Question

I am trying to check if my understanding is correct. This is not really a question but a request for validation. I hope this is allowed.

When painting with a heat reflective paint there are two options

A- The room does not contain a significant heat source. This will always lead to a reduction in ambient temperature as heat from the outside is not allowed in. Heat by convection and conduction will still penetrate but overall the energy transfer will decrease.

B- The room contains a heat source emitting IR rays. The rays will keep bouncing over the painted walls until it is absorbed by the air or the body of the heat source itself.

Depending on the ratio between the external and internal IR sources, a IR reflective paint can lead to either increase or decrease of ambient temperature

Answer 1

Your understanding is correct; heat reflective paint can lead to a reduction in ambient temperature in a room without a significant internal heat source by reflecting IR radiation, and in a room with an internal heat source, the effect depends on the amount of IR radiation present inside versus outside.

Step-by-step explanation:

Your understanding of how heat reflective paint affects a room's temperature is largely correct. Let's break down the scenarios you've presented:

Scenario A: Room without a significant heat source

In this case, applying heat reflective paint to a room that doesn't have a significant internal heat source will generally lead to a reduction in ambient temperature. The paint's reflective properties inhibit the transfer of heat from external sources into the room by reflecting infrared (IR) radiation away. While some heat may still enter through convection and conduction, the overall energy transfer is indeed lessened.

Scenario B: Room with a heat source emitting IR rays

When a room contains a heat source, such as an infrared lamp, the IR rays will reflect off the walls if they are covered with IR reflective paint. Eventually, these rays will either be absorbed by the air or return to the heat source. Depending on the balance of internal and external IR radiation sources, the room's ambient temperature could either increase or decrease. If more IR radiation is generated within the room than is being reflected out, the temperature could rise. Conversely, if the paint effectively keeps external IR out without trapping too much internal IR, the room could still cool down.

In both scenarios, the efficiency of heat transfer by radiation depends quite a bit on the color and reflective properties of the surfaces involved.