I am in the process of getting some new pre-hung fiberglass doors. I was told (by my brother) that I can’t use storm doors with fiberglass (or metal) doors. It turns into a greenhouse, and stuff then warps, including the parts of the storm door itself.

Is that true?

Thanks,
Brian

If your storm door faces the sun it can cause a temperature build up that is harmful to the fiberglas door. The manufacturer should spell this out in the installation instruction. You other option would be to not install all of the weather striping on the storm door but that may defeat some the efficiency of the door. Also consider a very light colored door, maybe white.

You can install storm doors over fiberglass or metal, absolutely! Here's the catch, for doors that have glass in them like a half moon or crest, it is possible for it to get so hot that it will break the glass, though speaking to a sales rep myself about this, I was told this has not actually happened but they have to warn you.
I have one myself installed for over 10yrs with no problems and my front door faces the sun during the hot part of the day,

So my advise it to install it and don't worry about it