In almost every large building, the exhaust steam from the engines necessary to run elevators and dynamos will suffice to heat the rooms, and this may be done in two ways. The exhaust steam may be forced or drawn through the radiators and transmit heat directly to the building, or it may be carried to a coil in a water tank in the basement, heating the water, and causing it to circulate through the pipes and radiators instead of the steam. By the latter method a more uniform distribution of heat will be obtained and any danger of back pressure on the engines will be avoided. This tank must be placed low enough to prevent any backing up of the water to the engine, and the circulation of hot water to the radia-tors may be laid out in a manner similar to the circulation from an ordinary heater, which has been previously described. The greater height and multiplication of radiators will require a much more complicated system of piping, but the main features will be the same. The most effective service will of course be obtained by putting as few radiators as possible on a direct circulation, but as this adds very much to the expense it is quite usual to run one or two large mains up to the top story and from a horizontal run in this story, to bring down the hot water to supply the radiators, continuing this pipe to the heater. This of course gives a better supply to the top stories than the lower ones, so the difference is made up by putting larger radiators in the lower stories.

The first story, being subjected to more glass exposure and cold from the doors, is sometimes supplied directly from the risers, and the discharge returned by separate pipes to the tank, while the other radiators, being supplied by a descending current, are supplied and discharged into the same pipe without interfering with the circulation. The system of indirect steam heating by a fan is often to be preferred for the large stores or corporation offices, which usually occupy the lower story of a city block. For the heating of the smaller upper offices it is a good plan to drop a riser, as described, between each pair of windows, placing a small radiator in front of each window. These may be supplied with fresh air by means of sash ventilators or other fresh air inlets, or they may warm the room by direct radiation.

RESIDENCE OF MR. W. W. WILLITS, HIGHLAND PARK, ILL.

RESIDENCE OF MR. W. W. WILLITS, HIGHLAND PARK, ILL.

Frank Lloyd Wright, Architect, Oak Park, Ill. Plan Shown on Opposite Page.

FIRST FLOOR PLAN OF RESIDENCE OF MR. W. W. WILLITS, HIGHLAND PARK, ILL.

FIRST-FLOOR PLAN OF RESIDENCE OF MR. W. W. WILLITS, HIGHLAND PARK, ILL.

Frank Lloyd Wright, Architect, Oak Park, Ill.

Exterior View Shown on Opposite Page.