Partners Group's PremiStar Adds MSS: Inside the $2B HVAC Roll-Up That PE Loves

On June 10, 2026, commercial HVAC platform PremiStar, owned by Zug-based private equity firm Partners Group, announced the acquisition of Mechanical Service & Systems (MSS), a Salt Lake City mechanical services contractor. The deal is PremiStar's 40th add-on acquisition since Partners Group took control of the platform in 2021 under the name Reedy Industries. No purchase price was disclosed. D.A. Davidson & Co. advised MSS on the sale.

If you follow PE-backed services roll-ups, you have seen this movie before. The question worth asking right now is not whether the deal closed. It is whether the math still works for the LPs sitting behind it.

What PremiStar Actually Is

Partners Group acquired Reedy Industries in 2021 at roughly a $1 billion enterprise value. The firm rebranded the platform PremiStar and handed CEO Joe Kirmser a mandate: consolidate fragmented commercial HVAC service providers across the country. Over five years, Kirmser executed that mandate aggressively. PremiStar now runs 62 branches across 19 states, employs more than 3,100 people, and has raised $2.09 billion in total platform funding. Revenue and EBITDA have grown more than 6x since 2019.

MSS adds Utah as state number 19 and plugs PremiStar into customers in manufacturing, aerospace, life sciences, and mining. Rick Cowley, MSS President, stays on to lead the Utah operation. Prior add-ons include Air Temp Holding and Armistead Mechanical, among dozens of others.

The business model is straightforward. Buy regional commercial HVAC contractors at 5 to 8x EBITDA. Centralize back-office functions. Cross-sell maintenance contracts. Grow recurring revenue. Then sell the combined platform at a materially higher multiple. That spread between entry price and exit price is what generates LP returns.

Why PE Has Decided HVAC Is the Trade

Global PE add-on transactions targeting HVAC service providers rose 88% year-over-year through early June 2026, per Capstone Partners data cited by S&P Global. PE firms accounted for 39 of 77 HVAC M&A deals year-to-date by that same measure. This is not a coincidence.

Three structural drivers explain the attention. First, the fragmentation is genuinely extreme. There are more than 29,000 private commercial HVAC service companies in North America. Most are owner-operated, generate $2 million to $20 million in revenue, and have no succession plan. That is a buyer's market for anyone with capital and a platform to roll into.

Second, the revenue profile holds up through downturns. Commercial buildings need their HVAC systems maintained whether the economy is expanding or contracting. Regulatory compliance, tenant retention, and liability all create non-discretionary demand. Maintenance contracts produce predictable, recurring cash flows that lenders and buyers underwrite at premium multiples.

Third, the data center buildout has changed the demand curve in a material way. Microsoft, Google, Amazon, and Meta are building cooling-intensive AI infrastructure at a pace the commercial mechanical services sector has never served before. PremiStar's customer mix already includes data centers. As that segment grows, so does the serviceable addressable market for the platform's highest-margin offerings.

The global commercial HVAC services market is valued above $350 billion and growing at more than 5% annually through 2033. Commercial is still earlier in its consolidation cycle than residential HVAC, per PKF Investment Banking. That timing argument has driven capital from Blackstone (Champions Group, acquired at roughly $2.5 billion and approximately 18.5x EBITDA in February 2026), Bain Capital, Goldman Sachs Alternatives, Altas Partners, and others into the sector simultaneously.

The Buy-and-Build Economics: Where the Returns Come From

Here is the core math you need to understand before evaluating any roll-up investment, including PremiStar.

Partners Group buys tuck-in contractors at 5 to 8x EBITDA. A regional HVAC operator doing $3 million in EBITDA might sell for $18 to $24 million. Once that business is folded into a $200 million-plus EBITDA platform with diversified geography, blue-chip customers, and contracted revenue, the combined entity commands a platform multiple of 15 to 20x. That same $3 million of EBITDA (now part of PremiStar) is implicitly worth $45 to $60 million at exit.

That arithmetic is called multiple arbitrage, and it is the primary return driver in buy-and-build strategies. Secondary drivers include organic revenue growth, margin improvement from shared services, and EBITDA growth from cross-selling. But the multiple expansion from tuck-in entry to platform exit is where the headline returns live.

Blackstone's $2.5 billion Champions Group deal at approximately 18.5x EBITDA sets a recent public comp. If PremiStar exits at a comparable multiple on its current EBITDA base, which has grown 6x since 2019, the platform-level return to Partners Group is substantial. The question is whether that multiple holds in 2027 or 2028 when Partners Group needs to sell.

Partners Group Context: $185B in AUM and LPs Who Need Returns

Partners Group is not a small fund. The firm reported $185 billion in assets under management as of December 31, 2025, up from $152 billion at year-end 2024, with a stated target of $450 billion by 2033. In 2025 alone, Partners Group generated $26 billion in realizations across its portfolio.

