WHY IS THE MYTH PERPETUATED?
It definitely favors ‘traditionally used’ fiber insulations made by large International Corporations, who regularly lobby & contribute to keep it in place, despite peer reviewed science that shows its limitations.
R-Value has long been part of the building and construction industry as the measure of thermal performance of a structure. It has been a long-held belief that a higher R-Value is the same as more efficient building insulation. Spray Polyurethane Foam (SPF) has changed some of the most common beliefs associated with the R-Value. There are many references to the R-Value “Myth” or “Fairy Tale” and the description of the 3 main heat transfer systems will expose the myth.
Conduction: transfer of thermal energy between neighboring molecules in a solid substance such as insulation.
Convection: transfer of air molecules through insulation and ultimately the building envelope.
The R-Value is a measure of a material’s resistance to heat transfer. The R-Value test performed under the guidelines of ASTM C518 takes into account the resistance of all three heat transfer mechanisms: conduction, convection and radiation; however, convection is given only minor consideration. Unwanted convection through the building envelope is the biggest contributor to energy loss.
Conduction typically accounts for 20% of a building’s heat loss, while convection accounts for up to 80% of the energy loss depending on the quality of construction. Any convective loops inside the insulation material are taken into consideration by the R-value test method, but air leakage through the entire composite building envelope is not considered at all. Closed cell spray foam at ¼” can stop 99% of heat loss by convection and at 3″ will prevent 95% of heat loss by conduction. Obviously, the same holds true for an air-conditioned structure.s
As a contractor in the spray foam industry, questions about R-Value are some of the most common concerns of home owners and builders. To help contractors and home owners alike, Paratus has compiled a short collection of Common Questions and Answers:
“The higher the R-Value the better, correct?”
Yes, higher R-Value in your home or building is somewhat better; however, it should not be overrated at all.
SPF’s ability to create an air-tight seal for your home is the most important factor in creating an energy-efficient, comfortable, and healthy home. About 80% of the energy loss of your home or building is caused by unwanted and uncontrolled air flow through the walls, ceilings and floors.
“What is the R-Value of your product?”
R-Values vary by manufacturer.
Closed cell SPF offers higher R-Values per inch than conventional insulating alternatives.
Most importantly, only spray foam provides total air tightness. As a matter of fact, just a little more than 2 inches (5 cm) of closed-cell foam provides a vapor barrier. No other insulation system can provide that! When promoting foam, the air-tightness alone should be a compelling reason to insulate with SPF.
Good understanding of R-Value, air leakage and air changes in a home or building is a crucial sales tool for any foam insulation contractor. Besides home owners, even professionals like builders and architects often have not thought through R-value vs. air leakage, and need to be educated by all of us in the foam industry.
What would the R-value of insulation be after it has been submersed in water or had a 20 mile per hour wind blowing through it? Obviously the ‘Effective’ R-value of fiberglass, cellulose, wool and/or cotton insulation would go to zero, but Spray Foam Insulation would be largely unaffected. Again, R-values are ‘funny’ numbers; they are meaningless unless we know all the relevant factors.
The use of R-values as the only criteria for insulation is absolutely ridiculous, yet we have Government Agencies mandating R-values of 30 to 50 today, despite any actual science to support these levels. Traditional insulation having an R-25-value installed in a wall/floor/ceiling, but not properly sealed will allow air to travel through it and/or moisture to saturate it – providing no real R-value at all.
R-Value is one of the most misused and misunderstood measurements in the world. The test results are determined in a 75-degree (F) lab with no wind load and ideal humidity. In such conditions the two insulation types are identical with respect to heat transfer. However, once the insulation is installed in a home in real world conditions, the heat loss/gain of fiberglass and cellulose are outrageous since cold and warm air move freely about them through convection. Spray Polyurethane Foam is an air barrier AND it is physically adhered to the wood framing members of a structure thus minimizing air infiltration. Think of fiberglass as a screen and Spray Polyurethane Foam as a window. Coincidentally, most furnace filters are made from fiberglass. These filters are obviously designed to allow the free movement of air through them.
R-values are a result standardized testing of heat flow through insulation in a sealed test fixture under controlled laboratory conditions, but these tests are not even remotely associated with the real world environment where insulation is commonly installed.
To calculate the actual installed performance of insulation, we also need to know its resistance to air penetration, to internal air currents, to liquid water, and to water vapor drive. What really matters is the ‘effective’ R-value when insulation is subjected to these real world conditions.
Fiber insulation is generally assigned an R-value of approximately 3.5 per inch, yet it can only achieve this value when tested in an absolute zero air-movement and zero moisture environment. Zero wind and zero moisture are not real-world conditions, as all homes leak air and water vapor from the outside air, showers, cooking, breathing, etc., constantly moving through our homes.
