Glass block windows good for both security and privacy
Question: We need to replace two living room windows. We looked at glass block windows because of the security for our family. Howenergy efficient are they and is it possible to get ones with ventilation?
Answer: When security along with privacy is a concern, glass block windows are one of the best options. If someone is determined to get in, the blocks can be broken with many blows from a large hammer. This would give your plenty time to call the police and prepare to defend your family.
Not only must the glass bl ocks be broken, but when they are mounted in concrete, all the webs must also be broken out to enter. High-security, commercial-quality glass blocks are also available, but they are typically too expensive and heavy for most residential installations.
Residential glass blocks are not solid glass even though they appear to be. They are made of two hollow shells which are fused together under extreme heat. As the air inside them cools down and contracts, it forms a partial vacuum inside to improve their insulation value.
Many glass block windows you see in homes and buildings are actually made of plastic. Tough, non-yellowing acrylic plastic is most often used for the two hollow shells and it looks identical to glass. These are lightweight and acrylic naturally blocks the sun’s UV (ultraviolet) fading rays.
When selecting your glass or plastic block windows, chose ones with low-e (emissivity) coatings on the inside of surfaces of the shells. This is the same coating used on efficient regular pane-type replacement windows. This coating saves energy both winter and summer.
For extra high efficiency, select blocks with a low-e film stretched in between the two shells. You cannot see the film inside the blocks, but it creates two insulating air gaps inside the block for insulation of R-3. This piece of film blocks even more of the fading UV rays.
Another advantage of block windows is the concrete or other material between each block creates a mini-louver effect. When the sun is high in the summer sky on a hot afternoon, it is blocked by the concrete web. The sun is lower in the sky during winter, so it can shine in for free solar heat.
Ventilation is possible with block windows. If you have only one window in a bedroom, code requires it must open and be large enough for egress in case of fire. For this, select a premade complete casement block window. It looks like a regular fixed block window when closed, but cranks open. These have two latch levers and multiple internal latch points for security.
Another option is an opening mini-awning window can be installed in place of a few blocks in the center of the window. This provides ventilation, but is too small for someone to crawl through.
The following companies offer glass and plastic block windows: Builders Accessories, (888) 9217086, www.acrylicblock. com; Circle Redmont, (800) 358-3888, www.circleredmont.com; Hy-Lite Products, (888) 256-2599, www. hy-lite.com; Pacific Glass Block, (888) 522-4527, www. pacificglassblock.com; and Pittsburgh Corning, (800) 545-5001, www.pittsburghcorning.com.