Are Historic Windows Energy Efficient?

By Scott Sidler February 27, 2017

Are Historic Windows Energy Efficient?This week were on to claim 2 of mine that is so often refuted by energy gurus, developers, and the replacement window industry. I’m going to take a wrecking ball to these ludicrous claims in this post and in the next 10 minutes show you irrefutable proof that an energy efficient old window is not a unicorn story spun by historic preservationists.

An energy efficient historic window is a very real and very attainable thing that can be accomplished by minimal upgrades to the original window that cost far less than replacement.

“Every single historical wood and steel window can be repaired and made to be as or more energy efficient than a replacement window.”


You see, the reason this one gets me so riled up is because windows are by far the most endangered pieces of historic buildings. They are being torn out and thrown away in the name of energy efficiency at a rate of over 30 million a year.

Not only is their removal and disposal a huge strain on our landfills, it is completely unnecessary. Here’s why:

Marketing, Lobbying, & Dirty Tricks

The replacement window industry has done extensive testing and knows the facts about their products. They know that the windows they are selling are engineered with obsolescence in mind. They can market them as energy saving because initially they save energy over a neglected, un-weatherstripped original window even though cradle to grave they use way more energy.

In fairness almost anything would save lots of energy compared to a beat up neglected old window (even an $8 sheet of plywood would!) so it’s not a high bar to beat. What they won’t tell you is that a restored and weatherstripped window will save more net energy than a new replacement window.

Here’s how the replacement window industry’s game works:

They Show You Your Problem

They convince you you have a problem: The problem is two fold, your old window is drafty and inefficient, your old window requires maintenance. That appeals to the two most powerful marketing triggers to all humans, time and money.

They Solve Your Problem

They offer you a single product (a window) that solves both of these problems! Cut your energy bills and never have to maintain that window again. Amazing right? Wrong.

The Warranty

They promise you their product has a “liftetime warranty” which it does, but only on “non-glass materials”. They don’t tell you about the 10 or 20-yr warranty on the glass. That is buried in the fine print which only dorks like me dig up and share with smart readers like you.

A warranty is only as good as the weakest link and their lifetime warranties don’t stand up to scrutiny because they are technically only 10 to 20-yr warranties due to the fact that if the glass fails then the only solution is to replace the whole unit.

Maybe at this point you’re thinking “Hey even 20 years is not a bad warranty.” They aren’t done with their dirty little tricks yet! That 20-yr warranty only covers materials NOT labor after only 2 years! Here’s a little excerpt from Pella’s Warranty on vinyl windows.

“If Pella is given notice of a glass defect occurring within twenty (20) years of the date of sale by Pella or its authorized dealer, Pella shall, at its sole option: 1) repair or replace the defective glass (with cost of labor included only within two [2] years of the date of sale by Pella or its authorized dealer)”

You want a little more naked truth about their “lifetime warranty” on “non-glass materials” keep reading! The US Census Bureau reports that Americans move approximately 12 times in their lifetime. If the average lifespan is 79 years (which it is in 2017) then that means on average we move every 6 1/2 years. What does that have to do with the “lifetime warranty” though?

Well, to use Pella again, that “lifetime warranty” is non-transferrable. That means that as soon as you move those windows are no longer warrantied and ripe for full price replacement as soon as they fail.

Pella isn’t stupid. They know these figures and while they will honor a lifetime warranty on vinyl windows for the handful of people who live in their house for 20+ years they know that most of their “lifetime warranties” will only have to be serviced for about 6 1/2 years. And anyone can make a window that can last that long.

And it’s not just Pella, it’s all the major window manufacturers who play this game. You can read more in my post Replacement Windows: The Real Story. But let’s get back to the question at hand.

Are Historic Windows Energy Efficient?

For the answer you don’t need to listen to my opinions or the marketing hype from the replacement window industry. You need cold hard facts not salespeople so here they are.

In 2011 the Window Preservation Standards Collaborative, a group of window restorers from all over the country, got together for their first summit to discuss this very topic. They had a hunch that historic windows were more efficient than the replacement industry was saying but no one had ever done definitive unbiased testing.

The testing was performed by a third party certified by the Building Performance Institute according to ASTM E1186-03 (2009) standards and the findings were astonishing! There were 5 different levels of efficiency upgrades tested and all of them exceeded to 2009 IECC energy requirements for windows. More than that, all but one exceeded the current 2012 IECC energy code requirements!

