<PAGE>   1
                                  EXHIBIT 10.25

                                 SHARED SAVINGS

THIS ENERGY SERVICE AGREEMENT (hereinafter, "Agreement") is made and entered
into as of The 20 day of December, 1999, by and between, WISCONSIN POWER & LIGHT
COMPANY, having its principal offices at P.O. Box 8880, Madison, Wisconsin
53704-8880 (hereinafter, "Utility"), and PENDA CORPORATION, a FLORIDA
corporation having its principal offices at Portage, Wisconsin (hereinafter,
"Client"), relating to property owned by Client at 2400 WISCONSIN AVE., PORTAGE,
Wisconsin, 53901 (hereinafter, "Premises", which are more particularly described
in Part I of Schedule A attached hereto).

            IT IS AGREED AS FOLLOWS:

SECTION 1. PURPOSES OF AGREEMENT

The purposes of this Agreement and the actions of the parties in pursuit thereof
are:

          a.       To accurately identify and agree upon certain baseline
                   information concerning the energy consumption characteristics
                   of the Premises (hereinafter, "Baseline Energy Consumption");

          b.       To designate certain equipment (hereinafter, "Equipment")
                   which, installed on the Premises in lieu of Equipment
                   formerly used by Client, is estimated by Utility to reduce
                   Client's annual energy consumption below Baseline Energy
                   Consumption ("Energy Savings") thereby providing an estimated
                   level of savings to Client; and

          C.       To set forth the obligation of the Utility to fund the
                   acquisition and installation of the Equipment in exchange for
                   the promise by client to share a portion of the value of the
                   Energy Savings ("Shared Savings") with Utility by paying such
                   amount to Utility along with payment of Client's regular bill
                   for utility service.

SECTION 2. BASELINE ENERGY CONSUMPTION

Client and Utility have to their mutual satisfaction analyzed the historic and
present operating practices of Client (hereinafter, "Baseline Operating
Practices") and the corresponding energy consumption characteristics of the
Premises and agree that the Baseline Energy Consumption on all (or a specified
portion, as the case may be) of the Premises for the purposes of this Agreement
shall be as set forth in Part 11 of Schedule A. The parties intend that such
Baseline Energy Consumption shall be conclusive and, except for material error
or misrepresentation with respect to the Baseline Operating Practices, each
hereby waives any objections to same, whether now existing or hereafter arising.

SECTION 3. EQUIPMENT PURCHASE, INSTALLATION, OPERATION AND MAINTENANCE
Within a reasonable period of time after the execution of this Agreement:
          a.       Client has purchased the Equipment specified in Part I of
                   Schedule B hereof and arranged for installation of the
                   Equipment at the Premises.
          b.       Client shall be responsible for obtaining all governmental
                   permits, consents and authorizations necessary for
                   installation of the Equipment, and Utility shall use its best
                   efforts to assist Client in obtaining such permits, consents
                   and authorizations.



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<PAGE>   2

As part of the initial installation and continuing thereafter, Client shall
provide Utility with mutually satisfactory access to the Premises for the
inspection of the Equipment, and with free and reasonable access to lights,
heat, power, water, and the like necessary for such inspection and any
associated submetering.

Client shall have exclusive responsibility for the operation and maintenance of
the Equipment in accordance with all manufacturer specifications and
recommendations and with such additional standards and procedures as may be set
forth in Part 11 of Schedule B. All costs and expenses incurred in connection
with the operation and maintenance of the Equipment shall be the sole
responsibility of Client. Client shall be solely responsible for enforcing any
manufacturer's warranties which accompany the Equipment and shall enforce such
warranties on its own or upon Utility's request.

SECTION 4. RISK OF LOSS

Client hereby assumes all risks of loss or damage to the Equipment while such
Equipment is in their care, custody or control. Client shall notify Utility
within 10 days of any loss or damage to the Equipment and shall keep Utility
informed of all developments regarding insurance rights and recoveries. Should
the Equipment be deemed a total loss or Client decides not to complete repairs,
Client shall to pay to Utility the Termination Value specified in Schedule C
hereto.

