FAQ for Building Code Officials

Can spray polyurethane insulation be applied directly to electrical wiring? What about installed electrical devices like recessed lights?

 

Spray polyurethane foam can be applied directly to electrical wiring. Recessed lights or other fixtures may require a certain amount of air circulation around them for cooling purposes. In these cases, a box can be built around the fixture with gypsum wall board; then spray foam can be sprayed directly to the outside of the box.

Can you insulate non-vented roof decks and attics with foam?

YES, with just about all brands of spray polyurethane foams. The International Code Council (ICC) Residential Code provides guidance for the proper design and installation for non-vented attic assemblies in the Residential Code (IRC) section R806.4.   This design is now referred to as “Unvented attic assemblies”.

While there is over 30 years of building unvented attics using SPF with local code approvals, the nationally known code bodies first authorized it in 2004. This approval has been modified and clarified in subsequent editions of the ICC Residential Code with the current 2009 issue having very good detailed instructions on the proper design and installation.

In all but the warmest/driest climate zones of the United States, the insulation used to insulate and seal off an unvented attic assembly must be an air-impermeable insulation, which just about all spray foams are, open and closed cell. Applicators should be sure the SPF manufacturer they choose to supply their material has certified the system as air-impermeable and at what minimum thickness.

What is the difference between a thermal barrier and an ignition barrier?

Thermal barriers are required by code to be installed between foam plastic, such as spray polyurethane foam, and the interior space of a home or commercial building. The most commonly used thermal barrier is gypsum wallboard found on the walls and ceiling. Ignition barriers serve a different purpose and are only used in attics and crawlspaces. A typical ignition barrier is ¼” plywood installed over the foam plastic. Some spray polyurethane foam manufacturers have their own spray-on liquid applied intumescent coatings that have been tested and approved to be used over their foam as thermal barriers and/or ignition barriers. The following paragraphs go into further detail about how the building codes classify them, common interpretations of the code in regards to each and the tests that are used to qualify each.

Spray foams are one form of “foam plastic”. Building codes (IBC & IRC) stipulate that foam plastic insulation shall be separated from the interior of a building by an approved thermal barrier of ½ inch gypsum wallboard or equivalent thermal barrier material. (There are also exceptions to this in the codes, but they will not be addressed here). In most interior applications, the gypsum wallboard is used to satisfy the requirement. In requiring the foam plastic to be “separated from the interior” there is no stipulation for the thermal barrier to be in contact with the foam plastic, nor is there any maximum distance stipulated between the foam plastic and the thermal barrier. It is fairly common to find applications with the thermal barrier a couple of feet away from the spray foam surface, and this is acceptable and within the requirement of the code.

Other approved forms of Thermal Barriers are cementitious or fiber based materials applied to the foam surface. These materials must pass two tests; one for temperature and one for the ability to remain in place in order to be classified as a “thermal barrier”. These materials are tested per the requirements of the building code and can be installed on any spray foam system.

There are some coatings (usually intumescent coatings) that have been tested so the combination foam/coating does not require a thermal barrier. The coating is not a “thermal barrier” but can be used in lieu of the required thermal barrier.   If the coating is tested only on vertical walls, it is only approved for use on vertical walls. If the coating is tested only on overhear horizontal ceiling assemblies, it can only be used in place of a thermal barrier for overhead applications.   The thickness of the spray foam membrane can not exceed that which was used in the coating test. The coating is also restricted to only the specific spray foam system used in the test. To determine these limitations requires a review of the test report or some type of Evaluation Report stipulating the coating approvals.

Ignition Barrier:   When spray foam is installed in an attic or crawl space where there is an opening which would permit a person to climb into the space (limited access) the building code requires the installation of an ignition barrier over the exposed surface of the spray foam. Ignition barriers are ONLY used in attics and crawl spaces. The IBC and IRC list 6 ignition barriers.   These are the only ignition barriers.   The code does provide guidance for testing the installation of spray foams without an ignition barrier. Many spray foam manufacturers test their spray foam systems with an intumescent coating in place of the ignition barrier. When the coating/foam combination passes the screening test, the combination is approved for use in the attics and crawl spaces, but the coating is not recognized in the building codes as an ignition barrier; instead, it is referred to as an installation without an ignition barrier. Where the building code provides the method to test a product and certify it as a Thermal Barrier, there is no provision in the building code to test and certify a product as an “ignition barrier”; therefore any coating or other covering is not an “Ignition Barrier”, but is an approved installation without an ignition barrier. If the same test is passed by a spray foam system with no coating or ignition barrier, then that spray foam system will be approved for installation with no additional covering/coating.

