Comfort Systems USA Quality People. Building Solutions. March 16, 2015

Safe Harbor Certain statements and information in this presentation may constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. The words “believe,” “expect,” “anticipate,” “plan,” “intend,” “foresee,” “should,” “would,” “could,” or other similar expressions are intended to identify forward-looking statements, which are generally not historic in nature. These forward-looking statements are based on the current expectations and beliefs of Comfort Systems USA, Inc. and its subsidiaries (collectively, the “Company”) concerning future developments and their effect on the Company. While the Company’s management believes that these forward-looking statements are reasonable as and when made, there can be no assurance that future developments affecting the Company will be those that it anticipates. All comments concerning the Company’s expectations for future revenues and operating results are based on the Company’s forecasts for its existing operations and do not include the potential impact of any future acquisitions. The Company’s forward-looking statements involve significant risks and uncertainties (some of which are beyond the Company’s control) and assumptions that could cause actual future results to differ materially from the Company’s historical experience and its present expectations or projections. Important factors that could cause actual results to differ materially from those in the forward-looking statements include, but are not limited to: the use of incorrect estimates for bidding a fixed-price contract; undertaking contractual commitments that exceed the Company’s labor resources; failing to perform contractual obligations efficiently enough to maintain profitability; national or regional weakness in construction activity and economic conditions; financial difficulties affecting projects, vendors, customers, or subcontractors; the Company’s backlog failing to translate into actual revenue or profits; failure of third party subcontractors and suppliers to complete work as anticipated; difficulty in obtaining or increased costs associated with bonding and insurance; impairment to goodwill; errors in the Company’s percentage-of-completion method of accounting; the result of competition in the Company’s markets; the Company’s decentralized management structure; material failure to comply with varying state and local laws, regulations or requirements; debarment from bidding on or performing government contracts; shortages of labor and specialty building materials; retention of key management; seasonal fluctuations in the demand for HVAC systems; the imposition of past and future liability from environmental, safety, and health regulations including the inherent risk associated with self-insurance; adverse litigation results; an increase in our effective tax rate; a cyber security breach; and other risks detailed in our reports filed with the Securities and Exchange Commission. For additional information regarding known material factors that could cause the Company’s results to differ from its projected results, please see its filings with the SEC, including its Annual Report on Form 10-K, Quarterly Reports on Form 10-Q, and Current Reports on Form 8-K. Readers are cautioned not to place undue reliance on forward-looking statements, which speak only as of the date hereof. The Company undertakes no obligation to publicly update or revise any forward-looking statements after the date they are made, whether as a result of new information, future events, or otherwise. Non-GAAP Measures Certain measures in this presentation are not measures calculated in accordance with generally accepted accounting principles (GAAP). They should not be considered a replacement for GAAP results. Non-GAAP financial measures appearing in these slides are identified in the footnote. See the Appendices for a reconciliation of these non-GAAP measures to the most comparable GAAP financial measures.

Comfort Systems USA 2 Leading mid-market HVAC and mechanical systems installation and service provider $1.4B Yearly revenues 7,000+ Employees 37 Operating companies Balanced construction & service portfolio

Broad Nationwide Footprint 3 37 companies | 92 locations in 83 cities | 7,000+ employees

Revenue/Stock Price History 4 Revenue ($ in millions) Acquisition Phase and Industry Growth Sale of Assets New Acquisitions Stock Price at 12/31

Lifecycle Product Portfolio 5 5+ million nonresidential buildings Building solutions a necessity Diverse revenue streams throughout lifecycle 10 - 20 year replacement cycle Recurring service Increasing technical content Essential to energy efficiency

Targeted Portfolio Strategy 6 Light commercial to heavy commercial Continue to grow construction Leverage existing construction capabilities into retrofit market Access to new customers through service Data and manufacturing Revenue by Activity

Market Sectors 7 December 2014 YTD Revenue Commercial Institutional Industrial

Book of Business 8 ($ in millions)

Diverse Project Mix 9 Average Project Size: $0.5M | Average Project Length: 6–9 months (Information as of December 31, 2014) Aggregate Contract Value Jobs <$1M (Value: $381M) Jobs $1M–$5M (Value: $683M) Jobs >$5M (Value: $924M)

Historical Financial Summary ($ in millions, except per share information) 10 (1) Adjusted EPS is a non-GAAP financial measure. Adjusted EPS excludes goodwill impairments, changes in the fair value of contingent earn-out obligations and tax valuation allowances. See Appendix IV for a GAAP reconciliation to Adjusted EPS. (2) Adjusted EBITDA is a non-GAAP financial measure. See Appendix III for a GAAP reconciliation to Adjusted EBITDA.

