The "R" Fairy Tale - The Myth of Insulation's "R"-Value
Story Contribution Courtesy of Gaco Western, Inc.
One of the fairy tales of our time is the "R-value." The "R-value" is touted to the American consumer to the point where it has taken a "chiseled in stone" status. The saddest part of the fairy tale is that the R-value by itself is almost a worthless number.
None of us would ever buy a piece of property if we knew only one dimension. Suppose someone offered a property for $10,000 dollars and told you it was a seven. You would instantly wonder if that meant seven acres, seven square feet, seven miles square, or what. You would want to know where it was — in a swamp, on a mountain, in downtown Dallas. In other words, one number cannot accurately describe anything. The use of an R-value alone is absolutely ridiculous. Yet we have Code bodies mandating R-values of 20's or 30's or 40's. A fiber insulation having an R-value of 25 placed in a house not properly sealed will allow the wind to blow through it as if there were no insulation. Maybe the R-value is accurate in the tested material in the lab, but it is not even remotely part of the real world. We must start asking for some additional dimensions to our insulation. We need to know it's resistance to air penetration, to free water, and to vapor drive. What is the R-value after it is subjected to real world conditions?
The R-value is a fictitious number supposed to indicate a material's ability to resist heat loss. It is derived by taking the "k" value of a product and dividing it into the number one. The "k" value is the actual measurement of heat transferred through a specific material.
The Test used to determine the "R" value:
The test does not account for air movement (wind) or any amount of moisture (water vapor). In other words, the test used to create the R-value is a test in non-real-world conditions. For instance, fiberglass is generally assigned an R-value of approximately 3.5. It will only achieve that R-value if tested in an absolute zero wind and zero moisture environment. Zero wind and zero moisture are not real-world. Our houses leak air, our buildings leak air, and they often leak water. Water vapor from the atmosphere, showers, cooking, breathing, etc. constantly moves back and forth through the walls and ceilings. If an attic is not properly ventilated, the water vapor from inside a house will very quickly semi-saturate the insulation above the ceilings. Even small amounts of moisture will cause a dramatic drop in fiber insulation's R-value — as much as 50 percent or more.
We understand air penetration through the wall of the house. In some homes when the wind blows, we often can feel it. But what most people, including many engineers, do not realize is that very serious convection currents occur within the fiber insulations. These convection currents rotate vast amounts of air. The air currents are not fast enough to feel or even measure with any but the most sensitive instruments. Nevertheless, the air is constantly carrying heat from the underside of the fiber pile to the top side, letting it escape. If we seal off the air movement, we generally seal in water vapor. The additional water often will condense (this becomes a source of water which rots the structure). The water, as vapor or condensation, will severely decrease the insulation value — the R-value. The only way to deal with a fiber insulation is to ventilate. But to ventilate means moving air—which also decrease the R-value.
“There is a problem with loose-fill fiberglass attic insulation in cold climates. It appears that, as attic temperature drops below a certain point, air begins to circulate into and within the insulation, forming “convective loops” that increase heat loss and decrease the effective R-value. At very cold temperatures (-20°F), the R-value may decrease by up to 50%.”
Nisson, J.D. Ned, JLC, “Attic Insulation Problems In Cold Climates”
The best known solid insulation is expanded polystyrene. Other solid insulations include cork, foam glass and polyisocyanate or polyisocyanurate board stock. Each of these insulations are ideally suited for many uses. Foam glass has been used for years on hot and cold tanks, especially in places where vapor drive is a problem. Cork is an old standby used in freezer applications. EPS or expanded polystyrene is used everywhere—from drinking cups and food containers to perimeter foundations and masonry insulations. Urethane board stock is becoming the standard for roof insulation, especially for hot mopped roofs. It is also used for exterior sheathing on many of the new houses. The R-value of the urethane board stock is better than any other solid insulation. All solid insulations will perform far better than fiber insulation whenever there is wind or moisture involved.
