Tag Archives: R-value

Considering the Differences Between Closed and Open Cell Spray foam

Originally published by: Fine Homebuilding — May 21, 2016 by Mr. Rob Yagid, a former editor at Fine Homebuilding. Excerpted from Mr. Rob Yagid’s article with contributions from ABTG Staff.

The following article was produced and published by the source linked to above, who is solely responsible for its content. The Pole Barn Guru™ is publishing this story to raise awareness of information publicly available online and does not verify the accuracy of the author’s claims. As a consequence, The Pole Barn Guru™ cannot vouch for the validity of any facts, claims or opinions made in the article.

In an article by Rob Yagid for Fine Homebuilding, which was sponsored by Versi-Foam Systems, the question addressed is what is open cell versus closed cell foam? Rob delves into the debate about the properties of open-cell versus closed cell with the following points:

Much of the information you’ll find about spray foam is dedicated to its R-value and its permeability.

These traits have an overarching impact on the performance of open-cell and closed-cell foams. In most closed-cell foams, an HFC blowing agent is captured in the foam’s cell structure. This gas has a better thermal performance than the air-filled open-cell foam and gives it a higher overall R-value.However, while HFC-blown closed-cell foam might initially have an R-value as high as R-8 per in., as the blowing agent evaporates through the cell walls and is replaced by air, its R-value diminishes.

Closed-cell foam’s “aged” R-value is roughly R-6 per inch. Some manufacturers produce water-blown closed-cell foams. These foams have the same performance properties as HFC-blown foam, but slightly lower R-values at around R-5.5 per in.

Closed-cell foam’s greater density, 2 lb. per cu. ft. compared with open cell’s 1⁄2 lb. per cu. ft., also increases its R-value and offers it the rigidity that open cell foam lacks.

Structural testing, by a variety of spray foam manufacturers has confirmed that closed-cell foam increases the lateral shear and wind pressure strength of conventionally framed walls. Closed cell foam also has a low vapor permeability rating (roughly 0.5 perms at a thickness of 3 in.) and is considered a class-II vapor retarder, meaning that it’s semi impermeable.

Open-cell foam has a greater expansion rate than closed-cell foam. It expands 100 times its initial volume (closed-cell foam expands only 30 times its initial volume), so less of the foam is needed to insulate a house.

Although both foams will dry if they ever get wet, open-cell foam is vapor permeable and dries much faster than closed-cell foam.

Open cell’s one major weakness is its lower R-value, roughly R-3.5 per in. This means that when used in a 2×4 exterior wall, it will create an assembly that’s approximately only R-12, which won’t meet code in most parts of the country.

Spray polyurethane-foam manufacturers can rely upon several facts when it comes to marketing their products. According to the U.S. Department of Energy, up to 30% of a home’s heating and cooling costs are attributed to air leakage. Spray polyurethane foam is an effective air barrier and significantly reduces energy loss. Combined with a higher thermal resistance (R-value) than most other forms of insulation, it’s no wonder spray foam is often relied on to help make houses ultra-efficient. The key to proper use is knowing your climate, construction practice, wall and roof assembly types and building code requirements with a particular focus on continuous insulation. For more resources on the value of spray foam, visit continuousinsulation.org.

Insulation Values Reflect Real-World Energy Performance?

Insulation R Values Reflect Real-World Energy Performance?

Energy efficiency has become huge for post frame building construction. More and more people are discovering post frame buildings as being a cost effective design solution for residential and commercial construction.

Long time readers of this column have seen article after article in this vein, increasing with time. You have also had an opportunity to witness questions from many current post frame building owners who wished they would have designed appropriately to begin with. Proper advance planning can certainly help to achieve desired results.

Let us assume, for a moment, you have created a post frame building with commercial 2×8 bookshelf wall girts and 22 inch high raised heel trusses. In your walls, BIBs https://www.hansenpolebuildings.com/2011/11/bibs/) fiberglass insulation 7-1/4” deep has been used. This will give a laboratory R value somewhere in excess of 30. In attic space, 20 inches of blown in fiberglass will provide a R value of over 60. You have done your work and are happy your decision will give a more than satisfactory end resultant.

Then along I come and poke holes in your investment.

Keep in mind, my very own post frame home has fiberglass insulation very much like our imaginary scenario above.

The most common yardstick for measuring insulation performance will be R value, but there’s a problem. Insulation packaging shows lab analysis of R values, but it’s based upon used testing completely eliminating air movement from results. This matters a lot with fluffy insulation materials because air movement greatly lowers real-world insulation performance. Drafts and air currents often happen within wall cavities and attics and this will be why real-world insulation performance can be significantly lower than advertised values.

Alternatively, insulation products not allowing air movement through them (spray foams and rigid foams, for instance) have real-world insulation values almost identical to what you see printed upon packaging and used in advertising. Their performance doesn’t decline. Air-impervious insulations can be more than twice as effective as air-porous insulations of identical R value under real-world conditions.

