When designing and building a cathedral ceiling using spray foam insulation you need to take into account code related to:
Unvented Cathedral Ceiling Code
Local codes based on IRC 2009: Section R806.4
Local codes based on IRC 2012: Section R806.5
Vented Cathedral Ceiling Code
Local codes based on IRC 2009: Section R806.1
Local codes based on IRC 2012: Section R806.1
Spray Foam Code
Local codes based on IRC 2009: Section R316
Local codes based on IRC 2012: Section R316
Building Thermal Envelope Code
Local codes based on IRC 2009: Section N1102
Local codes based on IRC 2012: Section N1102
To find out which code your local code is based on, go to http://bcap-ocean.org/code-status-residential.
Do I Need a Thermal Barrier?
In an occupied space, you need a thermal barrier adjacent to either low density or medium density foam - this could be ½ inch gypsum board, or a code-prescribed barrier per R316.4, depending on the spray foam section of your local code. See each Icynene spray foam product to check which paint-on or spray-on thermal barriers can be used.
If the space is unoccupied, you don't need a thermal barrier.
Do I Need an Ignition Barrier?
In an unoccupied space, you need an ignition barrier adjacent to either low density or medium density foam - this could be an intumescent paint, or from the list in R316.5.3, depending on the spray foam section of your local code. See each Icynene spray foam product to check which paint-on or spray-on ignition barriers can be used.
Do I Need a Vapor Barrier?
This depends on your local code requirements; it’s affected by climate and the elements in the building envelope.
What R-value* Do I Need?
This depends on your local building thermal envelope code requirements.
ICC code allows Icynene spray foam insulation to be installed with less than the prescriptive minimum R-value* and still meet the intent of the code.
Compliance based on simulated energy performance requires that a proposed residence (proposed design) be shown to have an annual energy cost that is less than or equal to the annual energy cost of the standard reference design that is based on the minimum prescriptive standard. When the air tightness of the building envelope is factored into the computer calculations, the building will require less R-value* than the prescriptive level mandates. Typically the R-value* can be reduced by 20-25%, depending on the code version that is being used. Icynene may be able to help with REM/Design analysis.
2006 IECC Chapter 4 Section 404.3 - Performance-Based Compliance
2009 / 2012 IRC N1105 - Performance-Based Compliance
Get Answers to Spray Foam Code Questions for Your Project
Contact Icynene Customer Service at 1-800-758-7325 or email firstname.lastname@example.org for more detailed help to find answers on these code requirements for your project. Many factors affect code requirements for a project, and we’d be happy to find the right expert to discuss your situation and local codes.
* R means resistance to heat flow. The higher the R-value, the greater the insulating power. Compare insulation R-values before you buy. There are other factors to consider. The amount of insulation you need depends mainly on the climate you live in. Also, your fuel savings from insulation will depend upon the climate, the type and size of your house, the amount of insulation already in your house, and your fuel use patterns and family size. If you buy too much insulation, it will cost you more than what you'll save on fuel. To get the marked R-value, it is essential that this insulation be installed properly.