Some types of insulation systems offer benefits in addition to their R-value that can make a real difference in overall energy efficiency. These properties should be factored into your cost-benefit comparison.
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Kraft paper on fiberglass batts provides a vapor retarder that adapts to the seasons, which is advantageous in mixed climates.
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Loose-fill insulations provide good coverage without the extra efforts of slicing to fit around wiring or plumbing and trimming to fill gaps and voids.
- Blown-in-blanket (BIB) is a loose-fill material held in place (in walls or cathedral ceilings) by netting, providing good coverage in irregular spaces and nooks and around obstructions.
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High-density damp spray cellulose in walls and attics provides good coverage like other loose fill products, allows less air flow through the insulation so it retains its rated R-value, increases the water storage buffer capacity of the wall and provides sound insulation. Its borate fire retardant and also has insect- and fungi-resistant properties.
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Rigid foam can be used as exterior sheathing in SIPS,ISPS, ICF and other systems. It provides high R-value per inch, full coverage without gaps or compressions, a vapor retarder that can adapt to the seasons (see Durable/Moisture Control segment) and, when sealed, an air flow retarder. Rigid foams (especially closed cell extruded polystyrene) can withstand being submerged in water and are well suited to wall assemblies designed to be cleaned and not need replacement in the event of flooding.
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Spray foams create very effective air sealing, which can justify the higher cost. They are especially well suited to insulate and air seal unvented conditioned attics, band joists, irregular and hard-to-access spaces, holes and voids. High-density (closed-cell) foam is especially flood-resistant. It can be used to partially fill wall cavities to achieve R-13 or higher while allowing air space to drain, flush and dry wall cavities after flooding without need for replacement (with flood-resistant exterior sheathing and interior wallboard).
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