Is it Necessary to Insulate Under a Slab in a Superinsulated House?
- INSULATION LOCATION & EXTENT for SLABS - CONTENTS: Here we answer the question: do I need to insulate under my basement slab in a super-insulated house?Do we insulated just the slab perimeter or the whole floor? Can we use uninsulated floor slabs to help with cooling? Critical insulation under radiant floors & passive solar floors. Advice for building insulation priorities
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
Slab insulation placement guide:
Tthis article discusses the question of insulating under a basement floor slab, and just where is the optimum placement of basement insulation.
This article explains that the location of building insulation is as important as its quantity. Sketch at page top is courtesy of Carson Dunlop Associates.
Green links show where you are. © Copyright 2015 InspectApedia.com, All Rights Reserved.
Floor Slab Insulation Advice for Well-Insulated Homes
Insulation Advice for Full Basements - Do We Need to Insulate Under the Basement Floor?
The accompanying text is adapted and expanded from the original article with permission from Solar Age Magazine - editor Steven Bliss.
Is it necessary to insulate under a slab in a superinsulated house? I assume an uninsulated slab would help cool the house in summer. -- William Lee, Cave Creerk AZ
Experts [in 1985] did not agree as to whether or how much to insulated below a slab. It is most important to insulated the perimeter of a slab down to the bottom of the footing.
Second most important [to insulating the slab perimeter down below the frost line] is to insulate under the first few feet around the edge of the slab.
In [moderate] climates where cooling as well as heating is an issue, it may be best to insulate only the perimeter and leave the underslab uninsulated, as you suggested, for cooling.
Full insulation is indeed recommended under the slab in some situations.
These include radiant heat delivery
See RADIANT HEAT FLOOR MISTAKES
or passive solar storage
See INSULATION LOCATION for PASSIVE SOLAR FLOOR SLAB
Also, if wood flooring or carpeting isn't planned, underslab insulations will make the floor feel warmer to bare feet.
See FLOOR, CONCRETE SLAB CHOICES.
And if your concrete floor is a "floating slab" without below-frost-line footings, such as our thoughtless contractor installed in Northern Minnesota, insulation under the entire slab may be critical to avoid pumping most of your heat into the ground during the heating season.
If you are installing a radiant heat basement floor system, insulation under the floor slab and the location of the heating tubing are critical -
see RADIANT HEAT FLOOR MISTAKES. --DF
The material of choice for insulating a slab would be high density, closed-cell rigid foam board insulation, such as extruded polystyrene.
Thermally break the interior finish of the basement floor from the concrete (e.g. with wood or solid foam board) to increase comfort and to control condensation if that's a problem in your area during summer months.
If you are installing a radiant heat basement floor system, insulation under the floor slab and the location of the heating tubing are critical - see RADIANT HEAT FLOOR MISTAKES.
The link to the original Q&A article in PDF form immediately below is followed by an expanded/updated online version of this article.
The question-and-answer article about Under-Basement Insulation , quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
Continue reading at INSULATION LOCATION for PASSIVE SOLAR FLOOR SLAB or select a topic from the More Reading links shown below.
Or see INSULATION LOCATION - WHERE TO PUT IT - article series home
Suggested citation for this web page
INSULATION LOCATION & EXTENT for SLABS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
Click to Show or Hide FAQs
No FAQs have been posted for this page. Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Ask a Question or Search InspectApedia
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
Technical Reviewers & References
Publisher's Google+ Page by Daniel Friedman
Click to Show or Hide Citations & References
-  ...
- Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones
- Wikipedia provided background information about some topics discussed at this website provided this citation is also found in the same article along with a " retrieved on" date. NOTE: because Wikipedia entries are fluid and can be amended in real time, we cite the retrieval date of Wikipedia citations and we do not assert that the information found there is necessarily authoritative.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
- The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, 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. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.