This entry was posted on December 4, 2014.
A Reflective Moment...
As the temperatures drop outside it is a good time to discuss insulation.
Most yurts use a LOW-E Radiant Heat Barrier type yurt insulation. Rainier Yurts offer a single layer and a double layer of this NASA developed material. This form of insulation is new to most people - including building departments. This blog is designed to educate you on Radiant Heat Barrier Insulation and give you informative tips when conversing with your local building department.
IN THE BEGINNING:
NASA was trying to find a way to protect the astronauts during space walks from the extreme temperature shifts ranging from -273 degrees Celsius to +238 degrees Celsius. They discovered that they would have to have a seven-foot thick protective layer on the space suit if they attempted to use conventional insulation. Obviously, this was way out of the question.
Instead of trying to insulate the suits, they turned to reflective technology and used aluminum foil radiant barrier to solve the problem. NASA reflected the heat of their own body back at the astronauts to keep them warm, while at the same time they used the foil to reflect the deadly direct radiation from the sun (radiant heat) out of the space suit to keep them cool.
BACK ON EARTH
Most people are familiar with traditional insulating materials such as fiberglass, cellulose, Styrofoam, and rock wool. These products use their ability to absorb or resist (slow down) convective and conductive heat transfer to insulate (R-value). A third, seldom discussed but dominant form of heat transfer exists: radiant heat transfer. A radiant barrier reflects radiant heat energy instead of trying to absorb it. This is the preferred type for yurt insulation.
A few decades ago, insulation wasn't given the importance that it is now. Power was much cheaper, so rather than worry about different types of insulation and what would best fit your home, it was much easier to simply crank the heat. However, as most homeowners today are all too aware of, this is no longer the case. Because of the increase in power costs and the emphasis on remaining environmentally aware, many more insulation types have come on the market and been refined as research and development teams uncover new technologies. Radiant Barrier Insulation provides a completely different type of protection than traditional insulation. visit: http://www.eshield.net/
BASICALLY PUT, IN A YURT
The foil on both sides allows it to reflect 95 - 97% of radiant heat away from a structure on the outside and back into a structure from the inside - thus working effectively in both hot and cold climates. This "green" insulation is highly effective when used with a consistent internal heat source thus by significantly reducing the amount of heat leaving or entering any structure where it is applied. When using a radiant barrier or reflective insulation, if a consistent heat source is present, 95-97% of the radiant heat will reflect back to its source when installed properly.
The R value of insulation is a measure of how effective it is at resisting two forms of heat transfer: conduction and convection. Conduction is when heat is transferred between solid objects, while convection is when heat is passed from one object to another through air circulation. Both of these forms of energy transfer can be straining on utility bills, which is why insulating homes with a high R value product is extremely important. However, most people don’t realize that insulation loses R-value over time, resulting in more heat lost and higher power bills. There is a third type of heat transfer, emission, which is actually far more detrimental to utility bills if homes are left unprotected.
Radiant barriers retard heat transfer by two means - by reflecting radiant energy away from its surface or by reducing the emission of radiation from its opposite side.
Emission is the direct transfer of heat from a radiant source – for example, the sun. Emission is the type of energy transfer that causes the biggest strain on utility bills. The ability to protect homes from emission is measured in E value, which standard insulation typically has a very low rating in.
YURTS AND THE BUILDING CODE
The question of how to quantify performance of other systems such as radiant barriers has resulted in controversy and confusion in the building industry with the use of R-values or 'equivalent R-values' for products which have entirely different systems of inhibiting heat transfer.
According to current standards, R-values are most reliably stated for bulk insulation materials.
Calculating the performance of radiant barriers is more complex. With a good radiant barrier in place, most heat flow is by convection, which depends on many factors other than the radiant barrier itself. Although radiant barriers have high reflectivity (and low emissivity) over a range of electromagnetic spectra (including visible and UV light), their thermal advantages are mainly related to their emissivity in the infra-red range. Emissivity values are the appropriate metric for radiant barriers. Their effectiveness when employed to resist heat gain in limited applications is established, even though R-value does not adequately describe them. The R-value for our single layer reflective insulation = R9 and our double layer = R10 however when used with a decent heat source these values more than sufficient in a round structure where heat bounces off the walls and back to the center. Sidebar: there in-lays the problem with building code officials...they just can't think outside the box and in the round!
Radiant barrier insulation is a vital part of your yurt’s complete protection against heat transfer. Able to stop more than 95 – 97% of radiant heat, radiant barrier reflective foil insulation is an exceptionally efficient and innovative solution to thermal insulation needs. Most types of insulation protect against conduction and convection, measured by R-values. However, they fall short of reflective insulation when it comes to E-value, which measures radiant heat transfer, the main source of lost heat in homes.
Radiant barrier insulation protects your yurt from heat radiation – the leading cause of heat loss and gain in homes. Also, fiberglass can compress or become damp over time and lose much of its r-value – or level of protection against conduction and convection, while a radiant heat barrier never absorbs moisture and retains its e-value – or level of radiant heat emissivity – for life!
- Class A, Class 1 Fire Rating (passed the ASTM 286 Fire Test)
- Has Sound Deadening Properties
- Insect Resistant
- Excellent Vapor Barrier
- Reduces Condensation
- A Permeability Rating of 13 – so no mildew or other moisture damage will occur
- Contains No Allergens
- Requires no Gloves, Masks, or Wire to hold in place
Q: Why don’t building codes specify E-values as well as R-values?
A: In the last century, the only cost-effective insulation for the home was mass insulation like fiberglass, cellulose and foam that reduced heat transfer by convection and conduction. The “R-value” was the measure of how good a job those insulators did. Yet R-value measures only the smallest part of residential heat transfer. E-value is the measure of emissivity, radiant heat transfer, the principle source of energy loss. New technologies make it practical to achieve extremely low emissivity in window glass and in a reflective film ideal for the attic. As these low-E technologies advance, the codes will catch up and E-value will replace R-value as the primary measure of energy efficiency.
Q: Will reflective foil barrier insulation trap mildew-causing moisture in my yurt walls and ceiling?
A: Low-E reflective barrier is designed to allow vapor to escape the yurt envelope with Perm Rating of 13 – it will not contribute to mildew growth in your home.
Q: Will reflective barrier insulation create a fire hazard in my yurt?
A: Reflective barrier insulation is fire-resistant with a Class A fire rating – Of course, like almost any material, it will melt and eventually burn if exposed to an open flame for prolonged periods of time.
Building code officials are reading from a old script dating back to the 60's and 70's. They need prodding to catch on to today's technologies and environmentally designed products. If you meet opposition to getting your yurt permitted because you cannot get a sufficient R-value for insulation; I encourage you to challenge them as R-Values do not adequately describe Emissivity Values which is the appropriate metric for radiant barriers.
Good luck and stay warm!
Enjoy the journey!