Proper Insulation Location in Buildings
InspectAPedia® -
What is the the best location to place building insulation for heating & cooling energy savings and construction cost savings
Cape-style building roof & attic knee wall insulation advice
Crawl space insulation placement advice, & basement insulation advice
Insulation advice for attached building spaces such as mud rooms & Insulation advice for sunspaces
Insulation advice for interior walls, stairs, plumbing fixtures
What is the proper insulation placement for basements, mudroom insulation, insulation for sunspaces, and insulation for "interior bumps" or discontinuities in buildings such as stairways, cabinets, kitchen soffits, or plumbing chaseways
Questions & answers about the proper locations for insulation in buildings
Building insulation location & placement: this article describes the optimum placement of building insulation for various building designs, problem spots, and hard-to-insulate or hard-to-ventilate building spaces.
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.
This article explains that the location of building insulation is as important as its quantity. Sketch at page top and accompanying text are reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
Where to Insulate Buildings - just where should insulation be placed?
This article explains the best options for insulating Cape-style homes, showing the heating and energy savings that come from proper placement of the building insulation. Next the article discusses the best placement for insulation in crawl spaces.
We add cautions about mold, moisture traps, and termite damage in crawl spaces depending on how insulation is installed.
Insulation Advice for Cape Style Homes
In the Cape-style under-roof insulation and ventilation plan suggested in this article and illustrated at page top, insulation location shown as option (B) at the right side of the sketch is the preferred insulation placement for a Cape-Cod home because
Less total insulation is required
The installation is easier
A larger area of heated floor space is provided.
The building heating costs will be less because there is less surface area through which heat may escape to cold spaces or to outdoors. Building and insulating knee walls (option (A) at page top) requires a larger insulated area so it is actually more costly to heat a building with this design.
But in any under-roof insulation scheme beware of these common Cape Cod insulation problems:
Under-roof ventilation: be sure to provide an adequate eaves-to-ridge air path as well as actual soffit intake and ridge outlet vent openings. See ATTIC VENTILATION and see ROOF VENTILATION SPECIFICATIONS for details. If you don't think roof venting is needed, see ROOF VENTING NEEDED?
Air leaks that defeat the building insulation scheme - see FRAMING DETAILS for BETTER INSULATION for details of how to avoid air leaks in buildings of this design
Insulation Advice for Crawl Spaces
Crawlspaces are common in homes in the southeastern U.S. as well as in some west coast cities such as Los Angeles. Crawl spaces are a breeding ground for wood decay and mold because they combine a mixture of moisture, wood, and warmth. As Mr. Bliss points out in part 1 of the article above, less insulation will be required to insulate the crawl space walls and building rim joist than to insulate under the floors.
In cold climates insulating the floor may also require extra insulation on plumbing to protect it from freezing in the colder crawl area. In warm weather insulating the floor loses the cooling effect of its location over the cooler ground surface.
In the crawl space insulation detail (sketch at left), beware of:
Crawl space moisture problems: contemporary best building practices call for installation of a 6-mil poly vapor barrier over dirt floors of crawl spaces; run the poly at least part-way up the foundation wall sufficient to cover the portion of the wall that is below-grade.
Crawl space ventilation does not necessarily reduce crawl space moisture levels and in some weather conditions it can actually increase crawl space moisture, condensation, and mold risks. That's why modern best construction practice converts crawl spaces from the old "vented" design to new "closed, conditioned space". Just be sure to also identify and correct roof drainage or surface runoff problems that are sending water into the crawl area.
Watch out: Hidden termite damage to the building - we have found termites and on occasion other wood destroying insects attacking the building sills, rim joist, and floor framing when the poly vapor barrier and insulation extend from the floor to the building wooden sills. Insulation provides a hidden path from soil top into the wood framing. In the sketch, the use of poly under the insulation reduces but does not eliminate this risk.
Additional links to articles on good crawl space design and solving crawl space problems are provided below.
Insulation Advice for Full Basements
Mr. Bliss prefers insulation on the basement interior for the same reason that apply to crawl spaces, including avoiding frozen pipes. He suggests using a section of rigid foam insulation to separate off hard-to-insulate basement locations such as steel bulkhead basement walkout doors.
Our photograph (left) shows styrofoam insulating foam board used on the inside of a basement foundation wall.
We prefer to use solid foam insulation in any below-grade location that is at risk of period high moisture, because our field and lab work have shown up frequent hidden toxic mold reservoirs in fiberglass insulation that has been used in those locations. See Mold in Fiberglass Insulation for details.
Insulation Advice for Mudrooms
In the articles above, the author suggests that attached spaces such as mudrooms that get frequent use should be inside the building's thermal envelope. If a mudroom is excluded from the building envelope of conditioned space (heated, dried, or seasonally cooled and dehumidified), there is an increased risk of mold since the rooms receive household moisture but little heat.
