Glass block is clear choice for efficiency


June 04, 1994|By James Dulley | James Dulley,Special to The Sun

Q: I want to replace several windows with ones more efficient and burglar-proof. Are block windows efficient? Can I install them myself and how can I get ventilation?

A: For security, privacy and energy efficiency, new designs of glass-block windows are an excellent choice. There are simple do-it-yourself installation kits and custom-made preassembled glass-block panels.

Although not burglar-proof, glass-block windows are much more difficult to break through than ordinary single or double-pane glass window.

A burglar first has to break many blocks and then has to deal with the mortar joints between them. For basements or other high-risk windows, install extra thick or solid glass blocks for greater security.

Depending on the degree of privacy you desire, you can choose from clear undistorted-view blocks to one of many privacy patterns. Reflective (from outdoors) glass blocks reduce the summer sun's heat and add more privacy. Gold-tone or bronze-tinted blocks also provide a more contemporary look.

Even with a heavy privacy pattern, 90 percent of the outdoor light still comes through the glass blocks for natural lighting. This is more efficient and attractive than having to draw curtains or lower blinds.

Glass-block windows are efficient for several reasons. Each glass block is not solid glass. It is made of two hollow halves fused together under high temperature. As they cool, an insulating vacuum forms inside.

Since they are often set in mortar, glass-block windows are airtight. This reduces drafts, dirt and outdoor noise. The many horizontal mortar joints between the blocks act as louvers to block direct summer sun.

For natural ventilation, install screened vent panels that crank out casement-style. The vent panel can be made of double-pane glass, or unbreakable clear bulletproof plastic.

For the do-it-yourselfer on a tight budget, one method uses clear plastic spacers and clear silicone caulking. This is easy to install and provides a totally clear view with nearly invisible joints.

If you prefer the standard mortar joints, you can use special plastic corner spacers to accurately position the glass blocks in the mortar. After the mortar is set, you twist off the exposed spacer ends and repoint those spots. The spacers strips are totally hidden inside the mortar.

Write for Utility Bills Update No. 599 listing manufacturers of glass blocks, preassembled block panels, ventilation panels and yourself installation methods. Please include $2 handling fee -- cash or check. Write to James Dulley, The Baltimore Sun,

6906 Royalgreen Drive, Cincinnati, Ohio 45244.

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