With a clear outer surface and a hollow core, translucent block is a versatile material. It transmits light while still providing a measure of privacy, thanks to several design styles that have different refracting qualities. Used to construct shower walls, sidelites, and windows, transparent blocks are made from either glass or acrylic.

Glass block is heavy, strong, and hard, and it resists most anything you can throw at it—literally. The same is not true of acrylic products. Although acrylic block displays great impact-resistance, it is significantly more susceptible to scratching and blemishing than glass, and should be treated carefully. Acrylic block should be cleaned with a soft rag and warm, soapy water because it cannot withstand abrasive household cleaners the way glass can.

The major benefit of acrylic block is that it is more than 70% lighter than glass, and is available almost exclusively in prefabricated fixed walls and windows, as well as in operable casement- and awning-style windows. Acrylic units can be custom-made to fit any size opening, making installation faster and easier than with glass block.

Acrylic Details

Values based on 8-in. by 8-in. by 2-in. block

R-value: 2.04

Price: $7.50 per block

19-in. by 25-in. casement window with 6-in. blocks: $330

Weight: 1 lb. per block

4-ft. by 4-ft. prefab unit: 55 lb.

Best features:

• Lightweight

•Easy to install

•10-year warranty against yellowing of block and grout

Installation: Building with individual acrylic blocks is rare, but it can be done by snapping the blocks together with plastic clips and sealing the joints with adhesive; no mortar is used. For the proper supplies and complete how-to information, visit www.acrylicblocks4less.com.

Glass Details

Based on 8-in. by 8-in. by 4-in. block

R-value: 1.96

Price: $6.50 per block

18-in. by 24-in. fixed window with 6-in. blocks: $355

Weight: 6 lb. per block

4-ft. by 4-ft. built-in-place unit: 230 lb.

Best featurese

• Excellent durability

• Fire-resistance

• Readily available in different shapes

Installation: Commonly built up block by block on site with mortar, although prefab fixed windows and panelized building kits are available.

Important note: Due to glass’s weight, added structural support often is required in house framing. This can lead to longer installation times and higher expense, especially in retrofits.