December 14, 2015

Windows play a major role in keeping our rooms well-ventilated and also allow for the entry of sunlight into our home.

However, windows have low insulation values, so they allow more heat or cold air to pass. As a result, the cost of heating or cooling your rooms with many windows is higher than the cost of heating or cooling rooms with more solid walls. Moreover, a window consists of several movable parts, so it is more likely to leak air into your rooms. This is exactly why we need windows with low U-value or high resistance to heat or cold.

Understanding U-value and R-Value

U factor simply implies the rate of heat loss through a window. The lower the U-value, the better its insulation value and the greater its resistance to heat flow. U-value is inversely proportionate to R-value, meaning that U=1/R. Windows usually have an R-value of two or three. In comparison, walls generally have an R-value of 13, and attics often have an R-value of 38. This simply means that windows are less resistant to heat flow. You’ll find windows with higher R-value, but you need to know certain things about them before making an investment.

A window with an R-value of 2 is 50 percent more energy efficient than a window with R-value of 1. You can improve the R-value of a window simply by adding glass with low thermal emissivity. Newer building codes often require a window to have a minimum R-value of 3. HVAC technicians suggest that for better results, you may consider having windows with R-value of 4, 5 or even higher.

Preventing Air From Leaking

One common issue with most windows is that they leak air. However, not all windows leak the same amount of air. For instance, windows with an added protection of a storm window are almost completely leak-proof. Double-hung windows leak more air than casement windows that open outward like a door.

Air leaking through a window is a common problem affecting the heating or cooling efficiency of an HVAC system. Thankfully, there are ways to block airflow through windows. In most cases, it does not take a lot of money to seal the windows. This is a great way to prevent heat loss and save more on your heating or cooling costs.

Depending on the type of windows you have in your house, you can take the following steps to increase the R-value of your windows.

Before you replace your existing window for a higher R-value, there are certain things to consider. You perhaps do not need to change your double-hung window that already has a triple track storm window. Replacing it to a double pane window would not make much difference. Installing a new double pane window may cost you around $400, but you will save up to around $7 per year. This means that it would take you years to recoup the cost of installation. However, if your windows have any major defects, you may consider going for a replacement.

If your windows are in good conditions, but do not have the extra protection of a storm window, you may be advised to install a triple track storm window equipped with Low-E glass. You can install a storm window inside or outside of your main window. That way you can easily meet the minimum requirement of R-3 in your windows.