How does Energy Improvements Radiant Barrier Shield Work?
Real World Examples
Summer Example
On a hot sunny summer day, solar radiant energy is absorbed by the roof, heating the roof sheathing and causing the underside of the sheathing and the roof framing to radiate heat downward toward the attic floor and ultimately your rooms below. With a radiant barrier placed on the attic floor (on top of your insulation), much of the heat radiated from the hot roof is reflected back toward the roof. (similar to car sun shades) Making the top surface of the insulation cooler than it would have been without a radiant barrier and reducing the amount of heat that moves through the insulation into the rooms below.
Winter Example
On a freezing wintery day, your house’s heat rises and is absorbed into your attic’s insulation. At the same time the colder and denser air settles into your insulation from above. Heat then moves to warm the colder insulation while at the same time the colder air continues to settle in lower. With a radiant barrier placed on the attic floor(on top of your insulation), much of the heat radiated from the rooms below is reflected back down into the rooms. The radiant barrier also keeps the cold denser air from settling into your insulation, by acting as a thermal blanket, this keeps the cold air from settling into your house.
Radiant Barrier and Heat
First principle of heat transfer, heat travels from a warm area to a cool area, mainly by a combination of conduction (direct heat flow), convection(heat rising), and radiation (heat moving from hot to cold) as illustrated below.
Conduction: happens when two solid objects touch each other, heat is transferred through the objects. A good example is when the stove gets hot, heat is transferred to the teapot.
Convection: happens when the air is warmed. The warm air expands, becomes less dense and rises, while the colder and denser air falls towards the ground. So when the heater turns on, heat goes up to the ceiling.
Radiant: The movement of heat from a warm space to a cold space. A good example is the heat from a fire to the colder areas surrounding the fire.
How Radiant Barrier Works:
Based on the above information. there are two properties on which the Energy Improvements Radiant Barrier Shield works: Reflectivity and Emissivity. First, the aluminum is reflective on the hot side, reflecting the heat back from where it came. (Similar to a cars sun shade) Meaning how much of the energy is reflected and not absorbed by the barrier. Second, and most importantly, the Energy Radiant Barrier Shield’s aluminum has a low emissivity rating of 0.03. This means that only 3% of the heat can get through to the air on the cold side of the Shield.
