What is the “MPG” of your windows?

What is the MPG of your windows? Sounds like a silly question right? After all, a window can’t actually be measured for miles per gallon.  That said, a window CAN (and is) be measured and rated for its performance and efficiency, very similar to the MPG on your car.

There is a long list of nerdy, complex ratings for a replacement window, both for thermal and structural performance. The big ones discussed by most experts however, would be U-value and Air Infiltration. Most homeowners learn enough about windows when shopping around to compare the U-value (essentially measures how well the window insulates), but Air Infiltration is not talked about quite as much. This is particularly ironic given that a top three complaint about your old windows will be “they are too drafty”.

So why isn’t this rating talked about more frequently? Frankly, because most windows stink in this area. It would be like a car maker advertising that their new model gets 8 MPG. Not gonna happen. That leaves the ball in your court as a consumer, to ask for and verify these ratings so that you can make an informed buying decision.

For a reference point, a window with an Air Infiltration rating of .20-.30 cfm(lower is better) is about like a gas guzzling truck or suv. Maybe 8-12 MPG. On the opposite end of the spectrum, you can find windows in the range of .05-.01 cfm, and those would be more like 40-50+ MPG hybrid or electric car. Of course there is everything in between as well.

Lastly, one of the best things about considering these ratings– air infiltration in particular– is that unlike mileage, these ratings can be great indicators of a window’s quality in addition to it’s performance and efficiency. A small, junky car with a small engine can still get pretty good gas mileage, but for a window to be very airtight, it needs to be engineered and built to exacting tolerances.


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.

What to look for in a Window Warranty

Replacement Window Warranty Factors

When shopping for replacement windows, one of the majors factors that folks consider is the window warranty.  The warranty coverage on your new windows is significant for many reasons, not the least of which is that you want some security in knowing that you will have long term support on a purchase of thousands of dollars. Like many things in the marketplace, window warranties are part real concern, and part sales and marketing. I like to break warranties down to two primary areas: Product Warranty and Installation/Workmanship Warranty.

Product Warranty:

The product warranty on a replacement window is exactly that. It is the length of time that a manufacturer will provide warranty coverage for manufacturer defects. Generally that will not include items such as damage from abuse, failure to maintain, etc.  However, it does provide for replacement parts should anything fail due to a manufacturer defect. Common items include failed glass seals in an insulated glass unit, defective hardware, warpage, etc.  Some manufacturers offer accidental glass breakage as part of their coverage as well. Most vinyl window manufacturers offer a lifetime warranty, while wood windows generally have some variation of a 20/10 warranty, meaning 20 years on glass and 10 years on everything else including the wood.

Things to watch for:

Transferability  is important if you are considering selling the home any time soon. This means that you will be able to transfer the product warranty to one or more future owners of the home. Proration is an often overlooked factor. “Prorated” means that while there is coverage for the entire warranty term, it goes down over time. This is similar to a car battery or roofing shingle, where you have 100% coverage for say the first 10 years, then the coverage starts dropping in increments where you are paying an increasing portion of that as time goes on.  Ideally, a warranty that is fully transferrable and not prorated is best.

What product warranties typically do not cover:

Abuse, acts of God (ie: fires, storms, etc. that would be covered be homeowner’s insurance). Product warranties typically will not cover any labor needed to install the replacements parts. That falls on you as the homeowner, or on the installation company if they offer that service, whether it be paid or at no charge to you. The “fail to maintain” provision can be tricky on wood windows where condensation can damage or rot the wood before the 10 years and potentially be denied as a claim.

Workmanship/Labor/Installation Warranty:

The installation warranty on your replacement windows while important, can vary wildly from one dealer to the next. One company may offer one year on workmanship/installation, while the next offers lifetime, and a third still somewhere in between. The fact of the matter is that most installation related issues will manifest themselves visually within the first year or two after install, so something like a 5 or 10 year warranty is generally adequate. That said, many companies offer 20+ years all the way through lifetime. A lifetime workmanship warranty may sound great in marketing, but remember that the installation warranty is only as good as the company offering it. If all else is equal, certainly a longer term only benefits you as a consumer.

Things to watch for:

Service call/diagnosis charges, coverage to install the parts that are provided under the manufacturer’s warranty and for how long, a list of items that are included or excluded.

What installation warranties typically do not cover:

Installation warranties are intended to cover any poor or defective installation practices. Therefore common things that would be considered maintenance items like caulking, cleaning tracks and such which could hinder operation, etc., are typically not covered or the coverage is limited.


Every window warranty is not created equal. “Lifetime warranty” whether on product or installation may not mean the same thing from one company to the next, so take a look at the details and make sure that you are getting the protection that you are expecting. Also keep in mind that those warranties are only as strong as the companies offering them. Company history and reputation are important tools to look at. Lastly, “Lifetime” does have a quantifiable definition in most states. Here in Wisconsin, “Lifetime” for warranty purposes is defined as 30 years. It is recommended that you determine how this is specifically defined in your own location.

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 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.

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.

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.