There are some good reasons to install storm doors, but reducing energy bills is rarely one of them.
Q: My father-in-law has been urging me to install storm doors on the house. He swears they will pay for themselves in energy savings. Is this really worth it?
A: Back in the day, installing storm doors was often recommended as a big energy saver. I installed a bunch of them. Then we started actually measuring things. I remember a project where we installed storm doors in a neighborhood and tracked the energy bills. Much to our surprise, in many of the homes with the new storm doors, the bills actually went up. As we drove down there to try to figure out what was going on, it became clear from the street: a lot of folks had the main door open, letting the sunshine stream in through the new storm door.
Letting more light into the house can have many benefits, but in this case, saving energy wasn't one of them. So, is it likely to make sense in your house? Here are a few things to consider:
1 What's the condition of your existing doors? If they are in really bad shape and very drafty, it would probably make more sense to replace the old door, particularly with an insulated door. In many cases, basic maintenance by replacing weather stripping and bottom sweeps may be more effective than a storm door.
2 How much sun does the door get? Putting a tight-fitting glass door over a door that gets more than a couple of hours of direct sun can have unintended consequences. If the primary door is wood, the heat build-up can deteriorate the paint or other finish very quickly. If it's metal, you can create a serious scald hazard, particularly for small children touching the door.
If the door is not in direct sun, a storm door can help protect it from the effects of weather and actually reduce necessary maintenance.
A well made, properly installed storm door can reduce energy use a bit, but it's very low on the list of things to do in most houses. Low-cost storm doors, on the other hand, tend to get caddywampus after a short time (yes, that's a technical term) and let a lot of outside air in around them. It's not worth it to get a cheap one.
Storm doors that double as screen doors in the warm season can sometimes save a few bucks by helping create cross ventilation and reduce the need to run the air conditioning, particularly in the spring and fall. Putting off using the AC for even a few weeks a year can reduce your bills, as long as you train the children (of whatever age) not to leave the main door open when the AC is on. And if the outdoor humidity is high, those cooling breezes will bring a lot of moisture into the house and make you uncomfortable (and turn your shoes green).
So what's the bottom line? Thank your father-in-law for his concern and appreciate the fact that he's trying to look out for you. Then show him you heard his concern by investing in some things that are more likely to save you money, like sealing your ducts, sealing between the house and the attic or getting a high efficiency water heater when it's time to replace your old one. There are some good reasons to install storm doors, but reducing energy bills is rarely one of them.