By: Adam McManus
Several factors can significantly drive up costs during the design phase of a New York City roof replacement project. For example, a roof that has tested positive for asbestos containing material (ACM) will require abatement. A deteriorated or unstable perimeter railing requiring major repair or replacement must conform to the most recent NYC DOB requirements, even if the building was constructed with a grandfather clause under a different building code.
According to the New York City Energy Conservation Code, theA insulation requirementA above a roof deck is R-25 or R-38 in the attic space. R-value is referred to as the thermal resistance and measures the ability of heat to transfer from one side of a material to another.
The average insulation thickness of an older roof assembly commonly ranges between 1a and 3a, and has an R-value between 5.6 and 17.4. In order to increase to an insulation thickness of R-25, all roof components including: drain bowls, railings, parapets, doors, roof-top-curbs, etc. may need to be modified or elevated. These necessary modifications to attain a thicker roof assembly can significantly compound costs.
The use of rigid polyisocyanurate (polyiso) insulation, with a fiberglass facer, over the deck is commonplace.A This product requires a minimum thickness of 4.5a to meet the new R-25 code. During the design phase of a roof replacement project, probes of the existing roof should be performed to verify the thickness of the assembly. Anticipating the necessary thickness is key to finding suitable alternate solutions for insulating roofs and/or planning for the height modifications of roof related features.
In light of these changes to the Building Code, as well as anticipated future changes, it is crucial that Building Owners retain the services of a design consultant that is not only familiar with the Code changes but also alternative means and methods available within the market. For example, it now may be more cost effective and/or less intrusive to install some, or all, of the insulation below the roof deck and achieve the required combined R-value of 38 (for insulation above and below the deck). Similarly, some old materials that had fallen out of favor in the industry, as well as some new materials, may become more appealing and should be considered. We’ve recently met with several manufacturers that are attempting to bring systems that have proven to work well in Europe to the U.S. market.