Choosing a Window based on Air Infiltration (CFM)

Picture this: you’re shopping for new windows and you’ve narrowed it down to three finalists. To the untrained eye they look pretty similar. Because so many window features are government regulated these days, the glass and and U-value (amount of heat transmitted through the window) are basically the same across the board. The material, appearance and price of the three windows are also very comparable. What other features will help you choose between these windows?


You can buy the best window in the world, but if it’s not installed properly it won’t perform properly. If you’re deciding between installation companies, one question to ask yourself is this: Do I want to choose a general construction company that only installs windows some of the time, or a specialized window company that installs windows every day?


Another factor to consider is the warranty. There are two possible warranties a window may have: one from the manufacturer and one from the installer. Some companies only warranty their windows for 10 years against manufacturing defects, while others offer a lifetime warranty. Some companies also warranty against glass breakage. You will also want to ask the installer if they include a labor and service warranty on their installations.

Air Infiltration or CFM

According to Energy Star, “heat gain and loss through windows accounts for up to 50% of a home’s heating and cooling needs,” depending on climate. One final factor that can help you choose between comparable windows is air infiltration. This is measured by the CFM/sqft, or cubic feet per minute per square foot of window area. The CFM/sqft rating describes how much air would leak through your windows each minute at a standard windspeed. This feature is also regulated by the government, and the industry standard is set at .30 CFM/sqft. But what does that number mean in reality? And what are the factors that affect air infiltration?

It’s hard to understand what .30 CFM/sqft actually represents in your home. And, let’s face it, when companies test their windows for air infiltration, they’re doing it in a lab under specific conditions that won’t always match the conditions in your home. A common visual representation that you may see companies use is a graph that shows how many “soda cans” of air are leaked per minute at .30 CFM/sqft vs. whatever their window’s CFM rating is. In these graphs, .30 CFM/sqft = 24 soda cans/minute; .23 CFM/sqft = 18.4 soda cans/minute; .15 CFM/sqft = 12 soda cans/minute; and .04 CFM/sqft = 3.2 soda cans/minute. The lower the CFM rating, the better, but once a window gets below .10 you likely won’t feel a difference in your home.

Factors That Affect Air Infiltration

What factors most affect air infiltration? As we mentioned above, proper installation is critical to a window performing well. We recommend choosing a company whose main focus is windows and doors.

The climate and weather conditions where you live also determine how much air will leak through your windows. Here in New England we definitely want to choose windows with a lower CFM rating whenever possible.

Finally, the design of the window will play a major role in air infiltration. Windows that don’t open (i.e. picture) will have less air infiltration than those that have moving parts. All windows that move will have pile (weatherstripping material) between the moving parts to help prevent air leakage.  Rubber or felt are the most common pile choices amongst window manufacturers. No matter how many times you open or close your windows, rubber will bounce back to its original shape. Over time felt tends to stay compressed and may not provide the same level of protection against air leakage that rubber does. Window frame material is another design factor that impacts CFM ratings. Materials that expand or contract due to weather conditions will be more likely to sometimes have gaps between the frame and the sash. Finally, some windows are designed specifically to provide superior protection against air leakage. These windows will likely be the ones that are in the under .10 CFM/sqft category. Look for windows that have their CFM rating clearly stated in their brochure or on their website.

Danielle Cleary is with of United Better Homes in Pawtucket, RI.  United is a leading installer of replacement windows in the Rhode Island area and they’re our recommended company in the area.  If you’re anywhere near The Ocean State I’d recommend you give them a ring.  

What is a Replacement Window Spacer?

When you’re in the market for replacement windows, you’ll probably hear a lot about the NRFC ratings, the glass and the installation itself, but another important factor is the replacement window spacer.

What is a Replacement Window Spacer?

Any replacement window that has more than one pane of glass will have some type of spacer system.

The spacer is not simply the space between the panes of glass but it is the material that is used to hold the glass in place from between the panes. It also keeps the seal of glass air tight to keep in inert gas like argon or krypton gas.

Here you can see a triple pane glass unit with 2 spacers. The spacers are the gray pieces that separate the pieces of glass and keep the gas sealed inside.

Why is the Type of Spacer Important?

The spacer is one of the factors that affects the overall efficiency of the windows.

If the spacer is aluminum, the efficiency of the window will not be as effective as a spacer made of stainless steel (which is less conductive).

Many window manufacturers are now offering ‘warm-edge’ spacers that are generally made of a composite material. This type of spacer can help to improve the condensation rating (and by improve, we mean lower the likelihood of condensation, but you can read more about that here).

