Dear Jim: I want to replace some old single-pane first floor windows with glass-block windows for security. Are they as efficient as other new windows, can they be opened and can I install them myself? – Kevin S.

Dear Kevin: Glass-block windows are an excellent alternative to standard pane windows for first floor and basement windows when you have security concerns. Although it is possible to break through them with a sledge hammer, it is unlikely a would-be thief would attempt this.

Glass-block windows will be better, but not as energy efficient as the best-quality replacement pane glass windows. Glass- or plastic-block (which look identical to glass) windows will have double the insulation value of your old single-pane windows. Glass-block windows are as airtight as a wall, so there will be additional energy savings from reduced air infiltration.

Glass-blocks appear to be solid, but residential ones are hollow. Two halves are fused together under heat and pressure. As they cool, a slight vacuum is created inside which improves the insulation level.

Also, commercial-quality solid glass blocks are available for ultrahigh security, but these are very heavy and expensive. Plastic-block halves, made from acrylic, are not fused with heat. The most energy efficient ones include a thin layer of metal atoms on the inside surface. This creates efficient low-emission properties similar to standard replacement pane glass windows, and it saves energy year-round.

You have several options to be able to open glass or plastic block windows for natural ventilation. Several of the blocks can be replaced with a small hopper-style window which opens. It is too small for someone to crawl through. Also, the clear panel is made of polycarbonate, bulletproof glass, so it is nearly impossible to break through.

Another option is to install an entire casement-style glass-block window. Similar to other replacement windows, it is custom made to fit in the old window opening in the wall. This glass-block casement is installed similarly to other windows. This is also ideal for the do-it-yourselfer.

There are several other do-it-yourself glass/plastic block options to save a few dollars. It is possible to install the blocks separately into mortar, as a professional would do, but you may not be happy with the results of the first several windows while you are mastering the technique.

Pittsburgh Corning offers several installation kits. One kit includes corner spacers to perfectly stack the blocks in the window opening. Once the mortar sets up, the exposed spacer ends are removed. Another kit includes clear spacers to position the blocks. Instead of using mortar, clear silicone caulking secures the blocks in place.

The following companies offer glass and plastic block windows: Builders Accessories, (888) 921-7086, www.acrylicblock.com; Circle Redmont, (800) 358-3888, www.circleredmont.com; Hy-Lite Products, (800) 655-9087, www.hy-lite.com; Pacific Accent, (888) 522-4527, www.pacificaccent.com; and Pittsburgh Corning, (800) 624-2120, www.pittsburghcorning.com.

Dear Jim: I live in a moderate climate and need a new heating and cooling system. I cannot afford the most efficient models of each. Should I get the most efficient furnace and cheaper A/C or visa versa? – Ron H.

Dear Ron: It depends upon your climate and your personal comfort. If your heating bills are more than your cooling bills, spend the extra for a high-efficiency furnace. If your cooling bills are higher, get the best A/C. If the bills are similar, invest in the better furnace. You have to heat your home during the winter. During summer, if your budget gets tight, you can turn off the A/C and open windows. When I was a kid, no one had A/C and we survived just fine.

Send inquiries to James Dulley, Bangor Daily News, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.dulley.com.