The firm's flagship private equity programs target institutional investors. Sovereign wealth funds, pension plans, and university endowments commit at minimums of $5 to $10 million or more. If you are an accredited individual investor, your access point is a feeder vehicle through platforms like iCapital or CAIS, typically at $100,000 to $250,000 minimums.

Partners Group's direct equity strategy has committed roughly $4 billion to services businesses since 2020. PremiStar is the clearest public example of how that capital gets deployed: identify a fragmented sector, acquire a platform, execute aggressive add-ons, and position for a premium exit.

Four Risks the Press Release Does Not Mention

The June 10 announcement is written for customers and recruits, not LPs. Here is what it omits.

1. Multiple compression is accelerating. When Partners Group bought Reedy Industries in 2021, commercial HVAC platforms traded at 10 to 12x EBITDA. Blackstone paid 18.5x for Champions Group in February 2026. That means the arbitrage spread between tuck-in entry (5 to 8x) and platform exit (17 to 20x) is narrowing mathematically with each year and each deal. The 40th add-on creates less incremental multiple expansion than the 10th did. If commercial HVAC matures into a fully institutionalized sector (which the current wave of capital is actively causing), exit multiples could compress back toward 13 to 15x before Partners Group finds its buyer. That compression directly reduces LP returns.

2. The year-5 exit overhang is real. Partners Group acquired PremiStar in 2021. Five years is the standard LP horizon for a buyout fund investment. At $185 billion in AUM, the firm needs to keep generating realizations: $26 billion worth in 2025 alone. LPs in Partners Group's flagship vehicles should be asking a direct question right now. Is PremiStar heading toward a recap, a secondary sale, or a strategic exit in 2026 or 2027? What does that exit look like when commercial real estate vacancy rates remain structurally elevated and a significant portion of the customer base serves office buildings that may never return to pre-2020 occupancy? A forced exit at an inconvenient point in the cycle is a known PE risk, and PremiStar is approaching that window.

3. MSS brings customer concentration you should price in. Utah's industrial base is dominated by mining (Rio Tinto operates the Kennecott copper mine, one of the largest copper mines in the world), aerospace manufacturing, and defense contractors. These are not the stable, non-discretionary customers that make commercial HVAC attractive in the first place. Mining capex is tied to commodity prices. Aerospace manufacturing is exposed to defense spending cycles and supply chain disruptions. If MSS's top three clients represent 40% or more of its revenue — a common pattern in regional contractors — PremiStar just absorbed meaningful concentration risk in a cyclical sector. That risk does not disappear once MSS is folded into the platform's financials.

4. The real LP cost through feeder vehicles is high. Individual accredited investors accessing Partners Group through iCapital or CAIS pay 1.5 to 2% annual management fees plus 20% carried interest on top of whatever the underlying Partners Group fund charges. On a roll-up already trading near peak multiples with a narrow arbitrage window, that fee structure requires the fund to generate significantly higher gross returns just to deliver competitive net returns to you. A 20% gross IRR at the fund level might net to 12 to 14% after layered fees and carry. That is not unreasonable for private equity, but it is not the 20% headline number either. Know what you are actually paying before you commit capital through a feeder.

What Accredited Investors Should Actually Do With This

PremiStar is a well-run platform executing a proven strategy in a sector with real structural tailwinds. Joe Kirmser's team has delivered 6x revenue and EBITDA growth in five years. That is not marketing copy. It reflects genuine operational execution across 40 acquisitions in a fragmented, relationship-driven industry.

But you are not evaluating PremiStar in 2021. You are evaluating it in 2026, after 40 add-ons, after sector multiples have re-rated upward by 60 to 80%, after five years of hold period, and with an exit window that is opening whether the market timing is favorable or not.

If you have exposure to Partners Group through your portfolio, the MSS announcement confirms the platform is still executing, and that is useful information. If you are considering a new commitment to a Partners Group vehicle or a similar HVAC roll-up fund, the right questions to push on are specific ones. What is the estimated hold period remaining on the flagship vehicle? What does the fund's current unrealized portfolio look like at current market multiples versus cost? What portion of the fund's EBITDA base serves commercial real estate versus more resilient customer verticals like data centers and healthcare?

The HVAC roll-up thesis is not broken. But at 40 acquisitions and a 17 to 20x sector benchmark, you are no longer buying early-cycle optionality. You are buying late-cycle execution risk at a price that reflects most of the good news already.

Watch the exit announcement when it comes, likely in 2027. That is the data point that will tell you whether the buy-and-build math held at scale.

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Disclosure: Angel Investors Network and Jeff Barnes, MBA do not hold positions in Partners Group (PGHN), PremiStar, or any related vehicle referenced in this article. This article is for informational purposes only and does not constitute investment advice. Private equity investments involve substantial risk of loss and are appropriate only for sophisticated investors who can bear the loss of their entire investment. Always consult a qualified financial advisor before making investment decisions.

Author Disclosure: Jeff Barnes, MBA has no personal position in any company, fund, or platform named in this article. Angel Investors Network has no current commercial relationship with any party mentioned. AIN provides marketing and education services, not investment advice. