I wouldn’t go as far as saying you 'couldn't' use spray foam below a slab, but I’m not sure why you’d want to. Many increase the under-slab insulating foam board thickness to 3 or 4 inches at the outer 2 to 4 feet of the slab. concrete, 4500-psi concrete for severe weathering areas. Many increase the under-slab insulating foam board thickness to 3 or 4 inches at the outer 2 to 4 feet of the slab. I've decided to edit my article, “Choosing Rigid Foam,” to include your advice. In this application, I would choose either extruded polystyrene (XPS) or Type IX expanded polystyrene (EPS). Stealman, I am astonished that an Rmax rep would recommend the use of polyiso under a concrete slab. Benefits of foam insulation under concrete slab . Designers generally insulate both directly under the slab and around the perimeter as well. Slab thickness may be reduced for significantly higher R. e3. Washington State covers a lot of area- can you be a bit more specific? Where to buy EPS foam (25 psi, termite-treated) for use under a concrete slab in West Virginia? The compression curve for foam plastic is usually pretty straight, so insulation rated at 15 psi would compress somewhere in the neighborhood of 0.015 of its thickness. Polyisocyanurate foam insulation properties: This article discusses the use of polyisocyanurate foam board insulation below concrete slabs. "Foamular 250" is one brand made by Dow Corning. Only closed-cell SPF can be used in a subslab installation; the open-cell foam does not have adequate compressive strength. There are two type of insulation - 30 psi and 45 psi These numbers are the crushing strength at yield or a 10% deflection (whichever comes first). CONCLUSION With building owners’ growing desire to save money on heating and cooling costs, and increasingly stringent energy codes, contractors will be installing below-grade and under-slab insulation on more of their projects. Minimum RSI ASTM C-518-91, C-177-85 R-VALUE/inch 5 75ºF mean temp. For example, with a forklift load on a typical 4-inch-thick slab, one calculation would indicate that 32 psi is applied to the insulation compared to only 2.5 psi under a more accurate calculation. For foundation and wall applications in which the foam insulation bears a minimal load, ASTM C 578 Type I (nominal density of 0.9 pounds per cubic foot) material is adequate. Applying the Theory of Plates on Elastic Foundations to Save Material Costs. Minimum 4-inch slab (5 inches for heavy trucks), 3500-psi (min.) As such, it is not uncommon for under slab insulation to be over-designed by a factor of 10 or more. XPS has a higher initial insulating R-value than does a similar thickness and density of EPS, but the R-value of XPS degrades over time. Rigid foam insulations, such as expanded polystyrene (EPS), have been used successfully under concrete slabs for more than 40 years. It comes in 2, 3, 4, and 8 lb strength. I figured I would verify his recommendation by asking folks who have used EPS in this sort of application in the real world who don’t have sales bias , Our foundation is a 4″ slab with 6″ thick stem wall, 3″ inches of rigid EPS under the slab and another 3 inches on the outside of the exterior of the stem wall. 2 is cheaper but is not meant for holding up a driveway. Thanks guys. This won't delete the articles you've saved, just the list. Akron, OH 44305 Monday: 7:30 am – 4:00 pm Tuesday: 7:30 am – 4:00 pm Wednesday: 7:30 am – 4:00 pm Thursday: 7:30 am – 4:00 pm That means that the soil under a typical garage slab only has to be able to support 125 psf. http://foundationhandbook.ornl.gov/handbook/images/Chapter%204/4-11_no-cap.png, http://insulfoam.com/wp-content/uploads/2014/04/13001-Below-Grade-EPS-Overview-TDS-WEB-8-16.pdf, Type I or Type VIII EPS under a concrete slab, Under slab sgtrength of EPS Type I rigid foam. Using a design equation based on a more rigorous analysis of the design conditions can help avoid over-engineering the insulation and save thousands of dollars on the project. I don't like it, but if the 40 psi figure is the compressive strength of the foam, I guess it is OK. There is the perception that the extruded styrene (blue or pink board) is required for under slabs, yet the white board (expanded EPS) is often significantly less expensive for such projects. For almost all residential slab applications Type-II EPS is fine. 1 Both products