Aluminum Clad Wood Windows

So far, one of the most challenging decisions we have had to make is what type of windows to purchase. If you are installing new windows you have several options: wood, wood with aluminum cladding (meaning the outside of the wood window is completely enclosed in aluminum), wood with vinyl cladding, wood with fiberglass cladding, fiberglass and vinyl/PVC.  There were several factors that we examined in our decision making process, namely (1) durability/maintenance, (2) aesthetics, (3) marketplace perception/cachet, (4) cost, (5) energy efficiency and (6) environmental impact.

We prefer the wood windows when it comes to aesthetics. We love the way the wood looks and feels inside the home and it is also a very versatile product in that it can be painted and stained a variety of colors.  Wood, however, has the greatest requirement for maintenance; you must paint (or stain) the interior and exterior part of the window upon installation and you must continue to maintain the windows over their lifetime. If you are not familiar with wood windows we would strongly caution you to not underestimate the amount of work and money required to maintain the exterior of wood windows over time. The wood will last a long time but only if you are diligently scraping, sanding, painting and repairing every few years. So while wood windows score very highly with respect to aesthetics, they score equally poorly with respect to durability and maintenance requirements.

Wood windows with exterior cladding remove the outdoor maintenance requirement since they are encased with vinyl/PVC, aluminum or fiberglass. All of these materials are extremely durable and hold up to the elements.  Most people do not paint these exteriors as they come pre-finished in a variety of colors (except for vinyl which is severely limited in colors).  Though vinyl/PVC cladding is quite durable, there is some evidence that this particular type of exterior cladding experiences fading over time, especially when exposed to lots of sunlight.

Our concern with wood-clad windows is that the cladding may actually inhibit your ability to see if there is water damage to the wood window.  In contrast, with an all wood window with a wood exterior it would always be fairly obvious when rot was occurring (and so you could repair the window before too much damage was done). With cladding, on the other hand, if rot was occurring behind the cladding you would not discover this problem until much later and, at that time, it could be much more expensive to fix. We did share our cladding failure concern with our home designer, Michael Chandler, a well-known green building guru who also writes for Fine Homebuilding, and he felt that the likelihood of this happening was very, very low (he also tends to specify wood, aluminum clad windows in the homes he designs and builds).

Vinyl/PVC and fiberglass windows do not have this problem, but they have a more limited color selection.  Additionally, it is important to note that vinyl/PVC windows have less perceived value in the marketplace.  They are generally perceived as an inferior product.  Because we are building a custom home this was an important concern for us.

We decided not to use a low-end vinyl/PVC window product because we believe they look inferior.  However, interestingly, there are high-end PVC windows now that look very good and which are very hard to differentiate from wood windows.  These were intriguing to us because we could simultaneously get (almost) the look of wood and the durability of vinyl/PVC.  Ultimately though, we were concerned that some people might frown on us for utilizing vinyl/PVC and we didn’t want that negative perception to extend to the rest of the house.  When we asked a very knowledgeable local realtor with whom we have both worked in the past what she thought of utilizing PVC windows in our home, her response was something to the effect of “Ummmmm……..I think you could get away with it.”  Not exactly a ringing endorsement.  Although the durability of vinyl/PVC is very good, the marketplace perception/cachet is not always there.

So far we have discussed the issues of durability, aesthetics and marketplace perception as they relate to different window types and we determined that wood, aluminum clad windows would score highly in all three categories (once we got comfortable with the fact that it’s very unlikely for the aluminum cladding to fail).

We haven’t mentioned three other factors though, namely cost, energy efficiency and environmental impact.  Generally, the environmental performance of the window during its useful  life is equated with its energy performance; the more efficient the window the better its environmental performance (because a building is using less energy to heat or cool and therefore reducing fossil fuel consumption).  So when we talk about environmental impact we are only referring to the beginning and end phases in the life of a window, the manufacturing process and disposal stage.

Therefore, window environmental impact as we have just defined it basically boils down to an evaluation of vinyl/PVC and whether one views this material favorably or unfavorably.  We will tackle this evaluation in more detail in a subsequent entry and for now will provide the cliff notes.

