Magic works through a series of runes, which as required magically tattooed onto the skin. The individual activates these runes by using their own will and focus. These runes create effects which are called spells, and last anywhere from minutes to months. Only one type of rune can be applied to the body at a time, and they can be removed the same way they were applied.
Special soldiers use these runes during wartime, in which they are covered by a suit of armor. The power of the spell can damage the unit when used, as it generates a lot of heat through the runic symbols covering the person. Therefore, they are covered with a counter spell, which protects the armor from the heat energy and preserves it for long term use.
The problem is that by countering the energy of the spell, the armor seals the heat inside itself. The individual is unable to excise excess heat, which can be fatal. The armor could end up cooking the person alive.
How can I create a suit of armor which protects it's wearer without these consequences?