Replacing Window-Mounted Air Conditioners With A Roof-Mounted System

By GREEN LINK Engineering.

KnuckleHeads are designed to support pipes of all sizes as well as HVAC equipment. 

Each KnuckleHead can support up to 600 lbs. Strut KnuckleHeads are designed to hold standard Unistrut type aluminum and steel channel to create a support system for mounting air conditioning units, chillers, mini-splits, heat pumps and related equipment.

In this particular installation, roofing contractors were engaged to replace window-mounted air conditioners with a roof-mounted system on a 227-unit apartment building in Ann Arbor Michigan, almost in the shadow of The Big House, the University of Michigan football stadium (seen in the background).

Because the risers were sloped, each KnuckleHead included PVC extensions—or “legs”—which varied in length to offset the slant of the risers.  KnuckleHeads are height adjustable—rotating the heads will lower or raise the head, making it easy to make on-the-spot field adjustment. For this project, contractors used the head rotation feature of the KnuckleHeads to fine tune the height, ensuring that each unit was perfectly level. HVAC equipment that is not level will perform less effectively, shortening functional life.

GREEN LINK Adhesive/Sealant was applied to bond the KnuckleHead bases to the risers and also the extensions into the bases to secure the support system.  KnuckleHeads have a unique feature in that they can be attached with mechanical fasteners, but also with adhesive. Unlike other adhesive/sealants on the market, GreenLink Adhesive/Sealant will bond not only to the nylon base of the KnuckleHead, but also to most roof membranes including EPDM, ModBit, PVC and primed TPO.  Bond strength reaches 250 psi and remains flexible and elastic even through harsh weather cycles. 

The project took place over a ten-month period and utilized galvanized steel channel supported by 154 Strut KnuckleHeads.  KnuckleHeads are molded from military grade glass-reinforced nylon. They have excellent weathering properties--KnuckleHeads have been in the field for more than 15 years and have shown no signs of deterioration.

The contractor team reported the installation went smoothly and that the KnuckleHeads were easy to work with.

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Source: GREEN LINK Engineering.