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The Inefficiency Of Single-Pane Windows On Display

We have had a recent cold snap and this puts the inefficiency of single-pane windows on display.

Arriving at the house, built 1973 with all its original windows, the temperature was 15F.  It had gotten down to about 7F during the night.

This is what the windows looked like from outdoors.

Every single window was icy.

Single-pane windows contain 1/8" thick glass and have an R-value (insulation resistance) of between .5 and 1.

Typical wall insulation, by comparison, is R-13.

In addition, since these are older windows, they do not fit tightly and so there are gaps all around and between the moving sashes.  Moving air can be felt at every window.

This is inefficiency on parade! 

Heat moves toward cold.  In the winter heat is escaping each window opening.  In the summer heat is trying to enter each window opening.

A house's energy efficiency breaks down to percentages - approximately 30% walls, 30% windows/doors, 30% attic insulation and upper-level lights, and 10% wall openings (like receptacles and switches).  That 10% increases if there is a fireplace.  A crawl space changes all that too.  And the direction the house faces.

If you add up the area of all the windows and doors in this  house the area adds up to about the equivalent of three exterior bedroom walls with R-1 or less!  That represents huge energy losses!

The house is vacant so the heat was not turned up very high.  As we increased the heat the ice inside the windows began to melt.  This created puddles here and there, which rested on wood surfaces, and on wood windows water is not a good thing!

Adding storm windows can increase the window insulation to between R-3 and R-4.  Storm windows are a cheaper alternative to replacement windows.

Newer double-pane windows with a 1/4" gap between the panes increases the insulation to about R-2.  If there is a 3/4" gap between the panes the R-value is bumped to between R-2 and R-3.  A good low-E coating on the inside of the two panes increases the R-value to between R-3 and R-4 and adds heat protection, depending on the quality of the window.  Really good replacement windows boast R-values of R-6 to R-9, but they don't come cheap!

If/when you buy replacement windows, look for the U-factor ratings.  If the number 1 is divided by the U-factor you arrive at the R-value.  So a lower U-factor is the higher the R-value.  In Virginia the Energy Star standard for new windows is a U-factor of .32 or less.  The low-E coating provides sun/UV/heat protection, called the Solar Heat Gain Coefficient (SHGC).

My recommendation:  one of the most common upgrades to older homes is to replace the windows.  This not only gives the house more energy efficiency (despite what the commercials say, cost break evens are variable, if ever obtainable) but the new windows work!  They don't stick or act like guillotines!  Cheaper than new windows, if the old ones still work well, is the installation of storm windows.  They add great efficiency more cheaply, and work too!

 

 

 

Jay Markanich Real Estate Inspections, LLC  

Based in Bristow, serving all of Northern Virginia.

Office (703) 330-6388   Cell (703) 585-7560

www.jaymarinspect.com


Comment balloon 47 commentsJay Markanich • January 09 2015 02:57AM

Comments

Good morning, Jay.... that reminds me of homes with metal framed windows in New England... those are made for a warm climate...moisture and ice build up on the wood window sill.....then it becomes rotted....

Posted by Barbara Todaro, Previously Affiliated with The Todaro Team (RE/MAX Executive Realty - Retired ) about 6 years ago

The metal causes heat conduction Barbara.  Covection is to, conduction is through.

Please remind me, which one is the 12 year old?  They are both the same size.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

Jay, the normal buyer pays no attention to insulation, windows and energy conservation! And they pay dearly for it! Enjoy your day! 

Posted by Wayne Martin, Real Estate Broker - Retired (Wayne M Martin) about 6 years ago

It's cold enough outside we don't need a airflow from faulty windows.  Think I just may hibernate today.

Posted by James Dray, Exceptional Agents, Outstanding Results (Fathom Realty) about 6 years ago

They pay attention once I am done with a home inspection Wayne!

It's not as cold here today as the past couple James, but still cold!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

I did an addition on my 1970's cabin - new space has foam insulation and Pella windows. Old space at least got wrapped with insulation when we replaced the siding with hardi board, but funds ran short before we could replace the windows. At least I have storms. You can tell the difference!

Posted by Jeanne Dufort, Madison and Lake Oconee GA (Coldwell Banker Lake Country) about 6 years ago

People don't realize how much comfort, and efficiency, storm windows can deliver Jeanne.  And it's much cheaper than replacement windows.

Hardi-plank was a great addition also.  Good thinking.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

Great advice on those windows and certainly needed at this time of year.  It is soooo cold outside.

Posted by Debbie Gartner, The Flooring Girl & Blog Stylist -Dynamo Marketers (The Flooring Girl) about 6 years ago

It gets cold there Debbie?

The post is somewhat of a tutorial.  Do you have good windows in your building?  If not, why not? 

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

I can't recall seeing single pane windows in a zillion years...but here...you would be paying mega bucks for heat.....and probably still freezing !

Posted by Sally K. & David L. Hanson, WI Real Estate Agents - Luxury - Divorce (EXP Realty 414-525-0563) about 6 years ago

Good morning Jay,

Depending on the window and conditions there are some unusual designs just like spider webs!

