Roof Insulation R Value Code

Types of roof insulation.

Roof insulation r value code.

Know exactly how much you need with our project calculators. Depending on where you live and the part of your home you re insulating walls crawlspace attic etc you ll need a different r value. See the department of energy s doe ranges for recommended levels of insulation below. R value is a measure of insulation s ability to resist heat traveling through it.

State applicable code ashrae zone minimum r value state local al alabama 2015 alabama commercial energy code 2 r 25 3 r 25 state. Building and energy codes almost always specify a required minimum r value for exterior walls and roof assemblies with above deck insulation so the minimum required r value in your local jurisdiction is something that you need to take into account when planning a building project. The table below shows what levels of insulation are cost effective for different climates and. If structural sheathing covers 40 or less of the exterior continuous insulation r value shall be permitted to be reduced by no more than r 3 in the locations where structural sheathing is used to maintain a consistent total sheathing thickness.

Minimum insulation r value requirements non residential above roof deck. These energy code r value requirements change from state to state and even city to city. The higher the r value the greater the insulation performance. The higher the r value the better the thermal performance of the insulation.

In addition the common belief that an average r value is just as good as the code requirements is just that a common belief not a fact. When determining how much insulation you need don t guesstimate calculate. Typical recommendations for exterior walls are r 13 to r 23 while r 30 r 38 and r 49 are common for ceilings and attic spaces. Energy codes and roofs.

2015 code requires walls to be insulated with a minimum of r 20 or r 13 5 13 5 means r 13 cavity insulation plus r 5 insulated sheathing. Insulation level are specified by r value. Tapered insulation is the most common method for creating a slope on a low slope roof but frustratingly neither code addresses compliance for tapered systems. R value measures how well certain building insulation materials can resist heat.

While the r value for a material is typically given per inch the rsi is typically given per millimeter so please be aware that the r values and rsi values for the materials in the following table are not for equivalent thicknesses.