SUPERTHERM ® - Thermal Tutorial
This tutorial is simply intended to give some of the basics of Thermodynamics , and how it relates to insulation and ceramic insulation coatings. It is not intended to be comprehensive. For a more comprehensive and technical explanation please refer to : HEAT TRANSFER TRAINING CLASS - SCIENTIFIC / TECHNICAL
Do we really understand heat? To understand insulation and how a unique product like SUPERTHERM ® works, we must understand the basics of heat energy transfer, such as: heat always seeks and moves to cold and more. Read this tutorial to increase your knowledge.
How does heat move?
There are three basic types of heat transfer: radiation, convection, and conduction.
Radiation
- Energy transferred through electromagnetic waves.
- Air absorbs very little energy from radiation. When radiative energy strikes a solid surface, it heats the surface, and the energy is converted to conduction.
- Example: energy from the sun is in the form of radiation, which is the largest source of heat gain in a building. Also interior sources of radiation such as radiators, lighting, body heat, etc. A microwave oven.
Convection
- Energy transfer through the movement of gases or liquids.
- Most of heat energy transferred in this manner occurs when heated gases start moving, forming currents that carry the energy from one location to another.
- Example: forced air heating uses convection to heat a room. A convection oven.
Conduction
- Energy transfer through solid objects.
- Different types of solids transmit heat differently than others, with metals being among the best for heat transfer, and ceramics being some of the most resistant.
- Example: heat from a cast iron frying pan moves through the handle to your hand. A stove.
SUPERTHERM ® works against all three forms of heat transfer. It is most effective against radiation, as it repels over 95%, ie. the energy from the sun, interior sources of radiated heat, etc.
SUPERTHERM ® reflects 100% convection because it allows no air movement through the coating, while avoiding taking up any heat from the air itself.
Only SUPERTHERM ® resists heat transfer through conduction as well, due to the unique ceramics used to resist the movement of heat through the coating itself.
Also note that energy is constantly being converted from one heat transfer method to another. Using an uninsulated roof can demonstrate this quite nicely:
- Energy comes down from the sun in the form of radiation.
- A small amount of heat is absorbed by the air, transforming it into convective heat.
- When the radiation from the sun and the convective heat from the air come in contact with a roof, they heat the surface converting this energy into conductive heat transfer, which heats the metal. SUPERTHERM ® coated on a roof prevents this from happening, by repelling the suns energy before it reaches the metal underneath.
- As the metal gains heat it is conducted through the metal and radiated to the inside. Have you ever stood a few feet away from an uninsulated metal door and felt the radiated heat? It then heats the air inside the building, forming air convection currents. When SUPERTHERM ® is used, the metal doesn’t have a chance to heat up, and thus the building remains cool.
In this way, heat builds up underneath the roof, and eventually the entire building.
Where does heat move?
A simple rule for the direction of transfer of heat is this: HEAT MOVES TO COLD.
- Heat always follows the path of least resistance: whichever direction is cooler is the direction the heat will move.
- What this means is that if there are two objects with different temperatures, the hotter object will always transfer heat to the colder object.
- For example, when the temperature on one side of a roof is hotter than the other, heat is transferred, through conduction, from the hot side to the cool side through the roof until the temperatures are equal.
- The belief that heat rises is only true in one circumstance: heated air will rise as it forms convection currents. Heat energy itself normally moves in the path with the least energy (the coldest surface), whether it be up, down, or sideways.
What is R-value? See the " R Value Fairy Tale "
An R value means the insulation loads and unloads with heat. This is why when the outside ambient temperature cools down at night the building is still hot inside ( requiring extra work by the HVAC equipment ). An R value only measures conduction and doesn't account for convection and radiation, the other two methods of thermal transfer. The R-value is simply a measure of how well bulk insulation resists heat transfer through conduction only. The greater the value, the greater the ability of the insulation to absorb conductive heat until it reaches saturation point at which time the bulk insulation becomes a " heat pump ", pumping the heat into or out of a structure.
A little bit of history:
- The R-value system was originally developed when the first mass insulation, fiberglass, was initially developed by Owens Corning Fiberglass Corporation, to give a rating for it’s ability to resist and absorb heat.
- When the tests were put into place, they were designed to measure the properties of fiberglass in a best case scenario, and to ensure that the highest results would be obtained.
- The tests were all done under very specific and controlled conditions with regard to the difference in temperature, humidity of the material, and an absence of air movement.
How does conventional insulation work?
- Normal insulations, including fibre-based (fiberglass, cellulose, etc.) or solid insulation (polyurethane foam, SM board, etc.) contains small pockets of gases, usually air.
- Heat is transferred slowly through most gases, and thus through the insulation.
- The pockets of air are small enough that minimal convection currents develop inside of the pockets, and thus the heat moves very slowly.
- The smaller the air pockets, the greater the resistance to heat transfer and thus the greater the R-value. This is why different insulations have different values.
- As a side effect, insulations absorb and hold heat as it moves from the hot side to the cold side of the material.
For example, an air conditioned building in the summer:
- The warm temperatures outside of the building are always attempting to penetrate into the cooler areas inside the building.
- Insulation in the building resists this heat transfer, slowly absorbing the heat until it is either saturated, or the temperature difference decreases.
- Once saturated, the heat passes through the insulation into the cooler area.
- In the evening, when the outside temperature decreases, the heat begins transferring from the warmer insulation, to the cooler air outside of the building.
The downside of R-value testing.
The R-value system only accounts for the abilities of insulation against conduction. Against the other two forms of heat transfer (convection and radiation) the effectiveness varies greatly depending on the type of insulation.
For fiberglass, the results of these tests change dramatically under even slightly different conditions:
- If 1.5% humidity is introduced, fiberglass loses roughly 35% of it’s R-value, due the fact that water is a much better conductor than air.
