Window Performance: Old Windows vs. Window Replacements

Windows are the eyes of a house—the most important character-defining feature creating the greatest visual impact on the overall appearance of a house.

So should you replace your old wood windows?

Should you consider restoring old windows?

And if you require window replacements, do you know what to shop for based on the design and style of your house?

The public has been brain-washed by marketers. 

Even an eight year old knows you need to replace your old wood windows to save energy and lower your heating bill.

Therefore, the three inches of air space you have between the two pieces of glass performs as a very good insulator.

Let’s look at this in another way.

• One measure of heat transfer is the U-value – the number of BTU’s per hour transferred through a square foot of material.  When comparing thermal performance, the LOWER the U-value the BETTER the performance (opposite of R-value).
• According to ASHRAE (American Society of Heating, Refrigeration and Air-conditioning Engineers), the U-value for single glazed old wood windows ranges from 0.80 to 0.99.  The addition of a storm window proudly reduces these figures to a range of 0.44 to 0.49.
• A double-glazed metal window has a U-value of about 0.60 and a double-glazed wood window ranges from 0.51 to 0.55.

Therefore, if you do not presently have storm windows, install them instead of window replacements.  You will spend much less money, receive much more insulation, and not add to the landfills.

This U-value CAN be lowered further, but at this point we are slicing peas.  With windows accounting for only 10% of heat loss, you really do not need to look further.  However, if you do, with a Low-E-Coating Storm Window you can lower the U-value to a .32 level.

You Must be an Educated Consumer

Keep in mind your source of information.  Does your information come from someone with a financial benefit? Are the statistics weighted?  Are they geared for new construction?

Don’t be blinded by the lure of tax credits when you can save ten times more money making an educated decision.

As with nutrition labels, there is some misrepresentation of U-value measurements.

See the following link where the author advises window shoppers to make an informed decision:

Traditional Building Magazine – Do You Replace or Restore Historic Windows

Old Wood Windows vs Window Replacements Energy Analysis

This is important folks. Here are three insightful documents that discuss the cost of window replacements versus historic wooden windows.

Saving Windows, Saving Money: Evaluating the Energy Performance of Window Retrofit and Replacement by The National Trust for Historic Preservation

This report analyzes do-it-yourself solutions such as window films and weather stripping to replacing older windows with new ones. This study builds on previous research and examines window options comparing the relative energy, carbon, and cost savings in various climate regions.

This link is a summary so scroll down and click on the links for an extremely through report.

 

A Comparative Study of the Cumulative Energy Use of Historical vs Contemporary Windows by Frank Shirley Architects.

This study compares the life-style costs of two residential window systems in a pre-1940 house in Boston, Mass. One is an original double-hung window with a triple track storm window. The other is a new, vinyl double-hung replacement window. 

 

Studies and Experts Prove Window Saving is Better

If you haven’t read enough and still don’t believe the Replacement Window Myth, here are some more links to random energy savings studies at Historic Home Works.

 

Window Replacements Are NOT Maintenance Free

A big myth is that replacement windows will eliminate maintenance.  In a way this is true because they are disposable.

You install them; 10-20 years later, you throw them out and, again, buy new windows.  Even so, the public has been sold on the myth of no maintenance, but there will ALWAYS be maintenance.

• For appearance sake alone, you certainly will be painting those windows even if they are vinyl.  They too will fade over time, just as aluminum sided homes, which were once touted as “maintenance-free” are being painted.
• When wood is continually maintained, its life expectancy can be about 200 years to indefinite.  On the other hand, according to studies, vinyl has a life expectancy of only about 20 years. The plasticizers in vinyl will evaporate over time, making the vinyl brittle and subject to cracking. And what cost are you imposing on future owners or your poor unsuspecting children when your venture doesn’t last?  Go with time-tested materials: paint on wood.
• How are you going to replace a double-glazed pane of glass when it breaks?  Manufacturers frequently modify their product line and technology quickly changes.  You may, therefore, need to replace the entire sash and frame.  Many other components of replacement windows deteriorate relatively quickly.
• The seal around double glazing can fail within 10 years, resulting in condensation between the panes of glass.  This will require replacement, too – not repair.  Many of the plastic and neoprene seals, which hold the glass in place in vinyl and aluminum and new wood windows, also degrade in ultraviolet light.
• “Insulated glass typically lasts from 10 to 25 years , with windows facing south often lasting less than 12 years”.  Try to imagine locating a replacement vinyl gasket 10 years from now, or the problem of replacing a bent aluminum channel.  With your original window you can always get parts at a local hardware store.

What are My Options to Save Energy?

• Install an Exterior Storm Window with low-e glass.
• Install an Interior Storm Window .
• Install the newly invented Pilkington Insulated Glass.

What is this Newly Invented Pilkington Insulated Glass?

Pilkington insulated glass is new for 2018. This glass will not only save heat and cooling costs but save the homeowner thousands of dollars for replacement windows. This is not good for the replacement window business. They will now have to apply more pressure on the homeowner.

Basically this insulated glass is the same thermopane glass used in replacement windows but reduced in thickness to that of a single pane piece of glass. It has improved insulation properties and can be inserted into your original historic window.

The problem I see is that your historic wavy glass will be replaced. I’m sure in time that there will be an option to have wavy glass.

Read more about Pilkington Insulated glass .

What About the Appearance of My Windows?

Repair or Replace – The Visual Impact

Appearance is Important. The National Trust for Historic Preservation addresses the following questions with great pictures in living color to really show comparisons.

• Should I repair my old windows?
• When are Window Replacements Necessary?
• Do the Benefits Outweigh the Costs?
• What Not to Do When Replacing My Windows?
• Do Window Details Matter?

Should Your Old Windows be Saved?

This article focuses on common problems with old windows and what you can do. Options of replacing old windows are weighed against the cost, complexity, efficiency, and preservation of historic character with a problem-and-solution approach. A Visual Guide to Historic vs Replacement Windows.

Window Myths

Replacement windows are not what you are led to think they are.

Vacuum Insulated Glass, Innovation for Historic Restoration

Brand new glass technology allows historic window sash to be retrofitted with insulated glass and still look historic. (except for the lack of wavyness)

NTHP Wood Window Tipsheet

A window tip sheet from The National Trust for Preservation

Now that you understand how to avoid being influenced by the false claims of window replacement marketing, it is very important to understand how windows effect the appearance of your house.