Fiberglass and mineral wool insulation is the low-cost solution for homebuilders to meet or surpass code air leakage rate requirements of 3 or 5 air changes per hour depending on climate zone. For homeowners, an airtight building envelope results in energy savings and increased thermal comfort. R-Value is a measure of insulation's ability to resist heat traveling through it.
The higher the R-Value the better the thermal performance of the insulation. The table below shows what levels of insulation are cost-effective for different climates and locations in the home. Learn how to take action today and Rule Your Attic! with ENERGY STAR.
Creating a conditioned attic space for mechanicals is more than just air. Insulation must also be kept clear of chimneys and exhaust flues, with the specific distance dictated by the appliance manufacturer's instructions, often requiring a minimum one-inch air space. A major technical standard involves attic ventilation, which is necessary to prevent moisture buildup and reduce heat gain in the summer.
1. Attic access is required by Section R807.1. 2.
The space is entered only for purposes of repairs or maintenance. 3. The foam plastic insulation has been tested in accordance with Section R316.6 or the foam plastic insulation is protected against ignition using one of the following ignition barrier materials.
For example, meeting the ceiling R-value in an uninsulated attic may only require adding more insulation. Because of interior drywall and exterior sheathing, meeting the R. Providing extra space between a roof and ceiling for insulation is the main reason for using a raised-heel truss.
The 2021 IECC requires more insulation R-value in residential attics in climate zones 2 through 8. Where it had been R-30, it is now R-38; where R-38, now R-49; and where R-49, now R. Learn how much attic insulation you need by climate zone.
Find R-value requirements, insulation depth charts, and signs your attic is under. What Roof R-Value Means R-value measures a material's resistance to heat transfer; higher values indicate better insulation. For roof systems, the R-value reflects the insulation layer within the attic or ceiling assembly and, to an extent, the air films on either side of the roof.
Install raised heel trusses or use another roof framing method that allows space to install insulation over the top plates of the exterior walls, or install high-R-value insulation, to achieve an R.