Green Roofs - Living Architecture Monitor - Spring 2014 - (Page 35)

ON SPEC DIRTY THOUGHTS THE CRITICAL COMPONENTS OF GREEN ROOF GROWING MEDIA SPECIFICATION AND PRODUCTION BY: SAM FERRO G reen roof growing media is not your everyday garden soil variety. Sure it has to retain water and nutrients and provide a hospitable environment for plant growth, but there is much more that is required. Growing media must be lightweight, provide effective drainage, and in many cases, retain significant amounts of water or at least slow runoff. With the intense performance requirements for green roof growing media, it should come as no surprise that native soils do not provide a proper environment. To ensure a quality growing media, specialized soils must be manufactured to meet project requirements. These specialized soils are typically manufactured from multiple components that may include sand, compost, light-weight aggregates and more. Locally sourced materials are the most cost-effective components for growing media, as they typically have lower shipping costs and fewer delays. Once components have been sourced, they have to be blended to create a consistent soil mix that meets project specifications and client needs. The desired green roof growing media can vary widely depending upon intended usage. Stormwater control requires something different than what wetlands would require. Intensive mix blends with their deeper depths are typically not the same as extensive mixes. Thus, proper components and component ratios are crucial to achieve desired performance. How do suppliers come up with mixes to meet project needs? It depends on the specifications, and a well written specification is critical to project success. Growing media specifications can be divided into two broad types. Material specifications call for what components to use and how much of each component goes into the mix. Performance specifications typically focus less on specifying particular materials, and more on detailing what the performance of the blend should be (permeability, wet weight, water retention, etc.). Performance specifications are often preferred because they allow for some flexibility in materials and focus on the characteristics of the final blended material. Regardless of specification type, it is imperative to know what performance is expected from the roof before a growing media can be prepared. Factors such as available materials, type of vegetation, water management, material depth, load limits and intensity of use must be considered. Laboratory testing should be a critical component of green roof specifications and production. An experienced lab can help make the mix development stage go faster and produce a better mix. Jeff Bruce of Jeffrey L Bruce & Co. equates media READ THIS ISSUE ONLINE AT WWW.LIVINGARCHITECTUREMONITOR.COM GREEN ROOF TRIAL GROWING MEDIA BLENDS Image provided by: Turf Diagnostics & Design production to water coming from a faucet: "you have to expect fluctuations." Testing by an experienced green roof lab can tell us what those fluctuations are. It is then incumbent upon the designer or other professionals to determine whether they are significant. On-site observations and proper care of the media delivered to the job site are also critical. Soils are living environments and must be treated as such. Timing of media installation and proper handling of materials are crucial. Green roof growing media are complex mixes, requiring multiple components blended at precise ratios. A team of professionals with diverse expertise is needed to design and create these mixes. When quality materials are combined with knowledgeable people, the growing media should perform well on the roof and provide optimal conditions for plant growth. Sam Ferro is the president of Turf Diagnostics & Design. Thanks to Jeff Bruce, Dick Hayden (American Hydrotech), Kevin Anderson (Missouri Organic), Scott Jenson (Utelite) and Charles Duprey (WeCare Organics) for their input. LIVING ARCHITECTURE MONITOR / SPRING 2014 / 35 http://WWW.LIVINGARCHITECTUREMONITOR.COM

Table of Contents for the Digital Edition of Green Roofs - Living Architecture Monitor - Spring 2014

Green Roofs - Living Architecture Monitor - Spring 2014
Contents
From the Founder
On the Roof With...
Policy and Standards
Research
Gap Leadership
Confessions of a Green 'Starchitect'
Sprucing Up
Green Roofs and Walls in Music City
Space in Transition
Big Box Retailers Embracing Green Roofs?
Exploring England's Green Roof and Wall Industry
New GRHC Corporate Members
GRHC Buyers Guide
Professional Calendar
Dirty Thoughts

Green Roofs - Living Architecture Monitor - Spring 2014