- All tests are done only at temperatures in which fiberglass would perform best. Above and below this temperature fiberglass rapidly loses effectiveness and the R-value is substantially lower. In full-scale attic tests at Oak Ridge national Laboratory, the R-value of 6 inches of cubed loose-fill attic insulation progressively fell as the attic air temperature dropped. At -18 F ( -27.78C ), the R-value measured only R-9. The problem seems to occur with any low-density, loose-fill fibrous insulation. Nisson, J.D. Ned, JLC, "Attic Insulation Problems In Cold Climates" March 1992, pp 42-43
- Air movement also greatly affects the R-value of fiberglass, as heated air moving through the fiberglass drastically reduces it’s conductive value. ( see "Attic Insulation Problems In Cold Climates" March 1992, pp. 42-43 Nisson, J.D. Ned, JLC, in the R Value Fairy Tale )
R-value testing methods do not reflect real world conditions, which can vary greatly with regard to all of these factors: material humidity, temperature differences, and air movement.
Unfortunately these same tests are still used today, despite the fact that new insulations have been introduced into the market. Solid insulations are even more effective than their R-value would suggest, as they are completely unaffected by humidity, temperature, and air movement, as well as having long-term thermal resistance. SUPERTHERM‘s ® performance is not affected by temperature differences, moisture or air movement.
Another downfall is radiation is not accounted for in R-value testing. If stopping radiation was included in R-value testing, SUPERTHERM‘s ® R-value equivalence would go up 'significantly' because radiation heat transfer increases by 4-th power of temperature difference. SUPERTHERM ® would outperform all other insulations.
As noted by PhD Inn Choi " When 95% of heat input into a substrate is blocked and only less than 5% of heat is allowed to enter into a substrate, the overall benefits from different material insulation properties for this 5% are trivial ".
How is SUPERTHERM ® different?
SUPERTHERM ® works against all three forms of heat transfer. It is most effective against radiation, as it repels over 95%, ie. the energy from the sun, interior sources of radiated heat, etc.
SUPERTHERM ® fights convection because it allows no air movement through the coating, while avoiding taking up any heat from the air itself.
Only SUPERTHERM ® resists heat transfer through conduction as well, due to the unique ceramics used to resist the movement of heat through the coating itself.
This simply means that heat never builds up. Normal insulations resist and store heat, thus preventing it from passing through the bulk. SUPERTHERM ® stops heat movement so effectively that heat hardly builds up at all. It strongly resists any energy movement through radiation, conduction and convection, through its unique blend of ceramics.
How can SUPERTHERM ® ceramic insulation coating help you?
- Lower energy costs, as air conditioners \ heating sources need to work less.
- Lower temperatures inside of unconditioned buildings.
- A longer life span for the surface it is coated on, as the substrate itself is protected from expansion and contraction due to the rapid heating and cooling cycles during the days. SUPERTHERM ® also blocks better than 99% of UV rays. While UV radiation only adds 3% to the total heat load; it is the principle cause of damage to any surface. It causes the tar to crack, the shingles to curl, the seams to split, the foam to crack, etc.
- The coatings themselves also protect against weathering and other damage from the environment such as acid rain. SUPERTHERM ® will provide a minimum of 20 years of protection in most environments.
- Less heat stress on personnel, livestock and stored agricultural products, equals increased productivity \ nutritional value.
- Reduced maintenance costs on equipment, due to less variance in ambient temperatures. Air conditioning \ heating equipment needs to work less often, and at a lower work load.
- Reduced maintenance \ replacement costs from Condensation and Corrosion. SUPERTHERM ® will not allow corrosion to develop under it. The ceramics bond tight to the substrate surface preventing the passage of moisture, air and atmospheric conditions to affect the surface. In all fiberglass wrapped pipes found in industrial or petrochemical plants, the pipes are all corroded when the fiberglass is removed. Fiberglass breaths the air, moisture and conditions into the air pockets and holds this mixture causing the surface of the pipes, walls, etc. to become corroded in a short amount of time.
- Reduced health risks as SUPERTHERM ® is extremely environmentally friendly. The VOC's ( Volitile Organic Compounds ) are only 21 grams/liter. The limit is 420 grams. SUPERTHERM ® is 11.9 times less toxic than that of typical latex paint which has a VOC of 250 g/L. SUPERTHERM ® has received a " K " rating by NASA for toxic off gassing which is the highest rating available. In addition to the inherent thermal deficiencies in fiberglass, there is also the possibility of some inherent health concerns. For further information regarding the very real possibility of fiberglass being as carcinogenic as asbestos visit the Fiberglass Information Network ( http://www.sustainableenterprises.com/fin/index.htm ).
How to choose an insulation application?
Basically, the energy costs must be examined. If heating costs in the winter are considerably less than the cooling costs in the summer, SUPERTHERM ® should be applied to the exterior of equipment or the building envelope ( and qualify for " LEED " points ). This is especially true where heating is not an issue: in coolers, freezers, and arenas where the sole objective is to maintain a low temperature.
If energy costs involved with heating are higher, then SUPERTHERM ® should be applied to the interior side of the building envelope or equipment.
Of course the optimum application would be to coat both sides, so that neither side could take on heat, in which case the substrate itself would become part of the insulation package. To the extent possible it is desirable to have the ceramics facing the heat source.
If one side of the substrate is uncoated and allowed to absorb heat, the heat will still be repelled once it reaches the ceramics. This was demonstrated by the use of infrared technology where the SUPERTHERM ® was applied to the exterior of a roof and then infrared scans were taken in the middle of winter to document the heat retention. http://www.eaglecoatings.net/content/supertherm/projectpictures/roofinsulation.htm
