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Replacement Windows Design & Performance

Read 21 replacement windows design & performance from industry experts, installers and homeowners. For pricing on different styles and frame types, try our window cost estimator.

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Gass Fills And Frame Fills

Sir, a further question if you don't mind. I have a cousin who works in the industry. He wrote to me: "Just don't get caught up in gas insulated glass. That is more money than it's worth. Look for insulated frames. Vinyl is very cold when not insulated."

I really haven't found any windows available locally that don't have insulated glass and do have insulated frames. I was all set to go w/ the Reflections 5500s. I got refs from two local homeowners who had them installed by a particular contractor and they were happy.

What do you think the insulated frame vs insulated glass issue?

Steve - Homeowner - from 2016

[Site Editor's Response]

Steve, most window manufacturers offer a standard glass that includes a low-e glass with argon fills. The argon is the gas and is pretty common in the industry. You certainly don't have to have the argon, but it does add some energy efficiency to the window, not a ton, but some. Over time, the argon can escape if the seals on the Insulated Glass Unit are weak or leak. I wouldn't spend a lot of time worry about whether you have it or not, but most windows do come with it. The gas is not an expensive add on as far as the overall ost of the window goes.

In terms of foam filled frames, I totally agree that the extra cost to have the foam injected frame is well worth the money. Different manufacturers have different options, some window series come with it standard, others offer this is an upgrade, while some lower end companies may not offer it at all. Make sure to ask the dealer who is selling you the window what the different options are.

At the end of the day however, you will be better served to concentrate on finding a quality window manufacturer who will offer these upgrades, but that builds a quality extrusion and uses quality components, along with professional installation. Get these two pieces of the puzzle right and the little extras and upgrades will be icing on the cake!

- Site Editor - from 2016

Window Snap In Sills

I've heard people talk about a snap in sill and that it's a bad design. Can you explain why this is and what the alternative to this is?

John - Homeowner - from 2015

[Editor's Response]

John, the snap in sill (also called a pocket sill or a capture sill) is a design from the 80s and 1990s that has an inherent flaw. When someone closes the sash, the bottom goes into the U shaped sill. This traps the water in the pocket, which then drains through the window frame and out the weep holes. Over time, those weep holes can get clogged with dirt, debris, pollen, etc. and can result in the build up of mildew and mold inside the frame itself. Manufacturers use the snap in sill because it is cheaper to make, but it can cause problems down the road.

Many manufacturers that make these sills argue vehemently that the criticism of this design is unfounded, which makes for some interesting back and forth on window forums around the internet. I would say this - if you live in an area that gets lots of rain and moisture, go with a stepped sill or a true welded sill, you will pay more but it should be worht it. If, howevevr, you live in an area with mild climates, it probably doesn't make a huge difference.

Tim - Site Editor - from 2015

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Also please consider filling out the free form on our site for 3 quality window price quotes — it’s how we afford to provide free consumer information. We’re not incentivized by ANY company and will help you with ANY questions you might have, and help you navigate ANY bids you receive. That’s our guarantee to you!

Alside Windows

I've put in a lot of different windows, and the Alside Sheffield is one that I really hate to see. I think it's just cheap. Instead of a sloped sill, like every well-designed window out there, the frame has the same extrusion on all sides. It's a cheap shortcut that saves millions on factory equipment. Unfortunately, most home owners don't pay attention and they'll buy it anyway.

Another problem the Sheffield has is the handle. When you lift up it puts stress on the glass. It's just a cheap and ugly way of doing things - a good window will have the handle in the sash rail.

Hartley - Installer - from 2008

Armaclad Issue

I'm not an Armaclad fan. The sill design causes rain to drain to the inside of the extrusion. Water and dirt and bugs collect there, leading to mold growth. I prefer a sloped sill that directs the water away from the window frame.

Will - Contractor - from 2009

Don Young

I'm based in Houston, and I sell a ton of Don Young thermally broken aluminum windows. They have an shgc that can compete with vinyl, .29 to .31, narrow frames that give you more glass, and they can come in a great bronze color that I really love. They do have a high u-value .31-.34 and they cost more than Simonton 5500s. If you get a lot of cold weather, they also don't have the energy efficiency that some windows do, but I really love them, especially the 8200 series, which is commercially rated and is really sturdy and durable.

