Windows provide the home with light, warmth, and ventilation. However, when windows are old or damaged they negatively impact a home’s energy efficiency resulting in expensive utility bills and an uncomfortable living environment.
Energy efficient windows help the planet by minimizing the negative environmental impact as their performance determines how much air enters and escapes the home. Certification programs such as those administered by the National Fenestration Rating Council (NFRC) and ENERGY STAR, provide ratings designed to indicate a window’s efficiency. Energy performance ratings such as U-factor, solar heat gain, air leakage, visible transmittance and condensation resistance measure a product’s effectiveness in insulating and blocking the effects of the sun, rain, and wind. The energy performance of all ENERGY STAR qualified windows, doors, and skylights must be independently tested, certified, and verified according to test procedures established by the NFRC.
U-Factor: measures the rate of heat transfer and tells you how well the window insulates. U-factor values generally range from 0.25 to 1.25 and are measured in Btu/h·ft²·°F. The lower the U-factor, the better the window insulates.
Solar Heat Gain (SHG): measures the fraction of solar energy transmitted and tells you how well the product blocks heat caused by sunlight. SHG is measured on a scale of 0 to 1; values typically range from 0.25 to 0.80. The lower the SHG, the less solar heat the window transmits.
Air Leakage (AL) : measures the rate at which air passes through joints in the window. AL is measured in cubic feet of air passing through one square foot of window area per minute. The lower the AL value, the less air leakage. Most industry standards and building codes require an AL of 0.3 cf·m/ft².
Visible Transmittance: measures the amount of light the window lets through. VT is measured on a scale of 0 to 1; values generally range from 0.20 to 0.80. The higher the VT, the more light you see.
Condensation Resistance: measures how well the window resists water build-up. Condensation Resistance is scored on a scale from 0 to 100. The higher the condensation resistance factor, the less build-up the window allows.
Those who opt to replace old, worn down or damaged windows with new Energy Star certified windows are eligible to receive tax credits that amount to 10% of the product cost (not including installation costs), on up to $200 for windows and skylights; up to $500 for doors.
If you are unsure as to whether or not you need to replace your windows keep an eye out for some key signs. The window frame, sash or muntins begin to rot, this will result in an increase of air escaping and infiltrating the room. Cracks or chips in your window pane, these will eventually spread which leads to an increase of dirt/dust. Broken Seals in your window will continue to crack or deteriorate resulting in a fogginess effect in your window pane, along with condensation and streaks, as this worsens over time it begins to affect your window frame, sash, and muntins.