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Home Improvement Replacement Windows Mullions Glazing and More

I love helping others figure out new and exciting ways to spruce up their home décor.

“A house without books is like a room without windows..."

.Horace Mann quotes

I love books, and I love bay windows. My love of architecture I believe is centered around the mullions in a window. Like a great book which you cannot put down, mullions in a window offer that point of interest from which we never grow weary. From casement sashes to double-hung, whatever the window shape - I love the addition of mullions. My favorite may be the oval windows with the curved mullions - the most complicated and probably the most expensive too! The octagon windows were all the rage in suburban Chicago - that didn't enthrall me at all; but oh, the delight of an oval window - with mullions - the rarest of the and the best of the best. My love affair may stem from my love of simple colonial homes, an Americana dream, and the possible decoration afforded these structures. Or it is simply the added intricacy in the details? Whatever it may be - enjoy the journey with me as we review over 12 different windows - all complete with my beloved mullions.

Mullions for my windows are a must for me!

“A house without books is like a room without windows..."

— Horace Mann

Diamond Mullions in a Living Room


Parts of a Window - Including Mullions


As with many things in life, there is often an "up charge". In the world of windows, a color other than white is an added cost. Likewise, if you add mullions to your windows, there will be an "up-charge". If the mullions in the windows fit your architecture, it may be a great investment that will return dividends on the resale value of your home. If the budget is tight, consider mullions only for limited quantity to obtain that much sought after curb appeal. Whatever, you do when you change your windows, or when designing your new home, consider the architectural value added to your investment with the simple addition of mullions in your windows.

"A mullion is a structural element which divides adjacent window units..." Nowadays, the mullion is no more than an insert giving the visual illusion of the individual panes.

Radiating Mullions

Specialty Shape Windows with Mullions

Curved Mullions

Curved Mullions Make the French Door

Bay Window with Double Hung Sashes and Full Mullions

Bay Window without Mullions

Mullions Double Hung Side Windows Only of Bay

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Casement Bay Window with Mullions and Copper Roof

Bay or Bowed Window with Mullions in Casement Sashes

Bay or Bowed Window with Mullions in Casement Sashes

Window Mullions - Interior Grid Options

Mullions Often Fake the Individual Window Panes

As we detailed above, often the mullion is fake - that is OK, the main item is the architectural appearance of your home.

How can the mullion add value to your home? Remember, value is always derived by supply and demand. What if you could increase the number of potential buyers in your home? In many cases, the higher number of buyers or interested parties, often the higher market price. The best way to increase your profits is take care of your curb appeal. And mullions in your replacement windows may be the best investment.

Adding Mullions to Existing Windows

Looking to put your home on the market sometime soon? Looking for that added market edge. Consider adding mullions to your existing windows.

Mullion molding is available for you to purchase and create your own. The mullion is installed typically on the inside of the window. Check with the replacement window section of your local hardware store, ready-made inserts might be available in the sizes that you need. Whatever your choice, it is a project that many of us, even the novice carpenter can do. The main item is to keep the mullions square and even. You are aiming for 90 degrees. Many times you will have several windows of the same size and you can quickly create a template and attack the job very efficiently.

Argone in Double Pane Windows and LoE2 Glass Options

If you are replacing your windows and the the installer has hit you with the "up sell" of installing or purchasing "argone billed double pane windows" or "LowE2" glass, carefully consider the advice given below:

"Note: don't let anyone sell you argon filled double pane windows. The argon is great if you are in Alaska and frequently experience 40 below temperatures. Its not so great in Houston where radiant heat is the primary culprit. The "LoE2" glass is what you need here. This glass is impregnated with microscopic flakes of metal that reflect a great deal of the radiant heat away from your air-conditioned space. "

Read more: Replacing-windows-older-home.html

Mullions in French Doors

The french door would still be charming but the addition of the added small wood grids called mullions greatly increases the character of the french door.

Curved Mullions in French Doors

Wish to bump up the charm factor of your french door once more? Check out the "curved mullions" in a french door.

This entrance with curved mullions on the french door complemented by the curved bluestone entrance stairway is classic and absolutely exquisite. Isn't is amazing what you can do with architecture even in very small places? That entrance will create lasting memories for that family from holiday to holiday. Dividends will be paid for the charm factor added. An excellent example of well-thought-out architecture and home design.