If the attic is not properly ventilated on a fiber insulated home, the water vapor generated inside a house will very quickly semi-saturate the insulation above the ceiling and in the walls. Even small amounts of moisture will cause a dramatic drop, as much as 50 percent or more, in fiber insulation’s performance.
Because such small amounts of moisture have devastating effects on fiber insulations performance, it is recommended that fiber insulation have a vapor barrier installed on the warm side of the insulation. This recommendation poses a completely new problem, which is the warm side of the wall?
Obviously, the warm side changes from summer to winter, even from day to night. If it is 30 degrees outside, the inside of an occupied house is certainly the warm side, conversely, during the summer months, when the sun is shining; the warm side is the outside of the wall.
Occasionally, a novice will put vapor barriers on both sides of the insulation, but this proves to be disastrous because the vapor barriers will stop most of the moisture but not all. Small amounts of moisture will still move into the fiber insulation, between the two vapor barriers and become trapped. Condensation will accumulate as the temperature swings back and forth, altering the direction of vapor drive forces, leading to significant mold growth, health problems, building rot and increased energy costs.
Fiber insulation must be ventilated on one side or you can end up with serious mold growth problems, as illustrated in these images. This required ventilation also allows air movement within the fiber insulation, significantly reducing its effectiveness AND R-Value.
Spray Foam Insulation does not have these limitations. It creates its own air-tight seal, while still allowing water vapor to pass through without accumulating or affecting its performance. This complete insulation, air barrier and moisture management solution is what makes Energy Solutions Spray Foam Insulation the intelligent choice for your home.
AIR CURRENTS IN TRADITIONAL FIBER INSULATION PRODUCTS
We all understand air penetration through the walls of our homes; we can even feel it in some homes when the wind blows. But what most people, including many engineers, do not realize is that there are very significant convection currents occurring within the traditional fiberglass, cellulose and cotton insulations. These convective currents move vast amounts of air, leading to significant energy losses.
Convective air currents are not fast enough to feel and are difficult to measure without sensitive instruments, but they are constantly carrying heat from the bottom of the fiber insulation to the top side, allowing it to escape.
If we attempt to seal off this air movement with traditional insulation, it will seal in the water vapor, where it will condense into a liquid, becoming a source of moisture for mold growth and rotting the wood in your home. This water vapor and resulting condensation will also seriously decrease the fiber insulation’s R-value and increase your energy costs. The only way to deal with fiber insulation is to ventilate, but to ventilate means allowing air movement, which decreases the R-value and increases your energy costs.
Once again, Spray Foam Insulation does not have these limitations, because it creates its own air-tight seal, while still allowing water vapor to pass through without accumulating or affecting its performance.
The filter for most furnace filters is made from fiberglass, the same spun fiberglass used as insulation. Fiberglass is used for an air filter because it has low resistance to the air flow, and it is cheap. In other words, the air flows through it very readily.
There are tremendous air currents that move through the walls of a typical home. To verify this, one can hold a lit candle near an electrical outlet on an outside wall when the wind is blowing. The average home, with all its doors and windows closed, has a combination of air leaks equal to the size of an open front door.
Even if we do a perfect job of installing the fiber insulation in a home and bring the air infiltration very close to zero from one side of the wall to the other, we still do not stop the conductive air currents from moving through the insulation itself vertically both in the ceiling and the walls.
Spray Foam Insulation is ‘air impermeable’ and cannot support internal air currents. As it is applied, it expands completely, filling every nook-and-cranny, creating a complete air-seal. The value of this total seal is almost impossible to overestimate because most of the heat losses in the floors, walls and ceilings of homes have way more to do with the air-seal, rather than the R-Value. The R-value of a material is of no interest or consequence if air can get past it!
Air infiltration can most effectively be stopped with Spray Foam Insulation. It is the only material, that when applied, will expand to fill all the corners, cripple studs, double studs, bottom plates and top plates, etc.
R-value tables are part of the Myth; they show Spray Foam and the fiber insulations side by side, implying they can be compared. The fact is, without taking installation conditions and air movement into account, these comparisons are meaningless.
Spray Foam provides its own vapor barrier, water barrier, and wind barrier – No Other Insulation Does!
No other insulation material can even come close to Spray Foam Energy Solutions Insulation’s installed effectiveness. Using spray foam insulation is guaranteed to save you energy and provide a healthier, more comfortable home for you and your family.
You only insulate once, but you’re going to pay for your Heating and Cooling costs for a long time.