What is a good U-factor for a window?

Energy Star rated windows should have a U-factor of 0.27 Btu/hr-sq ft °F or less for Northern climates, 0.3 Btu/hr-sq ft °F for North and South Central and 0.40 Btu/hr-sq ft °F for Southern climates zones.

What is the U-factor range for windows?

The insulating value of windows is rated by the whole window U-factor and the lower the value, the better. A windows U-factor value generally ranges from 0.25 to 1.25 and is measured in Btu/h. ft² °F.

How are aluminum window frames protected from corrosion?

Many manufacturers apply paint, lacquer powder coatings or baked-on enamel coatings to protect aluminum. These processes not only protects the aluminum but also allows manufacturers to incorporate colors and are organic. Powder coatings are popular in sustainable home development as they are known to emit zero VOCs. In some cases, manufacturers may opt to anodize aluminum.

Is anodizing sustainable?

Aluminum can be further protected through a process called anodizing, which is the process of thickening the surface by exposing aluminum to electrically charged acidic liquid. Anodizing was first applied in the lear 1920s to increase durability and weather resistance to aluminum products. However, this process creates two bioproducts; degraded sulfuric acid and aluminum hydroxide which is not environmentally friendly. Aluminum hydroxide is classified as hazardous by the EPA.

Do aluminum or metal window frames rust?

Due to its composition, aluminum does not rust like steel or iron, but it is prone to corrosion over time. The corrosion, aluminum oxide, is strong and attempts to prevent further damage or corrosion. Aluminum oxide corrosion appears as powdery white or dull grey in color, which makes it challenging to identify, unlike rust. It's important to note that aluminum corrosion does not quickly spread. Corrosion is more likely to occur when windows are in constant contact with moisture.

How do you convert U-value to R-value?

R-value and U-values are reciprocals of one another. R = 1/U and U = 1/R. As an example, an Energy Star window with a U-value of 0.27 = R-value of 3.7. But, the difference between U-value and R-value is more complicated. R-value only applies to specific material or component. U-value represents an entire system, such as a window system.

Learn about Aluminum or Metal Window Frame

Aluminum or metal frames for windows are a durable and low maintenance option. Aluminum or metal offer increased structural strength over vinyl windows while reducing the amount of visual material used. Heat tends to conduct through the aluminum or metal frame, but their energy efficiency is improved with thermal breaks in the frame to reduce the conduction of heat.

In colder climates, look for windows with a thermal break built into the frame. A thermal break is an insulating strip placed between the inside and outside of the frame and sash. For less harsh climates, opt for non-thermally broken windows frames.

Aluminum windows have high embodied energy compared to other types of window frames, but they are very durable and have a life expectancy of over 40 years. Aluminum windows are one of the most sustainable window options from a recycling perspective. The recycling process of aluminum frames only requires melting the metal, making it an inexpensive and efficient method for repurposing.

Early window frame materials included wood, iron, and lead. Of those, wood is still used today, and metal frames have graduated to aluminum, stainless steel, and coated steel, with insulation breaks to cut heat loss. Lead is no longer commonly used in window frames.

Learn about Aluminum or Metal Window Frame

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