A Builder’s Guide to Residential Foundation Insulation Basement Heat Loss Basement Condensation 54% Warm moist late Spring Heat Loss/Lineal Foot/Year 1ft. Basement air humidity and Summer air (conditioned basement) increases as a result humid 16% 2ft. outdoor air and soil Southeast Kansas moisture migration (Parsons) o 60 % 9% 3ft. 67 76,000 Btu Warm air flowing over Deeper soils remain cold from winter, cooling 7% 4ft. cool wall condenses Central Kansas uninsulated basement 50 % (Liberal to Kansas City) moisture producing walls o 5% 5ft. 97,000 Btu damp basement 63 40 % 4% 6ft. Northwest Kansas Water vapor in soil (Goodland) migrates to warmer air 3% 7ft. if damp proofing or 59 o 30 % 111,000 Btu vapor retarder fail 3% 8ft. 20 % 10 % 56 o Uninsulated Foundations Loose a Lot of Energy Uninsulated Foundations Cause Condensation Foundation Insulation Uninsulated Basement Annual Energy Costs Savings Wall Condensation 1 60 59 2 F o 58 As little as R-2 insulation 3 57 can essentially eliminate Slab-on-Grade 56 the risk of condensation 1 55 2 54 3 53 52 Crawl Space 51 Climate Zone 1 50 2 49 3 Ground Temperature, 48 Basement 64 66 68 70 72 74 o $0.00 $0.50 $1.00 $1.50 $2.00 $2.50 $3.00 Basement Air Temperature, F $/Lineal Foot/Year 70 % Rh 80 % Rh Minimum R-value Preferred R-value Foundation Insulation Heating Cost Savings Foundations Insulation Cuts Moisture Problems A wide variety of foam boards are well suited to foundation insulation. A Builder’s Guide to Residential Foundation Insulation Glass and mineral fiber batts of many configurations can be used Prepared for: on the interior of basement and Kansas Corporation Commission crawl space walls. Blown cellulose between furing Energy Programs strips. SW Arrowhead Road Topeka, Kansas 66604 785-271-3349 Foundation Insulation Jim Ploger, Energy Program Manager Prepared by: Joseph E. King, AIA Coriolis architecture energy 123 West 8th Street Lawrence, Kansas 66044 Polystyrene foam held in place with duct tape and cap flashing until 785-841-1906 backfill is complete. Gene Meyer, PE Engineering Extension Service Kansas State University Ward Hall Manhattan, Kansas 66506 785-532-4994 Wrapped batts are easily installed Fiberglass batts stapled to furring in crawl spaces. Fall 1999 studs. Installation Methods Disclaimer: This report was prepared by Coriolis and Kansas State University (KSU) as an account of work sponsored by the Kansas Corporation Commission (KCC). Neither the KCC, Coriolis, nor KSU, nor any person acting on their behalf: a) P makes any warranty, express or implied, with respect to the use of any information, apparatus, method, or process disclosed in this report or that such use may not infringe privately owned rights; or b) assumes any liabilities with respect to the use of, or damages resulting from the use of, any information, apparatus, method, or process disclosed in this report or its appendices. Prepainted sheet metal roll stock C matches siding, serves as termite This material was prepared with the support of the U. S. Department of Energy shield, and protects exterior foam (DOE) Grant No. DE-FG48-97R802102. However, any opinions, findings, from damage. conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the views of DOE. Acknowlegements: We greatly appreciate the support and encouragement of Jim Ploger, Director of Energy Programs at the Kansas Corporation Commission, and Steve Palomo of the U. S. Department of Energy’s Denver Regional Office. Cement board nailed to plate protects exterior foam from damage. Stucco over rigid foam board. Insulation Protection Residential Foundation Insulation The Purpose of a Building’s A team of building scientists at Oak < concrete foundation walls enclosing Foundation Ridge National Laboratory conducted a basements must be dampproofed with a comprehensive investigation of the bituminous material from the footing to Vitruvius set forth building design grade, impact of residential foundation guidelines in 1st century B.C. Greece, insulation practices. In The Building < masonry foundation walls enclosing stating that “Durability will be assured Foundation Design Handbook that basements must be parged with portland when foundations are carried down to cement prior to dampproofing, resulted, they concluded, “an the solid ground and materials wisely uninsulated basement may represent up < foundation walls of habitable rooms and liberally selected...,” a concept that below grade must be waterproofed, to 50% of the heat loss in a remains just as valid as we enter the 21st tightly-sealed house that is well < exterior foundation insulation must be century. insulated above grade.” protected from weathering, sunlight, and Foundations connect a building to the physical abuse, ground structurally, transferring the Kansas Residential Energy < all foam plastic exposed to the interior weight of the building to stable soil. A Disclosure and the Model must have a maximum flame spread rating of 75 and a maximum