Window Replacement Return on Investment

In addition to the curb appeal of your property, the replacement and/or repair of your windows can help with your energy bills. Consider this fact:

"According to the U.S. Department of Energy windows can account for 10-25% of your energy bill. Upgrading to ENERGYSTAR® Qualified Windows will reduce your energy costs."

Mullions in the Bay Window

Just about any window replacement can include a bay window. Bay windows range from custom to canted to square to bay windows with double-hung sashes to bay windows with casement windows. Whatever your choice, look at the difference the mullions can make in your bay window.

A bay window without mullions looks great but a bay window with mullions looks complete. Top off your bay window with a copper roof and you have a triple play or adding architectural charm to your home that will pay dividends time and time again.

Personal Favorite - Bay Window with Casements, Mullions and Copper Roof

Any home with these three is sure to be on my must-see list. The added walkthroughs when you go to sell your home is called by the Realtors "the curb appeal". Adding a great front cover to your book does sell a home. I know the adage is you cannot tell a book by its cover but in this competitive housing market, consider the investment in the future for your home's marketability by replacing a window with a bay and adding the charm of yesterday to increase your home's final selling price. Remember perception is reality especially in real estate. The bay window speaks of quality and sends a clear message that this home has been well taken care of and well-loved. The mechanicals must be in working condition and well maintained but you will not get buyers through the door to inspect the mechanicals if the curb appeal is not there first and foremost.

Bump up the charm factor of your home with the classic bay window with mullions - the mullions will pay more dividends than the bank today.

Mullion Options

The curved mullions are just one of many different mullion options. Check out the visual at the right to get a good idea of the many options. Remember to keep the mullions in order with the architecture and scale of your home and you will do well on your home improvement project.

Mullions can also be limited to the side of the bay window. The large front picture window may not need mullions too. Just another option to consider in your home improvement design.

Architectural Integrity

There is no right or wrong mullion use but if you mix different types you will have a major problem with "architectural integrity". If you use diagonal mullions, use those exclusively throughout. Additionally, keep the size and number of mullions consistent for all windows.

If you do choose curved mullions or diagonal mullions for your windows on one side of the house, that entire side of your home MUST have curved mullions. Think it through - you want a consistent architecture and flow. You are seeking to create harmony, this demands consistency and architectural integrity.

Mullion Options French Doors

Mullions Top of Double Hung

Painted Mullions



Mullions in the Custom Sunroom

Mullions on the French Door

Whether your french door is your main entrance or a back or side entrance, adding mullions to the french door is more often simply assumed. However, be aware there are different options - various mullion types for the french door. Check out the photo to the right for a primer on the many options and that is just for the french door!

Mullions on Upper Portion of Double Hung Sashes

Look at the impact even a partial section of mullions on double-hung sashes has on the architecture of this window to the right. Of course, the exterior would not be complete without the charming shutters also. It is about creating the whole curb appeal from start to finish - mullions and shutters for the exterior!

The same is true with the mullions in the bay - just adding the mullions to the side windows adds a tremendous amount of character.

Painted Mullions

A frugal alternative is "painted mullions". Look at the example to the right. Here they have chosen the architectural design of the "Gothic mullion" on the double-hung sash. This is one of the most ingenious decorating items I have found for adding character and charm to one's home. Imagine, painted mullions!

Points to Consider When Replacing Your Repairing Your Windows

Your roof and your windows make up a large part of your home's architecture. Aging roofs and aging windows can dramatically affect your comfort level and your costs to maintain your home.

Energy - 10%-25% of Your Heating Bill

Windows can account for 10% to 25% of your heating bill. Additionally, during the summer, your electric bill will also be affected. Curtains can help but here are a few tips.

Sun Belt Window Recommendation

If you live in the Sun Belt, consider windows that are "Low-E". These windows can cut the cooling costs by 10% to 15%.

Single Pane Windows

Many homes have single-pane windows, upgrading to double pane window with high-performance glass can help your heating and cooling costs. Do your research for your area. Each section of the country is different.

