Rigid-foam insulation packs a lot of R-value into a thin package, but not all rigid foam insulation performs equally. Choose you insulation materials wisely by educating yourself on the unique performance characteristics of each rigid foam insulation type. Review the insulation comparison table below, so you can weigh the benefits of using each type of rigid foam insulation side-by-side.
Insulfoam is a division of Carlisle Construction Materials, a wholly owned subsidiary of Carlisle Companies (NYSE: CSL), and is the nation's largest manufacturer of block-molded expanded polystyrene (EPS). For over 50 years, Insulfoam has been enabling building professionals to construct high-quality building insulation systems at a minimal cost.
With the widest range of faced, laminated and standard high-performance EPS insulation products Insulfoam has the right products for your needs while still providing the highest R-Value per dollar over any other rigid insulation.
There are three primary types of rigid insulation: expanded polystyrene (EPS), extruded polystyrene (XPS), and polyisocyanurate (polyiso). EPS and XPS are thermoplastics, which are non-cross-linked polymers so they are susceptible to deterioration in high temperatures (BSC 2007). Polyiso is a thermoset, which is made up of cross-linked polymers so it has a much higher melting temperature. While properties can vary among specific products, XPS and polyiso tend to be higher density, higher R-value, and lower permeance than EPS.
When rigid foam insulating sheathing is installed on the exterior walls of a home, the foam can serve as a drainage plane, taking the place of house wrap for time and cost savings. To serve as a drainage plane, the seams in the foam sheathing must be properly taped with sheathing and flashing tapes to provide continuity of the drainage plane at joints between panels. The tapes must be durable enough to prevent ingress of water at panel joints for the life of the system. Sheathing tapes and sometimes flashing tapes are also needed to integrate the top edge of diversion flashings (head flashings, flashings over penetrations, step flashings, kick-out flashings, etc.) with the drainage plane.
Continuous rigid insulation also provides an effective solution to thermal bridging. Thermal bridging occurs wherever assembly components with low R-values (such as wood or steel) span from the interior to the exterior of the building. In traditional building construction, while the wall cavities are filled with insulation, there is no insulation at the window frames, door frames, studs, top plates and bottom plates; together this framing comprises nearly one-fourth of the wall area. Rigid insulation can be attached to the exterior side of the framing to provide a continuous insulating layer that reduces thermal losses through thermal bridging.
More effective insulationWith R-values ranging from 3.6 to 8.0, rigid foam sheathing has much better insulation per inch than other materials (i.e. plywood has an R-value of 1.25 and fiberglass batts have an R-value of 3.14). This is especially critical in preventing damage (such as mold and rot) to framing and walls in areas with extremely cold or damp climates. Since rigid foam is applied on the outside it also prevents thermal bridging. Thermal bridging happens when there is a loss of heat due to an interruption in the insulation by a material that is more conductive. This typically happens when interior insulation intersects things like stud frames or electrical boxes.
Better at controlling moisture When it comes to controlling moisture, rigid foam serves two functions. It protects the wood sheathing or framing from any rain or water that leaks in under the siding. And it warms the interior sheathing or framing enough to prevent moisture accumulation from the heated interior air in the winter.
Better at preventing air leaksWhen sealed with proper techniques and a suitable adhesive, rigid foam is an excellent air barrier. The same principle mentioned above that prevents thermal bridging also applies to air transfer. Unlike house wrap, which works to prevent infiltration (air coming into the building) but is poor at stopping exfiltration (air moving out of the building), rigid foam is able to do both.
Must be installed properly to limit air leaks and act as a weather-resistive barrierRigid foam does not require specialized equipment to install it but you do need to follow strict seam-sealing procedures to meet code.
Slightly more expensiveAdding a layer of rigid foam on top of plywood or OSB sheathing will increase the cost of the project. However, this is just a short-term, fixed cost. Rigid foam often pays for itself with lower utility bills over the long term. And it may put off or prevent costly work to repair rot in walls or framing.
The lowest cost, highest performing rainwater management strategy is rigid polymeric foam sheathing with sealed joints (Lstiburek 2006, 2010). There is an existing construction challenge of sealing the joints in rigid polymeric foam sheathing in a reliable and durable manner to prevent water ingress.
