Why should we insulate with reflective insulation beneath our metal roofing?
Lets start with…
What is radiant energy?
Energy from the sun that travels 93 million miles through space to warm the earth.
How do we cool it?
· Conduction
· Convection
· Radiation (infrared)
What is conduction?
When two surfaces come in contact, the warmer surface gives up heat to the cooler surface as can be seen with a glowing burner on a stove heating the pot it is in contact with. In a building this is limited primarily to studs connecting outer and inner surfaces
What is convection?
The movement of air as a result of air being warmed. Warm air rises seeking the coldest point. Convection is visible as wavy lines above a hot road. Convection is a major concern in the winter, but not in the summer.
What is infrared radiation?
Electromagnetic waves that can only be seen as part of the rainbow. It travels at 186,000 miles a second.
Radiant energy travels in all directions seeking a cooler object to strike and then generates heat. Microwave ovens work on the same principles. Standard ovens heat the air, while a microwave heats what it sees. Infrared is like microwaves at lower frequencies. Most of us do not understand
microwaves or electricity but we use and enjoy the benefits of them. We may not understand infrared radiation, but we can learn to make it work for us by learning how to control it.
so again….. Why do we insulate??
1. For comfort
Lowers attic temp; when its winter, we want to stay warm. When its summer, we want to stay cool!
2. Reduce energy consumption
Reflective insulation keeps infrared from sneaking through ceilings thus leaving less for your utilities to cool/ heat
3. Help control condensation
Excellent vapor retarder- does not absorb moisture at all
What is an R-value?
The resistance to conductive heat flow which is only 3-7% of total heat loss
Does R-Value effect Infrared Heat?
No, in most cases, infrared is absorbed, stored, and escapes where we don’t want it
Does R-Value effect convective heat loss?
Some. Recent studies show that the colder your attic space gets, the more heat loss you have through convective currents.
What about moisture?
Most mass insulations absorb moisture, especially in the winter when warm moist convective currents find a cold surface. Once this occurs, the R-Values drop tremendously and in extreme cases the insulation must be removed.
When insulating, we must take into consideration all 3 forms of heat loss & gain. Over time, we’ve pretty much established solving conductive heat loss; what about the other 2?
Infrared
Is infrared blocking a new form of insulation?
No, its actually one of the oldest forms of insulation dating way back to the 1700’s but once the government confiscated aluminum, this shut down the reflective insulation industry. It wasn’t until the 1960’s that the space program NASA brought back infrared blocking in space suits, spacecraft insulation, and just about anything they sent into space.
In our everyday life we use Low-E benefits. When we bake a potato, we wrap it in aluminum. When we roast the Thanksgiving turkey, we cover the legs and back to keep it from scorching. Many food items are sealed in aluminum to keep them fresh.
For years, windows were the big problem in our homes when dealing with heat loss and gain, then they coated windows with a low-e coating, making them more efficient. Isn’t it time we make our homes as efficient??
What does Low-E mean?
All surfaces have an “e” rating from .01 to 1.0. The “e” stands for emissivity, which is the ability of a surface to reradiate or give off radiant heat to a cooler surface. The lower the “e” rating, the lower the amount of radiant heat the surface will give off.
We all know that we need insulation with good R-Values- which is the resistance to heat flow; the higher the R-Value the better is slows conductive and convective heat loss BUT R-Values and Regular insulation won’t stop radiant heat loss…. LOW-E WILL!
What is Low-E insulation?
The Low-E Insulation family of products are the most advanced, quality, reflective insulation products on the market today. These products are constructed of a core of environmentally agreeable foam bonded to two exterior faces of 99.4% pure, highly polished aluminum. This product meets the energy needs of today and addresses the concerns of the future by utilizing a polyethylene core that is made with recycled foam.
Why Low-E insulation??
It resists all three types of heat transfer, Conduction, Convection, and most importantly, Radiant Energy Transfer- which is the primary mode of all heat transfer.
Is a universal product- wrap your water heater to retain its heat, wrap pipes in the winter, AND MOST IMPORTANTLY place under your metal roof as a stand-alone roofing underlayment!
Turn your home into a thermos bottle; there has never been anything better for keeping something hot in the winter, or cold in the summer than the Thermos bottle!
Source: http://low-e.com
