Clarifying Building Codes

Building Codes Embrace the Use of Spray Foam Insulation

What is an Ignition Barrier vs. Thermal Barrier and when are they needed?

This is a relatively new addition to the Spray Foam Insulation world. It is true that some types of foam are slightly flammable and others provide zero fuel to a fire. All foams are less flammable than the wood decking and framing in a conventionally built building so the real concern is the smoke development. When a fire makes it to the spray foam surface, it will produce some degree of smoke and this why we must protect the foam.

Clarification: When do you need a thermal barrier and when do you need an ignition barrier?

Code can be interpreted in a couple of different ways and as usual, it is important to remember that it’s always up to the discretion of your code official. This is how we interpret the code:

Thermal Barrier – A thermal barrier as far as building code is concerned, is any product that has been ASTM tested and is considered to have a “15-minute thermal barrier” or an “index of 15”. An example of a thermal barrier is 1/2” sheet rock, 1/4” plywood or particleboard, and some fire proof coating.

Ignition Barrier – A product that prevents ignition from a spark or direct heat, but does not protect from direct flames over a period of time is an ignition barrier. Ignition barriers are usually sprayed on or brushed on coatings.

ASI Spray Insulation Professionals are willing and able to help you determine when and where to use an ignition barrier and/or thermal barrier. We will be happy to contact your building code official and provide all the documentation needed for code compliance. R-value—Do I need R-38 of spray foam?

R-value—Do I need R-38 of spray foam?

All insulations have a diminishing rate of return on efficiency. Spraying 1 inch of Icynene LD-C-50 will give you a 73% heat flow reduction and jumps up to 92% at 3 ½ inches. The maximum thickness we normally install is 5 ½ inches- which provides a 95% heat flow reduction. By doubling the thickness to 11 inches, the cost is doubled but you only gain 2% in heat flow reduction. This is the diminishing rate of return. Simply put, it just does not pay to install more than 5 ½” (R-20) of Icynene foam or 3” (R-20) of closed cell foam. We generally install 3 ½” (R14) of Icynene in the walls and 5 ½” under the roof which is code compliant with IECC energy code performance criteria.

Unvented attic space— Don’t I need ventilation under the roof?

With all fibrous insulation, you definitely need ventilation under the roof to reduce the possibility of condensation. Condensation happens when the warm moist internal air leaks thru the fiberglass to meet the cold underside of the roof. Ventilation will, hopefully, pull that moist air up and out thru the ridge vent before condensation has a chance to form. This is how homes have been built for years but the design is very flawed.

All fibrous insulation products work by trapping air pockets between the fibers— it’s the trapped air that is doing the insulating, not the fibers themselves. In a typical home, air enters the attic thru the eves and exits through the ridge vent. This creates a suction effect that pulls and moves air from the inside of your home— through the fiber insulation and out. This moves all those pockets of air and ruins the efficiency of the insulation. In short—It sucks.

We install the Spray Foam Insulation directly to the underside of the roof where it will not allow the heat to go right out of your home—the warm moist internal air will never meet a cold surface which eliminates the need for ventilation all together.

You may have heard that installing insulation to the underside of the roof will lessen the life of your roof shingles. This is true with fibrous insulation but not true with Spray Foam Insulation. Most people believe it is the heat that kills the shingle when it’s really the condensation.  Condensation can form under the shingles at night and  when the sun comes out (even in the winter) it will heat the shingles and steam off that condensation. It’s that steaming action that kills the shingle and the Spray Foam Insulation will eliminate this condensation problem—making it safe to install foam to the underside of the roof deck. This code approved practice is accepted by most major roof shingle manufacturers and does not affect their warranty.

Please see an ASI Spray Insulation Professional for more information and documentation.

Understanding the IECC energy codes

Energy codes provide three options when evaluating the building envelope:

The Prescriptive Approach, which is exactly what the IRC codes prescribe (R-20 in walls and R-38 in attic)

The Trade-off Approach is where the RES-check program used to be able to trade-off efficiencies. (i.e.: less insulation if you install a higher efficiency HVAC system) The 2009 changes to the RES-check program have virtually eliminated these types of trade- offs.This is where we hang our hat….

The Performance Approach. It permits us to perform a building analysis, using the REM design program, to show how well or how bad your home will perform when using a specific insulation material in the building envelope. Code states that you are compliant if documentation shows it will perform at least 30% better than traditional construction methods. Most of the time, Spray Foam Insulation will create a home that is 50-60% more efficient than fiberglass insulation.

Your ASI Spray Foam Professional will work with you to provide pricing for the Spray Foam Insulation as well as perform the REM energy analysis. This program will provide the necessary IECC code compliance documents as well as a side by side comparison that shows how much more energy efficient your home will be by using Spray Foam Insulation verses fiberglass. This is very educational and a great sales tool for you, the builder, to show the homeowner how you are setting yourself apart from your competition by caring about the future of your customers’ home and well being.