The layer of still air itself gives it a degree of extra insulation provided it is still otherwise it will be taking heat away through convection.
Does reflective insulation work.
How houses lose heat.
Reflective insulation reflects radiant heat and works best with a still air layer of at least 25mm 1 inch.
When the sun heats a roof it s primarily the sun s radiant energy that makes the roof hot.
Most common thermal insulation materials like fiberglass work by slowing conductive heat flow but reflective insulation works a little differently.
Dust accumulation on the reflective surface will reduce its reflective capability.
It is most effective when kept clean and dust free.
How does reflective insulation work.
This type of insulation is designed to reduce radiant heat gain.
The primary function of reflective insulation is to reduce radiant heat transfer across open spaces.
The low emittance metal surface of reflective insulation blocks up to 96 of the radiation and therefore a significant part of the heat transfer.
When the sun heats a roof it is primarily the sun s radiant energy that makes the roof hot.
This type of insulation is designed to reduce radiant heat gain.
Most common thermal insulation materials like fiberglass work by slowing conductive heat flow but reflective insulation works a little differently.
Radiant barriers and reflective insulation systems work by reducing radiant heat gain.
For foil insulation to be most effective the reflective surface should face an air space.
To be effective the reflective surface must face an air space.
To understand how insulation works it helps to understand the basics of heat flow which involves three basic mechanisms conduction convection and radiation.