Storm Windows

Often this is the best solution for single-pane windows. Some have attributed saving up to 25% to 50% of their heating bill.

Sun Options

Other options for the Sun Belt to consider are awning or reflective films.

Long-Term Savings Tip

Energy performance may not pay off for several years. The added comfort and the aesthetic value may be your only payout in the short term. Closely consider all your options.

Improve Existing Windows

"If your existing windows are in a reasonable condition and you would like to hold on to them, there are several options for improving their energy performance.

  • Check if the windows still hold up to the task»
  • Caulking and weatherstripping»
  • Storm windows»
  • Solar control window film»
  • Exterior shading»"

Financial Help for Replacement Windows

Look for financial help or incentives

A federal tax credit is currently available for replacement windows that meet specific energy-efficiency criteria. Your utility company and local or state government may also offer rebates, low-interest loans, or weatherization help. For income-eligible homeowners, the Weatherization Assistance Program offers free energy efficiency measures that may include window improvements or retrofits.

  • Tax credit for energy-efficient replacement windows»
  • Utility, state, and local incentives for window energy efficiency»
  • Weatherization Assistance Program»

Reglazing Your Window Mullions

Replacement Windows and Mullions

Whether you would like to improve the energy performance of your existing windows or replace them with new energy-efficient windows, several options are available.

Benefits of efficient windows include:

  • Energy savings,
  • Improved comfort,
  • Less condensation,
  • Increased light,
  • Reduced fading, and
  • Utility cost savings.

Benefits of mullions:

  • Added charm and curb appeal,
  • No added property tax for this addition,
  • Added showings when selling your home,
  • Added perceived value to potential buyers
mullions on three season porch

mullions on three season porch

mullions on sun room

mullions on sun room

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© 2010 Ken Kline


Carolyn on October 24, 2020:

Looking to purchase double hung with Diamond grilled in them

Usama Chaudhary from Burewala, Pakistan on April 24, 2020:

Yes , I agree a house without books is incomplete. Every house should have books in it. Books are really important part of life.

Kelly Kline Burnett from Madison, Wisconsin on November 14, 2011:


I agree - the mullions are classy.


I just took my mullions off today to stain them. They are purely wood - I would recommend checking with a handyman service for a GREAT carpenter. That would be the best source - typically they can repair the mullions. The historical society that I spoke with a couple of months back does not recommend replacing windows - they prefer repair and/or repair with storm windows. Hope this helps. Best of luck in your restoration project.

ron on May 11, 2011:

I want to repair a broken mullion (wood) from a house built in 1905. I think the mullions are newer but still quite elderly. Is there a source somewhere?

WallStickerDecals from US on January 04, 2011:

This is how I like my window will look, so classy and elegant.

Kelly Kline Burnett from Madison, Wisconsin on December 20, 2010:


Thank you so much for contributing - I greatly appreciate it.

The terms are confusing - thank you for the clarification - excellent explanation.

Jon on November 26, 2010:

Two things: 1. Mullions the bar separating windows that are mulled (built) together. The muntins are the items dividing the glass of one window unit into separate panes.

2. I disagree on your comment of needing to keep muntins (correct term) all the same on one side of the house. Depending on the architectural style, such as French revival, both diamond and colonial muntins are often used on one side, the diamond windows may be used in an "accent" location. Also, newer colonial styling often mixes short fractional styling, with 2 over 4 or 3 over 4 style, and even picture window styling where the center unit has clear glass, and the side double hung units have their own style. The key for a person to remember when replacing windows on their home and considering changes or additions in muntin style is to find out what the style of the home is if they are not certain, then chose a or a combination of muntin styles that pertain to that style.

Kelly Kline Burnett from Madison, Wisconsin on September 26, 2010:


Thank you for your kind words.

H P Roychoudhury,

The taste of the person, the books are reflected in the details. We, ourselves, take on the characters of our homes. No different than we as animal owners start to look like our animals? Hmmmm...An interior designers' dream.

H P Roychoudhury from Guwahati, India on September 25, 2010:

The ingredients of a house displace the taste of a person.

prasetio30 from malang-indonesia on September 17, 2010:

Another great hub from you. Good tips and I learn something new from this hub. Good work, my friend. Vote up.

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