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).
If you are looking for more details, kindly visit our website.
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 15°C 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.
Polyisocyanurate rigid foam insulation board with aluminum foil facing © Ecohome
The news of Polyiso's R value petering out when you need it most still hasn't permeated entirely through the building industry, so you still see it being installed occasionally on the exterior of walls in cold climates. It won't offer nearly the thermal protection you think it will in the dead of winter, and it may cause moisture damage due to its lack of permeability.
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 50°F or 10°C. 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.
XPS rigid foam insulation board © EcohomeNote: 1 perm and 60 ng are U.S. and Canadian equivalent rates of permeability, below that rate of permeability classifies a material as a type II vapour retarder, suitable for residential construction.
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 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!
Rated at R4 per inch; EPS foam insulation boards are more permeable to air and moisture than XPS, but it doesn't retain moisture to the same extent because of it's more closed cell structure and it's breathability which lets it dry out. Two inches of EPS foam board has a moisture permeability rate of between 60 and 75 ng (1 to1.25 perms), which is on the cusp of qualifying it as a type II vapour retarder, but on the more 'breathable' side of the scale which we would probably consider a good thing in most applications.
EPS rigid polystyrene insulation board © EcohomeFor reference sake, the traditional 6mil polyethylene vapour barrier has a permeability rating of 3.4 ng, making it about 18 times more vapour resistant than building codes allow.
The permeability of EPS can be handy at times if you want to add insulation to an existing wall assembly but are worried about trapping moisture, like retrofitting the exterior of buildings with additional insulation. Though to be absolutely sure you may be better with a mineral wool board which lets moisture pass right through - it all depends what moisture barriers are already in place or ar about to be installed.
The lower stated R value of EPS compared to XPS is in a way compensated for by having a higher R value per dollar, as it is somewhat cheaper. If you're not worried about losing an inch of space here or there, you'll get a higher R value with EPS for the same amount of money, albeit with a thicker wall, and this R-Value also stays pretty consistent over time - unlike XPS which tails off as it ages.
The performance of EPS may drop slightly when it's wet (reports I've seen indicate somewhere in the area of 10-15 %, so nothing too catastrophic), it will also dry out just as quickly as it got wet and return to its original performance. But there is nothing wrong with putting a little effort into keeping it dry if you can. The GWP of expanded polystyrene blowing agents is about 7 times worse than carbon, but that's a lot less than being times worse like standard XPS is. There is also the potential for a miniscule amount of off-gasing of some chemicals including potentially troublesome brominated fire-retardants from EPS foam products used in construction, but speculation as to whether or not this poses a significant risk to health doesn't seem to be based on any hard facts or testing. We'd be really interested to find any verifiable sources for EPS chemical off-gassing testing - if you find any please post them to the comments section below - as we are starting to think that EPS foam may arguably be the most Eco-Friendly insulation and this may sway our thinking against it.
Polyisocyanurate foam insulation panels come with a layer of foil on each side to keep the gases in, so there is the potential to solve a bit of a growing problem in wall assembly durability. Foil is a vapour barrier and a very good one at that, it fact it stops even more moisture than the normal 6 mil polyethylene normally used. So if you use it on the interior of a high performance stud wall design, you won't need to add an additional vapour barrier.
Here is the fun part - Since there is foil on either side of the panel, you end up with a harmless second vapour barrier, which is usually heresy in building design. But this can help in summer months when there is a risk of the vapour drive reversing due to air conditioning during hot humid weather. Any inward-bound moisture would be stopped at that inner layer of foil, which will be warmer than the foil on the other side, so you reduce your risk of summertime condensation.
That foil is the reason it can be problematic on the exterior, as you would be adding an exterior vapour barrier where you likely don't want one.
On the good news side, the GWP of blowing agents in Polyiso is similar to those in EPS, and in the right circumstances its R value is significantly higher, which deservedly or not helped earn it the reputation of being the 'greenest' foam. It can be a great choice when kept above freezing and away from moisture - so above grade for sure, and it makes a great interior thermal break when it's kept a bit warmer by batt insulation in stud cavities.
Being petroleum based should not result in foam being condemned by green builders on principle alone; it should be looked at in perspective. There are other great types of insulated sheathing (mineral wool, wood fiber and fiberglass to name three) and each will have their own benefits, drawbacks, carbon footprint and embodied energy through manufacturing, so even the greenest of the green will have some measurable impact. It takes energy to save energy, and manufacturing insulation is arguably one of the more noble things we currently do with fossil fuels. If you really want to go into depth about the tested performance values of Polyiso Foam panels in hot and cold clinates compared to EPS and XPS foam Insulation panels - see the article from Building Science Corporation here
The only rigid board insulation that is not a petroleum-based foam product shown in the main photo above is the brown one, which is mineral wool. It is a recycled product made with the stone dust from industrial blast furnaces.
Alternative Mineral Wool Rigid Insulation Panels - Roxul
Like any particulate, it is best not to inhale the fibers while installing rock wool insulation board, so like any batt insulation we recommend using eye protection and a mask, not to mention gloves to prevent skin irritation. As an insulation it is non-toxic, and unlike foam products there are no blowing agents that will off-gas into your home. That means it can lead to cleaner indoor air quality, and the R value will never change, whereas foam products will deteriorate over time as the gases escape.
Mineral wool is rated at about R 4, it is unharmed by moisture, it is not a vapour barrier at any thickness, nor is it an air barrier. It also provides better soundproofing, and being made with stone, it is fireproof.
Not being affected by moisture makes it is a great choice for retro-fitting insulation when finishing basement, either interior or exterior. It is also something of a fool proof exterior board insulation when renovating, as it will not trap moisture from the interior inside the wall.
