Glass Block Windows Save Energy, Add Security

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Question: I am remodeling my house and I plan to use decorative glass block windows on the exterior and interior as accents. Are they energy-efficient and are there low-cost do-it-yourself kits?

Answer: You have many options: individual glass blocks, simple do-it-yourself kits and complete ready-to-install glass block windows. There is a huge range of colors and patterns. Choose between plastic or glass blocks and ones that are fixed or open, like casements.

From an energy-efficiency standpoint, glass blocks are about as efficient as most double-pane thermal windows. Each glass block is hollow. Two halves are fused together under high temperature. When the block cools, it forms a partial vacuum, similar to the insulating wall of a Thermos bottle.


With all the new colors, decorative and privacy patterns and angled blocks for simple curves, glass and plastic block walls are becoming very popular. Some of the special angled blocks allow for a curve with a radius as tight as 12 inches. They can also be used to create a contemporary angular wall.

Some designer glass blocks have ornate etched patterns in the glass and are available in color tints. Others use parallel fluted surfaces for privacy or curved fluted surfaces to form continuous patterns.

In addition to the decorative aspects, glass block windows are secure. It would take a would-be thief quite a while to hammer his way through a standard glass block. Solid but less efficient security blocks are also available.

There are several glass-plastic block options for the budget-minded do-it-yourselfer. Complete glass block panels, with nailing fins or metal straps, are available to slip into the wall opening. By using various-width blocks for the center blocks, the width can be adjusted to fit most openings.

Several of the manufacturers make kits that use spacers to separate and position each block. When sealed in place with silicone, these provide an all-glass appearance. Others use natural wood between blocks for an elegant look.

For ventilation, consider installing a glass block venting panel. These are small hopper windows designed to fit in place of a couple of glass blocks. The glazing is made of double-walled polycarbonate (bulletproof glass) for security.


Another venting option, ideal for bathrooms, is casement-style glass block windows. These are units that fit into the wall opening. They often use lightweight plastic blocks instead of the heavier glass.


Write for ( Update Bulletin No. 402, a buyer’s guide of nine designer glass-plastic blocks and do-it-yourself window kit manufacturers. Please include $3 and a business-size self-addressed stamped envelope and mail to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, OH 45244.