<?xml version="1.0" encoding="utf-8"?>
<!--XBRL document created with Toppan Merrill Bridge  11.3.0.1 -->
<!--Based on XBRL 2.1-->
<!--Created on: 4/23/2026 4:02:53 PM-->
<!--Modified on: 4/23/2026 4:02:53 PM-->
<xsd:schema targetNamespace="http://www.comfortsystemsusa.com/20260331" attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xl="http://www.xbrl.org/2003/XLink" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:attributeFormDefault="unqualified" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:us-gaap="http://fasb.org/us-gaap/2025" xmlns:us-roles="http://fasb.org/us-roles/2025" xmlns:negated="http://www.xbrl.org/2009/role/negated" xmlns:fix="http://www.comfortsystemsusa.com/20260331" xmlns:enum2="http://xbrl.org/2020/extensible-enumerations-2.0" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2024-01-31" xmlns:ref="http://www.xbrl.org/2006/ref" xmlns:utr="http://www.xbrl.org/2009/utr" xmlns:srt="http://fasb.org/srt/2025" xmlns:deprecated="http://www.xbrl.org/2009/role/deprecated" xmlns:net="http://www.xbrl.org/2009/role/net" xmlns:dei="http://xbrl.sec.gov/dei/2025" xmlns:dtr="http://www.xbrl.org/2009/dtr" xmlns:xbrldi="http://xbrl.org/2006/xbrldi" xmlns:ecd="http://xbrl.sec.gov/ecd/2025" xmlns:ecd-sub="http://xbrl.sec.gov/ecd-sub/2025">
  <xsd:annotation>
    <xsd:appinfo>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureStandardAndCustomAxisDomainDefaults" id="DisclosureStandardAndCustomAxisDomainDefaults">
        <link:definition>99900 - Disclosure - Standard And Custom Axis Domain Defaults</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/StatementConsolidatedBalanceSheets" id="StatementConsolidatedBalanceSheets">
        <link:definition>995200100 - Statement - CONSOLIDATED BALANCE SHEETS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/StatementConsolidatedStatementsOfOperations" id="StatementConsolidatedStatementsOfOperations">
        <link:definition>995200200 - Statement - CONSOLIDATED STATEMENTS OF OPERATIONS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/StatementConsolidatedStatementsOfCashFlows" id="StatementConsolidatedStatementsOfCashFlows">
        <link:definition>995200400 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureGoodwillAndIdentifiableIntangibleAssetsNetIdentifiableIntangibleAssetsNetDetails" id="DisclosureGoodwillAndIdentifiableIntangibleAssetsNetIdentifiableIntangibleAssetsNetDetails">
        <link:definition>99940602 - Disclosure - Goodwill and Identifiable Intangible Assets, Net - Identifiable Intangible Assets, Net (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureDebtObligationsDetails" id="DisclosureDebtObligationsDetails">
        <link:definition>99940701 - Disclosure - Debt Obligations (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureLeasesSummaryOfOperatingLeaseAssetsAndLiabilitiesDetails" id="DisclosureLeasesSummaryOfOperatingLeaseAssetsAndLiabilitiesDetails">
        <link:definition>99940802 - Disclosure - Leases - Summary of Operating Lease Assets and Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureLeasesMaturitiesOfLeaseLiabilitiesDetails" id="DisclosureLeasesMaturitiesOfLeaseLiabilitiesDetails">
        <link:definition>99940803 - Disclosure - Leases - Maturities of Lease Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureStockholdersEquityNumberOfSharesDetails" id="DisclosureStockholdersEquityNumberOfSharesDetails">
        <link:definition>99941001 - Disclosure - Stockholders' Equity - Number of Shares (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DocumentDocumentAndEntityInformation" id="DocumentDocumentAndEntityInformation">
        <link:definition>995200090 - Document - Document and Entity Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/StatementConsolidatedBalanceSheetsParenthetical" id="StatementConsolidatedBalanceSheetsParenthetical">
        <link:definition>995200105 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/StatementConsolidatedStatementsOfStockholdersEquity" id="StatementConsolidatedStatementsOfStockholdersEquity">
        <link:definition>995200300 - Statement - CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureBusinessAndOrganization" id="DisclosureBusinessAndOrganization">
        <link:definition>995210101 - Disclosure - Business and Organization</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureSummaryOfSignificantAccountingPoliciesAndEstimates" id="DisclosureSummaryOfSignificantAccountingPoliciesAndEstimates">
        <link:definition>995210201 - Disclosure - Summary of Significant Accounting Policies and Estimates</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureRevenueFromContractsWithCustomers" id="DisclosureRevenueFromContractsWithCustomers">
        <link:definition>995210301 - Disclosure - Revenue from Contracts with Customers</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureFairValueMeasurements" id="DisclosureFairValueMeasurements">
        <link:definition>995210401 - Disclosure - Fair Value Measurements</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureAcquisitions" id="DisclosureAcquisitions">
        <link:definition>995210501 - Disclosure - Acquisitions</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureGoodwillAndIdentifiableIntangibleAssetsNet" id="DisclosureGoodwillAndIdentifiableIntangibleAssetsNet">
        <link:definition>995210601 - Disclosure - Goodwill and Identifiable Intangible Assets, Net</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureDebtObligations" id="DisclosureDebtObligations">