The most definitive and recognized guidance on testing spray foam without an ignition barrier is written in the Acceptance Criteria (AC 377) for spray foams published by the International Code Council Evaluation Services (ICC-ES). This publication can be found on the ECC-ES web site. www.icc-es.com

An attic is the space between the bottom of the roof deck and the ceiling. The ceiling has to be fixed in place to constitute an attic, as in gypsum board nailed/screwed to the ceiling rafters/joist. Drop in ceiling panels into a metal grid suspended from the roof deck does not constitute an attic space.   Therefore, in reality, the ceiling is the Thermal Barrier between the spray foam and the interior of the building and the floor decking/subfloor is the thermal barrier between the spray foam in a crawl space and the interior of the building. There is no code stipulation that the thermal barrier be within a specified distance of the spray foam surface. In many cases the separation will be some feet in distance.

An attic space may be created behind a knee wall when constructing a bonus room in the area typically left as attic space. If no access hatch into this space is required by other code stipulations, there is no requirement for an ignition barrier on the spray foam behind a gypsum board knee wall, because there is no access.

The key rule for Ignition Barriers…..they only come into consideration in an attic space with access (and no storage flooring permitted) and crawl spaces (all of which are required to have access). Basements are part of the interior of the building. Basement or ground level garage spaces are part of the interior of the building. Ignition barriers are not used in work shops, insulated storage sheds, detached garages, parking decks or any other such building.

What would be the proper thickness of closed cell foam to be applied to a crawl space under a house in North Florida?

 Check with your local building code official, but the International Energy Concervation Code states and R-13 is required under the floor.

How can I tell the difference between closed-cell foam and open-cell foam when I am doing inspections?

Here we will discuss insulation spray foams. Roofing spray foams are all closed-cell and any suspicion that the membrane foam has open cells from an “off ratio” misapplication will require sample analysis in a lab.

The first item for an inspection should be the Installer’s Certificate listing the type system being inspected.

With no other documentation or evidence of system properties, the simplest means is by gently touching the foam surface, with open cell having a soft cushion feel and closed cell having a harder rigid feel. One should take care not to push on the foam surface enough to damage the open cell membrane. Unlike flexible cushion polyurethane foams used for bedding and furniture cushions (which can be squeezed and spring back into shape) spray foams do not have the same recovery properties and may be compressed beyond the recovery point. This is particularly true with open cell systems.

Open-cell systems with a density measurement of 0.5 pounds per cubic foot are very soft. By comparison, closed cell insulation systems have a density measurement of 2.0 pound per cubic foot and are much stronger and harder. Lately, some alternate products are being introduced to the market with higher density open cell 2.0 systems and lower density closed cell 1.7 to 1.2 systems. As these systems find wider acceptance in the construction industry, inspector may be required to rely more on the Certifications by the installer.

Is spray polyurethane insulation code approved?

 Yes. Building codes provide for the use of spray polyurethane insulation in the Foam Plastic section. This section of the code also describes the use of thermal barriers.

A thermal barrier is a covering between the interior space of a building and the surface of the spray polyurethane insulation which will protect it for at least 15 minutes as tested in an ASTM test. ½-inch gypsum wall board, such as Sheetrock®, is an approved 15-minute thermal barrier. Building codes require the installation of a thermal barrier between foam plastics (such as spray polyurethane insulation) and any occupied space. Exceptions apply in some cases; review local codes and/or confer with your local building code officials. The building code provides for an exception to the thermal barrier requirement in attics and crawl spaces where entry is made only for the service of utilities. In such cases, the spray polyurethane insulation must be protected from ignition. There are many spray-on ignition barrier coatings for these areas.