AMENDMENT AND WAIVER LETTER

EXHIBIT 4.1(b)

                                               December 10, 2002

Harris Trust and Savings Bank                  U.S. Bank National Association
Chicago, Illinois                              Cincinnati, Ohio

Fleet National Bank                            Union Bank of California, N.A.
Stamford, Connecticut                          Los Angeles, California

LaSalle Bank, N.A.                             National City Bank
Chicago, Illinois                              Philadelphia, PA

Bank One, Arizona, N.A.                        Webster Bank
Phoenix, Arizona                               New Haven, Connecticut

Sovereign Bank
Boston, Massachusetts

Ladies and Gentlemen:

     Reference  is hereby  made to that  certain  Credit  Agreement  dated as of
September  26, 2002 (the "Credit  Agreement")  among the EMCOR Group,  Inc. (the
"Company"),   a  Delaware   corporation,   Comstock   Canada  Ltd.,  a  Canadian
corporation, and EMCOR Drake & Scull Group Ltd., a United Kingdom public limited
liability  company,  you (the  "Lenders")  and Harris Trust and Savings Bank, as
agent for the Lenders (the  "Agent").  All  capitalized  terms used herein shall
have the same  meaning  as in the  Credit  Agreement  unless  otherwise  defined
herein.

     As you are aware, the Company proposes to acquire (the  "Acquisition")  (a)
from Archstone-Smith  Operating Trust the indebtedness (the "Indebtedness") owed
to it by Consolidated  Engineering Services,  Inc. ("CES") and all of its shares
of CES capital  stock and (b) from all the other  stockholders  of CES all their
shares of CES  capital  stock for an  aggregate  purchase  price of no more than
$182,000,000 plus or minus an amount equal to a number determined by subtracting
the  consolidated  net worth of CES as of the closing date from its consolidated
net  worth as of June  30,  2002  (collectively,  the  "Consideration").  If the
difference  is positive the purchase  price will be decreased by that amount and
if the  difference  is negative  the  purchase  price will be  increased by that
amount.


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     This is to confirm our agreement with respect to the Credit  Agreement,  as
follows:

     1.  The Company consummate the Acquisition  notwithstanding  the provisions
         of Section 7.21 and Section 7.12 of the Credit Agreement; provided that
         it is hereby agreed that the $300,000,000  number referred to in clause
         (iv) of  Section  7.12(j) is  reduced  by the  Consideration;  provided
         further that after giving effect to the  Acquisition the Borrowers have
         Unused  Commitments of not less than  $55,000,000 and provided  further
         that CES and each of its majority owned subsidiaries (collectively, the
         "Acquired  Companies" and,  individually,  an "Acquired Company") shall
         constitute a Restricted Subsidiary and shall execute and deliver to the
         Agent the items required by Section 7.21 of the Credit Agreement.

     2.  The  following  provisions  of the Credit  Agreement are waived for the
         purposes indicated:

         (a)  Section 7.10 is hereby waived to the extent required to permit the
              Acquired  Companies to have outstanding  indebtedness  at the time
              each  such  Acquired  Company  becomes  a  Restricted  Subsidiary,
              provided such  indebtedness  is not incurred in  contemplation  of
              such Acquired  Companies  being  acquired by the Company,  and the
              amount of such  indebtedness  shall be  excluded  from the  dollar
              amount set forth in Section 7.10(K).

         (b)  Section  7.12 is hereby  waived to the extent  required  to permit
              each   Acquired   Company  (i)  to  retain  or  have   outstanding
              investments in, loans or advances to, any other Person, (ii) to be
              liable as endorser,  guarantor,  surety or otherwise for any debt,
              obligation or  undertaking  to any other Person,  (iii) to provide
              funds for  payment of the  obligations  of any other  Person or to
              supply  funds  thereto  or invest  therein or  otherwise  assure a
              creditor of another  against loss, (iv) to be liable to the issuer
              of a letter of credit which  supports an  obligation  of any other
              Person,  and (v) to subordinate any claim or claims it may have to
              the claim or demand of any  other  Person,  provided  in each such
              case such  investment,  loan or  advance,  endorsement,  guarantee
              suretyship,   other   arrangement,    agreement,   liability,   or
              subordination  is  outstanding  at the time the  Acquired  Company
              becomes  a   Restricted   Subsidiary   and  was  not  incurred  in
              contemplation  of such  Acquired  Company  becoming  a  Restricted
              Subsidiary.


     3.  Section 7.12 of the Credit  Agreement is hereby amended by striking the
         "; and" at the end of subsection (x) thereof and replacing it with ";",
         striking the "," at the end of  subsection (y) thereof and replacing it
         with "; and",  and adding  thereto a new clause  (z) as  follows:  "(z)
         investment in any securities or securities funds in an aggregate amount
         not in excess of (a) the  amounts  withheld  from the  compensation  of
         employees of the


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         Company or any subsidiary  pursuant to any deferred  compensation  plan
         and (b) amounts  representing  appreciation under any such plan of such
         withheld amounts.

     4.  Section 9.1 of the Credit  Agreement is hereby  amended by amending the
         paragraph  defining  "Disposition"  to read in its entirety as follows:
         "Disposition means the sale, lease,  conveyance or other disposition of
         Property  outside the normal  course of  business of the entity  making
         such sale, lease, conveyance or disposition."

     Please sign and return a copy of this letter to confirm your agreement with
the foregoing.

                                                  Very truly yours,

                                                  EMCOR Group, Inc.


                                                  By
                                                    ----------------------------
                                                    R. Kevin Matz
                                                    Vice President and Treasurer


The foregoing is hereby confirmed and agreed to:

Harris Trust and Savings Bank                     U.S. Bank National Association

By                                                By
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Fleet National Bank                               Union Bank of California, N.A.

By                                                By
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LaSalle Bank, N.A.                                National City Bank

By                                                By
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Bank One, Arizona, N.A.                           Webster Bank

By                                                By
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Sovereign Bank

By
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