If the mudroom or airlock entry space is used rarely, such as an enclosed porch, you can go either way - insulating it or not, but if an attached room on a house is left unheated, be sure that it is also isolated from the home's moisture by proper placement of vapor barriers.
Insulation Advice for Sunspaces
Mr. Bliss points out that sunspaces are always insulated from the outdoors, but asks "... should they be insulated from the house?"
In climates that have frequent periods of cold and cloudy weather, it's a good idea to insulate and seal between the sunspace and the house - assuming that you are not trying to keep heat in the sunspace to keep plants alive through cold weather. If plants are being maintained in a sunspace you may need to heat that area as well.
Insulation between the house and the sunspace can be less than that in other house walls facing directly outdoors because of the buffering effect of the sunspace. But the air space between the sunspace and the house should be tight to keep greenhouse moisture from entering and causing mold or other problems in the main building.
In sunny climates that can keep the sunspace mass warm all winter, uninsulated walls between the sunspace and the main building are fine. Night insulation is a good idea for these sunspaces since the sunspace glass is part of the thermal envelope.
Insulation Tips for Stairwells and Other Interior Discontinuities or "Bumps" in a House
Interior walls, built-in cabinets, stairs, and plumbing fixtures can disrupt the continuity of the building's thermal envelope or shell. Good planning during construction can avoid these problems by making sure that insulation and vapor barriers are properly placed. In retrofits to older buildings it's not so easy, Mr. Bliss notes.
For insulation retrofit on older buildings don't forget to watch for, evaluate, and if appropriate open and insulate these areas. A common example that we see on older homes is the failure to insulate below attic stairs whose ceiling is exposed to the otherwise heated and insulated main area of the home.
In our attic stairwell photo (left) the house exterior wall and the area underneath the stairs themselves were uninsulated, leaking heat out of this home.
Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
Original Solar Age Magazine Article on Building Insulation for Various Building Designs
"Where to insulate: the location of building insulation is as important as its quantity" - links to the original article in PDF form immediately below are followed by an expanded/updated online version of this article.
Where to Insulate in Cape Cod style homes & where to Insulate in crawl spaces - PDF form, use your browser's back button to return to this page
Where to Insulate - PDF form, part 2 addresses basement insulation, mudroom insulation, insulation for sunspaces, and insulation for "interior bumps" or discontinuities in buildings such as stairways, cabinets, kitchen soffits, or plumbing chaseways.
Questions & Answers regarding this article
Questions & answers about the proper locations for insulation in buildings
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years.
ASES leads national efforts to increase the use of solar energy, energy efficiency and other sustainable technologies in the U.S. We publish the award-winning SOLAR TODAY magazine, organize and present the ASES National Solar Conference and lead the ASES National Solar Tour – the largest grassroots solar event in the world."
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
Excerpts with updates and annotations expanding the original Best Practices Guide text can be found in the online review and book summary at BEST CONSTRUCTION PRACTICES GUIDE and also at DECK & PORCH CONSTRUCTION, at INDOOR AIR QUALITY IMPROVEMENT GUIDE, and in other articles found at InspectAPedia.com such as HOUSEWRAP AIR & VAPOR BARRIERS, SOUND CONTROL in buildings, and other topics.
ASHRAE resource on dew point and wall condensation - see the ASHRAE Fundamentals Handbook, available in many libraries. The following three ASHRAE Handbooks are also available at the InspectAPedia bookstore in the third page of our Insulate-Ventilate section:
2005 ASHRAE Handbook : Fundamentals : Inch-Pound Edition (2005 ASHRAE HANDBOOK : Fundamentals : I-P Edition) (Hardcover), Thomas H. Kuehn (Contributor), R. J. Couvillion (Contributor), John W. Coleman (Contributor), Narasipur Suryanarayana (Contributor), Zahid Ayub (Contributor), Robert Parsons (Author), ISBN-10: 1931862702 or ISBN-13: 978-1931862707
2004 ASHRAE Handbook : Heating, Ventilating, and Air-Conditioning: Systems and Equipment : Inch-Pound Edition (2004 ASHRAE Handbook : HVAC Systems and Equipment : I-P Edition) (Hardcover)
by American Society of Heating, ISBN-10: 1931862478 or ISBN-13: 978-1931862479
"2004 ASHRAE Handbook - HVAC Systems and Equipment The 2004 ASHRAE HandbookHVAC Systems and Equipment discusses various common systems and the equipment (components or assemblies) that comprise them, and describes features and differences. This information helps system designers and operators in selecting and using equipment. Major sections include Air-Conditioning and Heating Systems (chapters on system analysis and selection, air distribution, in-room terminal systems, centralized and decentralized systems, heat pumps, panel heating and cooling, cogeneration and engine-driven systems, heat recovery, steam and hydronic systems, district systems, small forced-air systems, infrared radiant heating, and water heating); Air-Handling Equipment (chapters on duct construction, air distribution, fans, coils, evaporative air-coolers, humidifiers, mechanical and desiccant dehumidification, air cleaners, industrial gas cleaning and air pollution control); Heating Equipment (chapters on automatic fuel-burning equipment, boilers, furnaces, in-space heaters, chimneys and flue vent systems, unit heaters, makeup air units, radiators, and solar equipment); General Components (chapters on compressors, condensers, cooling towers, liquid coolers, liquid-chilling systems, centrifugal pumps, motors and drives, pipes and fittings, valves, heat exchangers, and energy recovery equipment); and Unitary Equipment (chapters on air conditioners and heat pumps, room air conditioners and packaged terminal equipment, and a new chapter on mechanical dehumidifiers and heat pipes)."
