Living Roof Offers Retreat
for Hospital Patients
INFORMATION AND IMAGES COUR TESY OF JACOB WHITE CONSTRUCTION
DRIVEN BY FEDERAL CHANGES IN HEALTHCARE REGULATIONS, medical organizations are looking
for long-term strategies to conserve operational costs. The Katy
Medical Plaza is a high-performance building thanks in part to
its 15,593-square-foot green roof. Developed by Jacob White
Construction Company and managed by Transwestern, this
Houston-area property earned LEED Gold for Core and Shell.
Accessible to guests,
the roof is lined with a
pathway that encourages movement, reflection and serene views.
The native vegetation
is composed of gulf
muhly (a type of grass), the flowering perennial Lantana, and
Tradescantia pallida, a groundcover plant in the spiderwort
family. These varieties were selected for their ability to retain
water and thrive in the Texas climate, explains Jeff Mickler,
President of Jacob White.
The roof uses a soil composition that is engineered specifically for its foliage profile and regional weather patterns.
Weeding is minimal, about 30 minutes a week. While unlikely
to occur, Mickler recommends using a variety of plants so
one disease or pest doesn’t affect the entire system.
The base roof consists of a waterproof coating, 60-mil
reinforced scrim waterproofing membrane that is attached
to the sidewall, and loose laid drainage and filter media.
Non-vegetated aggregate is used in areas without soil. With
an average soil depth of 10 inches, the full roof system has an
R-value of 66.
The vegetation retains 73% of rainfall, totaling 362,819 gallons a year (approximately 30,000 gallons per month). The
remaining runoff from the parking lot, over 134,000 gallons,
is captured in an underground cistern. This collection system
can hold 250,000 gallons of water and satisfies the required
stormwater detention for the site, Mickler notes. The reserve
water is used to irrigate both the roof and 2.5 acres of landscaping, as well as to flush toilets. No connection is made to
public utility services for irrigation.
The roof is generally irrigated once a day. If the building’s
internal temperature gets too high, the BAS turns on the air
conditioning and simultaneously waters the roof, explains
Mickler. Using the principles of evaporative transpiration,
this action can cool the roof by 10-15 degrees.
Create an insulated envelope and capture rainwater.
Delivers an R-value of 66 and retains over 70% of rainfall. 2