What Type of Window Spacer Should I Get?

My two cents worth is that you can ask the company you’re considering hiring if they have a some type of ‘warm-edge’ replacement window spacer. Generally the cost to upgrade should be quite nominal.

It’s included in our triple pane windows at my company, but nearly any replacement window company worth it’s salt should be able to  upgrade double pane windows with a high performance spacer as well.

Andrew Zahn is the owner of Zen Windows in Central, PA.   Andrew has worked in home improvement sales, marketing and public relations before opening his own window company.  If you’re in central PA and you’re thinking about new windows you should reach out to Andrew.  He’ll be the easiest window company you’ve ever dealt with. 

2016 Energy Star & Condensation Resistance

Condensation Resistance Now a Critical Rating?

I have always been an advocate of using performance ratings to aid in selecting a good window. If you have spoken to more than one window sales rep, you probably know why. Misinformation, shady tactics, and high pressure are all too common in this industry, and third party certified ratings serve as a way to cut through the salesmanship and compare replacement windows objectively. Unfortunately for you the consumer, things just got more confusing in that area.

Enter Energy Star Version 6

Much like U-Factor and solar heat gain, condensation resistance is a rating certified by the NFRC. In the past, this rating has moved nearly linearly with U factor in most cases, as it generally improves as the thermal performance of a window improves.

Whether you are aware or not, there are some MAJOR changes taking place in this area, and it has to do with the new 2016 Energy Star requirements for the Northern Zone, which call for a .27 U-Factor.  To clarify, this rating only applies to the Northern Zone.

Other zones still use ratings that are more easily achieved, and still effective for those areas. On the plus side, .27  is a darn good U-Factor for double pane glass, and for the most part, to this point, only good to excellent windows have achieved that rating.  The problem of course, is that there are A LOT of middling to poor performing windows on the market that could not hit that number.  That is of course without utilizing glass technology that has side effects.

The standby in this area is a heavy coat (or more than one) of low-e, often 366 glass or comparable. This results in a pretty dark window that cuts a bit too much solar gain for many homes in colder climates.  The newest, and potentially more harmful option is a surface 4 low-e coating. This is a coating of low-e that is applied directly to the surface of glass that you can touch from the interior of your home. You might think that this would be cause for concern with scratching and durability, however, these concerns are largely unfounded. The larger issue is how this rating affects condensation resistance, particularly since the region of the country in question struggles with window condensation issues as is.

alside fusion ratings and reviews
For example, here are the ratings for the lower end Alside Fusion window with the typical Climatech Glass. Notice the U-Factor does not meet the Energy Star guidelines for the Northern Region, but the condensation resistance is 56 which is decent.
condensation on Alside window
Here are the ratings for the same window with the Climatech SF glass option. This lowers the U-Factor to meet the Northern Region requirements, but look at what it did to the condensation resistance. This window is MUCH more likely to develop condensation when it gets cold outside.

To very simply describe what low coatings do, they reflect heat. By placing this coating on the interior surface, you effectively keep that pane of glass and the airspace behind it from warming. Colder glass= MORE CONDENSATION when all other conditions are equal.  The condensation rating drops precipitously, by nearly 10 points in many cases.  Ratings in the upper 50’s and 60’s are dropping down into the 40’s in some products with the surface 4 low e coating.  While there are ways to mitigate the amount of moisture in your home to compensate, many homes in the Northern region have enough of a challenge doing that without injecting this additional difficulty into the equation.

What is the Solution?

Well, there are a few things that you can do actually. One, buy a double pane window that achieves a .27 or better without this coating. Incidentally, if you combine this with a good air leakage rating under .05 or so, you can be assured of getting a pretty darn good window. Two, buy triple pane glass, which in the Northern region should be given strong consideration anyway.  Three, forego buying an Energy Star rated window in favor of one that will actually be better suited to your needs and budget. Personally I’d opt for option one or two, however, option three is better than unknowingly installing windows that may end up looking like a shower door in your home. This issue is particularly important for wood interior windows, as interior condensation is one of the leading causes of damage that I see to wood windows installed in the last 30 years.

condensation resistance
It may be a little hard to tell from the picture, but this window has condensation on the inside of the house on a cold day. If you touch this glass you’ll get all wet.

Location is Key

One final thing to clarify, is that both the Energy Star rating in question, as well as the gravity of condensation as an issue are fairly unique to the Northern Zone and colder climates. This coating is not inappropriate in other regions, and in fact, is excellent technology when applied correctly.

