Energy Efficient Windows Explained

For years I thought windows were windows. When it was too warm we’d draw the shades and if it was too cold we’d make sure the windows were closed tight. But today’s windows are available with glass and coatings that can drastically alter the temperature in your home, thereby lowering your energy bill.
Have you ever run a window audit? It’s worth it to see how efficiently your home is using energy.
After touring the Marvin Windows factory last month we saw how each window was made-to-order and that also included the type of glass and coating that each window received. They actually offer more than 150,000 energy-efficient window and door options!

Window Technology
Marvin knows that windows and doors are key to your home’s comfort and energy efficiency. Today’s windows and doors are far more energy-efficient than those of even 10 years ago. Modern, energy-efficient windows and doors can save you 15 to 25 percent on your monthly heating and cooling bills, according to the U.S. Department of Energy.
New window technology has replaced the single sheets of glass that were once standard in most windows. There are now windows with multiple glass layers. Special coatings on the glass reflect sunlight and ultraviolet rays without dimming the view. Gases injected between panes create extra insulation. Advanced framing materials and innovative design provide further efficiency gains.

What’s Your Climate?
Where you live affects which type of window or door is best suited for your needs. Depending on the climate, you may want to give more attention to certain performance measures over others.

Northern Climates
In regions with cold winters, windows should keep heat where it belongs: indoors. That means you should look for windows that slow the transfer of heat, a performance measured by the U-Factor. The lower the U-Factor, the lower the rate of heat loss through a window.
In cold regions, your windows also can help you take advantage of solar radiation, which is free heat that eases the workload of your furnace or other energy-powered heat source. A window’s performance in this regard is measured by the solar heat gain coefficient (SHGC). A higher number means a window will allow more heat to pass through.

Southern Climates and Intense Sun

In warmer areas and sun-soaked regions with year-round mild temperatures, your windows should perform the opposite duty. Here you want to keep heat out by choosing windows that reflect solar radiation. Less heat coming into the home means lower air-conditioning costs and a reduced carbon footprint. In these regions, a lower solar heat gain coefficient is a crucial to the window’s energy efficiency.

Marvin Energy-Efficient Window Options
Marvin allows you to craft a customized solution for your homes’s unique needs. You can choose from thousands of dual-pane and triple-pane (Tripane) products — and couple them with the glazing and gas options that help you achieve optimal energy efficiency.
Marvin offers an extensive roster of products and options that meet ENERGY STAR standards. With windows and doors, the ENERGY STAR standards vary by climate – and Marvin offers ENERGY STAR options in each one.

Dual-Pane and Tripane
Marvin offers thousands of window and door options with two or three panes of glass. Dual-pane products with appropriate glazing options are versatile, beautiful and energy efficient.

Insulating Glass Coatings
Extremely thin coatings of special metallic material applied to glass panes used in windows and doors boosts their energy efficiency. The industry standard for energy-efficient glass coatings has become Low-Emissivity (LoE or Low-E) glazing. Coating a glass surface and gaps between each pane with LoE material can block a significant amount of heat transfer,reducing your home’s need for energy-consuming climate control systems.
Low-E coatings are transparent to visible light, and different types of coatings have been designed to allow for high solar gain, moderate solar gain or low solar gain.
LoE-180: A great insulator (low U-Factor) that allows the sun’s warming rays to pass through (high SHGC). LoE-180 Features a single metallic coating and an insulator that blocks heat loss to the outside while reflecting heat back into a room. This type of coating is ideal for applications where high solar gain is desired, such as northern climates.
LoE2-272: Features a double metallic coating on the inside glass surface to reflect heat into the room in winter and reject the sun’s warmth in summer, reducing damaging UV rays. This coating option provides better protection against heat loss than LoE 180. It has good solar gain control. Suitable for all climates except the Southern zone of ENERGY STAR.
LoE3-366: Features three metallic layers of silver. This coating offers the lowest U factor and lowest solar heat gain. It is often specified in the Southern ENERGY STAR zone where cooling costs are high and intense exposure to the sun is an issue.

Insulating Gases
Inert gases pumped into the spaces between panes of glass slow the transfer of heat, increasing the insulating power of a window or door.
Argon – Our standard windows come with argon gas between the panes to boost energy efficiency.
Krypton – Customers seeking to maximize energy savings can consider our blend of krypton, argon and air. This option Increases the insulating power of our Tripane products with narrow airspaces.

Further Options
Marvin offers these enhancements to further increase the energy efficiency of our windows:
Energy Panel – Often confused with storm windows, an Energy Panel is a glazing option consisting of a removable exterior glass panel finished on the edges by a surround. Energy panels cover the exposed glass surface of each sash, and offer added energy efficiency for wood windows with single glazing.
Storm and Screen Combos – A combination unit is composed of two movable glass panels and one movable screen panel. The individual panels can be configured multiple ways, and can be easily removed from the interior for cleaning. Customized commercial screens are also available.

Other Performance Notes
Low Air Infiltration – All Marvin window and door products meet or exceed the WDMA requirements for maximum air infiltration.
XL Edge Spacer – Marvin offers the warm-edge XL Edge spacer from Cardinal – the most durable spacer system on the market. The spacer helps prevent energy loss around the perimeter of the window glass.
With so many options it can seem confusing but Marvin dealers are well-versed on their product lineup and a quick conversation can lead you into the type of window you need and the glass that will work best for your home.

The Marvin Windows & Doors website has a lot more information on energy-efficiency that will help you make an informed decision before buying a window.
Top photo courtesy of Old Town Glass

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