        <link:definition>995210701 - Disclosure - Debt Obligations</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureLeases" id="DisclosureLeases">
        <link:definition>995210801 - Disclosure - Leases</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureCommitmentsAndContingencies" id="DisclosureCommitmentsAndContingencies">
        <link:definition>995210901 - Disclosure - Commitments and Contingencies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureSummaryOfSignificantAccountingPoliciesAndEstimatesPolicies" id="DisclosureSummaryOfSignificantAccountingPoliciesAndEstimatesPolicies">
        <link:definition>99920202 - Disclosure - Summary of Significant Accounting Policies and Estimates (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureRevenueFromContractsWithCustomersTables" id="DisclosureRevenueFromContractsWithCustomersTables">
        <link:definition>99930303 - Disclosure - Revenue from Contracts with Customers (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureFairValueMeasurementsTables" id="DisclosureFairValueMeasurementsTables">
        <link:definition>99930403 - Disclosure - Fair Value Measurements (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureGoodwillAndIdentifiableIntangibleAssetsNetTables" id="DisclosureGoodwillAndIdentifiableIntangibleAssetsNetTables">
        <link:definition>99930603 - Disclosure - Goodwill and Identifiable Intangible Assets, Net (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureDebtObligationsTables" id="DisclosureDebtObligationsTables">
        <link:definition>99930703 - Disclosure - Debt Obligations (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureLeasesTables" id="DisclosureLeasesTables">
        <link:definition>99930803 - Disclosure - Leases (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureStockholdersEquityTables" id="DisclosureStockholdersEquityTables">
        <link:definition>99931003 - Disclosure - Stockholders' Equity (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureSummaryOfSignificantAccountingPoliciesAndEstimatesIncomeTaxesDetails" id="DisclosureSummaryOfSignificantAccountingPoliciesAndEstimatesIncomeTaxesDetails">
        <link:definition>99940201 - Disclosure - Summary of Significant Accounting Policies and Estimates - Income Taxes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureSummaryOfSignificantAccountingPoliciesAndEstimatesInvestmentsDetails" id="DisclosureSummaryOfSignificantAccountingPoliciesAndEstimatesInvestmentsDetails">
        <link:definition>99940202 - Disclosure - Summary of Significant Accounting Policies and Estimates - Investments (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureRevenueFromContractsWithCustomersDisaggregationOfRevenueDetails" id="DisclosureRevenueFromContractsWithCustomersDisaggregationOfRevenueDetails">
        <link:definition>99940302 - Disclosure - Revenue from Contracts with Customers - Disaggregation of Revenue (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureRevenueFromContractsWithCustomersRemainingPerformanceObligationsDetails" id="DisclosureRevenueFromContractsWithCustomersRemainingPerformanceObligationsDetails">
        <link:definition>99940304 - Disclosure - Revenue from Contracts with Customers - Remaining Performance Obligations (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureRevenueFromContractsWithCustomersRemainingPerformanceObligationsDefaultDetails" id="DisclosureRevenueFromContractsWithCustomersRemainingPerformanceObligationsDefaultDetails">
        <link:definition>40304 - Disclosure - Revenue from Contracts with Customers - Remaining Performance Obligations Default (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureFairValueMeasurementsDetails" id="DisclosureFairValueMeasurementsDetails">
        <link:definition>99940401 - Disclosure - Fair Value Measurements (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureAcquisitionsDetails" id="DisclosureAcquisitionsDetails">
        <link:definition>99940501 - Disclosure - Acquisitions (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureGoodwillAndIdentifiableIntangibleAssetsNetChangesInCarryingAmountOfGoodwillDetails" id="DisclosureGoodwillAndIdentifiableIntangibleAssetsNetChangesInCarryingAmountOfGoodwillDetails">
        <link:definition>99940601 - Disclosure - Goodwill and Identifiable Intangible Assets, Net - Changes in Carrying Amount of Goodwill (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureDebtObligationsOtherDetails" id="DisclosureDebtObligationsOtherDetails">
        <link:definition>99940702 - Disclosure - Debt Obligations - Other (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureDebtObligationsNotesToFormerOwnersDetails" id="DisclosureDebtObligationsNotesToFormerOwnersDetails">
        <link:definition>99940703 - Disclosure - Debt Obligations - Notes to Former Owners (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureLeasesDetails" id="DisclosureLeasesDetails">
        <link:definition>99940801 - Disclosure - Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureCommitmentsAndContingenciesDetails" id="DisclosureCommitmentsAndContingenciesDetails">
        <link:definition>99940901 - Disclosure - Commitments and Contingencies (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureStockholdersEquityAntiDilutiveStockBasedAwardsDetails" id="DisclosureStockholdersEquityAntiDilutiveStockBasedAwardsDetails">