Most solid insulations are placed as sheets or board stock. They suffer from a very common problem. They don't fit tight enough to prevent air infiltration. It matters not how thick these board stocks are, if the wind gets behind it. We see this often in masonry construction where board stock is used between a brick and a block wall. Unless the board stock is physically glued to the block wall, air will infiltrate behind it. Air flows through the weep holes in the brick and around the insulation, rendering it virtually useless.
The only commonly used solid insulation that absolutely protects itself from air infiltration is spray-in-place polyurethane. When properly placed between two studs or against a concrete block wall, the bonding of the spray (plus the expansion of the material in place) will effect a total seal. This total seal is impossible to overestimate. In my opinion, most of the heat loss in homes has to do with the seal rather than the insulation. For physical reasons, heat does not conduct horizontally nearly as well as it does vertically. Therefore, if there were no insulation in the walls of the homes, but an absolute airtight seal, there might not be a huge difference in the heat loss. This would not be the case if the insulation was missing from the ceiling. Air infiltration can most effectively be stopped with spray-in-place polyurethane. It is the only material (properly applied) that will fill in the corners, the cripples, the double studs, bottom plates, top plates, etc. The R-value of a material is of no interest or consequence if air can get past it.
About mid-1975, I received a call from the division manager of a major fiberglass insulation manufacturer. The caller asked, "I understand that you are spraying polyurethane in the walls of homes?"
I told him that was true. He was calling because we were cutting into the fiberglass insulation sales in our area. He asked, "How can you do it?"
I knew what he meant. He wanted to know how I could look somebody in the eye and sell them a more expensive insulation than the cheap old fiberglass. I told him the way I did it is with a spray gun. Of course, that wasn't the answer he wanted. He wanted to know how I could not feel guilty. I told him of insulating one of two nearly identical houses built side by side. We insulated the walls with 1.25 inches of urethane. The other house was insulated with full thickness fiberglass batts put in place by a reputable installer. Not only did we use only 1.25 inches of urethane as the total wall insulation, but we had the builder leave off the insulated sheathing. At the end of the first winter, the urethane insulated home had a heating bill half of their neighbor's. I know that is not terribly scientific, but it is very real. I am not sure he was convinced, but it should be noted that same company jumped into the urethane foam supply business the next year.
One and a quarter inch of polyurethane sprayed properly in the wall of a house will prevent more heat loss than all the fiber insulation that can be crammed in the walls — even up to an 8" thickness. Not only does it provide better insulation, but it provides significant structural strength to the house.
One of my early clients was Brent. I had insulated several potato storages for Brent. He knew what spray-in-place urethane insulation could do. When he decided to build his new, very large, very fancy new home, he asked me to come insulate it. The builder pitched a fit. He "didn't need any of that spray-in-place urethane in his buildings. He made his buildings tight, and fiberglass was just as good."
Brent explained to the builder, "I know who is going to insulate the building. It is not as definite as to who is going to be the contractor. You can make up your mind. We are going to have the urethane insulation and you can build the building, or we are going to have the urethane insulation, and I will have some one else build the building." It didn't take the contractor long to decide he wanted to use urethane insulation.
We sprayed a lot of foam in Brent's house, and it was a large home. Afterwards, whenever I would meet him, he would tell me his heat bill was less than any of his rental houses or the homes of anyone else he knew. Of course, his home was two or three times larger. Also, the builder started having me insulate most of his new custom-built homes. He explained to his clients that the best insulation was the spray in place urethane. It would cost a little more, but it would save money in the long run. Most owners opted for urethane.
Never have I had a customer tell me that he did not save money by using the urethane spray-in-place insulation. You can spend all the time you want with R-values and "k" factors, and "prove" on paper there is no way the urethane can do the insulation job that the fiberglass will. In the real world, I can assure anyone there is no way fiber insulation can be as effective as spray-in-place urethane — not even close.
R-value tables are truly part of the "Fairy Tale." They show the solid and the fiber insulations side by side, implying they can be compared. The fact is, without taking installation conditions into account, comparisons are meaningless. Spray-in-place urethane foam provides its own vapor barrier, water barrier, and wind barrier. None of the other insulations are as effective without special care taken at installation. The fiber insulations must be protected from wind, water and water vapor. Again the tables need a second table to state installation conditions.
