Do you find that buildings under construction look at least as fascinating as they do when completed? Perhaps you believe some buildings look even better when all you see is their skeletons and metabolic innards, before they are masked by sometimes less-than-wonderful facades.

There's something undeniably intriguing about the indispensible systems of support, supply and control used to fashion buildings. Yet you may take these systems for granted, not noticing in a conscious way their shape, their relationships to other architectural phenomena, or their inner workings.

In fact, you may become keenly aware of building systems only when they fail. This was illustrated dramatically and tragically last month whenearthquakes collapsed hundreds of buildings in Mexico City. Soon thereafter, many buildings along the Eastern Seaboard suffered damage and loss of electrical power as Hurricane Gloria swept northward.

People who own or occupy buildings, long after architects and engineers have designed them and contractors have built them, presume that building systems serve unambiguous, essential purposes -- to provide unobtrusive support, uncompromised safety, and uninterrupted comfort. Little wonder, then, that when you feel secure in a building, without being too hot or too cold, your "system consciousness" is likely to be minimal.

The public's interest and values concerning its "health, safety, and welfare" have been translated into public policy and regulatory legislation. Building codes establish threshold criteria for the design and construction of buildings, particularly related to structural stability and fire safety.

Although most codes require acceptable margins of performance, they do not require ideal or esthetically pleasing designs. Much is left to the discretion of architects, engineers, regulators and fabricators. And market-oriented developers look for building systems to satisfy codes and consumer expectations. They want cost-effective, trouble-free, easy-to-construct buildings that keep tenants happy.

Specialized, structural, mechanical and electrical engineers -- often consultants to, or associates of, architects -- carry the burden of actually designing in detail most building systems. They, too, share the concerns of building owners and the public. But they also must consider nationally adopted standards and methods of their own professional discipline (which may advocate more conservative and costlier design), along with the aspirations of the architect (whose systems priorities can be more esthetically motivated).

To some architects, building systems are nothing more than service elements, functional components to be designed quantitatively by engineers after a building's architectural form has been determined. Such architects, feeling obliged only to provide "poetic delight" fantasies (budget permitting), rely on engineers for the provision of adequate "commodity" and "firmness."

On the other hand, many architects exploit building systems as inherent form-giving elements. From the outset of design, when basic concepts are first being explored, they may manipulate certain of these necessary building ingredients to regulate space, volume, and surface. Ultimately, composing and coordinating building systems may lead to desirable visual order and expressiveness, both inside and out.

What are the fundamental, behind-the-facade building systems and their respective roles, regardless of project size or type?Structural systems. A building's structural skeleton resists the forces of gravity, occasional wind-induced uplift, and lateral forces caused by wind and earthquake movement. Designed to remain in "static equilibrium" as loads change over time, a building's structural frame collects and transmits forces to the earth through foundations. Among all building systems, the structural system most affects, and is affected by, the architectural shaping and patterning of buildings. Mechanical systems. This set of subsystems (frequently referred to as the HVAC system -- heating, ventilating, air conditioning) artificially tempers the atmosphere within buildings and renders spaces inhabitable. Air is supplied and returned via ductwork connected to air-handling units. Heating, refrigeration, humidification and filtering equipment adds or removes heat, moisture and particulate matter. Buildings themselves also may contribute passively to atmospheric control, energy conservation and comfort through their inherent geometrical characteristics, independent of mechanized systems. Plumbing systems. These independent networks of piping perform multiple tasks. One network, connected to the public water-supply system or wells, distributes water under pressure throughout a building for purposes of drinking, cooking, washing and, in many buildings, fire suppression. A separate network of slightly larger pipes relies on gravity to collect waste water and lead it down and out to public sanitary sewer systems or on-site septic systems. Another network of pipes carries natural or propane gas from distribution mains or tanks to gas-fueled equipment -- furnaces, water heaters and stoves. Buildings heated by distributing steam or hot water have piping loops that connect boilers to radiators or convection units. Electrical systems. Made up of networks of cables, wire, transformers, switches and meters, electrical systems distribute electrical power in assorted circuits and voltages throughout a building to energize lighting fixtures, lamps and electrically powered equipment and applicances. Conveyance systems. Elevators and escalators are the most visible mechanical conveyance devices found in multistory buildings. However, from an architectural point of view, stairs are equally essential. Likewise, ramps and corridors are components of a building's complete system of conveyance for movement of people and goods. Communications systems. These are low-voltage electronic networks and equipment used for transmitting conversation, data and control signals within buildings. The telephone is the most common and familiar of these sytems, along with fire-detection and security systems. Interior enclosure systems. Once a building is framed and weather-proofed by roof and exterior cladding, and after some of its other systems are roughed in, nonstructural partitions and ceilings can be installed and finished. So-called integrated, suspended ceiling systems can combine overhead lighting, air supply and return, and acoustic control.

Each of the above systems is engineered, fabricated, furnished and installed by separate manufacturers, suppliers and subcontractors. Nevertheless, they must be carefully and artfully integrated by the design architect, who cannot treat them as separate and independent elements.

Like interrelated systems of the human body, building systems must be woven to form a single organism, something greater than the sum of its respective, functional parts. Indeed, they can be orchestrated and assembled in ways that make environments beautiful and orderly, as well as safe and comfortable. This is one goal that architects, engineers, owners, investors and the general public should share willingly, even though it's not written in the codes.

NEXT: Structure.