INSULATION: |
Consistent, well-installed insulation throughout a house - combined with a continuous and effective air barrier - keeps you and your house warmer in the winter and cooler in the summer. The effectiveness of any insulation is described in terms of its R-value. The higher the R-value, the lower the heat loss (in winter) or heat gain (in summer). There are many insulation choices to consider. The type and amount of insulation you choose will depend on the particulars of your house and your budget. Please note that insulation must be installed to the manufacturer's specifications and per local fire code. |
MINIMUM RECOMMENDED R-VALUES FOR TYPICAL VERMONT HOMES: |
Flat Attics |
R-38 (12" of blown-in or poured cellulose, fiberglass batts or fiberglass loose fill) |
Ceiling Slopes/Cathedral Ceilings |
R-30 (9" of fiberglass or cellulose) |
Walls, Including Wood-Framed Basement Walls |
R-19 (5.5" of fiberglass or cellulose) |
Foundation Walls |
R-10 (2" of foam board, for cement or cinderblock walls, or spray foam for the inside of uneven surfaces like stone) |
Determining The Depth of Existing Insulation: |
If you want to determine the depth of insulation already in your attic, use a tape measure to probe in a number of locations. Wear a high quality dust mask or respirator while doing this. To check for insulation in your exterior walls, find a hole or gap in the drywall. Then insert a nonmetallic probe (a bamboo skewer works well) in the gap as a measuring stick. Insulation will make it harder to move the probe around in the gap. |
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Proper installation is key. Poor installation of insulation can compromise R-value and lower its performance by as much as 50%. A good installation covers a surface completely and to a consistent depth. Look in attics and in walls and ceilings before installing drywall to see that insulation is placed tightly around all obstacles (such as electrical wires, boxes and plumbing), without any gaps, folds or wrinkles. |
TYPES OF INSULATION
Fiberglass
R-value: 2.5 to 3.5 per inch.
Available Forms:
Batts (with or without paper or reflective facing) or loose fill.
Characteristics:
Easy to install but ineffective at blocking air leakage. Performance is very dependent on the quality of the installation. Batts are intended for use in cavities that conform to exact batt widths. Loose fill, which can be poured or blown in by machine, tends to perform poorly in open attics because it is very susceptible to air movement.
Rigid Fiberglass Board
R-value: 4 per inch.
Available Forms:
Foundation insulation system or duct board.
Characteristics:
Effective at blocking air leakage if properly fitted. Very permeable to water vapor.
Cellulose
R-value: 3.2 to 3.8 per inch
Available Forms:
Loose fill manufactured from wood-based fibers, such as newspapers, and treated to resist fire, pests and (in some cases) mold.
Characteristics:
Very effective at blocking air leakage when installed at high density (3.5 pounds per cubic foot) in enclosed spaces such as wall cavities. Better than fiberglass for spaces of irregular dimensions. Cellulose has a high recycled material content. Cellulose is blown or poured into cavities or open attics. It can be damp-sprayed into wall cavities before drywall is installed.
Foam Board
R-value: 4 to 6 per inch, depending on type used.
Available Forms:
2' x 8' or 4' x 8' sheets, with and without facing (foil or paper).
Characteristics:
Very good air barrier and insulator when properly installed. Closed cell foam board resists penetration by water and water vapor and is an excellent choice for insulating foundations. Boards with foil facings are effective vapor barriers. All types should be properly caulked or taped around the edges and at seams. They also should be protected from ultraviolet light and physical damage.
Spray Foam
R-value: 3.5 per inch for open cell or 6.5 per inch for closed cell.
Available Forms:
Open- or closed-cell expanding foam material.
Characteristics:
Very good air barrier and insulator. Closed cell spray foams are good vapor barriers, have very strong adhesion properties, and conform very well to irregularities within framing cavities, and are ideal for use on stone foundations. Spray foams require specialized installation equipment. They also should be protected from ultraviolet light and physical damage.
| R-value/Inch | Density lb/ft3 | Air | Vapor | |||||
| Insulation Type | Low | High | Low | High | Barrier | Permeable | ||
| Cavity Materials | ||||||||
| Fiberglass | ||||||||
batts | 3.2 | - | 3.8 | no | very | |||
loose-fill | 2.2 | - | 2.9 | 0.5 | - | 1.0 | no | very |
| Cellulose | ||||||||
loose-fill | 3.1 | - | 3.7 | no | very | |||
dense-pack | 3.2 | 3.5 | semi | very | ||||
moist-spray | 3.4 | - | 3.7 | 2.8 | - | 3.8 | semi | very |
| Closed-Cell Foam | ||||||||
Corbond II | 7.3 | yes | no | |||||
| Open-Cell Foam | ||||||||
Icynene pour fill | 4.0 | yes | yes | |||||
Icynene spray | 3.6 | yes | yes | |||||
Sealection 500 | 3.6 | yes | yes | |||||
| Air Krete | 2.5 | - | 3.9 | 6.86 | - | 2.07 | yes | yes |
| Board Stock | ||||||||
expanded polystyrene | 3.8 | - | 4.4 | yes | semi | |||
extruded polystyrene | - | 5 | yes | semi | ||||
polyisocyanurate (foil-faced) | 7 | - | 7.5 | yes | no | |||
