Which Windows Win vs. Harsh Colorado Winters?

Colorado winter is a complex equation. Warm days, cool nights, deep snows, and bright sunshine…sometimes within 24 hours or less. As the first and last line of protection from the harsh Colorado winters, it’s an equation the Denver window replacement industry has been attempting to solve for years.

While there’s still no predicting the weather, some Colorado agencies have begun to quantify the quality of replacement windows.

Efficient Windows Collaborative (EWC), a non-profit organization that ‘provides unbiased information on the benefits of energy efficient windows’ published a 2016 study observing multiple window comfort and performance factors. The quantified rating of each of these factors produced a ranking scale of ideal replacement windows in Denver and Grand Junction, Colorado.

Which Windows Win?

According to the EWC report, titled Selecting Energy Efficient New Windows in Colorado, generally tri-pane, Low-E HSG glass with Non-Metal, Improved frames tested best as replacement windows in Denver, Colorado and tri-pane, Low-E MSG glass with Non-Metal, Improved frames tested best as replacement windows in Grand Junction, Colorado.

Without getting into the technical jargon too much, this means windows that allow moderate to high levels of heat in thanks to external UV scored ideal for Colorado winters. Increased heat from external UV offsets some internal heating costs, an advantage during long stretches of cold temperatures. These windows also had low U-factor1 scores, indicating high heat retention and proper insulation.  Furthermore, the visible transmittance through the top scoring window units was high.

So That’s It?

Not so fast. It’s important to note that the results from the EWC report represent the highest and lowest performing windows for the experimental parameters. Only personal preference can determine the actual best window for each custom window replacement in Denver and surrounding areas, but the factors observed in the study can help quantify that a bit.

Say, for instance that in that study Window A contains a high solar gain (HSG), indicating a large amount of external heat coming into the home through the window, scores top in all categories except summer comfort. Your individual home window space is South facing, so allowing for HSG in the Summertime could prove uncomfortable. Although a top performer in the test, Window A would not necessarily be the top performer for your unique custom window space. Instead, Window B, which scores slightly lower all around than Window A, but outperforms it in Summer comfort may be the better choice.

Frame Game

While Selecting Energy Efficient New Windows in Colorado observed the general makeup of each window system frame, exact frame types were not reported. For instance, a ‘Non-Metal, Improved’ could encompass a variety of modern window frame types. Again, ideal Denver window replacement is dependent mostly on personal preference. However, when considering the options, you should be aware that there are some modern frame types not recommended for the harsh weather of Colorado.

Window Types Available

  • Vinyl

Vinyl windows are temperature reactive, stretching and contracting with extreme changes in temperature and weather. Clearly, these windows are not recommended for the sudden and sometimes extreme weather changes typical to Colorado. The high UV climate of Colorado can also turn vinyl windows a dingy or yellow color in only 3-5 years in some cases.

  • All Wood Frame

Unless preserving a historical building or home site, all-wood framed windows are not recommended.

  • Aluminum Clad-Wood Frame

Aluminum Clad Wood refers to a wood frame enhanced, or ‘clad’, with external aluminum for optimum strength and performance. These windows are the preferred choice of most window replacements in Denver and surrounding areas. Combining the beauty of wood with the staying power of extruded or rolled aluminum, these windows are resistant to high UV environments such as Colorado. Aluminum Clad Wood windows are also completely resistant to temperature change.




  1. U-factor determines how well insulated a window unit by measuring amount of non-solar heat lost internal>external.