EXHIBIT 99.1


                            CERTIFICATION PURSUANT TO
            SECTION 1350, CHAPTER 63 OF TITLE 18, UNITED STATES CODE,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002



Pursuant to Section 1350, Chapter 63 of Title 18, United States Code, as adopted
pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, the undersigned, as
chief executive officer of Comfort Systems USA, Inc. (the "Company"), does
hereby certify that:

     1)  the Company's Quarterly Report pursuant to Section 13 or 15 (D) of the
         Securities Exchange Act Of 1934 (Form 10-Q) for the quarter ended June
         30, 2002 fully complies with the requirements of Section 13(a) or 15(d)
         of the Securities Exchange Act of 1934; and

     2)  the information contained in the Company's Form 10-Q fairly presents,
         in all material respects, the financial condition and results of
         operations of the Company.


                                       By: /s/ William F. Murdy
                                          ------------------------
                                       William F. Murdy
                                       Chairman of the Board and
                                       Chief Executive Officer


Dated: August 13, 2002