Do we really understand heat? To understand insulation and how unique products like Super Therm® work, we must understand the basics, like heat follows cold and more. Read this tutorial to increase your knowledge. This tutorial is simply intended to give some of the basics of heat energy, and how it relates to insulation and ceramic coatings. It is not intended to be comprehensive.
There are three basic types of heat transfer: conduction, convection, and radiation.
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.
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.
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.
Super Therm® works against all three forms of heat transfer. It is most effective against radiation, as it reflects over 95% of the energy from the sun.
Super Therm® fights convection because it allows no air movement through the coating, while avoiding taking up any heat from the air itself.
Only Super Therm® 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. Super Therm® coated on a roof prevents this from happening, by reflecting the suns energy before it reaches the metal underneath.
- As the metal gains heat, it heats the air inside the building, forming air convection currents. In this way, heat builds up underneath the roof, and eventually the entire building.
- When Super Therm® is used, the metal doesn't have a chance to heat up, and thus the building remains cool.
A simple rule for the direction of transfer of heat is this: Heat follows 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.
The R-value is simply a measure of how well a conventional insulation resists heat transfer through conduction only. The greater the value, the greater the ability of the insulation to resist and absorb conductive heat.
A little bit of history: The R-value system was originally developed when the first mass insulation, fibreglass, was first developed, 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 fibreglass, 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.
- Normal insulations, including fibre-based (fibreglass, 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 convection currents do not 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 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 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 fibreglass, the results of these tests change dramatically under even slightly different conditions:
- If 1.5% humidity is introduced, fibreglass 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 fibreglass would perform best. Above and below this temperature fibreglass rapidly loses effectiveness and the R-value is lower.
- Air movement also greatly affects the R-value of fibreglass, as heated air moving through the fibreglass drastically reduces it's conductive value.
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. Super Therm®'s performance is not affected by 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, Super Therm® would outperform all other insulation.
Super Therm® works against all three forms of heat transfer. It is most effective against radiation, as it reflects over 95% of the energy from the sun.
Super Therm® fights convection because it allows no air movement through the coating, while avoiding taking up any heat from the air itself.
Only Super Therm® 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.
Super Therm® 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.
Lower energy costs, as air conditioners need to work less to dispel heat that never has a chance to collect.
Less heat stress on personnel and livestock, equals increased productivity. A longer lifespan for the surface it is coated on, as the metal itself is protected from expansion and contraction due to the rapid heating and cooling cycles during the days.
The coatings themselves protect against weathering and damage from the environment. Super Therm® will provide 20 years of protection.
Basically, the energy costs must be examined:
If heating costs in the winter are considerably less than the cooling costs in the summer, Super Therm® is the choice. 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.
Insulation against frost:
If you need to insulate building against frost or cold - here will help common insulation. But better use solid foam insulation rather than glass-wool or another moisture absorbing material. Pay attention to foam insulation not to stifle Your house, therefore it has to be vapour-permeable, otherwise you wiil get heat in house but moisture and mildew too.
Most sophisticated high-vapour-permeable foam insulation on market is STYREXON (www.styrexon.sk).
We use STYREXON insulation in our combined systems for northern regions with colder weather. You will find more about in section COMBINED SYSTEMS.
Radiation - The process in which heat emanates from a body through open space by means of rays, for example solar radiation.
Temperature - The temperature level is measured in degrees Celsius (°C); temperature differences are measured in Kelvin (K).
Air leakage: - Penetration of air into a building through cracks or structural material.
Condensation: - Condensation is the change of vapour from the gaseous state to the liquid state upon contact with a cold surface.
Conductivity: - transfer of heat through, along or from a material to another material it touches.
Convection: - Transfer of heat via air movement.
Absorbency: - the ability to absorb incident solar radiation.
Emissivity: - Can be defined in two ways, as:
- Absorptive emissivity: (ability to retain radiant heat), is given as a measure of emissions released from a surface. Materials with matte black surfaces have high absorptive emissivity approaching the maximum limit of 1.0 retain a large volume of radiation. In contrast, bodies with lustrous surfaces such as mirrors or burnished aluminium have low emissivities around 0.08 and thus retain practically no radiation within themselves.Super Therm® has the incredibly low absorptive emissivity value of 0.05.
- Infrared emissivity: : (ability to shed radiant heat, emit it), is also given as a measure of emissions released from a surface. Super Therm® has very high (more than 95%, or 0.95 value) infrared radiative emissivity, meaning that it is extremely effective in shedding even the smallest amount of heat it might absorb.
Heat loss: The transfer of heat from internal spaces to the outside by means of conduction, convection and radiation.
Thermal conduction: The rate at which heat passes through a material, measured in Watts per square metre of surface over degrees Kelvin per metre of thickness, simplified to W/mK.
Thermal mass - is the mass of a building which is used in the absorption of solar heat in the course of a day, and then releases the heat at night.
Measured thermal resistance: R-thermal resistance is a physical quantity which expresses the thermoinsulative properties of the construction. The goal is to achieve the highest possible R-values. An R-value expresses the resistance of 1 m2 of construction to the transfer of thermal energy for a temperature difference of 1 K.
Vapour-permeable material: Vapour-permeable material prevents leakage of water yet still “breathes”, letting water vapour pass.
