- Glass storm doors act like an oven when they get direct sun all day. The space between the storm door and the main door heats up to very high temperatures and this causes the plastic trim around the glass to melt. There is also a bead of caulking around the glazing which can be melted as well and it oozes out and drips down the door.
- The color that you paint the door can have a big impact. Dark colors absorb the UV rays from the sun causing a heat build up in the trim. The higher the temperature of the trim the greater the expansion. Excessive heat absorption could lead to heat distortion of the door and its components. Colors are listed on the Light Reflectance Value index (LRV) and it is a good idea to stick with a paint with an LRV of 55% or higher. Some manufacturers will void the warranty on the door if the door is painted a color with an LRV lower than 55%. What the LRV means is the paint color's ability to reflect light and therefore reduce the surface temperature. Check out this LRV link for more info
If you insist on using a darker color you must assume the risk when it comes time to replace the door. One suggestion I sometimes make is to take out the glass in the storm door and install the screen year round. Even in summer the door will heat up like an oven because the sun is lower and there are no leaves on the trees to block the sun's rays.
Metal doors are the biggest culprits because they get so hot they can burn your skin if you touch them. Most metal doors come with some glass with plastic trim around the glass. If you have a south facing door I might suggest avoiding a metal door/storm door combination and certainly avoid dark paint colors. Even fiberglass doors can experience some of the same problems when painted dark especially when there are glass windows. Wood doors have less problems but what I often see is the wood expands so much that when it shrinks back to its normal size the panels tend to crack and then there is an ugly paint line all around the panels. Some door companies have counteracted this problem by making the panels double thick with two panels floating back to back so if the outer panel cracks at least the 2nd panel will keep out the air.
I guess the bottom line is to use common sense and to err on the side of caution. If you are not sure about a particular door and its pros and cons don't hesitate to ask me any questions.