DATE: February 2002
Press reports have been published concerning moisture damage to SIP (structural insulated panels) roofs on dwellings in Juneau, Alaska. SIPA has investigated this issue in cooperation with industry leading building scientists. This document has been prepared by SIPA to report on the findings related to the field installation of SIPs in Juneau, Alaska.
Questions and Answers:
What is the problem?
At the present time, approximately twenty multifamily buildings in Juneau, Alaska, built prior to 1996, have been reported as damaged due to moisture at the top OSB skin of SIP roof panels. It is hard to get a reliable figure giving the exact number of roofs involved because some of the buildings are multifamily units within a single building.
What actions have been taken by SIPA?
In the interest of homeowners, builders, industry professionals and manufacturers, SIPA facilitated an independent, third party assessment of the situation by retaining Joseph Lstiburek, Ph.D., P. Eng., of Building Science Corporation and author of the U.S. Department of Energy Handbook on Moisture Control. Mr. Lstiburek is also the author of the Builder’s Guides for four climates, distributed by the Energy Efficient Builders Association, and of Moisture Control in Buildings – Construction Principles and Recommendations, NewResidentialBuildings (Chapter 17 of ASTM Manual MNL 18).
What were the findings of the scientific investigation?
The pattern of damage in the SIP roofs investigated was concentrated at the panel seams towards the ridges of roof assemblies. Warm moisture-laden air exfiltrates at gaps in the SIP joints and migrates upwards within the joint toward the roof ridges, depositing moisture at the upper cooler exterior surfaces along the way. This results in wetting of the upper surfaces of the panel joints, OSB panel edges, and the underside of the roofing paper.
What were the conclusions relating to the cause of damage?
Results of the assessment by Lstiburek and his team of experts conclude that the damage is caused by the “lack of closure at the joints due to a lack of sealant or the lack of a continuous sealant or the failure of sealant at the joints.” The findings of the field investigation include, “…there are three categories of joint failure in the roof assemblies in Juneau, Alaska:
“In the first category, virtually no effort was provided to obtain an airtight joint. No sealant of any kind was installed. These assemblies clearly failed due to workmanship.”
“In the second category, sealant was applied but the applied sealant was clearly installed in a haphazard manner. In these assemblies the failure was again due to workmanship. Poor detailing at ridges was common. Air sealing was ineffectual due to lack of effort.”
“In the third category, sealants failed in adhesion. This last category of failures concerns us because it appears that the applied sealants themselves failed. Further investigation is warranted regarding sealant failure and surface conditions. The difficulty of applying sealants in the appropriate location under typical weather conditions in Juneau, Alaska is, in our opinion, a major issue.”
What were some further observations/findings of the building science team?
“Where joints were sealed, particularly at lower interior surfaces, no damage was observed.”
“If joints had been sealed at panel perimeters at the lower interior surfaces, failures would not have occurred.”
“The absence of damage away from panel edges or within the plane of the panels discounts vapor diffusion or the lack of a vapor barrier as a causal factor.”
Is this situation climate related?
Juneau, Alaska, is a coastal area with a hostile climate for all building materials. It rains or snows for close to 300 days each year, and there is sunshine only around thirty days a year. The average relative humidity is 75%, and on most days there are long periods of 100% relative humidity. The area is subject to frequent strong winds coming off the ocean.
It is important to recognize that conventionally built homes in Juneau experience a high incidence of moisture-related structural decay and failure, including roof failure. Juneau climate issues are problematic and have created widespread problems in all types of structures. Juneau climate conditions require close attention to building details with regard to moisture and vapor control for all construction methods.
SIPA believes that the problems reported in Juneau are related to poor workmanship and are not directly attributed to the Juneau climate. SIPA stresses that all SIP construction be done in accordance with SIPA member manufacturer recommended installation methods.
How many builders are involved?
Most of the roofs in question are on multifamily buildings put up by two Juneau area developers/builders, although a few other builders are involved.
Which manufacturers are involved?
Premier Building Systems and Insulspan/Idaho, Inc.. There were a few panels supplied by other manufacturers; however, in those cases, determining which panels are on which roof has been difficult, since builders have not maintained accurate construction records.
What are the manufacturers involved doing about the situation?
Panel manufacturers involved have responded by initiating on-site inspections, and retaining Joseph Lstiburek, to conduct an independent objective assessment. One-on-one conversations and meetings with the builders involved have been ongoing. Premier Building Systems has initiated a training and certification program for Alaska builders and installers. Some of the roofs have been repaired or replaced. Both Premier and Insulspan/Idaho have made technical people available in Juneau to help with repairs.
Who is investigating the buildings?
Several different individuals, associated with different organizations, have become involved in the investigations. Joseph Lstiburek, and his team including John Keys, P. Eng., Research and Projects Director of University of Alaska’s Cold Climate Housing Research Center (CCHRC), and Marquam George, a builder on the CCHRC staff, have provided investigative services to SIPA. John Cooper, a local engineer, is also investigating some of the units.
Are there any trouble-free SIP roofs in the Juneau area?
Yes. Current reports confirm SIP roofs put up by other builders using proper installation details or better quality management are performing well.
Are there quality issues involved?
There has been no suggestion that the panels themselves did not conform to the applicable manufacturing standards. There has been some suggestion that some panels may have been shipped to the site with splines installed, and with an air space between the factory-installed spline and the panel foam core that was larger than the specifications called for. It is not clear to what extent this issue relates directly to any specific documented problems.
Who is covering the losses incurred by homeowners in this situation?
Insurance carriers for the builders have inspected the roofs and determined that failures were installation related. The builder’s insurance carriers have undertaken to pay for roof repairs and replacements in many cases.
What is being done to prevent this problem in the future?
Again, this is an isolated situation specific to these projects in Juneau. It involves builders whose poor workmanship caused the problem. Many of the damaged roofs are currently being replaced with SIPs. The manufacturers are actively monitoring the installation for proper detailing to ensure the long-term performance of the roofs.
What research is SIPA conducting?
SIPA is exploring a research project with the University of Alaska Cold Climate Housing Research Center to develop and demonstrate SIP construction techniques in Alaska. SIPA would like to see test and demonstration structures using SIPs built in the Juneau area under controlled conditions, to provide further objective evaluation of construction systems and details.
What is SIPA doing to educate builders?
SIPA is committed to educating builders and installers on the correct methods of assembling SIP structures, and on appropriate design details for specific climatic conditions. At the present time, a task force drawn from the SIPA membership is working with Dr. Lstiburek to create a SIPs Builder’s Guide for proper installation of SIPs. This manual is intended to become a focal point for SIPA programs to train and educate SIP builders and installers.