It doesn’t save the money the window companies claim and the replacements rarely last more than a decade before the seals fail and you end up having to replace the windows again and again.
If you don’t believe me, read what Energy.gov says about replacing your windows.
“Unless the existing windows are missing glass or otherwise severely leaking, seeing significant annual savings in your space conditioning cost and energy use is unlikely.”
Still not convinced? Read more here!
So, if replacing your windows isn’t the solution, how can we lessen the energy loss that windows cause?
The low hanging fruit are solutions like weatherstripping, caulking trim, and repairing old windows so they are operating as efficiently as possible. Once those items are done, the next thing you should consider are storm windows.
The Advantages of Storm Windows
There a ton of advantages to storm windows, whether you decide to go with interior storms or exterior models. The advantages below make the storm plus original window combination a better performing alternative than replacement double-paned windows.
- Improved air-sealing (infiltration)
- Noise reduction
- Improved thermal performance
- Protects main window (exterior storms)
- Helps eliminate condensation
When fit and installed properly, storm windows can provide huge improvements in these areas compared to the smaller improvements afforded by replacement windows.
While noise and thermal improvement may be issues for certain folks, the biggest advantage is by far their ability to stop air infiltration.
According to a 1999 University of California Berkley study:
“Walls, infiltration, and roofs are the biggest contributors to heating loads in the old, uninsulated buildings.”
Source: Simulation Research
According to the study, infiltration accounts for approximately 28% of heat loss in older buildings and a major place in which that occurs is around ill-fitting doors and windows.
Another important study by The Center for Resource Conservation in Boulder, Colorado in 2011 showed that:
“It is possible to improve the overall energy performance of existing window systems by well over four fold through repairs, weatherization and installing storm windows with insulated frames.”
How Much Could Storm Windows Save You?
This depends on a lot of variables that can’t be determined without a personalized inspection of your house. Questions like climate, HVAC equipment, local power costs, issues with your individual house all make the calculations difficult, but the savings can be significant and the payback is quicker than most other home improvements.
Here’s the proof: Keith Haberern, a professional engineer in New Jersey, performed an energy audit study related to historic windows called “Old Wood Window Replacement Window Energy Analysis” in which he was trying to determine if replacement windows or storm windows would provide better performance and financial savings.
His findings were astonishing!
“The payback period for the new windows is 40.5 years. The payback period for the storm window is 4.5 years.”
Ultimately, the savings are greater in the more extreme climates. Especially heating climates like New England and the northern tier states in the US.
The savings are still there for warmer climates too. Whether the storm is helping to keep the air conditioning in or freezing temps out, they are helping to seal up your house more than most other options available. And they do it with minimal alteration to the original structure.
A typical un-restored, un-weatherstripped double-hung wood window could have an average CFM (cubic feet per minute) of about 0.5. Which means that every 2 minutes, your window leaks about 1 CFM of air.
Compare that same window with the addition of a storm window and you get 0.05 CFM. That means that instead of 2 minutes to lose 1 CFM ,it takes a full 20 minutes. That is a 90% decrease in infiltration!
The other area where you’ll find significant savings with storm windows is in stopping conduction of heat through glass. Glass is a terrible insulator. Duh! It’s not designed to insulate, it’s designed to let in light.
Double-paned windows try to resolve this conduction problem by putting a small airspace between the panes of glass. Sometimes that space is filled with argon of some other gas to improve performance even more.
Storms take the air space to the extreme! The air space between the panes of glass on a storm and the main window is much larger than in any double-paned sash which greatly increases its insulating ability.
Storm Window Makers
There are a lot of options out there when it comes to finding storms for your house. That means that there is one that will fit your needs and budget. I’ve listed some of the best storm window manufacturers around the country to help you shop better and find the solution that is right for you.
Mon-ray Storm Windows – Mon-ray has been making storm windows since 1947 and they have some very fine products. Lots of models and customizations are available and it’s still a family run business, which I love!
Allied Windows – For this post, I spoke to a lot of fellow window restorers and a name that came up very often was Allied. I don’t have any experience with this company, but when a group of the pickiest window people in the world says they’re good, you can take that to the bank!
Indow Windows – This Portland, OR based company makes some of the easiest to install interior storm inserts. These acrylic panels have a silicone compression bulb that creates a very tight fit with no hardware and no modifications. They are custom measured to fit your exact window and shipped right to you or your local dealer. (full disclosure: I am the Central Florida dealer for Indow because I’m that much of a fan.)
Innerglass – Innerglass makes a vinyl framed, glass interior storm window that mounts on the inside of your primary window using their Compression-Fit technology. Not quite as simple as Indow when it comes to installation, but they do have more options for operable models.
Austin Home Restorations – Yes, it’s my company so I’m biased but we make some of the best historic storm windows (and screens) you can find. Made from solid Cypress with traditional mortise and tenon joinery, we ship these custom made storms right to you. They fit perfectly on your historic home and look just like the originals.
SpencerWorks – John Spencer makes historic storms that are kind of a hybrid with screening options and removable panels. Ultimately, the storms look historic, but you get some of the benefits of newer models.
Olde Window Restorer – Dave Bowers makes another hybrid wood storm window that looks historical but has some modern convenience as well. Made from Eastern White Pine and treated to prevent rot and termites, he makes a mean storm that gets the job done nicely.
WPA – The most common place you can get historic wood storm windows is from a local window restoration shop. Luckily, in recent years this field is really expanding. For a list of professionals nationwide, visit the Window Preservation Alliance and find the pro in your area.