What w.ross is talking about is true--the air/water gap is the small amount of space some window manufacturers leave between the cladding and the wood frame. It allows any water that may penetrate the window to drain away from the wood. Manufacturers that don't leave the gap often have all this hype about how their windows are treated to help prevent rot. That's because if water gets in their windows it has no way out & the cladding sits right up against the wood so the water has no place to go except into the wood. This forum is actually where I learned about the importance of this feature. There used to be a few good threads on this topic on the forum, but I can no longer find them. I know they were very useful for me when we were looking at the different window options out there. There were some I remember that had excellent photos of the different window construction methods used. If you go to the Marvin site and zoom in on the photo of the cross-cut of the window you will see the small space between the cladding & the wood (hover over the photo titled 'tri-pane' in the link below to see the space zoomed). http://www.marvin.com/windows/wood-double-hung-windows/glass-energy-efficiency-and-screens/ Now click on the Jeld-Wen Site-Line EX link below to see how their cladding is applied in direct contact with the wood. http://www.jeld-wen.com/catalog/windows/siteline-ex/wood/double-hung w.ross--the only companies I know of that leave this gap are Marvin & Sun. I think it was eitherLincoln or Best that also left the gap, but I can't recall for sure. I've attached below what my window research found as posted on another thread. You may find it useful : Researched windows for months--until I had made myself crazy. Started out Pella(alum clad), then Jeld-Wen (alum clad), investigated M&W (vinyl & alum clad), Sun (alum clad), Andersen (alum clad), & Windsor (alum clad). Ended up convinced Marvin or Marvin Integrity are the way to go. Here's what I found: -Pella's aluminum clad windows are roll form aluminum which can dent easily & some question on the durability of the finish. Roll form is applied directly to the wood frame of the window--the wood is basically wrapped in the aluminum cladding. Should water infiltrate the frame of the unit, the design leaves no space for water to escape or drain away from the wood which is why Pella promotes how their wood is specially treated. Plenty of good reviews, plenty of bad reviews. Price was sky high. -Jeld-Wen Traditions are roll form aluminum so denting is an issue. SiteLine EX series are extruded aluminum clad wood which takes care of the denting, but the cladding is applied using same technique as roll form so no channel for water to escape should water infiltrate. JW also promotes how their wood is specially treated for just this reason. Plenty of good reviews, plenty of bad reviews. -M&W just not that impressed, recently merged with Ply-Gem so not reassured on how business will progress in future as far as quality & warranty. Vinyl clad line has wood frame wrapped in vinyl with no space between so potential water issue and no mention of wood being treated to help protect against rot. Did like the look of their aluminum clad line though. Plenty of good reviews, plenty of bad reviews. -Sun-Couldn't find enough reviews and information, but liked the look & they had the water drainage channel design. -Andersen-Seemed like practically everyone we talked to prior to researching the windows said stay away from Andersen. When asked why, the response was virtually identical each time--product not durable. Andersen stands behind their warranty but do you really want to have to be dealing with Andersen for the next 20 years on fixing warranty issues. We did price the Andersen 400s and the price was sky high. No personal experience with the product, but their windows sure did look nice. Plenty of good reviews, plenty of bad reviews. -Windsor-liked them, but not enough distributors in our area and the one we were dealing with seemed to always leave significant quantities of windows or the more expensive windows (arches, etc) off our quote. We're guessing they did this to make the bottom line look more attractive. So no faith in the supplier. -Marvin-beautiful windows. Ultimates are extruded aluminum clad with the space left between the wood and the cladding for water to escape. Reviews were primarily positive with only a few negatives (and they tended to be on older windows). Customer service and warranty reviews were excellent as well. Ultimately, the Ultimates are out of our price range. However, the Marvin Integrity windows did fall in our price range & they are also very nice windows in my opinion. They are a fiberglass window 8 times stronger than vinyl with no fading or chalking of the finish. They are available as wood clad with channels for water to escape or as an all fiberglass unit. Good U-Values & SHGC Values. Plus you have Marvin backing up the warranty should anything happen. So that's where we're at--Marvin Integrity is the window for us. Hope this helps!

