All You Need to Know About Window R-Value
Your home’s building envelope consists of roof, walls, floors, doors and windows. For designers who prioritize form over function in a residential setting, window facades usually come as an afterthought. However, considering windows account to about 20% of the total wall area, this should not be the case since. In an average building, this coverage is critical as this factors in to the rate of energy-efficiency, particularly insulation, in your home.
In short, it’s not about pitting form and function against each other, but it’s about merging the two design maxims so your home can achieve an optimal performance. With sustainability at stake, homeowners go above and beyond to implement energy-efficient measures. When your windows feature an excellent R-value, you are guaranteed of increased indoor occupant comfort, reduced condensation, decreased heating load, and all other plethora of benefits a standard single-pane glazing alone can’t provide.
But, what exactly is window R-value? First, we need to switch from macro to micro perspective for you to easily grasp this technical window concept. It might be tricky at first to understand these industry-specific terms, but through our window expertise, we will break these down to little tidbits of information so your home can well be on its way to a high-performing state.
Window R-value refers to the thermal resistance of window to heat transfer. In simplistic terms, it is the rating of window insulation. However, you can’t fully understand window R-value without its counterpart U-value. Whereas window R-value becomes the first line of defense from heat transfer coefficients, U-value acts oppositely on the offense and measures the thermal transmittance of a window, or to put simply, just how excellent of a conductor a window unit can be.
We can simplify this inverse relationship furthermore with this formula: R-value = 1/U-value. The higher the window R-value, and the lower the U-value, the better.
While both are indicators of energy-efficiency, window R-value only pertains to the specific component of the window unit such as the glazing, type of framing and gas fills. As such, U-value refers to the whole window assembly in itself. Here’s exactly the reason why it has become a norm for window manufacturers to label these fenestration with U-value instead of R-value.
However, glaziers are now giving merit and redefining the conventional with window labeling using R-value. For consumers and end users like you, it’s much logical to understand and remember that R5 window outperforms R1 window, rather than having to dissect that 0.5 trumps a 2.0 window U-value.
We all know that glass is known to be an outstanding conductor, but a very poor insulator. Nevertheless, it’s now an easier feat to revert these underperforming specifications with advanced glazing technology. Your next move to energy efficiency is as simple as retrofitting your outmoded single-pane to new construction standard of double or triple-pane glazing with argon or krypton gas fills – or in a few words, insulated glass units (IGUs).
Low-emissivity (low-E) glass coating currently becomes another innovative disruptor in the glazing market with its dual operation of light absorption and heat resistance. A pro tip on how you can use it as a benchmark comparison for window insulation: as window’s emissivity decreases, window R-value increases. Your standard clear glass panes emit a value of 0.84, while switching your fenestration to low-E double-pane glazing will give you an emissivity range of 0.35 to 0.5.
Convinced enough that you need to replace your out-of-date window glazing? Now that you speak the jargons of glaziers and window manufacturers, you can finally make the move from energy-wasting to energy-efficient when you drop by via scheduled appointment in our Manhattan showroom at 135 East 57th St 18-106.