(1) Always consult the manufacturer's recommendations for applications, because specific products may deviate from these nominal thicknesses.
(2) Rigid cellular insulating boards provide high R-values for a given thickness. Various thicknesses are available; 1-inch-thick boards can have the nominal R-values.
Insulating Board Type R-value for 1-inch
- Polystrene Expanded
- Polyisocyanurate and Polyurethane
Always consult manufacturer's recommendations for applications, since specific R-values depend on foam density and aging.
(3) Two blankets or batts may be needed for R-values above 30.
(4) Failure to install both proper thickness and density will result in reduced R-value. An increased initial installed thickness may be required to offset any decreases in R-values due to thickness changes after installation.
(5) These are initial thicknesses to allow for a nominal 20 percent thickness decrease after installation.
EXAMPLES OF WHERE TO INSULATE
- In unfinished attic spaces, insulate between the ceiling joists to seal off living spaces below.*
- In finished attic rooms with our without dormers, insulate:
- a. between the studs of "knee" walls,
- b. between the studs and rafters of exterior walls, and
- c. ceilings with cold spaces above.
- All exterior walls, including:
- a. walls between living spaces and unheated garages or storage areas,
- b. foundation walls above ground level, and ,
- c. foundation walls in heated basements (foundation can be insulated on inside or outside of wall).
- Floors above cold spaces, such as vented crawl spaces and unheated garages, and:
- a. any portion of the floor in a room that is cantilevered beyond the exterior wall below,
- b. slab floors built directly on the ground,** and
- c. foundation walls of crawl spaces and perimeter plates.
- d. Add storm windows as recommended.
*Well-insulated attics, crawl spaces, storage areas, and other closed cavities should be adequately ventilated to prevent excessive moisture buildup.
**Slab on grade is almost always insulated, in accordance with building codes, when the house is constructed.
Used with Permission of: Lincoln Electric System,
Copyright © 1998 Lincoln Electric System. All rights reserved.
Experts | Email Us | Disclaimer | HandymanWire homeCopyright ©1999-2016, Handyman USA LLC.
Articles | We welcome your feedback. | Privacy
your resource for advice on home improvement and repairs.
All rights reserved.