Barry - Installer in Dallas - from 2009


Earthwise is an average window, nothing special but a few nice features. They have a curved lift rail that looks really good, and colonial beading around the glass. They used to shadow groove the sash corners and I think they quit doing that. It looked really nice. Most windows in that price range, though, have triple weatherstripping and it only has double. Depending on the line of windows you're looking at, some have sloped sills and some pocket sills. I definitely like the sloped sill better. The only line from Earthwise I really like is Innovations. It has a lot of good features and performs well. It might be the only window of theirs that is worth the price.

Will - Contractor - from 2011


I sell the Energex Elite and always recommend them to buyers, along with two other brands I carry. The windows are very well engineered and designed. The corner welds are cleaner than just about all brands out there. They use a vinyl frame that has a .08" thickness and Guardian's Super Spacer IG, three point weatherstripping for the sash and a magnetic sash seal. They use a nice composte reinforcement on the meeting rail (this is standard on the double hung, but I believe an ugpgrade on other styles), the hardware is Ashland (they use the same tilt latches that Simonton uses on their 5500 series) and the chambers are foam filled. The window has an AI of .05 (solid) and comes with a nice warranty that includes glass breakage.

Mike - Contractor in Delaware - from 2012


I live north of Chicago, and have 16 windows to replace, a mix of sliders and single casements and picture windows. I got a lot of estimates, and I'm mainly looking at the Gilkey Series 6 or 10. At $11,800 it's a thousand more than the Series 6 but it has a .10 U-value, 99.9 UV block, .33 SHGC. Plus I think it looks a little nicer. The Series 6 has .16 U value, .36 SHGC, and 99.7 UV block. Not really sure which is better.

Gary - Homeowner in Illinois - from 2008

[Contractor Response]

Gilkey is a good choice, it will out perform most other brands at the same price point. They get good U-Values because of Heat Mirror, which some people don't like. As long as the price is right and the warranty is reasonable, Gilkey is a fine choice.

Wayne - Contractor - from 2008

Jeld Wen Window Quality

Jeld Wen has always made very good doors and I recommend them to many of my customers in my area. On the window side, I'm not as big a fan. I think there are better designed windows at the same price point and I usually steer my clients towards these. Jeld Wen is a big name though and if my customer feel more comfortable going with a national name, I would prefer to install Jeld Wen over other companies that market in the big box stores such as Silverline, Reliabilt (made by Atrium) and Pella Windows (their vinyl, not their high end wood clad). Their vinyl windows aren't bad, they just can't compete with companies like Amerimax, Sunrise and even Milgard.

Bobby - Contractor - from 2013

Marvin Window Options

The Integrity has a either an Ultrex or wood interior and Ultrex exterior. With a ufactor of 0.30 and SHGC of 0.32, the numbers are decent but not stellar. I like the look of a wood interior, but it costs about 10% more than the all-fiberglass. The Infinity costs about 25% more than a similar Integrity, but it feels a lot more solid and durable. The ufactor is similar, 0.29, but the SHGC is 0.21, so it has a little bit better ratings. The Infinity also has the Everwood interior, which looks like real wood and can be stained or painted however you like. I like it a lot better than the Integrity. If you really want an actual wood interior, you can look at the Ultimate series, which is similar. The Integrity is advertised as having a 10 year warranty, 20 years glass coverage. A lot of the salesmen for vinyl windows tout their lifetime warranties. Is the warranty long enough? Should I look for something with a better warranty?

Barrett - Homeowner - from 2009

MI Impact Windows

MI has a new Energy Core line that looks like it might be good. My biggest problem is it has a pocket sill, which I really don't like unless you have an impact window or some other good reason. Their other lines are nothing special. You can find plenty of others for around the same price with a much better track record as far as satisfaction, efficiency, and performance.

Holland - Contractor - from 2012

Milgard vs Hurd Windows

It seems like I looked at every window out there, Hurds, Milgards, Softlite, CerTainTeed, etc. Looking at the numbers and features, I finally think I've decided to go with Milgard Tuscany. It has a good AI and they offer a package called "extended performance" or something like that that can lower it even more to .08. I also like their color, I think their beige is a little darker and less green than a lot of companies.

Matt - Homeowner in Ohio - from 2009

Okna Window Ratings

The Harvey Tribute is a decent window, but it can't compare to the Okna. The Okna 500 has a U-factor of .25, DP structural rating of 50, and air leakage is .02. The Harvey has just OK numbers - U-factor .30, DP 30, and over 0.1 for air leakage. The Harvey loses in every way.

Michael - Contractor in New Jersey - from 2012

PlyGem vs Pella Windows

The Plygem Lifestyles is much much better than the Pella 20 Series. Ask for the stainless steel spacer, it makes a big difference. The PlyGem has a slightly flimsy sill (it's a second tier window) but as long as you aren't paying a premium price it isn't bad. I would get the energy package, you get reinforced sashes, foam filled frames, and a stainless steel spacer. They're a little more expensive but it's worth it. I would suggest taking a look at Okna, Hi Mark, and Sunrise if you have time, but the Plygem is not bad.

Kendall - Contractor - from 2012

Read more Plygem windows reviews.

Polaris vs Simonton Windows

The Polaris UltraWeld is a good window. Their casement is pretty nice, but they make just about the best bays and bows I've ever seen. Compared to Simonton windows, I think they win as far as energy efficiency and design both. With their new super spacer, they get a .28 u factor and have really good air infiltration numbers. Polaris uses Sturtz equipment in their manufacturing facilities, some of the best automation equipment that results in a good solid product with very few defects. I do prefer a stainless steel spacer, and they recently started making one, the UltraCept, which I like a lot.

Matt - Contractor in New Jersey - from 2011


The Silverline and Excalibur aren't as good as the other two, I would eliminate them right away. The Simonton 5500 is average, and the PGT is pretty nice, a 4" frame and exterior flange. It's comparable to the Simonton, but with better DP and AI numbers. I sell more of them than anything else.

Dan - Installer - from 2011

Serious And Kensington Windows

Serious Materials bought some of the assets that used to make up Kensington Windows. They took a lot of the designs and facilities and renamed them as Serious lines. They updated some of the designs a little, but they still have pocket sills on some of them. I know a pocket cuts down on air infiltration but it grabs all the moisture and dirt. They do have Heat Mirror, which I like. The Kensingtons had some issues with fit and locking due to poor design, and I don't know if Serious has fixed all those issues.

Buddy - Contractor - from 2010

Simonton Reflections 5500 Series

Simonton has some good windows, especially the Reflections 5500 and Prism Platinum. They are pretty much the same with only some minor cosmetic differences. I like the Prism Platinum best, it has the Super Spacer and double strength glass. If you are in the south, I'd go with the ETC Super 366 for the low solar heat gain. In the north, you want the solar gain so get the ETC Super Solar instead.

Steven - Contractor - from 2010

Soft-Lite vs Okna

Soft-Lite and Okna have windows with an AI of .01, while the Vinylmax Easton is .17. The same two have U-factors of .26, while the Eastons is .30. They have better DPs, too. The Vinylmax looks decent on its own, but when you compare it to the others you see how bad it is. You'll pay more for a better window, but to get the same numbers in an Easton you'd need tons of add-ons and packages and upgrades. I'd pay a little more and get a much better product.

Jim - Window Contractor - from 2010

Sunrise vs Soft-Lite

Sunrise Restorations, Vanguard, and the regular Sunrise are very similar. Some of the features that are options on the basic model are standard on the higher priced lines. They have fiber core reinforcements, which is nice for some installations but unnecessary for others. You might get more for your money if you get the basic Sunrise with triple panes and then add the features that you want. They do have a really great patio door, equal to Softlite, HiMark, or Okna. Pella, RBA, and Champion are overpriced and overrated.

Randy - Contractor - from 2010

Read more Sunrise window reviews.

Window World Quality

Window World is not a product a home owner should consider, and here is why. A good window has a sloped sill, but WW has the same extrusion on all sides. It's cheaper to make that way, you only have to cut a simple 45 degree angle and theres no need to invest in good robotic equipment to make different cuts and weld them together. It's cheap and it makes a rectangle frame, but I'd barely call it a window. The sills in these fill with water and dirt, and soon there's mold growing. You need a sloped sill for good drainage. There are very few companies that make such a low-quality, poorly designed window.

Hartford - Contractor - from 2010

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