In addition, it should be noted that Energy Star HAS proposed an equivalent certification where a lesser U-Factor can still qualify provided that the difference is made up by a higher SHGC. Unfortunately, those trade-offs are still somewhat challenging to achieve, and nobody wants to advertise a less efficient U-Factor since that is the number one rating that consumers use to compare.

Ultimately, the moral of the story is buyer beware. Do your homework when making a purchase of this magnitude. On the plus side, you are HERE, so that’s a great start!

Brandon Erdmann is the owner of HomeSealed Exteriors in Milwaukee, WI.  He’s a window installation expert, a supporter of this site and an all around great guy.  If you’re in the Milwaukee area and you’re thinking about new windows you should give Brandon a ring.  You’ll be glad you did.

2016 Window Tax Credit Details and Information

As an observant window shopper you may have heard about the 2016 window tax credit.  There have long been tax credits associated with energy efficient replacement windows and the federal government has just extended the tax credit for new replacement windows and energy efficient doors.

Which windows qualify?

Over the years there have been different methods for determining which windows and doors qualify for various tax credits.  In 2016 the government is using the Energy Star guidelines to determine which replacement windows and doors qualify.

If your new windows and doors are Energy Star certified then you’ll qualify for the tax credit.  Most manufacturers offer many qualifying options.

What are the 2016 Energy Star guidelines?

The guidelines vary based on where you live.  This is a pretty reasonable method as folks in Phoenix need different windows than folks in Maine.  The exact requirements for your location are shown here and your window installation company should be able to make sure they’re offering you windows that will qualify.

2016 Energy Star tax credit requirements for windows and doors
Windows and doors that meet or exceed the ratings shown here will qualify for the 2016 federal tax credit.

How much is the tax credit?

The tax credit for 2016 is based on the cost of the windows.  You’ll be eligible for a federal tax credit of 10% of the cost of the windows, not including labor costs, up to $200.

The tax credit for doors is similar.  It’s 10% of the cost of the doors, not including labor, up to $500.

This is only $200?

If you’re one of those people who says, “oh, it’s only $200 well that’s nothing” then please make a check out to me for $200 and drop it in the mail.

I know it would be better if it was $2,000, but c’mon $200 is $200.  Go buy your sweetheart something nice and quit your grumbling.

Is this a tax credit or a tax deduction?

This is a tax credit.  This means your tax bill will be reduced by $200.  There is no consideration for how much you make or how much you pay.  If you owed $10,000 in taxes you’ll only owe $9,800 if you spent over $2,000 on qualifying windows.

If you’re owed a tax refund (since starting a business I can barely remember what a tax refund is), your refund will increase by $200.  So, if your refund would have been $3,000 it will now be $3,200 if you purchased qualifying windows.

What if I already purchased windows?

If they meet the Energy Star requirements and you’ve purchased them in the last few years you’re eligible for the same credits.

What documents do I need?

You do not need to submit anything with your taxes.  You just let them know how much you spent on the windows and you get the credit.  It might be a smart idea to keep a copy of your invoice and the manufacturers certification statement in your files just in case you need to prove anything one day.

What if I used this tax credit last year?

If you’ve used a tax credit for any energy efficient home improvement in the past you probably cannot add this credit to that one.  You get one shot whether you use it for new windows, a new furnace or one of those fancy tankless hot water heaters (I just got one of those bad boys, endless hot water, I love it).

Should I ask a tax professional if I have questions about this?

Yes.  I’m a window person not a tax advisor.  This is the best info I have based on my experience.  Please don’t email me saying I cost you tax money.  Call your tax preparer with any questions.

Are Foam Filled Windows Better?

Are Foam Filled Windows Better?

One of the more common questions that we here in the Milwaukee area, is regarding foam filled windows. Are they actually better?  Is the upgrade worth the money? Which type of foam is better, injected or push-in? The answer like many things in life of course is… It depends.

Are foam filled windows better?
Here are two different types of foam filled windows. Is one better than the other? Check the U-Factor.

Foam Filled Windows have benefits

Foam filled windows will provide some benefits across the board, the debate really comes down to how much of a benefit, and is it worth the added expense. My first recommendation to replacement window shoppers is to check how this option affects the U factor of the window. Some foam filled windows will have a U factor that improves by 2+ points, others will not budge at all. There are a variety of factors for this, most notably in the design of the extrusion(the “inner-framing” of the window).  Windows that have many chambers will often see less impact on U factor, because those dead air spaces actually do a decent job of insulating. This is not necessarily reflective of product quality, it is just a different means to an end.  That said, the primary benefits to foam filled windows will be superior thermal performance (measured by U factor and condensation resistance), as well as a little bit of extra structural stability. It could be be conceivable to improve sound transmittance as well, however the impact here is probably negligible in most cases.

