Limited Power of Attorney for Section 16 Reporting Obligations

The undersigned hereby makes, constitutes, and appoints Trent T. McKenna
and Laura F. Howell, each acting individually, as the undersigned's true
and lawful attorney-in-fact, with full power and authority as hereinafter
described on behalf of and in the name, place, and stead of the
undersigned to:

prepare, execute, acknowledge, deliver, and file Forms 3, 4, and 5
(including any amendments thereto) with respect to the securities of
Comfort Systems USA, Inc., a Delaware corporation (the "Company"), with
the United States Securities and Exchange Commission, any national
securities exchanges, and the Company, as considered necessary or
advisable under Section 16(a) of the Securities Exchange Act of 1934 and
the rules and regulations promulgated thereunder, as amended from
time to time (the "Exchange Act");

seek or obtain, as the undersigned's representative and on the
undersigned's behalf, information on transactions in the Company's
securities from any third party, including brokers, employee benefit
plan administrators, and trustees, and the undersigned hereby authorizes
any such person to release any such information to the attorney-in-fact
and approves and ratifies any such release of information; and
perform any and all other acts that, in the discretion of such
attorney-in-fact, are necessary or desirable for and on behalf of
the undersigned in connection with the foregoing.

The undersigned acknowledges that:

this Power of Attorney authorizes, but does not require, such
attorney-in-fact to act in his or her discretion on information
provided to such attorney-in-fact without independent verification of
such information; any documents prepared and/or executed by such
attorney-in-fact on behalf of the undersigned pursuant to this Power
of Attorney will be in such form and will contain such information and
disclosure as such attorney-in-fact, in his or her discretion, deems
necessary or desirable;

neither the Company nor such attorney-in-fact assumes (i) any
liability for the undersigned's responsibility to comply with the
requirement of the Exchange Act, (ii) any liability of the undersigned
for any failure to comply with such requirements, or (iii) any
obligation or liability of the undersigned for profit disgorgement
under Section 16(b) of the Exchange Act; and this Power of Attorney
does not relieve the undersigned from responsibility for compliance
with the undersigned's obligations under the Exchange Act, including
without limitation the reporting requirements under Section 16 of the
Exchange Act.

The undersigned hereby gives and grants the foregoing attorney-in-fact
full power and authority to do and perform all and every act and thing
whatsoever requisite, necessary, or appropriate to be done in and about
the foregoing matters as fully to all intents and purposes as the
undersigned might or could do if present, hereby ratifying all that
such attorney-in-fact of, for, or on behalf of the undersigned, shall
lawfully do or cause to be done by virtue of this Limited Power of
Attorney. This Power of Attorney shall remain in full force and effect
until the undersigned is no longer required to file Forms 3, 4, and 5
with respect to the undersigned's holdings of and transactions in
securities issued by the Company, unless earlier revoked by the
undersigned in a signed writing delivered to the foregoing attorney-
in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney
to be executed in Harris County, Texas as of this 12th day of April, 2018.

/s/ William J. Sandbrook_____________________________________
William J. Sandbrook


Exhibit 24