January 25, 2003 - Washington Post: Tunisia RPCV Roger Lewis discusses masonry of Tunisia and St. Petersburg

Peace Corps Online: Peace Corps News: Headlines: Peace Corps Headlines - 2003: 01 January 2003 Peace Corps Headlines: January 25, 2003 - Washington Post: Tunisia RPCV Roger Lewis discusses masonry of Tunisia and St. Petersburg

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Tunisia RPCV Roger Lewis discusses masonry of Tunisia and St. Petersburg

Tunisia RPCV Roger Lewis discusses masonry of Tunisia and St. Petersburg

When the Temperature Plummets, Leaky Windows Can Undo the Best of Insulation Jobs

By Roger K. Lewis
Saturday, January 25, 2003; Page H11

January is a good time not to take thermal insulation for granted.

Two weeks ago, while I was attending a symposium in St. Petersburg, Russia, the temperature plummeted to a breath-stopping minus 30 degrees Celsius, or 22 degrees below zero Fahrenheit. Inside the minimally heated university building where we convened, we kept on our scarves, coats and, occasionally, gloves and hats. A few of us wore thermal underwear.

Shivering sometimes impeded serious thinking about cities and architecture.

I also recalled my two years in the Peace Corps in supposedly temperate Tunisia, where most buildings, including my architectural office, were neither heated nor insulated. Each November a bone-penetrating chill set in, persisting well into March. During those winter months I often sat at the drafting board wearing garments fit for skiing, with a pencil in my gloved hand.

Insulated and centrally heated buildings are a relatively recent innovation. Until the 20th century, humans depended primarily on thick masonry walls, or walls of solid wood, a natural insulator, to stave off winter's chill. If any heat was produced inside buildings, it came from burning wood, coal or peat in stoves or fireplaces capable of heating only a room or two.

But thick masonry walls, such as those throughout both Russia and Tunisia, do not provide effective thermal insulation. In fact, solid masonry gets cold and stays cold. It conducts heat fairly easily, and when moisture infiltrates porous masonry and mortar, thermal conductivity increases even more.

For insulation, we no longer rely on heavy masonry or solid wood walls. Today the primary insulating material is an invisible layer sandwiched between exterior and interior wall finishes. Yet the effectiveness of that insulation depends a great deal on where it is placed and how well it is protected from the elements.

Exterior walls of American homes framed with wood studs typically are insulated with thick batts of glass or mineral fibers placed between studs.

Even thicker batts of insulation are placed between rafters to insulate roofs. Within the batt, a dense tangle of filaments traps thousands of tiny air pockets. Because entrapped air is nature's great insulator, heat cannot flow easily through the batt.

Although batt insulation in walls does most of the thermal work, other layers of material that make up the wall also add insulating value: gypsum board attached to the interior of studs; sheathing attached to the exterior of studs; and brick veneer separated by an air cavity, or siding affixed directly to sheathing.

Yet one more component, a barrier managing the movement of air and moisture, is needed within such walls. These barriers are crucial for protecting exterior wall assemblies, inside of which airborne water vapor can condense and rot wood studs and sheathing, rust steel components and foster the growth of mold. Water is also one of nature's best conductors of heat, and if moisture permeates insulation, it substantially reduces thermal resistance, just as it compromises the insulating value of thick masonry walls in St. Petersburg or Tunisia.

Therefore preventing water vapor from getting into exterior walls and condensing is a major goal in construction, as is ensuring that any moisture inside the wall can escape. Insulation resists the flow of heat, but properly placed, it also keeps the wall's moisture-sensitive innards above the dew point and ensures that condensation doesn't form.

The walls of most commercial, industrial and institutional buildings are insulated with rigid boards made of foamed plastics such as polystyrene and polyisocyanurate. Ranging in thickness from less than an inch to several inches, these lightweight, durable, easily handled boards can be attached directly to exterior sheathing or concrete block. Their high insulating value per inch of thickness is attributable to millions of tiny, densely packed bubbles of air encapsulated within separate, closed cells created during the foaming process. Because each tiny cell of air is separated from adjacent cells by polymer membranes, water cannot infiltrate the foam and compromise its insulating qualities.

Rigid insulation frequently constitutes the core of metal-clad sandwich panels, components of the modular curtain walls that make up many building facades.

Wall insulation matters, but thermal attributes of windows within a wall are even more important. Superior wall insulation may be nullified by inferior windows with thin, single glazing, or by windows that are not tightly fitted and sealed when closed. Infiltration of cold air from outside is one of the major sources of heat loss in buildings.

If installed with proper sealants and weatherstripping, today's high-quality windows with thermal breaks and double or triple glazing can enhance comfort on even the coldest winter days. In St. Petersburg, newly renovated apartments in uninsulated 18th and 19th century buildings have become much more comfortable after being retrofitted with thermally sophisticated windows engineered in Sweden, Finland or Germany.

Insulating buildings well ensures wintertime comfort, yet it is also a "green" building strategy. Good insulation saves energy, reducing use of fossil fuels and improving air quality. In the middle of an often gray winter, knowing you are in a green building may make you feel just a bit more comfortable.

Roger K. Lewis is a practicing architect and a professor of architecture at the University of Maryland.

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This story has been posted in the following forums: : Headlines; COS - Tunisia; Special Interests - Architecture



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