Types of Foam Filled Windows

The two common methods to foam fill windows are injected foam, where spray foam is actually injected into the extrusion, and push in foam, where expanded polystyrene is cut and pushed in. Despite what sales people may tell you, both are effective methods when executed properly, and each does have its own minor pros and cons.  Injected foam is generally higher density, and therefore a better insulator.  This advantage is somewhat mitigated however by the fact that these are pretty small spaces, so the actual increase in R factor is minimal. The downside of injected is that spraying foam can produces air pockets and inconsistent fill. Push in foam eliminates that potential issue, however this type of foam must be cut to exacting tolerances where it provides a tight fit in the chamber to be effective. The manufacturers that do this right, have CNC machines that cut the foam precisely to fit.

Bottom Line

Ultimately, the option for foam filled windows is better, however the value of it depends on the price vs performance increase. This is generally a pretty inexpensive option, so it does make sense in many cases. The one thing to keep in mind, is that when comparing two different products, the type or even presence of foam filling does not necessarily make that product better than the other. A precisely designed and manufactured unit will be the better option, with or without foam.


Bow vs Bay Windows – What’s the difference?

We get asked about the differences between bow vs bay windows all the time. We finally decided it was time to whip up a post with the correct answer for all to see.

best replacement windows of 2015

To put it simply the difference is in the layout of the windows.  Both bow and bay windows stick out from the house, but they have a different look.  Bow windows are made up of equal sized lites or panels while bay windows have a center section that is larger than the sides.

We may need a picture for this one.  First we’ll start with a bay window.

bay window vs bow window price and cost

Ok, so that’s a bay window.  3 panels, and the center is larger than the sides.

Now, here’s a bow window:
bow-windowSee the difference?  The bow has several panels and they’re all the same size.  A bow window can have 3, 4, 5, 6 or more panels, but they’re always the same size.

Is a bow window better than a bay window?

Nope, it is really just a style difference.  Do you prefer the look of the larger picture window in the center or a bay window or would you rather have several symmetrical panels?  One is not better than the other, they’re just different.

What is the price difference between a bow and a bay window?

The difference in cost is typically pretty small.  Many manufacturers will charge more for a bigger window, but the difference between a bow and a bay is typically not a huge driver of the cost.  A bow window with many panels (called lites) will typically cost more than a bay window with only 3 lites.

A cost difference of a few hundred dollars wouldn’t be unusual, but you shouldn’t see much more difference than that.

As you’re shopping for new windows be sure to check out our detailed window reviews here.  If you’re looking for anything that you can’t find be sure to post a comment or send us an email.  We read every single one and we’ll do our best to respond.


NFRC Ratings Explained

As you’re shopping for new replacement windows you may have heard of NFRC ratings.  It’s important to understand what these ratings are and what they mean about your new windows.  First of all NFRC stands for the National Fenestration Rating Council.  They’re based outside of Washington DC in Greenbelt Maryland.  They are the national body that sets the standards for replacement window ratings.

Just about all new windows and doors offered today are NFRC rated as they need to be in order to qualify for the Energy Star program.  The mice thing about NFRC ratings is that they are clear.  Every new window will come with an NFRC sticker which clearly displays the ratings for that individual window or door.  There is no room for salesperson trickery.

champion window prices
Despite claims of their salespeople and long heat lamp demonstrations, Champion windows have average efficiency ratings.

The NFRC stickers will look like the example above.  As you can see they display the U-Factor and the Solar Heat Gain Coefficient (SHGC) on the top line and the Visible Transmittence (VT Rating) on the bottom left side.  These are the ratings that MUST be on each window.

On the bottom line this window from Champion Windows also shows the Condensation Resistance which is optional.  Some windows, like the Simonton window pictured below, will have a blank space in the lower right side.  There is nothing wrong with this, but it does indicate that they don’t want to advertise their rating.

Simonton Reflections 5500 window ratings
Simonton Reflections 5500 window ratings

Why are NFRC ratings important?

These ratings are important because they are solid.  They are not up for interpretation or subject to change at a moments notice.