        <link:definition>99941002 - Disclosure - Stockholders' Equity - Anti-Dilutive Stock-Based Awards (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureStockholdersEquityIncentiveAndOtherDetails" id="DisclosureStockholdersEquityIncentiveAndOtherDetails">
        <link:definition>99941003 - Disclosure - Stockholders' Equity - Incentive and Other (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureSegmentInformationDetails" id="DisclosureSegmentInformationDetails">
        <link:definition>99941101 - Disclosure - Segment Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/StatementConsolidatedStatementsOfStockholdersEquityParenthetical" id="StatementConsolidatedStatementsOfStockholdersEquityParenthetical">
        <link:definition>995200305 - Statement - CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureStockholdersEquity" id="DisclosureStockholdersEquity">
        <link:definition>995211001 - Disclosure - Stockholders' Equity</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureSegmentInformation" id="DisclosureSegmentInformation">
        <link:definition>995211101 - Disclosure - Segment Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureSegmentInformationTables" id="DisclosureSegmentInformationTables">
        <link:definition>99931103 - Disclosure - Segment Information (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureRevenueFromContractsWithCustomersNarrativesDetails" id="DisclosureRevenueFromContractsWithCustomersNarrativesDetails">
        <link:definition>99940301 - Disclosure - Revenue from Contracts with Customers - Narratives (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.comfortsystemsusa.com/role/DisclosureRevenueFromContractsWithCustomersContractAssetsAndLiabilitiesDetails" id="DisclosureRevenueFromContractsWithCustomersContractAssetsAndLiabilitiesDetails">
        <link:definition>99940303 - Disclosure - Revenue from Contracts with Customers - Contract Assets and Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:linkbaseRef xlink:type="simple" xlink:href="fix-20260331_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
      <link:linkbaseRef xlink:type="simple" xlink:href="fix-20260331_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
      <link:linkbaseRef xlink:type="simple" xlink:href="fix-20260331_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
      <link:linkbaseRef xlink:type="simple" xlink:href="fix-20260331_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:import namespace="https://xbrl.org/2023/calculation-1.1" schemaLocation="https://www.xbrl.org/2023/calculation-1.1.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/ecd/2025" schemaLocation="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/dei/2025" schemaLocation="https://xbrl.sec.gov/dei/2025/dei-2025.xsd" />
  <xsd:import namespace="http://www.xbrl.org/dtr/type/2024-01-31" schemaLocation="https://www.xbrl.org/dtr/type/2024-01-31/types.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2009/role/negated" schemaLocation="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd" />
  <xsd:import namespace="http://fasb.org/us-roles/2025" schemaLocation="https://xbrl.fasb.org/us-gaap/2025/elts/us-roles-2025.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
  <xsd:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
  <import namespace="http://fasb.org/us-gaap/2025" schemaLocation="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd" xmlns="http://www.w3.org/2001/XMLSchema" />
  <import namespace="http://fasb.org/srt/2025" schemaLocation="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd" xmlns="http://www.w3.org/2001/XMLSchema" />
  <xsd:import namespace="http://xbrl.sec.gov/ecd-sub/2025" schemaLocation="https://xbrl.sec.gov/ecd/2025/ecd-sub-2025.xsd" />
  <xsd:element name="MarketRatesAbstract" id="fix_MarketRatesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ContingentConsiderationObligationsMember" id="fix_ContingentConsiderationObligationsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <element id="fix_EffectOfUsingWeightedAverageCommonSharesOutstanding" name="EffectOfUsingWeightedAverageCommonSharesOutstanding" nillable="true" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ScheduleOfAdditionalMarginsTableTextBlock" name="ScheduleOfAdditionalMarginsTableTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <xsd:element name="DebtCovenantEffectiveDateAxis" id="fix_DebtCovenantEffectiveDateAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantEffectiveDateDomain" id="fix_DebtCovenantEffectiveDateDomain" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <element id="fix_DebtInstrumentInterestRateOptionsNumber" name="DebtInstrumentInterestRateOptionsNumber" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <xsd:element name="PercentageOfBusinessWhichHasRequiredBonds" id="fix_PercentageOfBusinessWhichHasRequiredBonds" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantRatioAxis" id="fix_DebtCovenantRatioAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantRatioDomain" id="fix_DebtCovenantRatioDomain" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantRatioRangeOneMember" id="fix_DebtCovenantRatioRangeOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantRatioRangeTwoMember" id="fix_DebtCovenantRatioRangeTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantRatioRangeThreeMember" id="fix_DebtCovenantRatioRangeThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtCovenantRatioRangeFourMember" id="fix_DebtCovenantRatioRangeFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <element