skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Empirically Derived Strength of Residential Roof Structures for Solar Installations.

Abstract

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,more » the actual load bearing capacity is several times higher than published values (NDS 2012).« less

Authors:
; ; ;
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
OSTI Identifier:
1166691
Report Number(s):
SAND2014-20600
553867
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English

Citation Formats

Dwyer, Stephen F., Sanchez, Alfred, Campos, Ivan A., and Gerstle, Walter H. Empirically Derived Strength of Residential Roof Structures for Solar Installations.. United States: N. p., 2014. Web. doi:10.2172/1166691.
Dwyer, Stephen F., Sanchez, Alfred, Campos, Ivan A., & Gerstle, Walter H. Empirically Derived Strength of Residential Roof Structures for Solar Installations.. United States. https://doi.org/10.2172/1166691
Dwyer, Stephen F., Sanchez, Alfred, Campos, Ivan A., and Gerstle, Walter H. 2014. "Empirically Derived Strength of Residential Roof Structures for Solar Installations.". United States. https://doi.org/10.2172/1166691. https://www.osti.gov/servlets/purl/1166691.
@article{osti_1166691,
title = {Empirically Derived Strength of Residential Roof Structures for Solar Installations.},
author = {Dwyer, Stephen F. and Sanchez, Alfred and Campos, Ivan A. and Gerstle, Walter H.},
abstractNote = {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).},
doi = {10.2172/1166691},
url = {https://www.osti.gov/biblio/1166691}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Dec 01 00:00:00 EST 2014},
month = {Mon Dec 01 00:00:00 EST 2014}
}