All of these windows were built in the 1930s and were single paned double-hung windows. The results are below:

  • Window 1: Restored, added exterior wood storm window, no weatherstripping
  • Window 2: Restored, added integrated metal weatherstripping, added exterior wood storm window with rubber gasket weatherstripping
  • Window 3: Restored, added integrated metal weatherstripping, added exterior metal storm product
  • Window 4: Restored, added rubber bulb weatherstripping to perimeter of sashes
  • Window 5: Not restored, added site-made interior air panel (similar to interior storm window)
  • Control Window: No improvements or upgrades

If you’re not a believer in numbers and facts then there is very little I can do for you, but this round of testing was the final nail in the coffin for replacements windows in my opinion. This shows that historic windows are indeed energy efficient.

Not to mention that you don’t have to worry about 10, 20, or even 30-yr warranties with historic windows. They have already lasted 80, 100, 120+ years and they will continue to last another century with minimal care.

If you want to learn everything thing from the basic to advanced techniques for repairing, restoring, and weatherstripping historic windows you can visit my resource page How To: Repair Old Wood Windows.

9 thoughts on “Are Historic Windows Energy Efficient?”

  1. My wife and I are restoring an 1868 Farmhouse. At some point someone replaced all the original beautiful radius top windows with standard square windows. We have 28 windows and want to eventually replace these windows with radius top (arched) windows. I wish we could find the original windows but that’s unlikely (there’s one in our garage). Any suggestions? Is custom our only option at this point?

  2. I highly recommend Old House Guy blog for more information and detailed analysis why new replacement windows don’t work stylistically with old houses, even expensive custom orders made to “match” the original by Marvin and Kolbe, especially if you want the casing to be a different color from the sash.. He also talks about the problems with window warrantees and various other topics. His blog is the best I’ve found on the importance of detail and proportion in historic buildings.. //

    Yet another way new isn’t as good as the old. Plus the old are a whole lot easier to fix. Too bad basic window repair knowledge seems to be a dying art. I appreciate all you have done to make this information available to homeowners. I just wish the hired handyman types knew this stuff these days, unlike their Dads and Grandfathers.

  3. Hi Scott, we are restoring a 1916 bungalow that has a craftsman style porch. Very plain inside. A 63 foot long hallway with four rooms along each side. We have had the pier and beam foundation redone as some of the original cedar stumps were here but not really supporting anything; a new galvanized roof (probably not what was on here in 1916 but was very old,; refinished the long wood yellow pine floors; removed some of the wallpaper covered and painted paneling which has shiplap underneath-to included the ceiling; had all PVC replaced with PEX; and, now we are starting on the outside. We were going to replace the water board and cap all the way around the house but after reading your blog and reexamaning the board decided that there were only a few small sections of the wood that were actually rotten (due to a handicap rail being badly installed). So, now it will be mostly a preservation project with about 80% of the original wood to be saved. We still have 33 windows to open and re-rope and an entire house of paneling to remove. We were going to remove a few walls to create an open floor plan but after living here for almost a year we have grown fond of the house in the original configuration and can’t seem to bring ourselves to “mutilate” the interior. No, we don’t have a gorgeous new house with smashing hard wood floors and granite countertops, but, we have a house we love and thanks to your inspirational blogs, one we can work on to restore and preserve both inside and out. It would be great to reprint portions of your blog in our town’s Preservation website; if I can get my foot in their door. Please advise if that is possible and how the credit should be written. Thanks for all you do.

    1. Glad to hear the you are keeping the original configuration. There are many advantages to “closed” floor plans, and it is so much cheaper to keep the original than ripping out walls and putting in support beams. Perhaps a scaled down version is possible to reduce the long hallway a bit or widen openings between rooms. Your house may already have the columnades and pocket or French doors that period homes used to create openness yet separation between rooms.

      1. Unfortunately no pocket doors. One French door was here in the 50s and opened the hallway into the first room on the left which is across the hallway from what we believe was the formal living, or sitting, room. A previous commercial resident cut a second French door between the formal living and what was used as a dining room in the 50s. We are also using it as such. We do have to continually move doors around as the house moves and a door that closed in one doorway today will have to be moved to a different doorway next month. It is very entertaining.

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