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4 Key Components to Custom Replacement Window Performance

window_imageWhen comparing two custom replacement windows from different manufacturers, you should compare several key factors that will affect your window purchase and performance now and into the future.

1. Can you see through the window and what are the VT (Visible Transmittance) Ratings?

This might seem like a no-brainer type of question, until you realize that many vinyl replacement windows have very wide profiles that significantly reduce the overall amount of glass in the unit.  Also, depending on the manufacturer's application of Low-E coating, the glass can have a dark appearance.  The question to ask is "Does the window have narrow profiles and maximum glass?"

Windows on Washington’s Okna HiMark Performance:

  • Glass Maximization - The HiMark 500 is one of the narrowest profile frame windows on the market today with the HiMark 800 only being slightly thicker. Our proprietary design accomplishes this without losing strength in the structure of the unit.  The HiMark 500 is a DP-50 (+170 mph wind load) and the HiMark 800 is a DP-60 (+190 mph wind load).
  • Glass Clarity - The HiMark 500/800 also demonstrates outstanding thermal numbers with a 2 coat Low-e, as opposed to a 3 coat Low-e.  Less Low-e = Less tint and more light and a clearer view.  Companies often tout 3 coat Low-e as the most energy efficient, but it has less application value for our climate region (the Mid-Atlantic) as it blocks out too much of the sun's warming rays and eliminates much of the passive solar heat (i.e. free energy) in the winter months.  There are exhaustive studies that demonstrate that an improperly selected Low-e range for this climate will actually make your window less efficient.  3 coat Low-e is, as a general rule, more climate specific for regions that are dominated by cooling seasons (i.e. Florida, Texas, etc).  Therefore, there’s no reason to incur the upgrade expense or reduction in visible light with its application to the unit.

2. How thermally efficient is the window?
Thermal efficiency is the measurement of how well the window resists the movement of energy through it.  The measurement of this efficiency is represented by U-Factor.  U-Factor is the inverse of R-Value (Ex. R-10 = U-Factor 0.10).  The U-Factor measurement demonstrates the rate of heat loss of each window. The lower the factor, the more resistance to heat flow.  A window with a lower U-Factor will keep more heat inside during the winter and more ambient heat outside in the summer, improving the energy efficiency of your home.
Windows on Washington’s Okna HiMark Performance:

  • The HiMark 500 and 800 have U-Factors that far exceed the current and proposed Energy Star Qualification.  U-Factors ranging from 0.15 to 0.26 are far superior to what is commonly available at 0.30.  Do some research on specific brands – their ratings vary widely, and better units will drive the efficiency of your home.

3. How airtight is the window?
Probably the most overlooked and under discussed aspect of window performance is Air Infiltration.   Air infiltration is important as it pertains to dynamic efficiency, which is how the window will perform in real world application and while installed in your home.  You want a window that is very airtight and therefore good at avoiding efficiency losses from air loss/gain. Air infiltration is second only to radiant losses when it comes to effecting energy efficiency and can sometimes be first depending on how leaky the existing window is.  The lower the value, the better the performance and you should lean towards windows with air infiltration rates of 0.10 or less.
Window on Washington’s Okna HiMark Performance:

  • The HiMark product line is far and away the best engineered window brand on today’s market.  The air tightness rating on the HiMark 500 and 800 are 0.02 and 0.01 respectively this value is 15 and 30X more airtight than the required ratings.  When you compare these extremely low Air Infiltration ratings to the competition, the numbers speak for themselves. 

4. Does the window have a good warranty and will it hold up?
One of the most important factors to consider when choosing a window is the manufacturer’s warranty.  The warranty is one measure that tells the consumer just how good the company considers their products. Manufacturers carefully calculate the cost of warranty work over the lifecycle of their products, and then create a warranty that will mitigate their long-term exposure.
Windows on Washington’s Okna HiMark Performance:

The HiMark product line in this case is covered by a lifetime warranty, as is Windows on Washington’s labor.  We use best-in-class products to install the window so that you will have a lifetime of trouble free operation and superb performance, including:

  • Highly skilled installers
  • Heavy gauge coil stock
  • Premium Sealants 
  • Low-expansion foam (This is an absolute must as it’s the proper way to prevent air leaking by sealing the new replacement window to the home.)

At Windows on Washington, we field a great deal of questions from our homeowners asking us to compare the various custom replacement windows available on the market.  We are committed to supplying our customers with the facts, and believe the beauty, performance and warranty of the products we install speak for themselves.   If you are considering replacing your windows and need more comparative information to make a product decision, please contact the experts at Windows on Washington, your HiMark and Okna Northern VA Dealer.

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Topics: Windows