Historical Financial Summary 11 (1) Operating income for 2011 excludes goodwill impairment of $57.4M. (2) Adjusted EBITDA is a non-GAAP financial measure. See Appendix III for a GAAP reconciliation to Adjusted EBITDA.

Balance Sheet Strength $32.1M cash at December 31, 2014 Positive free cash flow for 16 consecutive years Debt capacity $40M debt at 12/31/2014 $250M revolving credit facility 2019 maturity 12

Profile for Growth 13 Time Earnings Grow Service Innovate Acquire Service Commercial HVAC Grow Construction

Our Strengths 14 Long-term local relationships Collaboration Safety excellence Purchasing economics National service capability Bonding and insurance Balance sheet strength

Thank You 15 $1.4 Billion $1.4 billion in yearly revenues 92 Locations Operating 37 companies across America at 92 locations in 83 cities Over 7,000 of the most qualified HVAC and Mechanical systems personnel in the USA 7,000+ Employees

Appendix 16

 Appendix I – QTD & YTD Financial Performance 17 Three Months Ended ($ in millions, except per share information) 12/31/14 12/31/13 Revenue $356.5 $330.3 Net Income from Continuing Operations Attributable to Comfort Systems USA, Inc. $10.7 $5.6 Diluted EPS from Continuing Operations Attributable to Comfort Systems USA, Inc. $0.29 $0.15 Adjusted EBITDA (1) $20.8 $13.5 Operating Cash Flow $5.1 $14.6 (1)Adjusted EBITDA is a non-GAAP financial measure. See Appendix II for a GAAP reconciliation to Adjusted EBITDA. Twelve Months Ended ($ in millions, except per share information) 12/31/14 12/31/13 Revenue $1,410.8 $1,357.3 Net Income from Continuing Operations Attributable to Comfort Systems USA, Inc. $23.1 $27.3 Diluted EPS from Continuing Operations Attributable to Comfort Systems USA, Inc. $0.61 $0.73 Adjusted EBITDA (1) $63.5 $64.2 Operating Cash Flow $42.5 $38.4

 Appendix II – GAAP Reconciliation to Adjusted EBITDA 18 Note: The Company defines adjusted earnings before interest, taxes, depreciation and amortization (“Adjusted EBITDA”) as net income (loss) including non-controlling interests, excluding discontinued operations, income taxes, other (income) expense, net, changes in the fair value of contingent earn-out obligations, interest expense, net, gain on sale of assets, and depreciation and amortization. Other companies may define Adjusted EBITDA differently. Adjusted EBITDA is presented because it is a financial measure that is frequently requested by third parties. However, Adjusted EBITDA is not considered under generally accepted accounting principles as a primary measure of an entity’s financial results, and accordingly, Adjusted EBITDA should not be considered an alternative to operating income (loss), net income (loss), or cash flows as determined under generally accepted accounting principles and as reported by the Company. Three Months Ended December 31, Twelve Months Ended December 31, ($ in thousands) 2014 2013 2014 2013 Net Income Including Non-controlling Interests $11,821 $5,935 $28,599 $28,556 Discontinued Operations - (3) 15 76 Income Taxes 2,527 3,782 11,614 18,148 Other (Income) Expense, net 13 (20) (91) (204) Changes in the Fair Value of Contingent Earn-out Obligations 35 (950) 245 (1,646) Interest Expense, net 496 315 1,840 1,328 Gain on Sale of Assets (82) (222) (830) (589) Goodwill Impairment - - 727 - Depreciation and Amortization 5,974 4,653 21,336 18,554 Adjusted EBITDA $20,784 $13,490 $63,455 $64,223