are great for above-and below-grade residential and commercial applications such as perimeter/ foundation, cavity wall, precast concrete, under slab, and other applications. For Under Floor Slabs, FOAMULAR® 150 or 250 can be used for residential and light commercial applications where floors are subject to normal loads; use FOAMULAR® 400, 600, or 1000 for industrial applications where floor areas will be exposed to heavy loads. Take the case of a warehouse with a 6-inch-thick, 2,500-psi concrete slab on 2 inches of EPS insulation with a rated stiffness of 360 psi for one inch. Minimum RSI ASTM C-518-9, C-177-851 ... Compressive strengths† from 30 psi to 100 psi (210 kPa to 690 kPa) to meet the requirements of nearly every application. For example, with a forklift load on a typical 4-inch-thick slab, one calculation would indicate that 32 psi is applied to the insulation compared to only 2.5 psi under a more accurate calculation. Insulating the slab Using rigid foam insulation around the perimeter of the slab to minimize heat loss seems like an obvious step, but whether to place insulation under the slab is another story. We have to install 150 sheets total of 2" XPS foam so the radiant guys can come in and set up. Food for Thought: Lessons in Cold Storage, “Great things are done by a series of small things brought together.”, Increase Energy Efficiency with Continuous Insulation on Exterior Walls. this usually is not due to settling but improper installation of concrete. Extruded polystyrene closed-cell foam, ASTM C 578 Type IV, 25 psi minimum Shipped in poly-wrapped units with individually wrapped or banded bundles. Thanks guys. In this application, I would choose either extruded polystyrene (XPS) or Type IX expanded polystyrene (EPS). EPS insulation in an under-slab application Take the case of a warehouse with a 6-inch-thick, 2,500-psi concrete slab on 2 inches of EPS insulation with a rated stiffness of 360 psi for one inch. I agree, a poly and a foam board is the best option. A 4" slab contributes about 50 psf of load; add a 40lb live load and you're still below 1 pound per square inch. As such, it is not uncommon for under slab insulation to be over-designed by a factor of 10 or more. Use low-water-content air-entrained concrete (5% to 7% air entrainment) in freezing climates and 11/4-inch (top size) aggregate. Reclaimed EPS from commercial building re-roofing/demolition is fairly ubiquitous and cheap, typically 1/4-1/3 the cost of virgin stock goods from salvage outfits and foam reclaimers. engineer for correct compressive strength (PSI) for your application. The challenge will be finding a local to you source. I've looked around for reclaimed Type II and haven't found any in the Washington State area. Insulation located below grade, as required in Climate Zones 4 through 8, should extend the length specified in the table by any combination of vertical insulation, insulation extending under the slab, or insulation extending out perpendicular to the building Insulation extending perpendicular away from the building should be protected by pavement or by not less than 10 inches of soil. CUT TO THE CHASE if the subgrade is done properly (as mentioned) above and the foam is rated for under cement (psi) why would it not work. However, I often see disagreements on what type of foam board should be used. Use gravel fill … In addition, foam serves as a moisture barrier, humidity controller, noise barrier and strong support for heavy loads. As a minimum, I would specify a 6" thick 4000 PSI concrete slab with a low water-to-cement ratio. 1510 Bauer Blvd. Joshua, for most situations, type 2 if fine for sub-slab use. Thermal Resistance:The long term design thermal resistance of Celfort®and Foamular®insulation is 5.0 ft2hrºF/BTU for 1 inch thickness or RSI 0.87 (m2ºC/W) for 25mm thickness according to CAN/ULC-S770-00.1 Example: http://foundationhandbook.ornl.gov/handbook/images/Chapter%204/4-11_no-cap.png, The Type I EPS is rated at a compressive strength of 15-21 PSI, the Type IX is rated at 25-33 PSI. I’m right at the point where I need to purchase some EPS foam for our slab foundation / stem wall on a residential net zero project. Try searching your local craigslist for: rigid insulation, eg: https://boston.craigslist.org/search/sss?query=rigid+insulation, https://denver.craigslist.org/search/sss?query=rigid+insulation, https://sacramento.craigslist.org/search/sss?query=rigid+insulation. x 