In batt form is it a common alternative to fiberglass for its higher R value, and easier installation (at least for doing a good job) It does however cost more than fiberglass per batt.
Our personal overall preference due to its recycled content and versatile applications is probably mineral wool, but as for the petroleum plastic rigid foam insulation products - polyisocyanurate gets top marks for being 'eco' if you are in a warmer climate and can handle its moody disposition. EPS foam is versatile, great for below-grade applications and in the middle ground for performance, financial and ecological cost, and whilst XPS foam is a top performer on paper it comes with some unfortunate environmental baggage for which we'd probably rate it in last place. As soon as XPS completes its transition to less harmful blowing agents, I'm sure it will be welcomed into the green building community for above-grade applications.
Be sure to read the EcoHome Guide to High Performance wall construction here
And watch the Video Guide to high performance wall construction and insulation here
Home
»
Insulation
»
If you want to learn more, please visit our website Decai.
Insulation Materials
»
Rigid Foam Insulation
Your Dr. Energy Saver expert can help you choose the right type of rigid foam insulation for your needs.
When most people think of insulation, they think of fluffy materials that are easily compressed or torn. However, rigid foam board insulation is a unique insulation option that provides excellent durability and insulating capabilities.
Dr. Energy Saver provides quality rigid foam insulation for a variety of purposes, including basement, crawl space, and attic insulation. Our rigid foam options are proven to provide effective insulation and help make your home more comfortable and efficient.
If you're interested in rigid foam insulation for your home, call your local Dr. Energy Saver dealer today to get started with an estimate! Our rigid foam insulation will provide the solution you need for your home's energy loss problems!
The key difference between rigid foam insulation and traditional insulation is, as you might expect, the strength of the material. Unlike batt and blown insulation, rigid foam won't blow or shift out of place once it's installed. It also is water and pest resistant, making it perfect for basements and crawl spaces.
Rigid foam insulation also offers benefits as air barrier, which can be accomplished when the boards are sealed at joints and edges with tape and spray foam. Rigid foam panels come in a variety of thicknesses and widths, but 2-ft. x 8-ft. and 4-ft. x 8-ft. panels are the most common. Rigid foam cuts easily with a knife or saw to fit unusually shaped areas, and it's typically cut to fit and wedged (friction-fit) into place. If needed, it can also be glued to surfaces with caulk, panel adhesive or spray foam.
When choosing rigid foam insulation, you have three main options:
What are the pros and cons of rigid foam insulation?
Benefits of rigid foam insulation include enhanced mosture control, continuous insulation, and its ability to address thermal bridging. Thermal bridging is when components of the home, such as metal or wood, allow heat to enter or escape the home due to their higher conductivity. Rigid foam insulation prevents this transfer and keeps the home at a stable temperature.
One of the only disadvantages of rigid foam insulation is that it must be tightly fitted in order to prevent air from escaping. This can easily be addressed with air sealing measures such as taping or adding blown-in insulation on top.
Can I spray foam insulation myself? How about rigid foam?
There are DIY foam insulation kits available at some hardware stores, but there are a lot of ways it can go wrong. Spray foam application must be done continuously or clogs will occur inside the canister, rendering the rest of the mixture useless. This makes it all too easy to waste expensive materials and valuable time. Spray foam is also incredibly hard to remove, as it sticks to every surface it touches. Experienced contractors will have the skills and precision to ensure that the spray only goes where intended.
Rigid foam insulation is easy to cut, but it takes skill to fit it exactly together. Homeowners who DIY rigid foam insulation installation will have to take extra steps to apply tape or other forms of air sealing to make the foam boards effective. Rigid foam insulation is also ideally applied during new constructions or inside of walls, which is best handled by professionals.
What is the R-value of a 2-inch foam board?
The R-value of rigid foam insulation varies based on the materials used and how many layers are installed. For example, our polyiso rigid foam boards have R-values between 6.5 and 6.8 per inch. If two layers are installed, it doubles the R-value and cuts heat/conditioned air loss in half. For reference, plywood has an R-value of 1.25.
How thick should foam board insulation be?
How thick your foam board insulation should be depends on where in the home it is being installed, what climate zone you live in, and sometimes what kind of home heating you have. For example, the minumum R-value for crawl space insulation across the U.S. is R-13. At Dr. Energy Saver headquarters in Connecticut, which is zone 5, the recommended rating for crawl space insulation is between R-25 and R-30 for both gas heating and electric heating set ups. If your rigid foam boards are rated R-6 per inch, you would need between 4.2" and 5" of insulation in your Connecticut crawl space.
Some areas of the home will require more insulation than others. For example, attics in zone 5 require more insulation than crawl spaces (R-49 to R-60 vs R-25 to R-30).
Check your local guidelines for the correct formula to determine how thick your rigid foam board insulation should be. Or, call the experts at Dr. Energy Saver for a free rigid foam insulation estimate and we'll determine what works best for your home.
What kind of rigid foam insulation is best?
The best kind of rigid foam insulation is polyisocyanurate, also known as polyiso. It has the highest R-rating of any rigid foam insulation and comes with a reflective foil on both sides, allowing it to act as a radiant barrier as well. This closed-cell rigid insulation can be used in a variety of applications, including cavity walls, stud walls, masonry walls and vaulted ceilings.
If you need insulation for your basement, crawl space, or attic, rigid foam insulation is a good choice. Dr. Energy Saver can evaluate your home and recommend the right materials and services to give you the solutions you need. Call us today to get started on making your home more comfortable and efficient with an evaluation and estimate!
Get a Free Estimate!Related Pages
Contact us to discuss your requirements of Extruded Foam Insulation. Our experienced sales team can help you identify the options that best suit your needs.