Where does all of this leave us as post frame insulation specifiers and building owners?

When I added an exterior elevator shaft to our post frame home two years ago, my insulation choice was closed cell spray foam. I did make an error in that I did not listen to my own inner voice. Our local installer made recommendations for thickness I felt were insufficient, so I had roof and wall sprayed one inch thicker. I should have gone thicker yet as there was plenty of space available to fill. As a result the elevator shaft is cold and drafty into our living space.

Considering closed cell spray foam? Think it may be expensive? Consider its performance will probably be twice as effective as fiberglass and closed cell spray foam suddenly doesn’t seem so costly.


High R Value Overhead Doors

If your new post frame building will only ever be cold storage, then an insulated overhead door just might be all your will ever want, or need. For most people, I encourage them to go with insulated doors, just on the oft chance someone down the line will have different ideas. Insulated overhead doors do tend to ‘feel’ stiffer and to rattle less in a strong breeze.

But what about the R-values of those doors?

Consider this – insulated overhead doors are using polyurethane, which has an initial R-value of maybe as much as 7.5 per inch, however the R-value does decrease with age so a more realistic high end “aged” R-value would probably be closer to 6.5 per inch.

Several overhead door manufacturers report their polyurethane insulated door panels to be as much as R-9.0 per inch, which is both highly unlikely and technically impossible to achieve!

One overhead door company in Maine actually sent an overhead door with an insulated 1-3/8 inch thickness which was advertised as being R-12.76 to be independently tested. The door came back as being actually only R-7.83!

This same company now has what they call their “R-value challenge” to manufacturers. They will write a check to any manufacturer who can prove a 1-3/8 inch thick door is R-12! They have not had to pay yet, and probably never will.

To determine the true thermal performance of an insulated overhead door, one would need to know two things, the door’s ‘leakiness’ and the R-value of the entire door assembly.

The R-values used by garage door manufacturers are measured at the center of the panels, and it appears no one is reporting the R-value of the entire assembly which would include the panel edges, seams between panels and the perimeter of the door.

In comparison of manufacturer’s R-value claims with test reports of the installed doors as part of a system, it appears the R-value of a garage door installed is going to be about one-third of the value claimed in the manufacturer’s brochures!

Even if garage door manufacturers do decide to report whole door R-values, the big piece will still be missing – when it comes to thermal performance of garage doors, air leakage matters more than R-value.

Most important when looking at the thermal performance of an overhead door is a design which minimizes air leakage, with good gaskets between the panels, heavy-duty weatherstripping at the bottom of the door and weather seals up the sides and across the top of the openings.

Don’t Use Metal Building Insulation

When Good Information Gets into the Wrong Hands

When I want something done right, I go to an expert. I’ve got a friend working on re-restoration of my 1950 Chevy pickup truck right now. My friend happens to have taught auto restoration at a college for several years. When I talk with him about my truck, I hope I sound half as intelligent when I talk to people about their pole buildings. He really knows his “pooh”.

I actually do know more than just a passing amount about post frame construction and what does and does not work. Unlike some folks.

Please read on:

One of our clients had gotten some information from Menard’s on what was referred to as R-8 vinyl insulation – reported (by our client) to seemingly be used to insulate non-insulated overhead doors. To find out why this would NOT be a good idea: https://www.hansenpolebuildings.com/blog/2012/12/insulated-overhead-doors/).

Our client’s intent was to use this product to insulate the walls of his new pole building.

Metal Building InsulationThe client’s Hansen Pole Buildings’ Designer Rick forwarded to me the information they were provided by the folks at Menard’s (https://www.menards.com/msds/110522_001.pdf). The product turned out to be exactly what I guessed it actually was – Metal Building Insulation!

I’ve railed about Metal Building Insulation being used to insulate buildings with steel roofing and/or siding previously https://www.hansenpolebuildings.com/blog/2011/11/metal-building-insulation-in-pole-buildings-part-i/. But, it sounds like it is due to be brought up again.

The product description from Guardian Building Products (www.GuardianBP.com) sounds like some pretty great stuff! It, “Reduces Energy Costs, Helps Control Condensation, Improves Noise Control, Provides Enhanced Light Reflectance and Can Be Left Exposed!

The nifty little table gives available products by R-value, thickness and width. What the average consumer will not understand is the recovered R-values of these products are guaranteed prior to installation! There is even a small asterisk following R-Value on the table which leads to a very fine print footnote: Preinstalled values.

In the “Technical Data” box, it references Fire hazard Classification with three asterisks leading to another small footnote, “Excludes white vinyl faced fiberglass” – which is what most Metal Building Insulation is!

Oh…and don’t let this footnote slide by: “NOTE: Condensation blanket is NOT sold as a thermal barrier. The insulating value of the product is negligible and should NOT be utilized in conditioned or semi-conditioned buildings where thermal performance of any degree is required.”

As my Mother used to say, “…’Nuff said…” until the next time I hear someone wants to use metal building insulation under their wall steel!