Replacement Windows - A Smart Home Improvement Investment?
In times of rising costs for home heating and cooling and the need to reduce energy consumption, replacement windows are often considered. Replacement windows make your Colorado home more energy efficient, they will make it more comfortable, reduce drafts, reduce your heating/cooling costs and reduce your demand for petroleum products. Like other home improvement projects, replacement windows will also increase the value of your home. But are they a good investment based on energy savings? Let's use Heat Transfer to help understand window performance factors and leave the decision up to you.
Heat is transferred through solid surfaces from the warmer side to the colder side through a process called "conduction". Metal is a good conductor of heat. The best insulators (preventing conduction) are wood, vinyl, fiberglass and foam. Metals, such as aluminum, are the worst insulators. U-factor measures how well a product prevents heat from escaping. The rate of heat loss is indicated in terms of the U-factor (U-value is the inverse of the R-value) of a window assembly. The lower the U-value, the greater a window's resistance to heat flow and the better its insulating value. Top of the line replacement windows are around U=0.25 or R=4. Old single pane glass has U=R=1 so there is often a reduction in your conduction losses.
Air Leakage (Convection)
Air Leakage (AL) is indicated by an air leakage rating expressed as the equivalent cubic feet of air passing through a square foot of window area (cfm/sq ft). Heat loss and gain occur by infiltration through cracks in the window assembly. The lower the AL, the less air will pass through cracks in the window assembly. Houses require this natural ventilation or else mechanical ventilation is required and since windows are often evenly spaced throughout the house they are a good source for ventilation. If your natural ventilation is far above .35 NACH (Natural Air Changes /Hour) as measured by your energy auditor using the Blower Door, then you may consider replacement windows if other less costly air sealing methods are not successful. Conversely, if you replace your leaky windows, be sure to have the blower door test done afterwards in case you have lowered air changes where mechanical ventilation is required to prevent hazardous furnace back draft or air quality problems.
Solar Heat Gain Coefficient (Radiation)
Solar Heat Gain Coefficient (SHGC) measures how well a product blocks heat caused by sunlight. The SHGC is the fraction of incident solar radiation admitted through a window (both directly transmitted and absorbed) and subsequently released inward. SHGC is expressed as a number between 0 and 1. The lower a window's solar heat gain coefficient, the less solar heat it transmits in the house. We believe that in a predominantly cooling climate like Colorado, there are benefits to having high SHGC on your south windows.
Visible Transmittance (VT) measures how much light comes through a product. The visible transmittance is an optical property that indicates the amount of visible light transmitted. VT is expressed as a number between 0 and 1. The higher the VT, the more light is transmitted.
Condensation Resistance (CR) measures the ability of a product to resist the formation of condensation on the interior surface of that product. The higher the CR rating, the better that product is at resisting condensation formation. While this rating cannot predict condensation, it can provide a credible method of comparing the potential of various products for condensation formation. CR is expressed as a number between 0 and 100.
So What Can You Do?
We suggest you call or stop by as soon as you can for these money and energy saving deals. We also have great products, like Serious and Sunrise vinyl windows, Semco and Pella wood-clad windows, or our Velux Roof Windows.
"They did a great job. Kristian was easy to work with, very knowledgeable and flexible in
terms of scheduling.!"
- Denver Home Owner