SECTION 5. INSURANCE

The Client shall provide, maintain, and pay for commercial general liability
insurance with limits of at least $1,000,000 per occurrence so as to comply with
Section 14. Indemnification. Client shall also provide, maintain, and pay for
all risk property insurance with a minimum limit of the Termination Value of
this Agreement as specified in Schedule C hereto. In the event of any loss or
damage to the Equipment, the proceeds of insurance covering the Equipment shall
be applied toward the replacement, restoration, or repair of the Equipment in
accordance with Section 4. Risk of Loss. This insurance must be in effect from
the time that the first item of Equipment is delivered to the Client until the
end of the term. Each policy must contain the insurer's agreement to give thirty
(30) days written notice to Utility before cancellation or non-renewal of the
required insurance.

The Client agrees to provide certificates of insurance as evidence of the
required coverage to Utility. Failure of Utility to enforce the minimum
insurance requirements listed above shall not relieve Client of responsibility
for maintaining these coverages.


SECTION 6. DISCLAIMER OF WARRANTIES

UTILITY MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, CONCERNING
THE CONDITION OR PERFORMANCE OF THE EQUIPMENT, AND SPECIFICALLY DISCLAIMS ANY
AND ALL SUCH REPRESENTATIONS AND WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

SECTION 7. COMMENCEMENT DATE AND TERM

The "Commencement Date" shall be the first day of the first Billing Period
beginning after the date of this Agreement. The "Term" of this Agreement shall
begin on the date set forth on page one hereof and shall run continuously from
such date (unless this Agreement shall have been terminated by the parties at an
earlier date pursuant to the terms hereof) until the fifth (5th) anniversary of
the Commencement Date.



                                       50
<PAGE>   3
"Billing Period" shall mean any period of approximately one month's duration
coincident with the normal billing cycle between Utility and Client, and "Annual
Billing Period" shall mean a series of twelve (12) consecutive Billing Periods,
the first of which shall begin with the Billing Period which first begins on or
after the Commencement Date.

SECTION 8. COMPENSATION AND BILLING

Client agrees to pay Utility an amount equal to seventeen thousand one hundred
sixty dollars ( $17,160) in each Billing Period during the Term of this
Agreement following the Commencement Date, for a total of sixty (60) billing
periods. The foregoing amount (the "Shared Savings") reflects a sharing by
Client of the value of the Energy Savings estimated to be realized from the
operation and use of the Equipment at the Premises as outlined in Schedule D
with the present energy charge in effect under Utility's applicable Rate
Schedule. The foregoing amount (the "Bright Ideas" labeled on bill) shall appear
as a separate line item on Client's bill from Utility during each Billing
Period, and shall be payable by Client upon the same terms and conditions as are
applicable to the normal utility bill. The foregoing amount shall not vary due
to change in Utility's rates, returns, or charges authorized by the Public
Service Commission of Wisconsin. The foregoing amount is based upon an estimated
cost for purchase and installation of the Equipment and will be modified by
amendment to this Agreement to reflect the actual cost of such purchase and
installation upon completion thereof.

                 The above monthly amount of seventeen thousand one hundred
                 sixty dollars ($17,160) represents the principal amount of the
                 Shared Savings plus simple interest at 3.0% per annum in
                 arrears. The principal amount of the Shared Savings may be
                 prepaid in whole or in part at any time without penalty. If the
                 principal amount of the Shared Savings is prepaid in part, then
                 the monthly amount to be paid will be recalculated over the
                 balance of the Term of this Agreement.

SECTION 9. CONDITIONS BEYOND CONTROL OF UTILITY

If Utility shall be unable to carry out any of its obligations under this
Agreement due to events beyond its control, including, without limitation, acts
of God, governmental or judicial authority, insurrections, riots, labor
disputes, labor or material shortages, fires, explosions, or floods, this
Agreement shall remain in effect but Utility's obligations shall be suspended
until the uncontrollable event terminates.