Our research has led us to view vinyl/PVC unfavorably, or at least with enough skepticism that we could elect to not install it in a green home if it can be avoided.  This view is centered on two main concerns: (1) air quality adjacent to vinyl/PVC production plants and (2) vinyl/PVC end-of-life disposal issues. The USGBC’s Technical and Scientific Advisory Committee (TSAC) produced a report in 2004 entitled Assessment of Technical Basis for a PVC-Related Materials Credit in LEED.  The purpose of the report was to determine if the LEED standard should award points for the non-use of PVC in buildings.

The report shows instances where the air quality standard for vinyl chloride (a toxic, carcinogenic gas sometimes known as VCM) was exceeded by large amounts in communities/areas adjacent to vinyl/PVC production plants.  Because the data is old or spotty (not enough observations) the report says that “additional data are needed to determine the potential health risk of individuals living in neighborhoods near vinyl manufacturing facilities.”  With the potential for a major environmental justice issue we think it responsible to avoid vinyl/PVC to the extent possible until additional air quality data is collected.  We need more air quality monitoring stations installed adjacent to vinyl manufacturing facilities that are collecting robust, transparent and public data.

Our second environmental concern regarding vinyl/PVC is that it is super durable and lasts forever.  While this makes vinyl/PVC windows rank very highly in terms of durability/maintenance, it makes them rank very low in terms of end-of-life disposal issues. What do you do with the window when its life in a building is over? Vinyl/PVC windows are not often and are not easily recycled. Therefore, it either goes to a landfill where it sits around for a long, long time and does not degrade, or maybe gets burned in a backyard fire.  Our research shows that these disposal fires are much more common than is generally thought, and when vinyl/PVC is burned in this manner it releases cancer causing chemicals into the air.

Unless you have aluminum windows (which are not really used that frequently) the energy efficiency of the window is related to factors like how many panes of glass it has, what the material/gas is between them, and what type of glazing (if any) the glass has.  The window frames are essentially the same with respect to energy performance (except for aluminum which is a poor energy performer), so you are not actually choosing between different window types, rather you are just specifying different glass options.  A great resource in exploring this information, and windows in general, in more detail is the Efficient Windows Collaborative.

The windows we chose are Windsor Pinnacle wood, aluminum clad windows.  They are double-paned (we felt triple-paned in our climate was overkill) with a coating called LoE 366 that stops 95% of unwanted, harmful infrared and UV rays.  The windows have a U-factor of .32, a SHGC of .2 and a visible transmittance of .47.  Windows with lower U-factors have better insulating values.  The lower a window’s SHGC, the less solar heat it transmits; note whether a higher or lower SHGC is more desirable depends on the climate.  Visible Transmittance (VT) refers to the amount of visible light that is transmitted through the window.

Window Label

The requirements for Energy Star windows in Raleigh, NC are shown on this website.

Note that Raleigh is in the North/Central Energy Star Climate Zone.  Therefore, to qualify for Energy Star new construction windows must have a U-factor less than or equal to .32 and a SHGC less than or equal to .4, which ours do. Interestingly, with a SHGC much better than the Energy Star requirement we can really reduce our summer cooling demand, but we do lose some beneficial solar heat gain in the winter.  As Raleigh is very close to being in the South/Central Energy Star Climate Zone, this is probably sensible.

The last, and perhaps most important, factor that we have not yet discussed is cost.  There were some really efficient fiberglass windows that would have improved our U-factor by about 50%, but they were twice as expensive as the Windsor wood, aluminum clad windows so we were not willing to make that much of an upgrade.  Also, with these very efficient fiberglass windows one has to be careful because there can be visible transmittance issues.

The wood, aluminum clad windows we chose were about 10% more expensive than the high-end PVC alternative.  We had thought the price gap might have been larger here so we were actually pleasantly surprised that it was only 10%. The all wood windows were basically equivalent to the PVC windows in price.

Finally, there is a wood, fiberglass clad window that is produced by Marvin that we looked at. This was about 25% more expensive that the aluminum clad window from Windsor. We found some anecdotal evidence that shows fiberglass is superior to aluminum cladding in that it is more resistant to denting and scratching, but did not feel the price premium was worth it.

Windows from the Front

Windows from the Back

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