I sprayed 4" under the slab, 4" on the walls, and 5" on the underside of the roof (the fifth inch was added as a safety margin). Chet, the plant manager, was pretty worried because he had stuck his neck out going with non-traditional insulation and a non-traditional building for Meadow Gold Company. Well, the building progressed on schedule, but the equipment to cool the building did not arrive on time. By summer, only one of the two refrigeration compressors had arrived. Two compressors were needed (per the Meadow Gold engineers) to handle the needs of the building based on using 10" of expanded polystyrene.
Chet decided that a temporary solution to his predicament would be to turn one of the older freezers that was presently being used as a cooler back into a freezer. Then, maybe he could make a cooler for the new building with just one compressor. It was not an optimal arrangement, but it might work. Chet kept telling us that he would know as soon as he turned on the freezer equipment whether or not the idea would work. When I pressed him, he said that normally it takes five days to bring a freezer down to the -10°F needed for ice cream. But, when he turned on the new freezer, with only that one compressor, the temperature dropped to -18°F degrees by the second morning. They had their freezer. It ran the entire summer using only the single compressor.
A few weeks later, I was visited by a Meadow Gold engineer from Chicago. He wanted to know exactly what we had done to insulate the freezer. One compressor should not be able to hold a freezing temperature as well as it was doing. I explained to him exactly what we had done. He seemed satisfied and he left. A few weeks later he showed up again with his boss. We went to the plant and verified with an ice pick the thickness of the foam. It was indeed four inches in the walls and five inches in the ceiling. Here again they reiterated that the building should not be operating as it was. What they were telling me was that even though I had used one inch of urethane to replace 2.5 inches of expanded polystyrene, the building was still requiring only 50 percent of the normal compressor power for cooling. As you can imagine, the experience made me a lot more bold, and I used the information to sell more freezer insulation jobs.
One of our largest freezer insulation projects was a sixty thousand square foot freezer at Clearfield, Utah. I was able to talk the general contractor into letting us insulate with spray-in-place polyurethane foam the brand-new all-concrete freezer he was building. This building was the 12th in a chain of freezers. My friend Bob had taken it upon himself to make the switch from the ten inches of expanded polystyrene to four inches of urethane with a fifth inch on the roof. The building was built with tilt up concrete insulated on the interior side of the concrete with spray-in-place urethane. We then sprayed on a three-fourths of an inch thick layer of plaster as the thermal barrier. Over the pre-stressed concrete roof panels, we put five inches of spray in place urethane and then covered it with hot tar and rock. (This is an old CPR-specification).
Urethane Conserves Energy
Excellent thermal resistance is the primary performance benefit of urethane foam insulation, but it is not the only one. Urethane also has these advantages as a construction material:
a) Its closed cell structure makes urethane most effective initially and in the long run.
b) When protected by skins or other covering, urethane will not absorb water. Consequently the x-factor (thermal conductivity) is virtually constant.
c) Sprayed-on foam has the advantage of no seams or joints.
d) Urethane’s thermal resistance means that only one thickness of material is need for most jobs.
e) It has a low moisture permeability (1-3 perms).
Where circumstances demand thinner walls or roofs, urethane — with its superior insulating capability — makes it possible to reduce the thickness of the insulation component with no loss of thermal resistance. Or the thermal resistance of an assembly can be increased without enlarging the size of the member. Urethane helps to offset the design restrictions imposed by the fact that most building materials are constant in thickness and weight.
“Urethane Foam as an Energy Conserver,” How to Conserve Energy: in commercial, institutional and industrial construction, Mobay Chemical Corp. Pittsburgh, PA: 1975, p 3
I was on the job the last day. As we finished up the owner showed up. He had expected to see ten inches of expanded polystyrene, and here was four inches of urethane. I told him he would like the four inches of urethane as it would be even better than the expanded polystyrene, based on my previous experience. He told me he was sicker than a dog because he felt like there was no way that could be true. It was too late for him to do anything about it. If he could have, he would have changed the contract instantly, but he was stuck and felt stuck.
