This Technical Advisory is intended to serve only as a general resource and to identify potential issues for consideration by industry professionals. Each person using this Technical Advisory is solely responsible for the evaluation of the Technical Advisory in light of the unique circumstances of any particular situation, must independently determine the applicability of such information, and assumes all risks in connection with the use of such information. The materials contained in this Technical Advisory do not supersede any code, rule, regulation, or legislation and are not intended to represent the standard of care in any jurisdiction.
Billions of square feet of roofing are replaced or repaired every year, and the existing roof insulation is typically removed and disposed into landfills. However, when roofs are recovered or repaired, the existing insulation is typically left in place rather than removed. Roofs are generally replaced when reaching the end of the useful service life or experiencing widespread/uncontrolled water entry. Owners, designers, and contractors may consider reusing the existing roof insulation when replacement of the roof system is performed. As such, IIBEC recommends members review the following when considering reuse of existing roof insulation on roof replacement projects.
The 2015 IEBC, Section 706 Reroofing, 706.3 – Recovering versus Replacement, states: New roof coverings shall not be installed without first removing all existing layers of roof coverings down to the roof deck and where any of the following conditions occur:
The 2015 IEEC, Chapter 4, states that building thermal envelope assemblies shall meet the required R-value based on the climate zone specified in the IECC.
To ensure adequate long-term service life of a new roof assembly, it is vital that:
The most common types of insulation and cover boards found in low-slope roofs include fiberglass, fiberboard, perlite, stone wool, phenolic foam, cellular glass, expanded polystyrene (EPS), extruded polystyrene (XPS), spray polyurethane, gypsum and concrete roof boards, and polyisocyanurate. Many of the roof insulations described have their advantages and disadvantages.
In general, roof insulation material manufacturers stipulate their tested R-value. Polyisocyanurate insulation manufacturers specifically promote using the long-term thermal resistance (LTTR) properties of the material when determining the overall thermal resistance of the roof assembly.
Many factors should be considered during the evaluation of an existing roof assembly to determine the feasibility of reusing the existing insulation during roof replacement. These factors include, but are not limited to, the following:
There are two approaches to roof insulation reuse that may be considered:
The removal of the membrane allows for visual examination of the top layer of insulation or cover board in addition to confirming any roof moisture survey results. In addition to spot removal of damaged insulation and/or cover board, the manufacturer of the new roof system may require that additional procedures are followed to meet the performance requirements of the new system.
Fully adhered membrane roof assemblies create challenging conditions for reusing existing insulation. For example, delamination of the insulation facers or damage to the core of the insulation boards is likely to occur during membrane removal. This is especially true when new materials must be adhered over the existing materials. In addition to a moisture survey to check that the insulation is adequately dry, field testing may be required on the existing roof assembly to ensure appropriate uplift values can be obtained. ANSI-SPRI IA-1, “Standard Field Test Procedure for Determining the Uplift Resistance of Insulation and Insulation Adhesive Combinations over Various Substrates,” is one such test procedure that can be followed for testing the uplift resistance.3 Negative pressure testing per FM Global Property Loss Prevention Data Sheets 1-52, “Field Verification of Roof Wind Uplift Resistance,” is another procedure. 4 The new system would not otherwise be a tested assembly.
Further, if the proposed new roof assembly is not a tested assembly, the local jurisdiction should be consulted to ensure the onsite testing and results thereof would be acceptable. To meet Factory Mutual (FM Global) requirements, test procedures and roof assemblies should be submitted and evaluated by FM Global. Also consult FM Global for FM Global-insured buildings since they may not approve testing they did not perform.
For roof membrane replacement projects, after the removal of the existing roof membrane, the condition of the existing roof insulation must be investigated. Evident deficiencies to the existing insulation that will impede the functionality of the new roof system and therefore may negate reuse are as follows:
Wind uplift resistance of low-slope roofs often relies on adhesion of roof system components to the roof structure. On concrete roof decks, adhesion is more commonly used for system component securement than mechanical fastening, because the installation of fasteners into concrete is more difficult than into steel or wood decks. As such, adhesives are often used, and they must be able to perform in moist and alkaline conditions. Elevated moisture levels in concrete can negatively impact the adhesion of adhesives, asphalts, and vapor retarders/membranes and must be considered prior to installation.
For roof recover projects that do not include the removal of the existing roof membrane, a roof moisture survey is typically required by the manufacturer of the new roof system. The most common standard, non-destructive, test procedures used to identify the presence of moisture beneath a roof membrane are:
All non-destructive test methods require confirming findings by extraction of roof core samples. At that time, the properties and condition of the existing roof substrate materials can be visually observed at the roof core sample areas, provided large enough openings are made. Manufacturers may require a moisture survey, without defining test methods for determining the condition of the roof assembly; one of the three test methods listed above should be considered. High- and low-voltage testing can also be used, but are limited to identifying breeches in a membrane and do not identify the presence of moisture directly under roof membranes.
When considering roof recovery and repairs, IIBEC Technical Advisory IIBEC-TA-013, “Removal and Replacement of Roof Substrate Materials Damaged by Moisture,” should be reviewed.8
The purpose of this Technical Advisory is to provide information to IIBEC members and the industry for consideration during a condition assessment or roof design to determine the feasibility of reusing the existing roof insulation. The reuse of roof insulation should be confirmed and discussed with the manufacturer to ensure all performance requirements are met during construction. The physical properties of the roof substrate and materials may be adversely affected if excessive moisture has existed. Thorough testing using consensus-based standards and methods, along with field testing and evaluation of the materials present, is required to achieve long-term performance. In addition, confirm with the jurisdiction having authority and/or FM Global if any special testing and results thereof will be acceptable.
Reuse of roof insulation may result in cost savings to the project, reducing transportation, materials, demolition, and installation labor. Roof re-cover projects present various long-term performance issues when adequate drainage capacity is not provided, incompatible materials are used, damaged or deteriorated materials are not replaced, and a minimum of ¼-inch per foot or positive slope is not provided. The long-term performance of the roof may be significantly reduced if proper testing and analysis of the existing roof assembly are not performed.
1 2015 International Existing Building Code, Section 706 Reroofing, 706.3 Recovering versus Replacement, p. 33.
2 2015 International Existing Building Code, Section 706 Reroofing, 706.3 Recovering versus Replacement, p. 33.
3 Available from SPRI at: https://www.spri.org/download/standards_and_technical_reports/current_ansi_spri_standards/ANSI-SPRI-1A-1- 2015-Standard-Field-Test-Procedure.pdf.
4 Available from FM Global at: https://www.fmglobal.com/research-and-resources/fm-global-data-sheets.
5 Available from ASTM International at: https://www.astm.org/Standards/C1153.htm.
6 Available from SPRI at: https://www.spri.org/download/standards_and_technical_reports/current_ansi_spri_standards/NT-1-2017-ANSISPRI-RCI-Detection-and-Location-of-Latent-Moisture.pdf.
7 Available from ASTM International at: https://www.astm.org/Standards/D7954.htm.
8 Available from IIBEC at: http://rci-online.org/wp-content/uploads/TA-013-2017-moisture-damaged-roofmaterials.pdf.
Download the Document: IIBEC-Technical-Advisory-No.-016-2018-Reuse-of-Roof-Insulation
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