id="fix_LineOfCreditBorrowingCapacityAccordionOption" name="LineOfCreditBorrowingCapacityAccordionOption" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_DebtInstrumentVariableRateSecondaryClassificationAxis" name="DebtInstrumentVariableRateSecondaryClassificationAxis" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_DebtInstrumentVariableRateSecondaryClassificationDomain" name="DebtInstrumentVariableRateSecondaryClassificationDomain" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_StockRepurchaseProgram2007Member" name="StockRepurchaseProgram2007Member" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_NewConstructionMember" name="NewConstructionMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ExistingBuildingConstructionMember" name="ExistingBuildingConstructionMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ServiceCallsMaintenanceAndMonitoringMember" name="ServiceCallsMaintenanceAndMonitoringMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_EducationMember" name="EducationMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_RetailRestaurantsAndEntertainmentMember" name="RetailRestaurantsAndEntertainmentMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_MultiFamilyAndResidentialMember" name="MultiFamilyAndResidentialMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_PercentageOfRevenueFromContractWithCustomer" name="PercentageOfRevenueFromContractWithCustomer" nillable="true" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_RenewableServiceMaintenanceAgreementsTerm" name="RenewableServiceMaintenanceAgreementsTerm" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ServiceProjectsMember" name="ServiceProjectsMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_OfficeBuildingCustomerMember" name="OfficeBuildingCustomerMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_HealthcareSectorCustomerMember" name="HealthcareSectorCustomerMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_GovernmentCustomerMember" name="GovernmentCustomerMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_NumberOfOptionsToRenew" name="NumberOfOptionsToRenew" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ScheduleOfLeaseAssetsAndLiabilitiesTableTextBlock" name="ScheduleOfLeaseAssetsAndLiabilitiesTableTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_VariableLeaseAndShortTermLeaseCost" name="VariableLeaseAndShortTermLeaseCost" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_ChangeInRightOfUseAssets" name="ChangeInRightOfUseAssets" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_UnbilledAccountsReceivableAllowanceForCreditLoss" name="UnbilledAccountsReceivableAllowanceForCreditLoss" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour" name="LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="fix_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFour" name="FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFour" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <xsd:element name="DebtMaturityDateAxis" id="fix_DebtMaturityDateAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="DebtMaturityDateDomain" id="fix_DebtMaturityDateDomain" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="MaturityYearOneMember" id="fix_MaturityYearOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="MaturityYearTwoMember" id="fix_MaturityYearTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="DebtCovenantRatioRangeFiveMember" id="fix_DebtCovenantRatioRangeFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="TechnologyMember" id="fix_TechnologyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="ManufacturingCustomerMember" id="fix_ManufacturingCustomerMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="MechanicalSegmentMember" id="fix_MechanicalSegmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="ElectricalSegmentMember" id="fix_ElectricalSegmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriodPercentage" id="fix_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriodPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="OtherDebtMember" id="fix_OtherDebtMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="CenturyContractorsInc.Member" id="fix_CenturyContractorsInc.Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="InvestmentMaturityPeriod" id="fix_InvestmentMaturityPeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="InterestIncomeRefundOfIncomeTaxes" id="fix_InterestIncomeRefundOfIncomeTaxes" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="InterestIncomeNetOfTaxExpenseOnRefundOfIncomeTaxes" id="fix_InterestIncomeNetOfTaxExpenseOnRefundOfIncomeTaxes" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="RightWayPlumbingAndMechanicalLlcMember" id="fix_RightWayPlumbingAndMechanicalLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="MechanicalContractorNewYorkMember" id="fix_MechanicalContractorNewYorkMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="FeyenZylstraHoldingsLlcMember" id="fix_FeyenZylstraHoldingsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="MeisnerElectricIncMember" id="fix_MeisnerElectricIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
</xsd:schema>
