They take away if it's hooked up to a cooling duct w/ fan. Imagine it as a dual pane glass. It prevents a large amount of radiant heat from transferring freely (as it would without it). That mixed with a fan that blows through the tube and transfers the hot air away will lower the temperature. A normal reflector? I'm unsure of what you mean but if there is no opening in the reflector to allow air flow to cool it, then the metal+air inside the fixture will heat and heat until transferring that to your setup