Drawing and Specification Updates.pdf

HVAC Renovation Building 990 Naval Station Newport

Amendment 0007 12 October 2023

1) Reason for the amendment: Supplemental information is being provided, please see below.

AMENDMENTS TO THE SOLICITATION

Roof Duct Supports

Three sets of duct supports are located between the return duct roof penetration and the connection of the return duct to the existing roof-top air conditioning unit. Current plans/specs calls for the supports to be left in place for re-use to support the new ductwork. This is a photo of a typical support.

Photo 1 A drawing of the actual construction of the support, Figure 1, is shown below and it lacks a physical connection between the sleeper and the only structural component of the roof, the steel deck which is not sufficient. Please see following figure 2 for an acceptable assembly.

Figure 1 In the sketch below, Figure 2, the sleeper is connected directly to the roof deck. Typical roofing components are shown to ensure a watertight assembly. An arrangement to connect the sleeper to vertical and horizontal steel (galvanized) members firmly affixed to the ductwork can be similar to the existing assembly. The intent is to have the ducts supported but also held down to resist wind loads. This work will require cutting into the existing roof which includes remnants of the built-up roof that may be under the more recently installed (approximately 10 years ago) membrane roof. The older built-up roof that was installed during the original construction of the building tested positive for asbestos containing material (ACM), please see the building hazardous material documents included with the solicitation documents.

Figure 2

Supply and Return Ducts New Curbs of a size compatible with the dimensions of the specified supply and return ducts will be provided. Connection to the roof deck and required roofing components to accommodate the new curb will be as in Figure 2 above with the dimensions of the curb to be of sufficient strength to support the duct, but at least 4” thick. Curb heights will be sufficient to clear the final roof elevation by an amount recommended by the Curb manufacturer and adjusted to meet the configuration of the ductwork shown on the drawings to connect to the AHU supply and return outlets. Roofing will seal the curb assembly with kant strips, flashing, membrane plys, etc., in accordance with generally accepted roofing practice and recognized standards. This work will likely result in disturbing remnants of the old built-up roof with similar results in that encountering ACM should be expected and be addressed with the proper mitigations.

Curbs and associated Materials Curb materials and installations will comply with the guidance that is already a part of this specification. Curbing that would comply with Roof Curb Cap Assembly (RPA-1) of this specification is expected to be in compliance with the requirements of the roof curbs above. Other guidance for curbing and associated materials is found in this specification, sections 05 50 13, 07 22 00, 07 42 13, 07 53 23, and 07 60 00.

Further guidance for Roof Curbs is provided below:

Roof Curb: Provide a roof curb that mates with the ductwork to provide support and be completely weather tight. Provide curb with sealing strips to ensure a weather-tight seal between the duct and mounting supports elements. Mount curb to allow ductwork to be directly connected to the curb. The Roof Curb must be of sufficient height so that standard roofing methods to seal against weather elements may be executed in full.

**End of Amendment 0007**