Give Me Some Skin - Understanding Insulation Specifications and the Skin Pitfalls
A few weeks ago, I noticed an item in a foundation specification that I have been glancing over without any real thought. “Rigid, cellular thermal insulation with closed-cells and integral high density skin, complying with ASTM C 578.” What caught my eyes was integral high density skin. Are they trying to call out a specific for Extruded Polystyrene (XPS) Insulation because standard Expanded Polystyrene (EPS) would not naturally have a skin without adding it?
This triggered a technical conversation about skins on Rigid Insulation.
Does rigid insulation need a skin? What are the advantages or disadvantages of having a skin?
It is always helpful to go back and review the main function of insulation. Insulation’s main purpose is to insulate and provide R-value. Knowing the main purpose of insulation, do insulation skins provide more R-value? Skins can add R-value and skins can reduce R-value. A foil faced insulation could add R-value when it is used in the right circumstances such as a gap behind a masonry wall. Some skins like a clear poly laminated has no effect on R-value. Does an integral high density skin in XPS offer additional R-value? No, in fact according to newer research, it may have the opposite effect. How can this be? Why specified it as something important?
During a manufacturing process, XPS creates a type of skin during the extruding process and some call this an integral high density skin. This skin is maintained on the face and back of the board but the sides and the ends are trimmed during the manufacturing process. Many believe that trimming the sides actually expose and opens the board to moisture infiltration at a higher rate. The face and back have this skin but the ends and sides are open. Interesting, when you consider below grade insulation and how water moves down the foundation wall, water hits the top part of the insulation and water wants to enter in, however the top end does not have the integral high density skin. We know by testing, when XPS insulation is installed below grade, it takes in moisture and its R-value is reduced by 48%, from 5 R/inch to 2.6 R/inch. Some believe this phenomena is caused by water entering in easier at the edges and partially trap in by integral high density skin. So specifying this integral high density skin as a benefit, ultimately points out another reason not to use XPS below grade. Why pay a huge premium for XPS Insulation and get 1/2 of its R-value performance?
What about skins on EPS? Standard EPS does not naturally have a skin, however another advantage of EPS Insulation is that skins can be added. Many different types of skins with different properties can be added. A few examples of skins are ones that can be reflective, skins that allow permeability, skins that are vapor retarders and even skins that can provide high strength. In foundation insulation, where EPS is more effective, a permeable skin could be added to give even more strength. This skin could be even more effective against rough backfilling and fastener pull. This type of product would function great allowing any moisture that enters into to the insulation board to flow freely out and not trap the moisture in.
In this case, the specifier thought that XPS insulation with an integral high density skin would be a better product for below grade application. Unfortunately, it's not. With research showing that XPS insulation can loss 48% of it’s R-value below grade, Engineered EPS Insulation is a much better, safer choice.
12 Reasons Why to Change Insulation - XPS vs EPS
Many myths about rigid insulation have been spread over the years, especially concerning EPS. Some of these EPS myths refer back to an extinct product called bead board. Modern day Engineered EPS is so different and technologically advanced, it’s amazing some still get confused. EPS have made major advancements in chemistry, fusion, expansion, steam quality and TQM. Plymouth Foam, the leader in foam, has state-of-the-art proprietary manufacturing technology to make the product even better.
Lab and field research have lead to new conclusions about the two rigid insulations especially in below grade applications. EPS rigid insulation is certainly been found to be superior to XPS in so many ways. The following is just 12 reasons why.
1) Higher R-Value Retention:
EPS does not suffer from the same plight as XPS in regards to “Off Gassing.” XPS has blowing agents that initially give it a higher R-value, but these gasses escape over time, lowering the R-value.
2) Durability
Engineered EPS can be made in various densities and can achieve compressive strength up to 8,640 lbs/ft and flexural strength up to 10,800 lbs/ft. It is amazing that such a light product, that is 98% air, is so strong.
3) Moisture Management
EPS insulation is non-hygroscopic and does not readily absorb moisture from the atmosphere. Its closed-cell structure reduces the absorption of moisture into the insulation material yet it can readily expel any absorbed moisture.
4) 100% R-Value Warranty
Due to the R-value stability of EPS, Plymouth Foam offers a lifetime limited 100% R-Value Warranty. XPS offers a 90% R-value warranty.
5) No Harmful Chemicals
EPS does not have VOCs or other harmful chemicals in its product. XPS use of chemical HFCs has been deemed to have a high GWP.
6) Cost Advantage
R-value cost per inch is far less in EPS insulation vs XPS Insulation. Value engineering can be used to save $1,000s on projects.
7) Superior Bonding
Due to the manufacturing process, EPS and XPS provide a far different exterior surface. EPS cell structure provides superior bonding.
8) Made in USA - Made in Wisconsin
Plymouth Foam’s EPS is made in Wisconsin and brings jobs, reduces taxes and helps create a better economy for our state. Made in USA.
9) Customizable
Engineered EPS is superior in customizing thickness, lengths, shapes, tapers, chases and can even have reflective laminates attached.
