ADVERTISEMENT
Part window, part wall—glass block has properties that set it apart from all other building materials. While they are most often used in commercial and public buildings, glass blocks and panels can be used to create clear divisions between residential spaces. Suitable for nonstructural interior and exterior applications, glass block can enhance or even define a kitchen, bathroom, laundry room, entryway, breezeway, or other living area.
Controlling Light and Heat
The first environmental benefit of glass block is its transparency. By allowing natural light from the outside in, or between interior rooms, glass block reduces the need for artificial lighting. Natural daylight also helps some people keep their emotional balance, or regulate
cycles of waking and sleep.
Unlike sheet glass, however, glass block maintains privacy. Depending on the surface pattern and overall thickness, a window or wall made with glass block can obscure vision without requiring other coverings, such as blinds or curtains. The styles that provide the greatest privacy, such as those with fibrous glass inserts or thick-faced block, still transmit at least 50 percent of the visible light that strikes them. With solid glass block, 80 percent of the light is transmitted. Flat sheet glass allows 90 percent of light through, but without the
many advantages offered by glass block.
the block, which helps improve insulation and control condensation later on. An edge coating of polyvinyl butyral (PVB) resin allows for expansion and contraction, and helps mortar bond to the glass.
Compared to sheet glass, which has a heat transmission value (U-value) of 1.04, glass block provides far better insulation. Solid glass block has a U-value of 0.87, while standard glass block has a U-value of 0.51.
Other Environmental Benefits
Another benefit is impermeability. Because glass block is a masonry product, it keeps out all the elements. Correctly sealed, it can provide weather resistance equal or superior to any other material. Where air or water infiltration is a problem, glass block can help you control the indoor atmosphere. This becomes important when you or family members are sensitive to airborne dust and pollen, or when moisture control affects livability.
Insulation is another benefit of using glass block. The space between the two faces provides insulating value comparable to a double-pane window, without any drafts or leaking. This buffering space also minimizes condensation on the surface. Unless glass block is on an exterior wall facing direct exposure to sunlight, it brings both improved control over the interior environment and reduced heating and cooling costs.
One feature every homeowner wants to have, but no one wants to test, is resistance to fire. Glass block is available with fire ratings of 45, 60, or 90 minutes of resistance. Because glass is considered a window material instead of a wall material, though, this rating only affects how well glass block remains intact, and prevents the passage of smoke and fumes, during a fire. If you want to see the details, look for the standards ASTM E-2010 and NFPA 257.
One more thing: Glass block is made using simple processes and common materials, which translates to reduced environmental impact in manufacturing. Glass is made without the use or production of VOCs; it can also be broken down and recycled after use, helping reduce disposal work, landfill volumes, and replacement material costs. Its life cycle impact, one way of measuring environmental effects, is impressively low.
Exterior and Interior Uses
Most glass blocks made and sold today are either 3 or 4 inches nominal. The actual thicknesses are 37/8 inches, and 31/8 inches. Regular glass block, the thicker of the two, is intended for applications that require durability, insulation against temperature changes and sound, and resistance to fire. This thickness offers the greatest variety of surface patterns and block sizes. Thin glass block is usually meant for use in ready-made panels, such as sidelights for entryway doors. This glass block can only support its own weight, not any other materials.
When used in exterior walls, glass block must meet the same requirements as other materials. One factor that affects exterior walls and not interior ones is wind resistance. To be approved for outside use, a glass block panel has to resist 20 pounds of pressure per square foot, the equivalent of hurricane winds. The maximum area for glass block panels allowed by most building codes is 144 square feet—12 feet squared or a rectangle of the same or less surface area. The limit for overall height is 20 feet, while the greatest length allowed is 25 feet.
Interior walls made with glass block have far fewer restrictions. They do not need to hold back the elements, just lateral loads of 5 pounds per square foot. That means interior walls can use up to 250 square feet of glass block, or nearly twice as much as exterior walls.
In either location, glass block can only support itself. An opening for a glass block panel should have support above, just the same as for doorways or large windows. A header beam distributes the weight to the sides of the glass block, and from there to the foundation. A glass block panel that is used to support additional weight is likely to crack and fail over time.
Designing with Glass Block
Available as individual bricks, in panels, or as part of larger assemblies such as vented basement windows, glass blocks are made in many sizes, shapes, and patterns. Most are hollow, although solid blocks are made as well. Square, flat blocks of 6, 8, or 12 inches are the most common; rectangular blocks, curved shapes, angled pieces, bullnose edgers, and other variations increase your design options.
Dozens of surface patterns are available from several manufacturers, giving you almost unlimited choices for combinations of transparency and privacy. From clear surfaces to waves, ribs, stippling, and cross hatching, glass blocks offer visual variety along with safety, security, durability, aesthetic qualities, and low maintenance.
If you plan to install glass block yourself, make sure you read the manufacturer’s instructions carefully. Some of the differences between glass block and other masonry products may surprise you. For example, cleaners that contain acid may work well for concrete, brick, or stone, but they can defeat the waterproofing qualities of the mortar
used with glass block. And while some general rules apply to most glass block installations, such as adding horizontal reinforcement at least every 16 inches, some makers will have specialized materials, accessories, or techniques that vary from standard practices.
Before you buy the tools to install glass block on your own, contact at least two or three professional contractors. They may be able to complete the job for only a little more money than the cost of materials alone. That leaves you free to handle other tasks, and then just
enjoy the results.
0 comments:
Post a Comment