Published on : January 13, 2011
Take All Three!
How do you choose between environmentally friendly construction, economically friendly construction, and a building that functions well for the current and future occupants? What if you can have all three? Is it really possible to build an environmentally friendly building while improving the functionality for tenants and do it all on par with traditional construction costs?
I have long been a firm believer that the world at large will become environmentally friendly on a very consistent and predictable basis when we succeed in making the environmentally friendly choice the economically friendly choice. Repeatedly, I’ve heard from designers, engineers, contractors, subcontractors, and product manufactures that it is impossible to be economically and environmentally friendly. After pursuing an opportunity since 2000, the perfect opportunity to prove an environmentally friendly and occupant friendly medical office building could be delivered under the constraint of traditional construction costs came to fruition in late 2007.
In 2000, I put together a plan to develop a medical office building on the campus of the St. Anthony North Hospital in Westminster, Colorado. I located the building in the most logical area of the campus which was in a north parking lot adjacent to the hospital’s ER, OR’s, and labor and delivery rooms. At the time there was really no thought to environmentally friendly positioning or solar loads. There was an administration change at the hospital and the development came to a stop. A few years later, a new developer executed a ground lease with the hospital, located the building in roughly the same place and proceeded to complete design work. The leasing effort did not produce the needed results and the traditionally designed building was not constructed. In 2007, after winning a new request for proposal from the hospital, I was now locked into the location on the campus, but given the opportunity to design and build a new building.
How often does a perfect case study with similar buildings on the same hospital campus with two complete sets of plans, one traditional and one environmentally friendly, present itself? The project that was never built was a 3-story traditionally constructed steel frame building with 50 percent brick and 50 percent stucco project with punched windows. The building used a traditional over-head HVAC system with three rooftop units with DX cooling and gas heat connecting to VAV boxes throughout the building. Floor heights were between 14’4” and 15’4” depending on the floor to ensure sufficient height to provide an acoustical ceiling with a 9’ height. Given the soil conditions, the building needed to be constructed on caissons. The hospital provided me with 12-month-old price from a reputable general contractor right at $110 per square foot for the core and shell construction. This pricing was determined in 2006, so we were heading into a market timing in which construction costs were still rising.
With a very solid baseline for traditional construction costs established, it was time to throw out the traditional plans and start from scratch with a creative design team using and integrated design approach that include weekly meetings of the entire design, development and construction team. The location on campus, shape, and size of the building was dictated by the hospital. The exterior coloring and brick material was provided by the remainder of the campus as well. We still had many opportunities to do something different. We started by implementing a low-pressure under floor air delivery system using radiant heat and cooling at the perimeter provided three key advantages: (1) increase flexibility in zoning and tenant comfort, (2) vastly improved energy efficiency and (3) lower floor to floor heights of 13’4” still allowing for 9 -10’ acoustical ceiling heights.
Pricing and comparing the under floor air system to a traditional overhead system requires considering many factors, not just HVAC components. Overall, because we are delivering air from below, instead of above, cooling is more efficient.
Overhead systems start by blowing cold air from the ceiling through the hottest air in the space hard enough to mix the air completely in the room and achieving our desired temperature. As such, all the air in the space is conditioned, even the air that is well above the people in the room near the ceiling. To accomplish this, overhead systems generally deliver supply air at 55 degrees. This supply air is delivered using fans capable of producing 2-3 pounds of pressure in the ducts.
By comparison, the under floor air is delivered at 65 degrees that rises naturally as it warms. As such, the floor plenum is pressurized with only a half-pound of pressure. Providing warmer air at a lower pressure combined with low-E glass gave us the ability to eliminate one roof top unit as compared to the traditional overhead design.
Overhead space usually contains duct work, fire sprinklers, plumbing, light fixtures, and wiring. By eliminating duct work from above and providing some room under the floor for some services, everything can compress and create more usable space. We were able to reduce the floor to floor height to 13’4” and still provide a 9-10’ acoustical ceiling. With the reduction in floor to floor heights because of the raise floor eliminated three feet of exterior skin system and structure from the entire building. Similarly, the raised floor provides a plenum for air delivery and there is no duct work required. So we were able to eliminate the cost for ductwork.
More efficient glazing and the radiant perimeter system helped reduce the load required of the RTU’s and allowed us to eliminate one RTU completely with a minor upsizing of the remaining two RTU’s. The radiant perimeter system is comprised of two water loops, one hot and one cold. The hot water loop ties into base board radiators and is just a traditional radiant heat system. The heat from the radiators rises across the perimeter walls and helps prevent exterior cold loads from entering the building. In the ceiling is a similar concept, but using chilled water. As the solar load on the building’s skin system creates a heat load on the perimeter, the heat rises into a plenum that contains the chilled beam – basically a radiator with cold water circulating through. The chilled beam then drops the cold air in front of the perimeter skin system shielding the remaining space from the exterior heat load.
Combining the reductions in cost – less building skin, no duct work and one less RTU with the added costs of a raise floor and the perimeter radiant heating and cooling system the net cost of the under floor air delivery system was less than the traditionally constructed system. The under floor system also calculated to be approximately 40 percent more energy efficient which translates into lower operating expenses. The efficiency comes largely from the supply air being 10 degrees warmer and using radiant heat and cooling at the perimeter to handle the skin loads. In the first year of operation, the building uses significantly less electricity and gas than the traditionally constructed building, adjacent to the campus. Adjusting for differences in square footage and occupancy between the two buildings, the under floor air delivery system averages $0.45 per square foot less in utilities.
Other cost effective and environmentally friendly choices included recycling to help offset the cost of construction waste removal, white TPO membrane roof, which is the same price as black but reflects heat instead of absorbing it, solar ban 60 glazing was an inexpensive upgrade given that solar ban 80 had just come out and the improved glazing over traditional helped lower our overall load calculation for the HVAC equipment and careful attention to material selection throughout the project.
The final cost of the core and shell of the LEED Gold certified 60,000 square foot building including construction management fees was $106 per square foot. Because there were no VAV boxes or duct work to procure as part of tenant improvements, the tenant spaces were constructed below the market average for medical tenant improvements as well.
With a little extra effort to map a new course instead of just doing things the way we always have, it is truly possible to “take all three” and construct environmentally friendly, economical buildings that work very well for the occupants.
About the Author and Centrum Health Properties:
James C. Turpen is the Chief Executive Officer of Centum Health Properties. He is responsible for business development, acquisitions/dispositions, ground up development, and leasing. James has over 15 years experience in the field of healthcare real estate. His experience includes leasing over one million square feet of healthcare space, managing several million square feet of medical office space, ground up development, management of physician tenant improvements, acquisition, and brokerage of over $100 million of healthcare real estate, coordination of the facility side of JACHO review and more. James was employed at Aardex LLC during the construction of the above case study. Centum Health Properties offers a full range of acquisition, development, leasing and operation services in the healthcare real estate market focused primarily in the central and western states.