SECTION 10. REMEDIES UPON DEFAULT BY CLIENT

          a.       Utility's Remedies. In the event Client fails to pay Utility
                   its compensation when due, or any other Event of Default by
                   Client occurs, (defined as a failure by Client to timely
                   perform any of its obligations under this Agreement), Utility
                   may, without an election of remedies:

                   1)       disconnect all electric service to the Premises in
                            accordance with the rules and regulations of the
                            Utility as approved by the Public Service Commission
                            of Wisconsin and in effect at the time of breach;
                            and

                   2)       declare the Termination Value specified in Schedule
                            C immediately due and payable from Client and
                            exercise all remedies available at law or at equity
                            or



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<PAGE>   4

                            other appropriate proceedings including bringing an
                            action or actions from time to time for recovery of
                            amounts due and unpaid by Client, and/or for damages
                            which shall include all costs and expenses
                            reasonably incurred in exercise of its remedy
                            (including reasonable attorney's fees), and/or for
                            specific performance; or

                   3)       without recourse to legal process, terminate this
                            Agreement by delivery of a notice declaring
                            termination, whereupon Utility may enter the
                            Premises and dismantle and/or remove the Equipment
                            from the Premises, without liability in any suit,
                            action or other proceeding to Client or Lessor of
                            Premises, if any, on account of such actions.

          b.       Liquidated Damages. In the event Utility terminates this
                   Agreement due to an Event of Default, at Utility's request
                   Client shall pay to Utility, as liquidated damages, the
                   Termination Value set forth in Schedule C, plus all costs and
                   expenses reasonably incurred in exercise of its remedy,
                   including reasonable attorney's fees.

          C.       Termination. Utility may terminate this Agreement and declare
                   the Termination Value specified in Schedule C immediately due
                   and payable should:

                   1)       Client cease use of the Equipment or the conduct of
                            commercial operations at the premises, or

                   2)       any creditor of Client commence legal proceedings
                            against Client involving any debt or obligation of
                            Client for which the Equipment is pledged as
                            collateral, or

                   3)       Client commence or have commenced against it any
                            proceedings in bankruptcy, receivership or
                            insolvency or make any assignment for the benefit of
                            its creditors, or

                   4)       Client cease to take or receive electric and/or
                            natural gas service from Utility.

 SECTION 11. REMEDIES UPON DEFAULT BY UTILITY

 In the event of material default by Utility, Client shall have the following
 remedy:

          a.        Terminate this Agreement by delivery of a Notice declaring
                    termination, and paying the Termination Value indicated in
                    Schedule C (less the cost of any future maintenance and
                    energy related services included therein, as agreed to by
                    the parties), whereupon Utility shall have no further
                    rights, obligations or claims under this Agreement.



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<PAGE>   5

Client may terminate this agreement by paying the Termination Value indicated
in Schedule C.

SECTION 12. ARBITRATION

Except as otherwise provided herein, any dispute, controversy or claim arising
out of or in connection with or relating to this Agreement, upon the request of
either Client or Utility, shall be submitted to and settled by arbitration at
the locality where the Premises are situated in conformance with rules of the
American Arbitration Association then in effect. Any award rendered shall be
final and conclusive upon the parties and a judgment thereon may be entered in a
court of any forum, state or federal, having jurisdiction. The expenses of the
arbitration shall be borne equally by the parties to the arbitration, provided
that each party shall pay for and bear the cost of its own experts, evidence and
counsel. This Section 12 does not apply and shall not limit Utility's rights to
seek redress in any forum in the event Utility seeks to invoke any of the
provisions of Section 10 herein.

SECTION 13. ASSIGNMENT

Utility may (a) transfer or assign all or any part of its rights and obligations
herein to any party, (b) pledge its rights hereunder to its creditors, or (c)
utilize contractors and subcontractors, provided that any assignee or transferee
agrees to honor the terms of this Agreement. Unless otherwise approved in
writing, Client may not transfer or assign this Agreement and its rights and
obligations herein. If such assignment is permitted, Client shall condition
assignment on assignee assuming in writing all of Client's rights and
obligations under this Agreement.

SECTION 14. INDEMNIFICATION

Client agrees to indemnify, defend and hold Utility harmless from any and all
claims, actions, costs, expenses, damages and liabilities, including reasonable
attorney's fees, and claims of third parties arising out of, connected with or
resulting from Client's operation, installation, use, maintenance or repair of
the Equipment, or from the negligence or misconduct of its employees or other
agents in connection with their activities within the scope of this Agreement.
However, Client shall not be obligated to indemnify Utility against claims,
damages, expenses or liabilities solely to the extent such claims, damages,
expenses or liabilities directly result from the negligence or willful
misconduct of Utility or its employees or agents. The duty to indemnify will
continue in full force and effect notwithstanding the expiration or early
termination of this Agreement with respect to any claims based on facts or
conditions which occurred prior to termination.

SECTION 15. MISCELLANEOUS

          a.                       This Agreement shall be governed by and
                           interpreted pursuant to the laws of the state of
                           Wisconsin without regard to its conflict of law's
                           provisions.

          b.                       This Agreement constitutes the entire
                           understanding and agreement between the parties, and
                           supersedes any and all prior representations and
                           agreements, whether written or oral between the
                           parties as to the subject matter hereof. No wavier,
                           alteration, consent or modification of any of the
                           provisions of this Agreement shall be binding unless
                           in writing and signed by a duly authorized
                           representative of all parties hereto bound.



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<PAGE>   6

      IN WITNESS WHEREOF and intending to be legally bound, the parties hereto
 subscribe their names to this instrument on the date first above written.

 ATTEST:                                    WISCONSIN POWER & LIGHT COMPANY
 /s/ Mark Mierdirk                          By /s/ Chuck Ashe
 -------------------------                    ------------------------------
                                            Title  Account Manager

 ATTEST:                                    PENDA CORPORATION
 /s/ Samuel Mostkoff                        By /s/ Leo E. Waner
 -------------------------                    ------------------------------
                                            Title  VP & CFO
                                                 ---------------------------



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<PAGE>   7



                                   SCHEDULE A
                                PENDA CORPORATION
                             DESCRIPTION OF PREMISES
                                     PART I
                                   DESCRIPTION

CITY OF PORTAGE PARCELS 2521 & 2536; COUNTY TAX ID #11271 CP02521.8 LOT 2 OF CS
V.5P. 15331161 R331-303 R471-440; COUNTY TAX ID # 11271 CP02536 PRT OL 153 &
144, LOT 1 CS V.5P. 115 & 1123 EASE EXC R67-322 R 262 - 702



                                     PART II
                       ENERGY CONSUMPTION CHARACTERISTICS

              Historical Energy Consumption and Facility Operation
                      Floor area of facility: 300,000 s.f.


<TABLE>
<CAPTION>
                                                  PERIOD #1                         PERIOD #2
                                            01/01/98 - 12/31/98
<S>                                         <C>                                     <C>
        ELECTRIC
        AVERAGE DEMAND (KW)                            6,746                             0
        INTERRUPT DEMAND (KW)                          4,500                             0
        ON-PEAK ENERGY (kWh)                      16,956,578                             0
        OFF-PEAK ENERGY (kWh)                     23,574,622                             0
        NATURAL GAS
        ENERGY (THERMS)                               28,000                             0
        OTHER FUELS
        OTHER FUEL 1                                       0                             0
        OTHER FUEL 2                                       0                             0
        FACILITY OPERATION
        HOURS OF OPERATION                             8,500                             0
        HEATING DEGREE DAYS                                0                             0
        % OCCUPANCY                                        0                             0
        PRODUCTION (UNITS/YEAR)                            0                             0
        PRODUCTION (UNITS/YEAR)                            0                             0
        PRODUCTION (UNITS/YEAR)                            0                             0
</TABLE>


      COMMENTS:




                                       55
<PAGE>   8




                                   SCHEDULE B
                                PENDA CORPORATION





                                     PART I
                                   EQUIPMENT
<TABLE>
<CAPTION>
Item      Description                    Manufacturer                  Model Number           Quantity
<S>       <C>                            <C>                          <C>                     <C>
1.        #12 THERMOFORMER               BROWM S/N 13757.              R-244                         1
2.        #13 THERMOFORMER               BROWN S/N 13878               R-244-E                       1
3.        #4 THERMOFORMER                BROWN S/N 11164               R-244                         1
</TABLE>