They had 12 other similar size freezers, except the others were insulated with expanded polystyrene. The normal way of operating them was to use three large compressor assemblies. Two of the compressors would be needed all summer to keep the building cold, and the third one would be a standby unit, in case one of the other two had problems.
About a year later, I received a phone call from one of the managers. He asked me if I had time to insulate another 60,000 square foot freezer in Clearfield, Utah. I assured him we had the time, the inclination, and the excitement to do it, but I thought the owner wanted nothing to do with urethane foam insulation. The manager explained to me that not only had the Clearfield freezer operated better than any other freezer in their line, it had operated for less than half the costs of any others. They were adding another 60,000 square feet without adding more compressors. The compressor power available to them because of the urethane insulation efficiency allowed them to do it. The building had run very nicely through the hot part of the summer with just one compressor. Now they would be able to run two buildings off of two compressors and still have a spare.
Again, this is anecdotal evidence, but let me assure you that you will get the same results if you do the same thing as we have. I have insulated too many buildings now that I know that this will happen in every case. Never can you use an R-value from a fiber insulation and compare it to the R-value of a foam insulation. Nor can you use the R-value of a foam insulation if it is in sheet form and compare it to the R-value of spray-in-place foam insulation. Spray-in-place polyurethane is an absolute minimum of three to ten times as effective as any other insulation available today.
During the late 1970s, the FTC went after the urethane foam suppliers for misleading advertising especially with regard to fire claims. A consent decree followed. It destroyed a tremendous amount of confidence in the use of urethane. Up to that point, Commonwealth Edison would give Gold Medallion approval for homes insulated with 1.25 inches of spray-in-place urethane in the side walls of masonry constructed homes. True, that was anecdotal evidence, but also true, it worked. Much work was done in the early 1970s using a 1.25 inches urethane as a replacement for wall insulation in a home. Not only did it replace the wall insulation, it also replaced the exterior sheathing. Buildings are stronger and better insulated when sprayed with 1.25 inches of urethane.
Understanding the two purposes of insulation gives a standard to measure the insulations:
The graph shows that 70% of heat loss from conductance is stopped by a 1 inch thickness of spray-in-place urethane foam. (remember we are going to stop nearly 100% of the heat loss from air infiltration with the first quarter inch of urethane foam). The second inch of spray-in-place urethane stops about 90% of the heat loss and the third inch 95% and so forth.
Thermal Diffusivity — Heat Sinks
You can see from the graph that urethane thicknesses beyond four or five inches is practically immaterial. We use three inches for most of our construction. Two inches will do a very superior job. We have insulated many metal buildings with one inch of urethane and the drop in heat loss is absolutely dramatic. Obviously the first quarter inch takes care of the wind blowing through the cracks (It usually takes an inch to be sure the cracks are all filled). The balance of the inch adds the thermal protection.
2) Surface temperature control:
An engineer from the Upjohn company explained this. He drew for me a graph as shown here. It shows that thicker insulation is absolutely necessary to maintain higher interior surface temperatures. One and a half inches of urethane on the walls and ceiling of a potato storage would control the heat loss from the building, but it took a minimum of three inches of urethane to control the interior surface temperature. Four inches was even better. With five inches the difference is practically negligible. The only place where we have felt the need for five inches of urethane was insulating the roof or ceiling of a sub-zero freezer.
Underground housing — surface temperature control vs heat loss control
My experience is that R-value tables can be used as indicators. However, they need modifications to make them relevant in real world conditions. To accomplish this, the tables must show equivalents clarifying the fact that one inch of spray-in-place urethane is equal to four inches of fiberglass in a normal installation. Footnotes to the table should define degradation of insulation according to real world conditions. Only then will the "R-value" Fairy Tale become a legitimate real world success story.
Reduction in Overall Heat