Get the Right Windows
Three basic steps to make sure you’re up to date with the changing window market.
Synopsis: Asa Christiana details the three basic steps when it comes to choosing windows: choosing function, material, and glass. He outlines the different types of windows, from tilt-turns to fixed-frames to swingers and sliders, along with details of the performance pros and cons of each. He describes relative costs of different materials from vinyl to aluminum to fiberglass, composites, and wood, along with their durability and popularity. Finally he discusses glazing, including the use of double-pane vs. triple-pane and the prevalence of low-e glass. The article also breaks down a ratings label for window glass and what the various numbers mean, from U-factor to solar heat-gain coefficient (SHGC) to air leakage (AL).
Whether you’re building or remodeling, you’ve got one good shot at getting the shell of the house right. In terms of energy efficiency, windows are always the weakest link in the building envelope. So it pays to make a wise choice. Windows also have a big effect on the way a house looks, feels, and functions.
Contrary to popular belief, your builder or local window dealer might not be the best source of information. Most builders’ main incentive is to keep things straightforward and minimize risk, so they tend to stick with the same suppliers. Window dealers also have established relationships, limiting your product selection. More than ever, it pays to hire an architect or designer, who will be open to a wider variety of solutions.
Window performance should be kept in proportion with the performance of the rest of the building envelope. With glass making up only 20% of the walls of the average home, and windows being a lot pricier per square foot than the rest of the shell, you should invest first in better-performing walls, roofs, and basements. But if you’ve already upgraded the rest of the house to better than average, you can take the comfort, efficiency, and functionality of your home to a new level with new window options. It takes just a little bit of inside knowledge.
Performance translates to comfort
While most homeowners think about price and aesthetics first, experts recommend flipping the script and focusing first on performance and long-term value. Energy savings add up quickly, and energy-efficient windows make a home more comfortable. For instance, the innermost pane of a triple-pane window is much closer to room temperature than the inner pane in a double-glazed unit, letting you sit close to the window without feeling heat or cold radiating off it (a situation that is often confused for a draft).
Low-cost windows can often be pricier than they first appear. Like any weak link in the building envelope, poor-performing windows require a larger HVAC system and ducting, which is more expensive up front and more costly in the long run. For Steve Baczek, a Boston-area architect who specializes in high-performance homes, it’s a simple dollar shift. “With much better-performing windows, I can sometimes do one $5000 minisplit HVAC system instead of a $30,000 ducted distribution system.”
Whenever possible, experts also recommend choosing tilting or swinging windows over sliding models like traditional double-hungs. That’s because swinging casements, awnings, hoppers, and tilt-turns have hardware that pulls them tightly against their frames, with compression gaskets that leak far less air than the weather seals around sliders, no matter how good the seals are.
Old answers don’t always hold up
Window categories and materials have changed in the last decade, and yesterday’s biases and assumptions don’t always hold true. The vinyl (PVC) category is being transformed by new formulations that are more stable and more durable, as well as new window innovations adopted from Europe. The composite category has also expanded, with true fiberglass windows sometimes confused with composite blends of PVC and sawdust. Products vary widely in the wood and clad-wood markets, too, where some older designs are beginning to find new favor.
Glazing is just one more area that is being disrupted and transformed. Once-exotic features like low-emissivity coatings and gas fills are now standard on higher-quality windows, and increased demand for triple-pane glass units are bringing their prices down across the globe.
As building-science experts evaluate the latest window technologies, we are learning that where you live doesn’t matter quite as much as it once did when it comes to choosing windows. Well-insulated windows with low-e coatings that block solar heat gain help lower heating and cooling costs almost as much in New Mexico as they do in New Hampshire.
Price ranges are harder to pin down within various window categories. With technological advances in every area, from frame to glass to function, and a new emphasis on energy efficiency, performance and prices range widely. In general, though, vinyl tends to be the least expensive, followed by fiberglass and composites, with clad wood remaining the highest-ticket option. But there are exciting new outliers in every category.
Step 1: Choose a function
The options for window function are often tied to their size. For instance, if your design calls for large expanses of glass, it could limit your options for frame material, and whether those windows can open and close. That’s because some materials are too flexible to support a very large, heavy window that hangs on hardware. On the other hand, if you make your largest windows fixed, you’ll have a wider range of choices for the frame and glazing, and are likely save money at the same time.
Step 2: Pick a material
Your next decision is what the window is made of; specifically, the sash and frame. Technically, the frame is what attaches to the house, and the sash holds the glass, but both are frames in the general sense. These two frames are usually made with the same materials and a similar anatomy, which have a big effect on everything that matters about a window: durability, function, looks, sightlines, and thermal performance.
Step 3: Get good glass
There is big news in the world of glazing, too. Glass units are manufactured by just a few companies, making them less proprietary than window-frame anatomies, for example, and more of a commodity. That’s good news for consumers. As energy-efficiency expectations have climbed, glazing has improved dramatically with once-costly elements coming way down in price, and with lower-priced options
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