Green Roofs - Living Architecture Monitor - Spring 2012 - (Page 19)

advantage of modular systems is their inflexibility; they offer a one size fits all approach; which typically doesn’t consider individual roof characteristics. Modular systems - even with soil-to-soil contact - are like little planters; which require higher maintenance. The third major disadvantage is the number and size of gaps between planters. These gaps reduce energy efficiency, decrease roof protection and limit root space. Implementation of modular systems usually cost more and increases the carbon footprint. Two functional attributes that must always be present onsite are storm water management and roof protection. In the end it’s all about functionality. SCOTT TORRANCE, GRP Principal, Scott Torrance Landscape Architect Inc As far as I am concerned the main difference comes down to cost. If cost wasn’t an issue, I would probably specify a modular system over a loose laid system. This way I could inspect the plantings at the nursery, trouble-shoot potential problems with plant species prior to installation and have more control over the final installed project. There are advantages and disadvantage of both systems; it really depends on the range of the project to define the system. Advantages of a modular system include prevegetation and less components: There are only plants, growing medium, a tray and a slip sheet. The one disadvantage of a modular system is in its cost, they are far most costly then loose laid systems. Loose laid systems really are the most cost effective when budget drives the design. Additionally they are incredibly flexible and customizable from plant species, growing medium, drainage board, filter sheet, root barrier and irrigation systems. The one main disadvantage in a loose laid system is the factor of time. You have to wait for plants to establish giving the project a lesser visual impact at completion of installation and there is more potential for substitutions during bidding, which adds more work for the consultant to determine compatibility. kELLy LUCkETT, GRP President, Green Roof Blocks The biggest advantage offered by the modular green roof concept continues to be mobility. We are seeing a great number of specifications calling for modules that are pre-grown to a minimum of 80% vegetative coverage prior to delivery to the project. However, that only tells half of the mobility story. Modules that remain mobile throughout their lifespan can be easily moved when roofing work is required. Such was the case at our 4000 square foot project for Cook + Fox Architects in Manhattan. When their roofing needed replacement we were able to temporarily relocate all of the green roof modules on an adjacent section of the roof. Once the roofing contractor removed the old roofing to install the new roofing system, we simply repositioned the modules to their original location; not losing a single plant. I truly believe module designs that lose this feature by either biodegrading or by removing soil containment devices really shoot themselves in the foot. jOy SCHMIDT President, Xero Flor Canada Ltd Trays have been introduced recently when compared to built up systems and do not have proven long-term data documenting their longevity and sustainability. There is a longterm maintenance and sustainability concern regarding plants becoming root-bound in tray systems. The inability for root systems, drainage and moisture to grow and move freely within the green roof growing media limits plant sustainability long-term. Regardless of the recycled content or the ability of the trays to biodegrade, trays still introduce a large quantity of plastic into the environment. Tray systems are not readily adaptable to more freeform designs and may limit the best design options. Mat systems have a long-term proven track record. They are economical, light-weight, easy to install, easily retractable and reusable. They are flexible and can fit to most landscape design. Loose-laid or built-up systems have flexibility of landscape designs. There is data showing long-term performance, more flexibility of plant selection, depth of growing media, positive drainage and no risk of root bound. There are no exposed edges which can also be a hazardous concern. ED SNODGRASS Owner, Green Roof Plants/ Emery Knoll Farms The choice between Modules vs. Loose Laid is a function of design intent, budget and site requirements. One of the problems with making the optimal choice lies many times in the low knowledge level of the customer to really understand the differences partly due to the lack of independent test data and the sales pressure from the different vendors. Loose laid may outperform modules in terms of storm water retention and detention but no local authority requires performance based standards. Modules may be subject to less weed pressure but maintenance may not be required as part of the project. The Proof is in the Roof. • Proven Track Record 600+ projects 2 million+ square feet • Industry Best Support • Time Saving Design Tools • Climate Specialized Plant Options (800) 875-1392 www.liveroof.com sales@liveroof.com The PROVEN Hybrid Green Roof System LIVING ARCHITECTURE MONITOR / wINTER 2012 / 19 http://www.liveroof.com http://www.liveroof.com

Table of Contents for the Digital Edition of Green Roofs - Living Architecture Monitor - Spring 2012

Green Roofs - Living Architecture Monitor - Spring 2012
Contents
From the Founder
Seen & Heard
Bookshelf
Special Thanks
On the Roof With…
Innovation
Urban Agriculture Summit in Toronto August 15th – 18th
Citiesalive in Chicago Oct 17th – 19th
Policy and Standards
We Asked Experts Their Opinions on Modular or Loose Laid Green Roof Systems, Check Out What They Said
I Guess Size Really Does Matter! — Growing Media Insights
Eleanor Mckinney Taking Austin by the Horns
New Industry Products
Green Roof Falls Flat in New York City
Green Roofing Leader Shows Industry What They’re Made Of! Tremco Incorporated
Plant Profile
New GRP’s
Professional Calendar
New Corporate Members
GRHC Buyers Guide
On Spec

Green Roofs - Living Architecture Monitor - Spring 2012