With great success, we have used Eagle, Kolbe and Marvin windows. These are three manufacturers that build high quality and very durable products that are also very similarly constructed. We generally seek three bids from each division of our building scope, so we find comfort in these three as the highest quality. The decision between the three is then made based on the manufacturer's ability to meet the project's required specification and of course, the price estimates. Most all higher-end wood window products today contain standard options like stainless steel hardware, hidden multi-lock casement lock systems, folding cranks and pivoting sashes for ease of cleaning without the requirement for ladders or scaffold. Many offer an array of standard clad color choices and interior wood species. If you'd like to make an educated decision on your window choice, compare items such as U-value, air infiltration rating, design pressure ratings and warranties. After you have narrowed your selection down based on this criteria, take a look at the individual corner/cut sections of the windows. This is likely the most practical method of foreseeing the durability of a windows construction, if the veiwer has some common sense in how different materials should be joined or applied to each other. In regards to a previous post, it is true that there is great strength in wood sash or frame construction, just like there has been for hundreds of years. Some companies provide a cosmetic wrap known as roll-formed aluminum cladding over the exterior of the wood, which also helps protect the exterior wood from the elements. Other companies use a heavy gauge extruded aluminum cladding that allows for structural corner jointery within the extrusion and combines with the wood sash to enhance the overall structural integrity of the sash and frame. The latter construction method will likely be found to provide greater DP ratings and potentially a more durable product. To further comment on the above post, it is true that reputable companies using roll-formed aluminum sash construction do not experience color differentiation between the sash and extruded frame in short time periods. This differs from less reputable companies using the same construction methods in that the correct way to protect the light gauge metal is to utilize a special "kynar" blended paint to assist in color retention. This is critical due to the paint application differences in roll-formed and extruded aluminum. Roll-formed aluminum requires a light flexible paint to allow the metal to be bent or shaped after the paint has cured. Extruded aluminum is already formed, and thus recieves a hard durable paint finish somewhat similar to how a car body is painted. I personally have nothing against the Pella product noted in the above post. On the contrary, I have a lot of respect for Pella, as a maker of fine products in the Heartland of our country. However, I think that all consumers should receive unbiased information on such critical home fixtures. If you find the price levels of a good quality and highly durable window product out of your home's budget, be sure to closely view the corner sections of each product line within the window manufacturer's different products that fit your budget. My recollection of Proline Series windows from Pella shows that there are more than just options that differentiate that product line from the Designer and Architecture Series, although it might be true that this is what separates the latter two Series. One will only know for sure if they look at the corner/cut sections of the different product lines. Keep in mind, just because a company excels in one product line, doesn't mean that their other product lines hold the same value. I personally don't agree with manufacturers saturating the market with different product lines and relying on their previous reputation to further sales, but it appears that all companies are doing just that these days. I feel that one should do what one does best and concentrate on doing the best in their immediate field of expertise, so be careful in your window decision. Also, I feel strongly that at all costs, one should push the limits of their home construction budget on the permanent fixtures of the home. This includes, but is not limited to, excavation/soil compaction, foundations, framing components, insulation, interior or hidden plumbing, windows and wiring. Having to re-engineer or replace any of these components in the future can generally cause a major disruption to the whole building envelope.

Pella windows are superior than Andersen and I'll tell you why. Andersone uses a vinyl cladding that uses fusion welds at the corners. Now these welds are extremely stong but ther problem is that vinyl (plastic) has a large expansion and contraction rate. With temps. ranging from 100 deg. to minus 0 your vinyl cladding will try to move but the fusion welds will not allow it. Whats happens?? The vinyl has to go somewhere so it either bows and buckles or it pulls away from the glazing. Ghink about it, take for example vinyl siding. When installing vinyl sididng you don't nail it directly to the house, you hang it. The reason is because you have to allow for the expansion and contraction. Secondly, vinyl fades over time, no if ands or buts about it.It will also chalk. Rub your hands across vinyl siding tha is a year or more old and you will notice that it chalks all over your hand, the same thing will happen with the window and will make it utterly a pain in the keaster to clean --- Now, in terms of Pellas aluminum cladded windows your are one getting a solid wood window but also a durable high gaged alauminum that does not fade or chalk. It does not use welds or other agents at the joints either, instead it miters its' joints and overlaps them in a watershed technique, just as roofing, siding, and all other H20 proofing does. Moreover, Pellas windows match the historic look of older homes much better then the rest which is one of the many reasons I use them. I have never had a problem getting historic approval in all of New England with Pella which I can't say for Andersen nor many others. Pella windows are constructed so much better its really not even funny. I messed aroun d for many years using different windows on my projects but for the last six to seven years I have only used/recommended Pella and have created a solid and satisfied base of people I ve built homes for that love their windows. Lastly, their service is truly been second to none in my book. They really stand by their product from my experience. So, in my 20 years of building homes on both coasts I have to say Pella is going to provide you with a better looking and more durable window.

At the risk of getting lambasted again by all the anti Pella people on here, my choice would not be either one of Jeld-Wen or Bonneville. I prefer Pella hands down the service in this area for Jeld-Wen and Bonneville in this area is non existent.The quality of the windows is fair at best, and depending on series being used Pella can be comparable in price. Lead time on the Pella is running about 3 weeks. Just my ever so humble opinion. I know there will be those who come out of the woodwork to slam Pella, but I have been installing them for many years and never had a major problem, when a problem does arise such as a broken balance or a stress crack, I have never had a problem in getting service out to take care of it