WHAT grade-school boy hasn't dreamed of dismantling the buildings that imprison him on a beautiful October day?

Bob Beaty is living that dream. But for him, it's an act of respect, not rebellion. Along with his partners, Beaty runs an architectural salvage and deconstruction company called Provenance (www.phillyprovenance.com).

Walking through their store at 16th and Fairmount, like the Architectural Antiques Exchange in Northern Liberties or Restore in Kensington, is like walking through a giant, neatly sorted and stacked pile of rubble.

Doors, shutters, mantels, stones, bricks, doorknobs, tiles and railings are transformed from waste into resources by all that careful stacking.

Recently, I watched a team from Provenance race the clock to deconstruct what they could from the Church of the Transfiguration at 56th and Cedar in West Philadelphia. Any day now, the church will be demolished.

In one of those bittersweet ironies that Philadelphia produces, Beaty attended the parish grade school next door to the church (as did Mayor Nutter). That building today houses the Boys' Latin charter school, which bought the complex in 2006 and wants to expand.

While a church falling under the wrecking ball can be a shocking image, the expansion of a local school creates opportunities within the neighborhood that the church no longer provides.

The cold reality is that neither the archdiocese (which closed the church, school, convent and rectory complex in 2000) nor the charter school needs a church on that corner. But how it comes down raises an important question for our city of obsolete buildings. Does a building whose end has come produce waste for a landfill or resources with enduring value?

Beaty and his team paid for the chance to salvage the parts of the church that could be resold either for their artistic or material qualities. There has already been a lot of "recycling" from this parish complex. Four 1928 stained glass windows from the transept now grace St. Raymond's in Fairfax County, Va.,which also reused the main altar and altar table. And of course, Boys' Latin is an example of the ultimate in recycling, refitting a completely new school facility inside the envelope of the former parish school.

Given the tight time frame at Transfiguration, Beaty will only salvage the parts of the church that he's already sold. There just isn't time to pull all the beautifully designed and crafted tile and stone work out of the church and store it. That means tons - literally - of valuable material will be reduced to rubble during the demolition.

That turns a resource into a problem. The city's Greenworks plan, which I had a hand in creating during my year in City Hall, commits to increasing the percentage of Philadelphia's total waste stream that goes somewhere other than a landfill from about 50 to 70 percent by 2015.

Construction waste is a big part of that stream and every stone salvaged for reuse is a stone diverted from landfill - one that can go toward reuse, recycling or energy production.

My rowhouse contains more than 77,000 bricks (I know because it's the kind of exercise you do in architecture school), almost 75 tons' worth. So, about 13,000 row houses (approximately the number on Licenses &Inspection's dangerous list) would contain more than a billion bricks. Should we treat that billion bricks as landfill or as valuable material to be reused?

Go into the remodeled Sansom St. Oyster House or Marc Vetri's latest restaurant and you can see what can be done with salvaged building materials.

BACK IN 2006, I wrote that reconciling old and new Philadelphians was the most important issue facing the next mayor. Deconstruction rather than demolition is a great example of how that can happen.

By transforming waste into a resource, and by helping rebrand Philadelphia as a city of the future, deconstruction should become a bigger part of our sustainability strategy. For example, why not make a salvage certification part of the demolition permit?

Sometimes unbuilt is as important as built.

Mark Alan Hughes teaches at PennDesign and Penn's TC Chan Center for Energy Studies. E-mail him

at mahughes@design.upenn.edu.