A display apparatus for a control unit in an environmental control system; the display apparatus including: a display area presenting a plurality of first loci, a plurality of second loci and at least one third locus; each respective first locus of the plurality of first loci being responsive to pressure for effecting a respective response; each respective second locus of the plurality of second loci presenting information using a fixed segment data format; at least one third locus of the at least one third locus presenting information using a dot matrix data format; the display apparatus configured to allow textual system status messages to be displayed.