Insulation questions
What R-value should my attic have in Ohio?
Short answer: ENERGY STAR recommends R-60 for an uninsulated attic in Ohio, and adding R-49 if there are already 3 to 4 inches. That is about 14 inches or more of blown insulation. Ohio is in climate zones 4 and 5, and the advice is the same for both [1].
The numbers
| Climate zone | Attic, uninsulated | Attic, 3 to 4 inches there now | Floor |
|---|---|---|---|
| 4A | R-60 | add R-49 | R-19 |
| 5 | R-60 | add R-49 | R-30 |
ENERGY STAR, Recommended Home Insulation R-Values, for retrofitting existing wood-framed buildings. ENERGY STAR notes the guidance is based on the 2021 International Energy Conservation Code [1].
What that looks like in inches
Settled cellulose runs about R-3.2 to R-3.8 per inch and loose fill fiberglass about R-2.2 to R-2.7 [2]. So R-49 is roughly 13 to 15 inches of cellulose, or 18 to 22 inches of blown fiberglass. ENERGY STAR's own rule of thumb for an attic check is cellulose at 3.7 times the depth and loose fiberglass at 2.5 times the depth [3].
New homes and old homes
For new homes, Ohio's code is the 2019 Residential Code of Ohio [4], and it calls for R-49 in ceilings in both of Ohio's climate zones [5]. The newer 2021 model energy code raises that to R-60 [6]; Ohio has not adopted it. A house that is already built does not have to be brought up to new-home code: Unaltered portions of the existing building or building supply system shall not be required to comply with this chapter
[5]. It is still the right target.
What we see around here
A lot of older homes in Central and Southeast Ohio have about 4 inches in the attic. That is roughly R-11. We measure what is there before we price anything, and we bring it up to the target with blown fiberglass or cellulose. How we do attics.
More questions
How many inches is R-49?
Roughly 13 to 15 inches of settled cellulose, or 18 to 22 inches of loose fill fiberglass, based on the DOE's R-per-inch ranges.
Sources
- ENERGY STAR. Recommended Home Insulation R-Values.
- U.S. Department of Energy, Building America Solution Center. Loose-Fill Insulation.
- ENERGY STAR. What to Look For: DIY Checks and Inspections.
- International Code Council. Ohio code listing: 2019 Residential Code of Ohio, 2018 IRC amended, effective July 1, 2019.
- Ohio Board of Building Standards. Residential Code of Ohio, Chapter 11 Energy Efficiency (rule 4101:8-11-01, effective July 1, 2019), Tables 1101.7 and 1102.1.2.
- International Code Council. 2021 International Energy Conservation Code, Chapter 4, Table R402.1.3.