Rimkus was retained by the design-build contractor to provide consultation in upgrading the building envelope in order to meet the established energy performance criteria.

Background

The 18-story, 500,000 square, steel framed building, was enclosed by relatively thin precast concrete panels, with tinted insulated glass units that were considered state-of-the art at the time of the original construction in 1964. The solid portions of the walls had practically no insulation, nor air or vapor barriers of any real value. The precast panels were considered too fragile to be removed, requiring the upgrade of the enclosure to be performed exclusively from the inside. The window frames were custom-made 12-inch deep by 1-inch thick extruded aluminum “boxes”. 

For the sophisticated energy-saving mechanical systems to perform properly, the insulation of the envelope had to have an average R-Value of 24, which required the thermal improvement of the window system to R-10. This was accomplished by adding a second layer of highly insulated glass to the inside edge of the 12-inch deep frames.

Services / Solutions Provided

Rimkus’ work included consultation and peer reviews of the team’s design partner’s building envelope concepts. The work focused on reviewing the proposed vapor barrier installation, the possibility of condensation forming within the improved window assembly and the roof design. Design documents were reviewed at the 60% and 90% completion-milestones, and some in-place work by a subcontractor that was in conflict with the design documents was evaluated during construction.

Specific services completed by Rimkus included:

• Hygrothermal computer modeling of the existing envelope to establish a baseline of performance, followed by modeling of new design alternatives;
• Review of the energy efficiency of the proposed wall system;
• Review of the proposed improvements to the window assembly, with particular emphasis on potential fogging and frost over.
• Review of roof slope and roof penetrations for water tightness, code compliance, GSA standards and maintenance;
• Evaluation of the work of a subcontractor whose work was in conflict with the construction documents, with recommendations for remediation.
• Onsite field inspections