Make yourself a great day.

Posted by Raymond E. Camp, Licensed Real Estate Salesperson Greater Rochester (Howard Hanna Real Estate Services) about 6 years ago

It doesn't take a Rhodes Scholar to figure that single pane windows are not energy efficient.

What's so surprising is the "thermal" double pane windows that aren't much better.

Posted by Lenn Harley, Real Estate Broker - Virginia & Maryland (Lenn Harley, Homefinders.com, MD & VA Homes and Real Estate) about 6 years ago

S&D - ay ay Cap'n.

Raymond - unusual to be sure, but I still see this a lot.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

Lenn - but new windows work better!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

Jay, I have a saying the most energy efficient window out there is the one that is not there 

Wow who has a R-6 to R-9 window? 

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) about 6 years ago

Most excellent posting and subject matter....Keep up the good work and thank U

Posted by Richie Alan Naggar, agent & author (people first...then business Ran Right Realty ) about 6 years ago

Meester Dohn - I have heard radio ads by local companies.  One window rep I did an inspection for said his windows were R-10!  While I didn't believe him, I was not going to argue on a home inspection!

I have seen windows in custom new homes with U-factors of .15.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

Richie - thanks!  Did you mean to say, "thank U-factor...?"

; >)

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

My daughter bought a new old house this summer, and yesterday I was at her house and noticed all her storm screens were still down. 14 windows in all were freezing her out. Good thing her Dad is a home inspector and notices stuff like that. She called last night and said how much warmer her house was. Bingo.

Posted by Scott Seaton Jr. Bourbonnais Kankakee IL Home Inspector, The Home Inspector With a Heart! (SLS Home Inspections-Bradley Bourbonnais Kankakee Manteno) about 6 years ago

Jay Markanich ... the windows in our "newer" home are not the best.  Add on top of that issue, we are built upon a high water table.  The result is that we get wet windows way too often, even with a de-humidifier going in the middle of window.  I like the idea of the storm windows .. at least until we tackle the remodeling we have in mind.  Thanks for the little push and great idea!

Gene

Posted by Gene Mundt, IL/WI Mortgage Originator - FHA/VA/Conv/Jumbo/Portfolio/Refi, 708.921.6331 - 40+ yrs experience (NMLS #216987, IL Lic. 031.0006220, WI Licensed. APMC NMLS #175656) about 6 years ago

I haven't had single pane windows in a million years.  If I still had them, I would feel the "pain" in my wallet when I looked at my utility bill.  Thank goodness for storm windows.

Posted by Joel Jadofsky, One of the Top Realtors in Panama City Beach Area (Keller Williams - homes for sale - Florida - Gulf - Beach ) about 6 years ago

Great advice! We're looking to replace the windows are on our house, which are double paned but are old and have failed. Thank goodness for thick curtains! Thanks for posting!

Posted by Laura Foreman, Copywriter, Buffini & Company (Referral Maker Real Estate CRM) about 6 years ago

Heat loss, moisture, mold blackening the bottom with the wetness. Triple glazed and high performance windows and what the heck. Add some roman insulated shades to lower and seal up at night. Makes the place warm, toasty and money to show up. Left over from down the drain of wasted heating costs.

Posted by Andrew Mooers | 207.532.6573, Northern Maine Real Estate-Aroostook County Broker (MOOERS REALTY) about 6 years ago

I grew up in a house that had jalousie type windows, my dad used to remove the screens every winter and wrap them in visquene and put them back up to keep drafts from blowing in...lol, I think you call that -R value!

Posted by Fred Hernden, CMI, Albuquerque area Master Inspector (Superior Home Inspections - Greater Albuquerque Area) about 6 years ago

Hi Jay, it is well worth the investment for homeowners to put in new windows.  Thanks for sharing.

Posted by Sybil Campbell, Referral Agent Amelia Island Florida about 6 years ago

I bet you are just a picky a fellow when you work for home buyers Scott.  I got a call today from a friend who put in what the HVAC company called a "terrific" new heat pump.  She said her small house (1500 sq ft) doesn't get warmer than 59F.  I asked her to read me the numbers on the plaque.  It's a 5 ton unit!  Ummm...

Gene - I'm hearing builder grade!  But storms may help you, but I say that not knowing what kind of windows you have.

Joel - I would have believed you if you had said 500,000, but really, a million?

Laura - thick curtains help!  And the double-cell shades.

Andrew - all that ought to work even in Maine!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

Our rear addition had jalousie windows too Fred.  They were not at all efficient.  But still, we didn't wrap the screens.  Instead of R-value, don't you mean W- value?  You know, Wrap- value.

Sybil - agreeing with you that comfort is worth what it takes, but it's not exactly a $ investment!  Still, would I want new windows?  Yes.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

It's amazing what new windows can do to keep the house warm.  And the utility bill down. 