1996 Ashrae Handbook Heating, Ventilating, and Air-Conditioning Systems and Equipment: Inch-Pound Edition (Hardcover), ISBN-10: 1883413346 or ISBN-13: 978-1883413347 ,
"The 1996 HVAC Systems and Equipment Handbook is the result of ASHRAE's continuing effort to update, expand and reorganize the Handbook Series. Over a third of the book has been revised and augmented with new chapters on hydronic heating and cooling systems design; fans; unit ventilator; unit heaters; and makeup air units. Extensive changes have been added to chapters on panel heating and cooling; cogeneration systems and engine and turbine drives; applied heat pump and heat recovery systems; humidifiers; desiccant dehumidification and pressure drying equipment, air-heating coils; chimney, gas vent, fireplace systems; cooling towers; centrifugal pumps; and air-to-air energy recovery. Separate I-P and SI editions."
Principles of Heating, Ventilating, And Air Conditioning: A textbook with Design Data Based on 2005 AShrae Handbook - Fundamentals (Hardcover), Harry J., Jr. Sauer (Author), Ronald H. Howell, ISBN-10: 1931862923 or ISBN-13: 978-1931862929
Energy Savers: Whole House Systems Approach to Energy Efficient Home Design [copy on file as /interiors/Whole_House_Energy_Efficiency_DOE.pdf ] - U.S. Department of Energy
"Energy Savers: Whole-House Supply Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Supply_Vent.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
"Energy Savers: Whole-House Exhaust Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Exhaust.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
"Energy Savers: Ventilation [copy on file as /interiors/Energy_Savers_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Natural Ventilation [copy on file as /interiors/Energy_Savers_Natural_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Energy Recovery Ventilation Systems [copy on file as /interiors/Energy_Savers_Energy_Recovery_Venting.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
"Energy Savers: Detecting Air Leaks [copy on file as /interiors/Energy_Savers_Detect_Air_Leaks.pdf ] - ", U.S. Department of Energy
"Energy Savers: Air Sealing [copy on file as/interiors/Energy_Savers_Air_Sealing_1.pdf ] - ", U.S. Department of Energy
"Insulation: Adding Insulation to an Existing Home [copy on file as/interiors/Insulation_Adding_DOE.pdf ] - ," U.S. Department of Energy - tips on how to do your own check for the presence of absence of insulation in a home
Insulation: Selecting Insulation for New Home Construction [copy on file as /interiors/New_Home_Insulation_DOE.pdf ] - , U.S. Department of Energy - "Your state and local building codes probably include minimum insulation requirements, but to build an energy-efficient home, you may need or want to exceed them. For maximum energy efficiency, you should also consider the interaction between the insulation and other building components. This is called the
"whole-house systems design approach." [copy on file as /interiors/Whole_House_Energy_Efficiency_DOE.pdf ] -
"Insulation Types [copy on file as /interiors/Insulation_Types_DOE.pdf ] - ",
table of common building insulation properties from U.S. DOE. Readers should see INSULATION R-Values & Properties our own table of insulation properties that includes links to articles describing each insulation material in more detail.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.
Asbestos products and their history and use in various building materials such as asphalt and vinyl flooring includes discussion which draws on Asbestos, Its Industrial Applications, D.V. Rosato, engineering consultant, Newton, MA, Reinhold Publishing, 1959 Library of Congress Catalog Card No.: 59-12535 (out of print).
The National Institute of Standards and Technology, NIST (nee National Bureau of Standards NBS) is a US government agency - see www.nist.gov
"A Parametric Study of Wall Moisture Contents Using a Revised Variable Indoor Relative Humidity Version of the "Moist" Transient Heat and Moisture Transfer Model [copy on file as/interiors/MOIST_Model_NIST_b95074.pdf ] - ", George Tsongas, Doug Burch, Carolyn Roos, Malcom Cunningham; this paper describes software and the prediction of wall moisture contents. - PDF Document from NIS
"Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
Mobile View