 Appendix III – GAAP Reconciliation to Adjusted EBITDA (Historical) 19 Note: The Company defines adjusted earnings before interest, taxes, depreciation and amortization (“Adjusted EBITDA”) as net income (loss) including non-controlling interests, excluding discontinued operations, income taxes, other (income) expense, net, changes in the fair value of contingent earn-out obligations, interest (income) expense, net, loss (gain) on sale of assets, goodwill impairment and depreciation and amortization. Other companies may define Adjusted EBITDA differently. Adjusted EBITDA is presented because it is a financial measure that is frequently requested by third parties. However, Adjusted EBITDA is not considered under generally accepted accounting principles as a primary measure of an entity’s financial results, and accordingly, Adjusted EBITDA should not be considered an alternative to operating income (loss), net income (loss), or cash flows as determined under generally accepted accounting principles and as reported by the Company. Year Ended December 31, ($ in thousands) 2008 2009 2010 2011 2012 2013 2014 Net Income (Loss) Including Non-controlling Interests $49,690 $34,182 $14,740 ($36,492) $11,849 $28,556 $28,599 Discontinued Operations 107 (1,282) 5,824 4,018 (355) 76 15 Income Taxes 30,855 20,307 11,193 (5,463) 10,045 18,148 11,614 Other (Income) Expense, net (68) (17) (247) (934) (145) (204) (91) Changes in the Fair Value of Contingent Earn-out Obligations - - (1,574) (5,528) (662) (1,646) 245 Interest (Income) Expense, net (1,154) 622 1,506 1,758 1,571 1,328 1,840 Loss (Gain) on Sale of Assets (290) (106) (527) (236) (491) (589) (830) Goodwill Impairment - - - 57,354 - - 727 Depreciation and Amortization 12,325 12,635 16,718 18,982 20,569 18,554 21,336 Adjusted EBITDA $91,465 $66,341 $47,633 $33,459 $42,381 $64,223 $63,455

 Appendix IV – Supplemental Non-GAAP Information (Historical) 20 Note 1: Operating results from continuing operations attributable to Comfort Systems USA, Inc., excluding goodwill impairment, changes in the fair value of contingent earn-out obligations, tax valuation allowances and out of period adjustment are presented because the Company believes it reflects the results of the core ongoing operations of the Company, and because we believe it is responsive to frequent questions we receive from third parties. However, this measure is not considered a primary measure of an entity’s financial results under generally accepted accounting principles, and accordingly, this amount should not be considered an alternative to operating results as determined under generally accepted accounting principles and as reported by the Company. Note 2: Net income (loss) from continuing operations attributable to Comfort Systems USA, Inc. is income (loss) from continuing operations less net income attributable to non-controlling interests. Note 3: The tax rate on these items was computed using the pro forma effective tax rate of the Company exclusive of these charges. Note 4: Correction of prior period accounting errors in 2013 resulted in net after-tax income of approximately $1.3 million, or $0.03 per diluted share. Year Ended December 31, 2008 2009 2010 2011 2012 2013 2014 Diluted income (loss) per share from continuing operations attributable to Comfort Systems USA, Inc. $1.24 $0.86 $0.54 $(0.88) $0.35 $0.73 $0.61 Goodwill Impairment - - - 1.20 - - 0.01 Changes in the fair value of contingent earn-out obligations - - (0.02) (0.14) (0.02) (0.04) - Tax valuation allowances - - - 0.05 - - (0.08) Out of period adjustment - - - - - (0.03) - Net income from continuing operations attributable to Comfort Systems USA, Inc. excluding goodwill impairment, changes in the fair value of contingent earn-out obligations, tax valuation allowances and out of period adjustment $1.24 $0.86 $0.52 $0.23 $0.33 $0.66 $0.54

 Contact Bill George Executive Vice President and CFO 1-800-723-8431 bill.george@comfortsystemsusa.com www.comfortsystemsusa.com 21