What You Need to Know: Insulation and R factors
There are several types of insulation with various “R” values and prices. Some are easy to install yourself; others may require a contractor or special equipment.
| Insulating material | “R” value per inch | |
| Batt & Blanket |
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Mineral wool | R—3.15 to 3.85 |
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Fiberglass | R—3.15 to 3.85 |
| Loose Fill (Pour in) |
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Mineral Wool | R—2.88 to 3.31 |
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Fiberglass | R—2.88 to 3.31 |
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Cellulose Fiber | R—3.70 |
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Vermiculite (Expanded) | R—2.13 to 2.27 |
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Perlite (Expanded) | R—2.70 |
| Rigid Insulation |
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Expanded Polystyrene Extruded Plain (Styrofoam) T.M. | R—5.00 |
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Expanded Polystyrene (Beadboard) | R—3.57 |
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Expanded Polyurethane (Foam) | R—6.25 |
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Fiberglass (rigid board) | R—5.00 |
NOTE: To assure fire safety, rigid insulation should be covered with 1/2″ gypsum wallboard when installed.
No matter what kind of insulation you buy, be sure it meets federal standards for fire and vermin resistance. Check for approval codes listed on the packaging.
The list below tells you which places in your home need insulation. An unconditioned space is an area with no heat or air conditioning; a conditioned space is heated in winter and air conditioned in summer.
| Where to insulate a home | How much |
| 1. Ceilings with unconditioned spaces above | R—38 to 44 |
| 2. “Knee” walls of a finished or conditioned attic | Between studs R—11 |
| 3. Exterior walls or walls between conditioned and unconditioned spaces | R—19 (New Constr.) |
| 4. Floors over unconditioned or outside spaces | R—19 |
| 5. Perimeter of a concrete floor slab close to grade level | High R sheathing on the outside |
| 6. Walls of finished or conditioned basement | R—11 to R—13 |
| 7. Top of foundation or basement wall. (Rim joist or band joist) | Fill with fiberglass batts |
| 8. Sloping rafters—Leave an air space for ventilation between the insulation and the roof deck. Select insulation thickness accordingly. | R—11 (2″ x 4″) R—19 (2″ x 6″) |
And don’t forget…
- Add insulation to your attic door.
- Wrap insulation around heating and air conditioning ducts which pass through unconditioned spaces.
- Wrap hot water pipes with insulated pipe wrap.
- Add insulation to foundation wall.
- Seal bypass areas.
Installing insulation
- Do not block soffit vents with insulation.
- Provide a 3-inch clearance around heat-producing fixtures such as recessed ceiling lights.
- Watch for nails that stick through the roof sheathing above your head.
- Wear work gloves, loose-fitting clothing and a long-sleeved shirt to avoid skin irritation; wear a mask to prevent inhaling insulation particles.
Besides insulating, caulking and weather-stripping, a very important step in weatherizing your home is finding and sealing bypasses.
A bypass is any hole, crack or crevice that allows conditioned air to leak through your home’s insulation. Bypasses are found in interior and exterior walls, around vent pipes, recessed light fixtures, plumbing and electrical wire passages, and chimneys. Seal bypasses before insulating; if your attic is already insulated or floored, you may have to remove insulation or floor boards to plug the bypasses. If bypasses are not sealed the insulation only “filters” the warm air on its way to the attic, and your roof will still be warm, and will possibly develop ice dams.
Source: McCool’s Property Inspection
