Keeping Cool with CMU

Armory Park, Tucson, AZ
Architect: Lizard Rock Designs, Tucson, AZ
General Contractor: W.E. O’Neil. Phoenix, AZ
Masonry Contractor: Hobbs Masonry, Phoenix, AZ
Block Producer: Superlite Block

In Tucson, AZ, Armory Park is a residential project devoted to elderly housing. At six stories high, it is also one of the tallest post-tensioned buildings in the nation. Relying on a proprietary CMU configuration, the blocks create a loadbearing masonry wall system with superior thermal performance properties.

With 143 one and two-bedroom units in 139,000 ft2 (12913.5 m2), this low-income project was an important one for the owner Senior Housing Group, which was looking to develop a sustainable building. Lizard Rock Designs Architect Tom McQuillen designed this building to Leadership in Energy and Environmental Design (LEED) Gold standards. He was able to achieve that designation on a very tight budget, thanks in large part to the post-tensioned CMU construction.

Sustainable and Cool

“Initially we designed the building with insulated concrete form (ICF) wall construction,” McQuillen said, “because we thought it was a good way to get the energy savings we wanted and it would be cost effective.” But the general contractor W.E. O’Neil convinced him otherwise. “The contractor said the system was fine for lower buildings, but they had experience with ICF on buildings six  stories and higher, and hadn’t been pleased with the results; it was too hard to get the forms straight all the way up.” And the extra work required on the forms would drive the cost up.

McQuillen found the proprietary block to be a great product and is pleased that the CMU can be hydraulically post tensioned and then the cells filled with foam, enhancing the energy conservation and contributing positively to LEED points. “This wall system was the main reason we came in 28 percent better on utility use than the most stringent energy codes,” he said. “ And we even got points because the block was locally-sourced.”

Safe and Quiet Gives a Lot of Peace

The building is all block construction, and interior partitions are set at 28-foot (8.5 m) modules and are built of standard CMU. The driving force for the block interior walls was fire code compliance, but there was an unanticipated bonus. “Combined with precast floors, the masonry interior walls prevent most of the sound transmission,” reports McQuillen “This is a really quiet building.”

Published July 2, 2019
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