Glass block win­dows good for both se­cu­rity and pri­vacy

The Palm Beach Post - Residences - - Front Page -

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.cir­clered­; Hy-Lite Prod­ucts, (888) 256-2599, www.; Pa­cific Glass Block, (888) 522-4527, www. paci­fic­glass­; and Pitts­burgh Corn­ing, (800) 545-5001, www.pitts­burgh­corn­

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