The Carlisle Mosquito Online

Friday, June 18, 2010

Placement questioned for new school heating units

Rooftop units have access problems, higher maintenance costs

Concerns were raised at the June 10 meeting of the Carlisle School Building Committee (SBC) about the design of the new building and the location of the heat, ventilation and cooling (HVAC) systems. The latest design of the building puts the HVAC systems on a flat roof, approximately six feet lower than two sharply angled roof lines, creating a “bowl” effect. While the rooftop units would be less expensive initially, Carlisle School Supervisor of Building and Grounds David Flannery believes that indoor units would be safer to access and less expensive to maintain long-term.

When the design was questioned, HMFH Architect Laura Warnick replied, “MSBA does not fund enclosing the rooftop. We’d have to make significant changes to bring it [the HVAC systems] inside.” HMFH Architect Arthur Duffy added, “We explored it.”

SBC member Bill Risso asked, “What is the mechanical sustainability of the equipment in the bowl?” Duffy replied, “We have about 19 or 20 feet clear around the units. The units are eight feet wide and they need 30 inches maintenance clearance.” The units are meant to be outdoors, Duffy said. “We can’t avoid snow filling up that space. That is a maintenance concern.”

Risso replied, “It’s not a convenient way to maintain roof units.” Flannery preferred locating the HVAC units indoors, “Putting them outside is not the best way. It’s not good building design to have the units outside,” Flannery said. He continued, “Good building design includes appropriate space for maintenance. There is nothing to maintain safety in that type of design. It’s a sad state of affairs when we must accept something that is not a good design for mechanicals. If the Commonwealth of Massachusetts is telling us [to use this design] it’s too bad. We should be looking over sustainability. I don’t agree with it.”

Warnick again noted the MSBA does not reimburse for creating a “penthouse” for the HVAC systems. She said if a roof is built, “we will be looking at having to cut” something from the project.

Contacted later by email, Flannery explained his objections in more detail. “The equipment is exposed to the weather,” he said. “Although the equipment is manufactured for outdoor application, wind, rain, snow and ice take a toll over the years. When equipment is on the roof it is prone to having all kinds of debris collect on it and in it.” Insects, pollen, dust and tree droppings can interfere with the efficiency of the units, he said. “In the winter fine snow gets drawn into the ductwork causing what appears to be a roof leak (this happens in Corey now).”

Flannery repeated that maintaining the existing roof units has been difficult. “Especially in the winter months, with ice and snow, this is a concern. Many times the roof has several inches of snow or ice and in a snow storm it is difficult to access the unit. Then think of the reverse conditions when it is 95 degrees out and the sun is out. You really bake up there. In the Corey Building there is an interior hatch with a scuttle ladder. It is almost impossible to get up through this hole onto the roof with your equipment safely.”

Flannery reiterated, “In my opinion as a facility manager it is not a good design and owners should weigh the options and costs of having the HVAC equipment enclosed in a mechanical room. The Spalding building and Wilkins Building have all of their HVAC equipment inside and these systems are: 1. least costly to maintain, 2. easiest to maintain, 3. safest to access, and have been the most efficient and longest-lasting systems on campus. For the record I brought this issue up to the architect and building committee early on during the master plan existing conditions evaluation. Whatever we do at this point in the process to change from this design will increase the project cost.”

Contacted later, SBC Chair Lee Storrs said the SBC will “have the architects look into options for addressing this issue and the costs associated with putting the HVAC units inside.”

Carlisle’s Owner Project Manager Sean Fennell of Daedalus, Inc. suggested construction bids may come in lower than expected, freeing funds to cover a modification to the roofline. “In Stow the bids were 26% lower.” ∆


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