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Insulation 101

From “Websters New World Dictionary”,

Insulate is defined as :

1. “to set apart; isolate”

2. “to cover with a non-conducting material in order to prevent the escape of electricity, heat, sound, etc.” 

Insulation is defined as:

1.  “insulating or being insulated”

2.  “material for this”

From this we can assume that there are insulations directed at thermal, acoustical, and electrical applications.  We know the auto industry spends millions trying to insulate riders from vibration.  The Insulation Man only involves itself with thermal insulation systems.  In truth, some acoustical remedies are a side effect of a good thermal system.  In fact, the fiberglass batt industry sells the exact same material for both applications.  

From the thermal standpoint: Insulation works by holding some medium still.  The medium is air in most systems.

In a closed cell foam system the insulating medium is a refrigerant gas. In 2005 the EPA forced foam manufacturers to remove all Ozone Depleting Chemicals from their products. Now we use Honeywell’s Enovate material as the blowing agent in most applications.

Still air has an insulating value of R-5 per inch of thickness.  Gasses used in closed cell urethane foam systems have R values of 6.3 per inch of thickness.  Most building insulation systems have an R value in the range of 3.5 to 7.2 R’s per inch.  Several products have been introduced in the past couple years that claim the have R values above R-7 per inch. Claims of R value above R-7 per inch of thickness are fraudulent and will eventually be proven as such. There are physical limits to how well anything can insulate. If it sounds too good to be true, it probably is not true.

R-Value

What is an R anyway?  One R is the inverse of one U.  U value is a measure of the rate of heat flow due to conduction across an insulation system measured in BTU’s per hour per square foot.  Heat flow can be called heat loss or heat gain.  Confused?  Just accept that R value is a measure of a systems resistance to heat flow by conduction.  The greater the R-value, the greater the insulation power of the insulation.

Is that all?  Nope.

Heat Loss

How do we prevent heat flow?  There are three components of heat loss.  They are conduction, convection, and radiation. 

Conduction is the movement of heat through a substance by traveling from molecule to molecule.  Since gasses have fewer molecules than solids or liquids, and these molecules are farther apart, the heat traveling through a gas is more restrained.  Lighter gasses will be better at stopping conduction than heavier gasses.  Since air is a comparatively heavy gas it is not as efficient at stopping conduction as refrigerant gasses like Enovate.

Convection is the movement of heat with a medium.  Gasses are the best products to stop heat loss by conduction, but gasses move easily.  If the heat is stuck in the gas, but the gas moves, the heat moves too.  Lighter gasses move easier than heavier gasses.  Testing by labs such as Oak Ridge National Labs, and the National Association of Homebuilders Research Center, among others has shown that convective heat loss (Air Infiltration) will account for about 40% of the total heat loss in a home. 

Radiation is the movement of heat as energy.  Hard to explain, but easy to describe.  Stand near a camp fire, the side of you toward the flame is hot, the side away is cool.  Heat is radiating to you. When you are in a grocery store next time, walk by the freezers and notice that you feel cold. In reality, the air you are standing in is the same temperature as the air in the rest of the store. You feel cold because your body is radiating heat to the freezer to try to warm it. Heat goes to cold.

Until very recently, mainstream building science completely ignored heat loss by convection and radiation.  Since all the emphasis was on conduction, R values dominate the knowledge of builders, suppliers, and consumers when insulation systems are discussed.  Unfortunately, the best insulation systems in terms of price verses performance are often overlooked because the R value is relatively low when compared to the cost.  Worse yet, several “Super Insulated” home projects have been undertaken where framing and construction details were changed to increase R-Values but convection and radiation were still ignored.  This resulted in expensive houses with 12 inch thick walls that were not all that efficient or comfortable.  

Today there is research supporting the theory that if Convection and Radiation are controlled, Conductive heat loss can be satisfactorily limited by application of R-15 or less in wall systems.

So what are the properties of a good insulation system?

A good insulation system will control heat loss by all three processes.  Conductive heat loss is in the codes, it is quantified, and we must follow the code.  Convective heat loss is more elusive, but it can be successfully restrained using blown and foam products.  Radiation is usually not addressed.  However, since this is the movement of heat as energy from one surface to another, forcing the surfaces in question to be at the same temperature as the rest of the surfaces in a room will effectively stop heat loss by radiation. 

Back to insulation. 

Are there insulation products that will stop all three components of heat loss?  Yes, there are. They are Fiberglass, Cellulose, and Foam.  

Are all of these products the same?  Absolutely not.  The differences are in the installation process.  

Fiberglass batt insulation alone is only effective against conductive heat loss.  Fiberglass Batt insulation will fail miserably if it is asked to stop even the slightest air movement.  That is why the building codes today provide for exterior air barriers like Tyvek, and interior vapor retarders like polyethylene and kraft paper.  Imagine the practicality of installing a 3 dimensional barrier that will stop all air movement and vapor migration in a home.  It is frequently a practical impossibility to provide these barriers. 

Blown Fiberglass and Blown Cellulose are much better at stopping all components of heat loss.  By design these products will fill all voids in insulated spaces.  They are also typically installed at higher densities than fiberglass batt insulation.  These two properties cause them to be much more suitable to stopping convective heat loss.  The R value of these products will be more stable in adverse weather conditions than batt products because of their higher density.  The limitation on these systems is they will not work in areas where they will be unsupported, and they cannot effectively be installed in wall cavities thinner than 4 inches. 

Urethane Foam is the most complete system.  This system fills all voids and it has a stable R- value in adverse weather.  Urethane Foam is not susceptible to failure due to convective heat loss.  Urethane Foam is self supporting, so it will perform equally in closed wall cavities and unsupported areas.  Urethane Foam is easily installed in narrow and closed cavities.  The only real objection to Urethane Foam is price.  Truthfully, if a consumer understood the difficulty and cost involved to bring a fiberglass batt insulation job up to the performance standards of Urethane Foam, he would understand the price.  However, since the federal standards recognize only R value, and they make no provision for convection and radiation, the standards make these systems seem equal.  This is like comparing a Yugo and a Mercedes and saying they are both cars.

So what is the best insulation system?

Cost is a justifiable, absolute parameter.  The best system is cost effective and performs the best.  The best system will cost more than fiberglass batts and less than Urethane Foam.  The best system is not one system, it is a combination of using Urethane Foam where it is most effective and blown insulation in the other spaces.  The Insulation Man can provide this combination approach to customers in our service area.

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