smoke- properly designed and constructed Energy Code developed rating of 450 (ASTM E-84) foundation insures a building endures The Energy Policy Act of 1992 strongly and shall be covered with a ½” gypsum seasonal changes in temperature and encouraged states to upgrade their wall board or equivalent thermal barrier. moisture with little movement. residential building energy standards to These requirements and all other health Foundations also connect a building to require efficiency levels at least equal to and safety requirements of codes the ground thermally. the Model Energy Code. In response, adopted by local jurisdictions prevail < The common statement that “soil the 1997 Kansas legislature required all over the MEC and any suggestions in temperatures are constant and therefore new homes have a disclosure form this guide. below grade insulation is of little value” itemizing their energy performance is not correct. features, or stating the home complies Benefits of Foundation < Unless geothermal heat is present, the with the Model Energy Code (MEC). Insulation heat that comes from deep in the earth is Compliance with MEC provides a insignificant compared to the flow of Insulating a home’s foundation offers solar energy at the junction of the air and home buyer with assurance that the many benefits. the ground. home has an integrated set of energy < Foundation heat loss can be reduced features meeting significantly and space heating costs can minimum stand- be reduced as much as 50% in an ards, and it almost otherwise well insulated home. always requires < Insulation improves foundation moisture foundation insula- control and indoor air quality. Insulation tion. This guide is on either side of the wall results in a intended to provide warmer interior surface, reducing the home builders and potential for condensation and associated mold growth that reduces indoor air home buyers with quality and can cause material damage. concise information < The warmer surface also results in a more on available foun- comfortable space, not only in the dation insulation basement, but also the floor above. materials, installa- < Exterior insulation provides protection tion details and for dampproofing or waterproofing, methods, installa- extending their life. tion costs, and These benefits are evaluated in detail in Soil Temperature Change with Depth and Season benefits. the following sections. Foundation Foundation Heat Loss < While the earth is often thought of as a Building Code Requirements stable temperature mass, soil Soil can hold a great deal of thermal temperatures at depths less than eight Several requirements of the widely energy, particularly if damp, but it is not feet vary considerably during the year. adopted CABO One and Two Family The graph above shows how soil a good insulator. Depending on soil temperature varies with depth and season Dwelling Code affect foundation type,7-11feet of soil would be from both ground water and mean air insulation: required to provide the same insulation temperature which ranges from 56o in < drains are required around all concrete as two inches of foam or three inches of o northwest Kansas to 62 in the southeast. and masonry foundations enclosing fiberglass insulation. Uninsulated habitable or usable space below grade, 1 Residential Foundation Insulation basement walls loose the most heat below shows three widely recognized such as windows, walls, or attic where exposed to winter air above Kansas climate zones. insulation, to offset lower performance grade and at shallow depths where the The table below shows typical net in another area, such as foundation ground is annual heat loss, in Btu per lineal foot of insulation. often frozen. foundation, for the three major founda- MEC Minimum R-Value Floors above tion types in the three climate zones. crawl spaces Zone 1 Zone 2 Zone 3 can be Kansas Climate Zone Full 10 10 8 insulated but 123Basment are often not Full Crawl 16 16 10 to prevent Basment 111,000 97,000 76,000 Space pipes in the Basement Heat Loss Crawl Slab-on- 5 5 5 crawl space 47,000 41,000 32,000 from freezing. Heat passing from the Space Grade (min. 4 ft) (min. 2 ft) (min. 2 ft) floor into the crawl space is lost through Slab-on- 60,000 52,000 40,000 Foundation Insulation R-values the foundation wall similar to base- Grade ments. (MEC prescriptive minimum) Annual Foundation Heat Loss For a more detailed evaluation of such Slab-on- (Btu per lineal foot per year) grade floors trade-offs investigate the MECcheckä wick con- Potential Cost Savings software developed by Pacific Northwest National Laboratory for the siderable While foundation insulation has many heat to the U. S. Department of Energy. This easy benefits, the principal criteria for to use software is available from the exposed determining how much should be slab edge Kansas State University Engineering installed is the economic value of Extension Service (785-532-4994) or it often result- energy savings.