Which is exactly why ECHOtape launched our new, next generation seaming tape. PE-M4535 is a proprietary high-performance building tape, made from an advanced polyester backing, which makes it extremely strong and easy to apply. Available in red, silver and white, it is a versatile product used in a wide variety of building envelope sealing applications, including cold weather applications. As excited as we are about PE-M4525, ECHOtape R&D team is continuing to develop additional seaming products to meet the needs of a rapidly changing building industry, products that will adhere to a wide range of building materials and surfaces including house wrap, exterior, and rigid insulation, sheathing, vapor barriers and a variety of underlayments.
When building or renovating a high-performance building envelope there are really three main kinds of rigid foam panels you are going to have to choose from - Polyisocyanurate known as Polyiso (PIR), Extruded Polystyrene (XPS) - often called Styrofoam - and Expanded Polystyrene (EPS).
Before choosing, you should know exactly what you expect these foam insulation panels to do, to make sure you buy and benefit from the right one. These three products we're comparing here are all petroleum-based, but their characteristics, performance and ecological impacts vary significantly. Alternatively, depending on application and budget, you could always choose natural Green Insulation Products, Like Hemp Insulation panels or Batt Insulation or mineral wool - demonstrated here in roof insulation.
PIR, polyiso, or ISO, is a thermoset plastic product typically produced as a foam and used as rigid thermal insulation panel - most often with aluminum foil facing. Thermal performance is rated at R6-6.5 per inch, but don't count on that if your winters are cold for the reasons we're about to explain. Most insulation products actually perform a bit better the colder it gets but polyisocyanurate breaks that rule. As of about 15C its performance starts to deteriorate, and badly. By the time you get down to the -20s Celsius it's nowhere near that. It can be a great product to use as long as you keep it warm, which is a really odd thing to say about an insulation product.
Polyiso insulation boards are the most widely used low slope, above-deck commercial roofing insulation. As a versatile choice for commercial roofing applications, polyiso is designed to be part of any modified bitumen, built-up, or single-ply roofing system. Polyiso products feature a facer for high strength and excellent absorption for both hot mopping and adhesive attachment methods. The product also is designed to perform well with mechanical fasteners, possibly under Green Roof membranes.
Polyiso Foam Panel Insulation Conclusion: In real terms, using polyiso foam insulation panels is probably a poor choice if your winter temperatures dip below 50F or 10C. To put that statement into perspective, a wall or roof assembly in Chicago was tested for the whole of December then averaged out. The first assembly using 2\" Polyisocyanurate foam panels was compared to the same assembly using 2\" of EPS foam and was found to be losing 30% more heat in this study (see below)!
XPS is Rated at R5 per inch, but it will off-gas and lose some insulation performance over time - especially below-grade and when tested in real-world applications. Above grade XPS foam acts as a vapour retarder (and becomes even less moisture permeable the thicker it is - 1 inch is about 1 perm, 2 inches about .5 perms); when taped it can act as an air barrier; the manufacturers and standardized testing state that it does not absorb moisture, nor is it affected adversely by it. However, with some of the EcoHome team having real world experience to the contrary, we \"dug-deeper\" and found that many contractors have also noticed potential issues with XPS foam boards retaining moisture, backed up by reports like this citing a large source of correlated testing and which would lead us to conclude that XPS rigid insulation panels should be avoided for below-grade applications like basement insulation - which is the opposite of much of the information out there.
Also, rather regrettably for traditionally produced XPS, the hydro fluorocarbons (HFCs) most commonly used as blowing agents are far more damaging to the climate than those used with other rigid foam insulation boards. Some manufacturers speak of a transition to more eco-friendly foam insulation blowing agents; that will be great news when it happens across the board! And credit where it's due, the \"real\" Styrofoam, as in the DOW Chemicals blue product, is now manufactured with HCFC blowing agents which have 94% less ozone depletion potential. As HFCs have a global warming potential (GWP) that is 1430 times worse than carbon, this really does demonstrate how important it is to choose rigid foam insulation boards very carefuly to reduce their environmental impact. All XPS panels are not equal! 59ce067264