                                     PART 11
                       ADDITIONAL STANDARDS AND PROCEDURES




                                       56
<PAGE>   9



                                   SCHEDULE C
                                PENDA CORPORATION


                               TERMINATION VALUES



<TABLE>
<CAPTION>
Billing                                      Billing                                     Billing
Period          Value                        Period          Value                       Period             Value
<S>        <C>                               <C>       <C>                              <C>            <C>
     1        955,000.00                        21        652,426.68                       41             334,359.94
     2        940,227.50                        22        636,897.75                       42             318,035.84
     3        925,418.07                        23        621,329.99                       43             301,670.93
     4        910,571.62                        24        605,723.31                       44             285,265.11
     5        895,688.05                        25        590,077.62                       45             268,818.27
     6        880,767.27                        26        574,392.81                       46             252,330.32
     7        865,809.19                        27        558,668.79                       47             235,801.15
     8        850,813.71                        28        542,905.46                       48             219,230.65
     9        835,780.74                        29        527,102.72                       49             202,618.73
    10        820,710.19                        30        511,260.48                       50             185,965.28
    11        805,601.97                        31        495,378.63                       51             169,270.19
    12        790,455.97                        32        479,457.08                       52             152,533.37
    13        775,272.11                        33        463,495.72                       53             135,754.70
    14        760,050.29                        34        447,494.46                       54             118,934.09
    15        744,790.42                        35        431,453.20                       55             102,071.43
    16        729,492.40                        36        415,371.83                       56              85,166.61
    17        714,156.13                        37        399,250.26                       57              68,219.53
    18        698,781.52                        38        383,088.39                       58              51,230.08
    19        683,368.47                        39        366,886.11                       59              34,198.16
    20        667,916.89                        40        350,643.33                       60              17,160.00
</TABLE>




                                       57
<PAGE>   10



                                   SCHEDULE D
                                PENDA CORPORATION



CONTRACT: THERMOFORMER 12, 13, 4


This contract includes the following projects:
<TABLE>
<CAPTION>
----------------------------------------------------------------------------------------------------------
                                               CUSTOMER's GROSS ANNUAL                       Project
                                                        SAVINGS                              Cost ($)
-------------------------------------------------------------------------------------------
PROJECT                                  Bill KW        kWh          Therms           $
----------------------------------------------------------------------------------------------------------
<S>                                    <C>         <C>              <C>           <C>           <C>
EFFICIENT THERMOFORMER 12                 178.00     1,260,193        28,578        73,399        911,000
----------------------------------------------------------------------------------------------------------
EFFICIENT THERMOFORMER 13                 178.00     1,260,193        28,578        73,399        911,000
----------------------------------------------------------------------------------------------------------
THERMOFORMER 4 ELE. UPGRAD                 80.00       120,000             0        12,435         12,000
----------------------------------------------------------------------------------------------------------
TOTAL                                     436.00     2,640,386        57,156       159,233      1,834,000
----------------------------------------------------------------------------------------------------------
</TABLE>



                                       58

<PAGE>   11
                                    CONSENT

                                          Dated as of December 27, 1999



      The undersigned, Tri-Glas Corporation, an Alabama corporation, as
Guarantor under the Subsidiaries Guaranty dated July 15, 1995 (the "Guaranty")
in favor of the Agent, for its benefit and the benefit of the Lenders Parties
party to the Credit Agreement referred to in the foregoing Amendment, hereby
consents to such Amendment and hereby confirms and agrees that (a)
notwithstanding the effectiveness of such Amendment, the Guaranty is, and shall
continue to be, in full force and effect and is hereby ratified and confirmed
in all respects, except that, on and after the effectiveness of such Amendment,
each reference in the Guaranty to the "Credit Agreement", "thereunder",
"thereof" or words of like import shall mean and be a reference to the Credit
Agreement, as amended by such Amendment, and (b) the Collateral Documents to
which such Grantor is a party and all of the Collateral described therein do,
and shall continue to, secure the payment of all of the Secured Obligations
(in each case, as defined therein).

                                          TRI-GLAS CORPORATION

                                          By /s/ Samuel Mostkoff
                                             -------------------

                                          Title: Vice President
                                                 --------------