Insulation resists heat flow, and its performance is rated as R-value — higher is better. The two keys to getting the rated value are choosing the right R for the location and installing it without gaps or compression.
Target R-values
General ranges; climate and code vary — check your climate zone.
| Location | Typical R-value |
|---|---|
| Attic | R-38 to R-60 |
| Exterior walls | R-13 to R-21 |
| Floors over unconditioned space | R-25 to R-30 |
Installation
Cut batts to fit snugly between studs or joists without crushing them; compressed insulation loses R-value. Fit carefully around wiring and boxes rather than smashing the batt over them. With faced batts, the facing goes toward the conditioned (warm-in-winter) side in most climates — and never double up vapor barriers, which traps moisture.
Frequently asked questions
What R-value do I need? Roughly R-38+ in attics and R-13–21 in walls; confirm with local code.
Which way does the paper facing go? Toward the heated living space in most climates.
Does compressing insulation matter? Yes — squashing a batt reduces its R-value.
Wear a respirator, gloves, and long sleeves when handling fiberglass or mineral wool, since the fibers irritate skin and lungs. And don’t block soffit vents in the attic — fit baffles to keep airflow, or you’ll trap moisture and risk mold despite the added insulation.