10) Smoke Development
ASTM E84 test method for burning characteristic show that typically EPS has a lower smoke development than XPS.
11) Lower GWP
EPS, the safe insulation, has a lower Global Warming Potential than XPS. Transportation costs are usually lower also lowering GWP.
12) Recycle Accessibility
With over 200 EPS recycling centers in the United States it is easy to see that not only is it 100% recyclable, but it easy to do.
(Learn More about these 12 reasons)
As EPS continues to grow even more popular and gain market share, competitors have continued to spread these old myths. The bad news for them is these myths have been BUSTED. Numerous studies done around the world are proving that EPS is not only “the safe insulation” but that it holds its R-value better, is extremely durable, great in freeze-thaw cycling, has great drying potential and outperforms all other rigid foam insulations.
(Get the 12 Reasons Brochure)
Metal Roof Retrofits- Insulate the weakness?
The most popular solution is adding some insulation and retrofitting a new roof membrane over the top. This is were roof insulation Flute Fillers play an important role. Not only do they add R-value to the system but they can transition a flat surface for a new roof retrofit system. I typically see flute filler level with the top of the ribs/seams and one additional layer on top of that smoothly bridging the top of the ribs/seams. The question is can this system be improved upon?
The one area of thermal weakness in this system is where the original metal roof has seams (connection point of the two pieces of metal roof) that allow heat loss at those points. By installing only one layer of insulation over these seams, it allows for the potential of thermal loss at these junctures were the insulation joints meet these metal roof seams. This thermal loss could cause condensation and stress the membrane disproportionately causing future issues.
Some may say, there is insulation under the metal roof system already, those joints don't leak heat. Really? Take an infrared camera and scan that metal roof and look at the seams, you might be surprised what you find.
There are two solutions to fix this potential problem with retrofitting over a metal roof. The first solution is to add another layer of insulation and offset the joints. The second solution is to use Plymouth Foams RetroDeck™ with a cover board. This system has a built in seam offset. No roofing system is perfect, but eliminating as many potential problems can help a roof system last longer creating better value for our customers.
Swimming Pool Geofoam Project -not too deep to revitalize
The Ashwaubenon Community and School District faced a dilemma - what do you do with an indoor pool that is over 48 years old and has outlived its expected life? Think “outside of the pool” and fill it in with Plymouth Foam’s Durafill GeoFoam and give new life to the building!
Restoring this aged pool was not a viable option as there were too few of lanes and replacement parts were no longer available. The community decided to build a new pool, but what do you do with the old one?
The building that housed the pool was still in good condition. Filling it in with Engineered EPS Foam and pouring 5” of concrete on top “gives this building a new purpose.” This new area will be used as a commons area with tables and chairs for students to eat lunch.
Like all schools districts, needs change. Filling the pool in with foam has a number of possibilities for the district. Foam can be removed and the area can be repurposed for maybe stadium seating or a performance stage. The possibilities are endless.
Filling in a pool sound easy, but reducing in-fill weights and loading pressures of traditional fills such as gravel or stone can be impractical or unachievable. Geofoam to the resue, however filling in a pool with different depths and various slopes is not an easy task.
Boldt Construction’s design team working together with Plymouth Foam Geofoam Consultant, John Calkins, and was able to offer DuraFill Geofoam blocks that were manufactured in various sizes to fit to the contour of the pool. The pieces were labeled and shop drawings were used to install the pieces. Boldt Construction was the general contractor and they “did an excellant job of making the pieces work and come together.”
Using a local contractor and a local manufacturer has many benefits for the local ecomony. Tax money collected for the school district is being spent locally and benefits from the “local multiplier effect.” This multiplier means the money is recirculated 3-5 times in the local economy and is a key tool for creating more local jobs. The school district saved money on transportation cost since the manufacturing facility is less than 75 miles away - now that is “thinking outside the pool.”
What Insulation is the Best in Roofing?
- R-Value
R-value is more than the R-value per inch. Polyisocyanurate (ISO), starts out with a higher r-value per inch, but then the blowing agents escapes and the R-value is reduced. (learn more) Expanded Polystyrene (EPS) has a lower R-value per inch but can be make thicker to match any R-value requirement. EPS’s R-value increase in colder temperature while ISO decreases. Many would give ISO the edge because of R/inch, but taking into consideration overpaying for R-value that does not stay stable in lower temperature, the advantage has to good to EPS.
- Environmentally Friendly
- Combustion
- Cost
- Design Flexibility
- Moisture Retention
Expanded Polystyrene, when compared to polyisocyanurate, certainly has more reason to be use in roofing. It seems over the last few years, many designer have lost sight of the purpose of insulation and the importance of R-value long-term. Some designer only considered combustibility and its superior importance, when in all likely hood this physical property will never ever be used. A feature such as long-term R-value, which performs daily in that system, or even moisture expelling capability, get lower considerations. When all of the major features of insulation are considered, EPS seems to be the clear winner.