Green Roofs - A growing Market

by Terry Olsen

To view photos from last month's meeting click here.

Cool tour.  Cool roofs.  Literally.  The CSI season kicked off with a tour of Prairie Technologies / ERSystems on a gorgeous September day, exposing our members to cool roof systems, including green roofs, white roofs, and other green technologies.  Arriving through traffic-jammed freeways from downtown Saint Paul, Prairie Technologies in Rockford, Minnesota is remote, and appropriately immersed in nature.  

This LEED-registered factory building is an exciting display of what to do right.  Even before entering, it is clear this is an environmentally-conscious design, from the solar-panel canopy over the front door to the mini wind turbines (cute!) mounted on the parapet; from the pervious parking stalls to the recycled-content parking bumper stops; and from the native prairie grasses surrounding the building to the “sunflower” fixed pole-mounted solar panels.  Precast wall panels include recycled content fly ash.  Upon entering, the environment is fittingly healthy, with low VOC paints and carpets, wheatboard wainscot, motion-detector sensor lighting controls, and even toilets with dual-flush options.

Topping it all, however, is the roof.  With examples of extensive green roof areas (3” to 4” of -don’t say soil - growing medium and sedum varieties), extensive green roof areas in pans, black EPDM roof areas, white-coated EPDM roof areas, white PVC membrane roof areas and paver areas, it is a demonstration tool in addition to a weather-barrier that is used for documentation, education, and experimentation.  Live demonstrations of thermal heat reflectivity comparing the black roof area to the adjacent white-coated roof area showed a 16 degree difference, even at 5:30pm on September 10th with lower sun angles and reduced overall daylight.  Midday in July or August one would expect, naturally, a significant difference in thermal emissivity, but it shows what a difference a white roof makes even as the sun angle drops later in the year and into the evening. 

For a little more background on the extensive green roof, and pulling in a tidbit or two of the fascinating facts measured by Tim Leonard, green roof performance charts similar to a white roof, except that the thermal mass causes a delay in the heat gain and heat loss, which can be advantageous to controlling the temperature swings HVAC units must accommodate.  This also helps protect the roof membrane from wide-ranging swings in temperature, thus enhancing the life of the membrane. 

Anecdotally, of the real-world examples Tim gave, the poultry example (not a paltry example) was a golden nugget (not baked, not fried).  Taking two nearly identical chicken coops with similar bird counts, the control coop kept its galvanized steel roof whereas the test coop was covered with a white coating.  Results showed the energy usage of the control building was higher, and the mortality rate of the birds in the control building was higher.  However, water usage was higher in the test coop.  This was investigated further, only to find that healthier birds eat and drink more, and the slightly lower but more constant interior temperature of the coop with the white roof helped reduce the stress on the chickens when the temperature exceeds 85 degrees.  With the price of chickens, the reduced mortality rate increased profit even more than the savings experienced by the reduction of energy use.  This non-human example shows that while a savings in energy consumption is achieved, even greater benefit is achieved by productivity gains.

The green technologies market has been growing, both expanding in sales and vegetative density, sometimes with less-than-honest green-washing by some manufacturers.  This building, however, is truthful and is an excellent example of how to make a positive difference on many levels, including the roof terrace level.  As a green freak, this building makes me green with envy.  With a BS in Aerospace Engineering, the forward thinking of CEO Tim Leonard, LEED AP is the energy behind this factory’s movement.  If you missed out on the tour, give Ric Riebe a call.  It really is worth the drive.