4 ft. x 8 ft. R-15 Squared Edge Insulation Sheathing. Not enough to worry about. One EPS insulation brand available throughout the U.S. has k values ranging from 360 to 1860 psi for one inch of insulation thickness. In cold climates it is advisable to use a minimum of 2 inches of extruded polystyrene under the slab. Two-pound foam. But under footings or load bearing posts it may need to be something denser. Our designers spec 25 psi foam. P = concentrated load on concrete slab in pounds, K = Subgrade reaction modulus of total EPS insulation in pounds per cubic inch (k/t), k = Stiffness of one inch of EPS insulation in pounds per square inch, E = Modulus of elasticity of concrete in pounds per square inch (57000√ f’c), f’c = specified concrete compressive strength in pounds per square inch. Not enough to worry about. If the designer assumes that this load distributes at a 45-degree angle through the slab, the 8,000 pounds ends up distributed over … How about factory seconds where the boards are not of uniform density? 100 PSI minimum EXTRUDED POLYSTYRENE (XPS) RIGID FOAM INSULATION Owens Corning® FOAMULAR ® & FOAMULAR NGX™ 400/600/1000 are high strength Extruded Polystyrene (XPS) Insulation products designed for use in engineered applications requiring additional load-bearing capability such as under slab, concrete floors, foundations, We have to install 150 sheets total of 2" XPS foam so the radiant guys can come in and set up. Below-Grade Under Slab with FOAMULAR® XPS insulation. They both come in various rated compressive strengths from 10 psi to about 80 psi. ... Extruded polystyrene closed-cell foam, ASTM C 578 Type IV, 25 psi minimum Shipped in poly-wrapped units with individually wrapped or banded bundles. FOAMULAR® NGX™ 250 contains the additional benefit of being Mike McCann Save my name, email, and website in this browser for the next time I comment. Additional insulation is applied along the edges of the slab, because that is a primary surface for heat loss. I wouldn’t go as far as saying you 'couldn't' use spray foam below a slab, but I’m not sure why you’d want to. A resource to point them to for example calculations is the article “Right-sizing Under-slab Insulation,” in the April 2014 issue of Structure magazine. 8. Under Floor Slabs. you need vapor barrier-2 in. The U.S. Department of Energy (DOE) estimates insulating the exterior edge of slabs in slab-on-grade buildings can reduce winter heating bills from 10 to 20 percent. Far more important than bearing capacity is the base’s ability to provide consistent support. The stuff here is typically 25 psi; I was advised by an engineer to use the 60 psi under a garage slab, and I think that is also OK under footers. under slab insulation radiant/snowmelt ... 25 PSI insulation was used below the truck dock at the Target Store we did in the mountains. Its compressive strength is similar to sandy soil. The compression curve for foam plastic is usually pretty straight, so insulation rated at 15 psi would compress somewhere in the neighborhood of 0.015 of its thickness. EPS insulation in an under-slab application. Compressive strengths†from 30 psi to 100 psi (210 kPa to 690 kPa) to meet the requirements of nearly every application. Product Description FOAMULAR® 600 3 in. Polystyrene (XPS) Rigid Foam Insulation are great for under slab, cold storage installations, concrete fl oors, foundations, plaza and parking decks, roofi ng, roadways and rail beds, permafrost protection and other high load-bearing applications • Designed for use in high load bearing applications. Two-pound foam. The problem is that designers often do not adequately account for how the concrete slab and underlying subgrade interact. For foundation and wall applications in which the foam insulation bears a minimal load, ASTM C 578 Type I (nominal density of 0.9 pounds per cubic foot) material is adequate. Insulating a slab on grade depends on at least four factors: the climate, the type of foundation, whether the slab includes hydronic tubing for radiant heat, and the severity of the local termite problem. Only closed-cell SPF can be used in a subslab installation; the open-cell foam does not have adequate compressive strength. CAN/ULC -S701 01,ASTM C518 5.4 40ºF mean temp. 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