Never heard of such a thing.

Here is a quote from another website.

"I am in the process of replacing 4 windows on the south side of our mansard roof. I am drawn to the Marvin windows due to the aluminum clad that is thicker than Pella plus the spacing to ensure that water does not penetrate the wood. I also like the hardware for the tilt which looks far more durable that the Pella's plastic slides. I am reading many very negative comments on line about Marvin along with poor follow service if needed. How would you compare these windows for the Chicago area?"

Sold wood and aluminum clad wood windows (inc Marvin and many others) for 20 plus years and I have never heard of that. It is true that Marvin's aluminum is thicker due to the fact that it is extruded on both the sash and the frame while Pella is extruded frame and roll form (trim coil or soda can like material)sash. And if anything I believe very strongly that there will be much more negative on Pella than Marvin.

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!

Ok, mydreamhome I do remember the gap your speaking of but never associated it as for weeping or drainage and never really thought of that way either. I do know that Marvin also treats there wood with a preservative for rot resistance as well. I also agree with your basic reviews on the other products and the fact that there are generally more bad reviews than good is due to the fact that unhappy customers definitely will complain and make more of a stink than satisfied customers.