Posted by Kevin Mackessy, Dedicated. Qualified. Local. (Blue Olive Properties, LLC) about 6 years ago

That's probably true Kevin, depending on what is being replaced.  The cheapest form of energy improvement would be?  Caulking.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

Fortunately, storm windows look pretty good these days versus the old steel looking ones. Anodized frames can look good from the street. I use storm windows on my older rental properties so that I don't deal with lost seals on doubles.

Posted by Joe Pryor, REALTOR® - Oklahoma Investment Properties (The Virtual Real Estate Team) about 6 years ago

Joe - when I was first married (1977) we rented a townhouse and I suggested that the owner put on storm windows.  They were the color of the trim and looked pretty good.  I drove by the place the other day and they were still there!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

We have new windows and they leak air in the center where they raise up and down.  Dont know if they put them in wrong or what.  These are expensive ones too.

Posted by Ricki Eichler McCallum, Broker,GRI,ABR, e-Pro, TAHS (CastNet Realty) about 6 years ago

Ricki - they may be missing the thin, hairy strip that goes in there.  Lift the lower sash up and look to see if there is an air block of some sort in there.  If the block is there and it is leaking then it's the window.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

Good info; I was not up to spped on the R factor and calcs.  Understand them much better now.  And glad we have newer double-paned windows.  Doors are our problem with air leaks.
Mel

Posted by Mel Ahrens, MBA, Kelly Right Real Estate, Customized Choices for your Real Estate Needs (Kelly Right Real Estate) about 6 years ago

They are as important as windows Mel.  But sometimes air flow is easier to block.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

Jay, I can't find any windows that claim higher than r-5 and they are hecka expensive.  I am doing a post on getting away from insulated glass windows all together

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) about 6 years ago

Jay Markanich I have seem some posts that mentioned double pane windows can have the seal broken hence not so effective or energy efficient. So which is better? (Of course your post has the answer  - however, wondering.....)

Posted by Praful Thakkar, Andover, MA: Andover Luxury Homes For Sale (LAER Realty Partners) about 6 years ago

You have too much time on your hands Charlie!  I can't remember brands off the top of my head, but I have seen U-factors as low as .15. I just quick went to Andersen and their best is .26.

Personally I think storm windows are the way to go.  And I look forward to your blog!

Praful - I had a blog just last November on broken seals.  Over time any double-pane window that is gas filled can cloud up from broken seals.

http://activerain.com/blogsview/4543558/what-do-i-do-about-broken-window-seals-

The broken seal does not affect the efficiency that much.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

U factors are one thing, and R-value is another---not directly related to each other.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) about 6 years ago

I don't know Charlie, I thought they were.  Dividing the U-factor into 1 gives you the other!

http://pressroom.pella.com/fast_facts/153/confused-about-rvalues-and-other-window-and-door-terms

Pella uses them interchangeably. 

Maybe I misunderstand what you mean.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

Great post Jay!

Being from the warmer coast, I have a question. What is a storm window?

Posted by Tom Arstingstall, General Contractor, Dry Rot, Water Damage Sacramento, El Dorado County - (916) 765-5366, General Contractor, Dry Rot and Water Damage (Dry Rot and Water Damage www.tromlerconstruction.com Mobile - 916-765-5366) about 6 years ago

It is the smaller version of a storm door Tom.  Do you have those?

Think more square.

; >)

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

Did some quick Googling, it looks like a window install over the existing window, much like a storm door Jay. this is new to me Jay; I must live a sheltered life.  :)

I can see how this would be less expensive than replacing the windows.

Posted by Tom Arstingstall, General Contractor, Dry Rot, Water Damage Sacramento, El Dorado County - (916) 765-5366, General Contractor, Dry Rot and Water Damage (Dry Rot and Water Damage www.tromlerconstruction.com Mobile - 916-765-5366) about 6 years ago

Tom - I thought you were joking!  I'm sorry!  I gave you back a flip answer!

In warm climates storm windows might be cumbersome, but still effective toward insulating windows during the AC season.

Funny, when I was in South America I ran into a Canadian who had never heard of M&Ms!  I thought he was kidding!  He wasn't...

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

had to come back to this Jay Markanich   ...since i have some Andersen 20 year insulated windows that frost a bit in the subzero weather...I'm wondering whether that means i need to replace soon...

Posted by Ginny Gorman, Homes for Sale in Southern RI and beyond (RI Real Estate Services ~ 401-529-7849~ RI Waterfront Real Estate) about 6 years ago

No problem Jay.

Maybe Canadians have a different alphabet eh?

Posted by Tom Arstingstall, General Contractor, Dry Rot, Water Damage Sacramento, El Dorado County - (916) 765-5366, General Contractor, Dry Rot and Water Damage (Dry Rot and Water Damage www.tromlerconstruction.com Mobile - 916-765-5366) about 6 years ago

If they are 20 years old, Ginny, they may not have the current ability they once had, but I have NO experience with sub zero temperatures so I don't know.

Well, Tom, hopefully they call them J&Js there?

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 6 years ago

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