We hear stories about salespeople with all sorts of bogus info.  We see R-Values getting thrown around and hear about promises made to customers that are just plain impossible.  The NFRC ratings provide a way to really evaluate what you’re actually getting to make sure it meets the promises you were made.

What should you do it the sticker does not match what you were told?

Whatever claims the company makes about the energy efficiency of their windows make sure to get them in writing.  Let them know you’ll be checking it agains the NFRC stickers.  If they match you’re doing great and if they don’t somebody has some explaining to do.

If you feel like you’re getting fishy numbers during the sales phase ask them for the real NFRC ratings.  If the ratings you get don’t match what you were previously told then you know they were being tricky with you.  If they were I would suggest you find another company.  There are plenty of fish in the sea as they say.

Hopefully you caught these shenanigans during the sales process.  If they’re not caught until the products are installed it will be harder to figure out a solution.

What if the windows do not come with NFRC stickers? 

This probably means that the company removed them prior to installation which is a huge red flag.  it may mean that they’re trying to hide something from you and there may be very little you can do about it at this point.

What’s the bottom line?

NFRC ratings are a great way to evaluate the differences between various window products.  We see customers struggling with these evaluations all the time.

In fact, just today I got a call from one of our reps who was out meeting with a customer.  The customer had asked our guy how thick the gap between the 2 panes of glass is.  Before we go answering that question it’s important for us to identify what the customer is actually asking.

Does the customer care if there is 1/2″ or 3″ of space in there?  Nope.  What they want is an energy efficient window and some other company probably told them that you need to have this much space or that much space in order to be efficient.  Of course the simple way to tell how efficient one window is compared to another is to look at the U-Factors on the NFRC sticker.  If one is lower than it’s better and if it’s higher than it’s worse.

Does the space in-between the glass make any difference?  Who cares.  Either the ratings are better or they’re not better.  The measurement of this dimension or that dimension don’t matter one bit.  This is how NFRC ratings make window shopping easier.

Find more info on replacement window ratings here and you can find the most comprehensive and detailed replacement window reviews on the internet right here.

Have fun!

If you’re looking for a window company right now, the best advice we have is to join Angie’s List.  For just a couple bucks you can get a 1-month membership and it’ll be worth much more than a caramel macchiato in the long run.  You can find the best pricing for Angie’s List on the internet right here


2015 Replacement Window Tax Credit

Perhaps the most common questions we get are about tax credits for replacement windows.  As we get towards the end of 2014 the big question on everyones mind is whether there will be a tax credit for replacement windows in 2015.  The answer right now is probably not, but it’s nothing to worry about.

best replacement windows of 2015

We know that’s not a very good answer, but it’s our government at work.  The latest update is that after the Democrats lost badly in the mid-term elections in 2014 they quickly moved to pass legislation before they lose control of the senate.  The initiatives they’re currently focusing on are tax credits related to ideas they support.  Energy efficient windows and doors are certainly something the Democrats can get behind.

Will the legislation pass before the Republicans take control of the senate in 2015?

Nobody knows.  What we do know is that last time tax credit legislation passed it was retroactive as long as folks purchased windows that met the current Energy Star guidelines.  Our best advice is to make sure the new windows you’re considering for your home meet the more stringent 2015 Energy Star guidelines.

This newer generation of windows is more efficient than the older 2014 models and they’ll save you money in the long run.  They will  also likely be included in any new tax credit legislation.

If there is a 2015 replacement window tax credit our best guess is that it will be retroactive to 2014 purchases and frankly by mid-November most windows purchased now will be installed in 2015 anyway.

We encourage you to go ahead with your window purchase and to make sure you’ll be getting windows that will qualify just in case there is a tax credit next year.  Any reputable company should be abel to tell you which windows will qualify and we have a post on the subject right here.

Have fun!


R5 Windows Volume Purchase Program

You may have read about the R5 Volume Purchase Program that the US Department of Energy came out with several years ago.  The idea was to encourage the manufacture of R5 windows which would drive down the cost.

It was a decent idea, but it hasn’t produced much in the way of results.  In fact most windows that meet these ratings cost the same today as they did back then.  We’re not aware of any R5 window products on the market that have come down in price since this program was established.

Which windows qualify for this program?

The Department of Energy decided that any windows with a U-Facotr of 0.22 or lower would qualify.  Of course most if not all manufacturers already offer windows that meet this criteria.  About the only reason the costs of these windows are sometimes high is that the manufacturers price the most efficient options to provide the highest margins.

