Reducing Soft Costs of Rooftop Solar Installations Attributed to Structural Considerations.
Abstract not provided.
Dwyer, Stephen F.↗
Engineering topics
Dwyer, Stephen F.
Publications and source records attributed to Dwyer, Stephen F..
Confirming the Strength of Residential Roof Structures for Solar Installations
The rooftop solar PV permitting process involves a number of steps and varies greatly, even between neighboring cities. Jurisdictions follow state or national codes, but each may interpret the codes in their own way and insert additional requirements. In some locations, a rooftop structural analysis conducted by a professional engineer is required before a rooftop solar permit is issued. The extra step is not universally applied across states or municipalities, and can alter scheduling logistics and add hundreds of dollars to the cost of the system.
14 SOLAR ENERGY↗
Confirming the Strength of Residential Roof Structures for Solar Installations
Researchers at the U.S. Department of Energy’s Sandia National Laboratories conducted a first-ofits- kind study to help dispel misperceptions that many existing rooftops cannot carry the actual load created by rooftop solar photovoltaic (PV) installations. Test data on rooftop structure load capacity wasn’t previously available to the industry, and research to collect such data was made costly by the need to test each scaled structure to the point of failure. The Energy Department funded this study to provide scientific data to the industry that can decrease uncertainty, help eliminate misperceptions, and ultimately alleviate extraneous solar PV permitting costs.
Dwyer, Stephen F.↗
Empirically Derived Strength of Residential Roof Structures for Solar Installations
Engineering certification for the installation of solar photovoltaic (PV) modules on wood roofs is often denied because existing wood roofs do not meet structural design codes. This work is intended to show that many roofs are actually sufficiently strong given the conservatism in codes, documented allowable strengths, roof structure system effects, and beam composite action produced by joist-sheathing interaction. This report provides results from a testing program to provide actual load carrying capacity of residential rooftops. The results reveal that the actual load carrying capacity of structural members and systems tested are significantly stronger than allowable loads provided by the International Residential Code (IRC 2009) and the national structural code found in Minimum Design Loads for Buildings and Other Structures (ASCE 7-10). Engineering analysis of residential rooftops typically ignores the system affects and beam composite action in determining rooftop stresses given a potential PV installation. This extreme conservatism combined with conservatism in codes and published allowable stress values for roof building materials (NDS 2012) lead to the perception that well built homes may not have adequate load bearing capacity to enable a rooftop PV installation. However, based on the test results presented in this report of residential rooftop structural systems, the actual load bearing capacity is several times higher than published values (NDS 2012).
Dwyer, Stephen F.↗
Structural Code Considerations for Solar Rooftop Installations
Residential rooftop solar panel installations are limited in part by the high cost of structural related code requirements for field installation. Permitting solar installations is difficult because there is a belief among residential permitting authorities that typical residential rooftops may be structurally inadequate to support the additional load associated with a photovoltaic (PV) solar installation. Typical engineering methods utilized to calculate stresses on a roof structure involve simplifying assumptions that render a complex non-linear structure to a basic determinate beam. This method of analysis neglects the composite action of the entire roof structure, yielding a conservative analysis based on a rafter or top chord of a truss. Consequently, the analysis can result in an overly conservative structural analysis. A literature review was conducted to gain a better understanding of the conservative nature of the regulations and codes governing residential construction and the associated structural system calculations.
Dwyer, Stephen F.↗