Maxime Darnis, CRITT Horticole
Greenroof Research: Philippe Faucon, CRITT Horticole
Another Sedum variety, changing with seasons, very drought tolerant.  Photos Courtesy Maxime DarnisA very promising Sedum cultivar, colorful! A very drought tolerant and carpeting Artemisia species growing into 8 centimeters substrate depth; Photos Courtesy Maxime Darnis
The CRITT Horticole is a regional center of innovation and technology transfer specialized in horticulture approved by the French Ministry of Research and Universities. Our team of 10 engineers is located on the West Coast of France (oceanic climate), and works on several subjects related to the Horticulture Industry: greenhouse engineering, market analysis, plant death research activity and technology transfer to industrial, environmental and energy diagnostics for horticultural companies, horticultural activity support? and more recently: extensive green roofs.

We focused our research program on extensive vegetated rooftops with low maintenance because we think this is the most sustainable way to ?green? buildings. Now, the main topics are:
- Widen the range of species used on green roofs (plant diversification)
- Understand and model green roof thermal behavior in order to quantify the benefits
- Get references on commercialized systems (costs, environmental performance?)
A Green Roof ModuleGreen Roof Modules Platform
Here is a short description of our green roof research and development program, partially financed by the European Community (EC):

Plant Diversification - We are looking for physiologically and morphologically adapted species to withstand rooftops' extreme environmental conditions. We try to identify some native species to improve the green roof relationship with the local environment, facilitate biodiversity development on the roof and also promote local identity. Moreover, a review of plant species associations is conducted to create new design patterns and more sustainable vegetation covers. The use of special plant communities with sustainable and self sufficient vegetation can reduce maintenance and resource input on green roofs. For instance, Fabaceae species, by fixing nitrogen, could enrich the soil locally and help other plants' development.

A 200 square meter (2,153 sf) green roof platform was initially installed at CRITT Horticole, and we have recently extended the trials for a total area of 300 square meters (3,229 sf). It reproduces a double layer extensive green roof system with different substrate depths. Two hundred plant species have been tested here since 2009. Two hundred more species or cultivars are going to be planted.

Thermal Performance Studies - We are developing an energy balance model of a vegetated roof and integrating it in a building energy simulation program (TRNSYS) in partnership with the LEPTIAB (Universit? de La Rochelle). At the same time, in order to understand precisely the phenomenon, we study and quantify thermal and mass fluxes. The roles of growing media, vegetation and drainage layer characteristics on thermal behavior are evaluated experimentally on a green roof modular platform. The experimental results will be usable for model validation.

The platform consists of 30 green roof modules (1 square meter or just under 11 sf each). These are made in stainless steel covered with root-proof membrane and filled with different green roof systems (single layer with 2-substrate depth, multilayer with different drainage layer types). Vegetation structure and density may also influence thermal efficiency of green roof. Therefore, two plant types were planted: grassy forms (Festuca glauca) and carpeting plants (Sedum acre and Sedum album). The green roof modules are in a greenhouse in order to control climatic conditions but will be transported outside for other experiments (see below for further research).

Additional thumbnail photos:

An Erigeron species blooming generously; Photos Courtesy Maxime DarnisARRDHOR CRITT Horticole Green Roof ResearchGreen roof modules suspended from load cells; Photos Courtesy Maxime DarnisA Green Roof ModuleGreen Roof Modules Platform; Photos Courtesy Maxime Darnis
Read more about the CRITT Horticole Green Roof Research in the October 2009 Guest Feature on by Maxime Darnis and Philippe Faucon titled "A French Green Roof Research & Development Program" here. ARRDHOR CRITT Horticole is located at 18 rue de l'arsenal, 17300 Rochefort/Mer; tel +33 05 46 99 17 01; fax +33 05 46 87 28 63. For complete information, visit the ARRDHOR CRITT Horticole website here.
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