There is no manufacturing difficulty in producing a product like this and about everyone already does it.  Could any company sell these products for less?  Sure, but the Department of Energy is not likely going to be able to help.

Does this mean the R5 Windows Volume Purchase Program was a failure?

Not necessarily, but it certainly hasn’t been the success the DOE hoped for.  Most if not all window manufacturers offer windows that meet this criteria, but homeowners in the most of the country don’t pick them with much consistency.  For example, many (if not all) windows will need to go to triple pane glass to get that rating.  Triple pane glass costs about $100 additional per window.  If you have 10 windows in your house that would add about $1,000 to a typical project.

Will you get much benefit from windows like this vs typical Energy Star rated windows?

Probably not.  If you live in a harsh climate the impact of the more efficient windows will be greater.  If you’re in Maine or Minnesota you may want to consider this option, but if you’re in the more temperate parts of the country the savings will be much smaller.

That isn’t to say triple pane windows are always a bad deal.  If you’re going to be in the home for a while and are looking for the most efficient option they can represent a great value.  The bang for the buck gets smaller as the windows get more efficient so just keep in mind that the increase in cost will be greater than the increase in efficiency.

You can find more info on replacement window ratings here and you’ll find the best replacement window reviews online right here.

Have fun!



Replacement Window U-Factor vs R-Value

Shopping for replacement windows can be a bit daunting and even comparing replacement window ratings can be much more difficult than you might expect.  Why is this?  Because companies don’t want you to make sense of it.  The companies that offer the “best windows ever produced by mankind” know full well that their windows aren’t really any better than other windows offered by hundreds of other local companies.

How then can you sort through all of the nonsense to get to the real info?  First you need to understand the ratings.  U-Factor and R-Value are common ratings used to measure efficiency.  You may be familiar with R-Values as they’re used in insulation.

Simply put the U-Factor is the inverse of the R-Value.  For example a windows is an R-4 then the U-Factor is 1/4 or 0.25.  Of course if it were that easy everyone would understand it and there would be no need for this post.

Here’s a little history.  Back in the day (say before 2008) windows were commonly sold based on R-Values.  These are nice round numbers that are easy for consumers to understand.  A very common sales pitch included prices for windows with an R-4, R-7 and R-10.  The higher the R-Value the better so the R-10 cost the most and the R-4 cost the least.  That pitch was very effective due to its simplicity.  It was easy to teach the salesperson and it was easy for the customer to digest.  The problem was that it wasn’t very accurate.

In 2008 the federal government came out with expanded tax credits for replacement windows that were based on specific U-Factors and SHGC ratings.  Intently the R4-7-10 pitch went out the window as folks were now concerned with the 0.30 U-Factor required to qualify for tax savings.

Why did the feds base the tax credits on U-Factors?  

We know a lot of things the government does don’t make much sense, but this one did.  U-Factors as determined by the National Fenestration Ratings Council (NFRC) are a measure of the entire window.  They take into account the frame, the glass, any additional options and they provide a clear measure of the effectiveness of the product.  This is why the U-Factor remains the best measure of efficiency of a window long after the federal tax credits have gone away.

Why do some companies still use R-Values?  

Because they don’t want to offer you an easy comparison.  R-Values as given out by window salespeople are often measures of just the center of the glass of the window.  This is the most efficient part of any window as it doesn’t take into account any spacers or frames or other parts.  Of course you’re buying an entire window not just the glass.  Looking at just the glass measurements doesn’t do you any good.

We routinely see companies advertising R-10 windows as being special, which is just silly.  To accurately describe this an R-10 window would have a U-Factor of 1/10 or 0.10.  Do these windows have U-Factors of 0.10?  They do not.  Why don’t the numbers add up?  Because they company was trying to be tricky with the ratings.

So know you know that just about any window company offering R-Values is not being clear about the ratings, it’s important to remember that the Department of Energy put out an R5 volume purchase program a few years back.  The ratings in this case were accurate.  This was setup to drive down the costs of windows that exceeded the previous standards.  It hasn’t been much of a success just yet, and we’ll have another post on the subject.

So how do you sort through all of this to find a great deal?

The easy way is to look at the NFRC ratings for the products you’re considering.  Don’t take some R-Value from the salesperson.  Just ask them for the real NFRC ratings and don’t take any excuses as to why the company can’t or won’t provide them.

Once you have that, you’ll be able to compare the options directly and you’ll be on your way to cutting through all of the clutter to find yourself a great deal.

You can find more info on replacement window ratings here and you can find detailed replacement reviews here.

Have fun!