Green roofer extraordinaire merges technology biology

April 18, 2011
| By Pete Daly |
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"We were just selling plants," recalled Dave MacKenzie, who acquired a landscaping nursery in 1983 on M-104 a couple miles east of Spring Lake. Soon, the business was named Hortech Inc.

During the 1990s, some of those plants ended up on top of buildings in the early versions of "green" roofs. Then one day about eight or nine years ago, Ford Motor Co. called him to ask about what kind of plants to grow on a really big green roof they were planning and about how to do it, and the next thing you know, MacKenzie became a roofer — a green roofer.

Since then, MacKenzie and LiveRoof, a subsidiary of Hortech, have become among the best-known names in the burgeoning green roof industry in North America.

Modern green roof technology is still relatively new here, but its North American roots go back to the 19th century. Many of the sod houses built by homesteaders on the Great Plains had sod growing on top to help insulate the interior from both heat and cold, an early form of green roof.

Modern green roofs were first developed in Germany in the 1960s, according to Lawrence Technological University in Southfield, which had a 10,000-square-foot green roof installed on the school's A. Alfred Taubman Student Services Center in 2006. Layers of insulation are covered by a flat roof membrane with a drainage fabric on top of that. Then there is a layer of synthetic soil about 4 inches deep, in which grow nine species of sedum groundcover. At a total of about 9 inches thick, the vegetated roof offers more effective insulation than traditional roofs, and expands and contracts with seasonal changes. Being protected from the rays of the sun, it is expected to last about 40 years — more than twice the lifespan of a traditional flat roof.

The Lawrence Tech green roof also controls and reduces storm-water runoff. With normal rainfall, about 60 percent of the water will be absorbed by the plants, with the remainder drained into a 10,000-gallon cistern to be used for flushing toilets and irrigating the landscaping.

In June 2003, Ford Motor Co. completed the 10.4-acre green roof on top of its new truck assembly plant in Dearborn, which made the Guinness World Records as the largest living roof. MacKenzie was involved as a plant supplier and consultant to Ford, but that was before he formed LiveRoof.

MacKenzie was born in Detroit but grew up in Ferrysburg. He graduated from Hope College in 1983 with a degree in biology and a goal of starting a career in horticulture. Right after he graduated, he and a partner were offered the chance to take over a landscaping nursery, which they eventually bought and named Hortech. But MacKenzie also kept his day job for three or four years, working as a salesman for a landscape maintenance company.

Dave MacKenzie


Company: Hortech Inc./LiveRoof LLC
Title: General Manager
Age: 49
Birthplace: Detroit
Residence: Nunica
Family: Single
Business/Community Organizations: Michigan Nursery and Landscape Association; West Michigan Nursery and Landscape Association; Green Building Council; Green Roofs for Healthy Cities; West Michigan Environmental Action Council; National Federation of Independent Businesses.
Biggest Career Break: Getting a call right after college from a Spring Lake nurseryman, inquiring if he was interested in buying his business.

"We were growing small shrubs and also groundcovers," said MacKenzie. Over time, he began to specialize in groundcover.

In 1983, the roots for a good future career in horticulture were taking hold, although it didn't look like it at the time. A recession was going on and unemployment was high, according to MacKenzie. Landscaping, like construction, was flat.

But then the economy started coming back and there was the beginning of "a renaissance period for horticulture," according to MacKenzie. It was contained within a larger popular movement symbolized by the start of the "This Old House" series on PBS in 1982, and carried further by people like Martha Stewart over the next couple of decades.

"All of a sudden, people were looking at gardening and landscaping as fashionable," he said.

Groundcovers were "a good product line" because they are relatively low-maintenance, compared to the manicured lawns that had been in favor since World War II. While people wanted nice landscapes around their homes, the growing economy was generating more disposable income, giving people more interesting things to do in their leisure time than mow grass, "so 'low maintenance' really became a buzzword," said MacKenzie.

Low maintenance is even more important when it comes to green roofs, and eventually Hortech found itself supplying the sedums and other drought-resistant groundcovers for small green roofs. MacKenzie approached that market as a plant biologist, and that expertise led Ford to seek him out.

Not long after the Ford job, a contractor to whom MacKenzie had been supplying green roof plants asked him to come to Chicago to look at some problems he was having. One of the big problems with a green roof was getting the new plants started under a hot sun, and coping with wind and rain that sometimes washed away the soil medium before the plants grew enough to anchor it.

MacKenzie started thinking about a new planting system, and in 2006, he started LiveRoof, which manufactures and markets a unique design for the plastic trays that contain the plants.

There are a lot of challenges to successfully grow a green roof. When asked to summarize the problems, MacKenzie said he realized those challenges range from the choice of plants, the way they are planted, the soil they are planted in and the design of the module — the modular plastic trays that contain the plants.

LiveRoof has formulated a soil medium from a lightweight, mostly inorganic material that lasts, while conventional potting-soil type mediums don't tend to last. Regional nurseries around North America that are licensed to grow plants for LiveRoof installations can adapt the soil mixture for their particular climates.

LiveRoof also has a patent pending on its module design. The LiveRoof plants are not "plugs" (seedlings) but fully established plants, so when the modules are placed on the roof and the LiveRoof Soil Elevator is removed, the soil from each module is in direct contact with soil in all adjacent modules and there are no plant-less seams in the roof vegetation.

MacKenzie said about 20 plant companies across the country are licensed to install LiveRoof systems. Two of the largest installations thus far are the new Haworth corporate headquarters building in Holland (45,000 square feet), and City Hall in Toronto (36,760 square feet). Other facilities in West Michigan that have a LiveRoof include Steelcase, The Rapid, Van Andel Institute, Grand Rapids Ballet, Saint Mary's Health Care, Grand Rapids Community College and Muskegon Community College. GVSU has "three or four," said MacKenzie, and John Ball Zoo has two "and they're doing a third one this year."

Other LiveRoof installations range from Boston to San Francisco. MacKenzie estimates that more than 500 are installed.

The cost of installing a green roof ranges from a low-end of $13 or $14 per square foot to as much as $25 per square foot, he said.

MacKenzie said that, today, there are about 20 significant green roof companies, and while LiveRoof isn't the largest, it is the only one that offers a "true hybrid system" that merges technology with biology.

LiveRoof employs about 20 people, with another 60 working at the Hortech facility.

In 2009, according to Green Roofs for Healthy Cities, the green roof industry grew by 16 percent. An estimated 10 million square feet are installed each year.

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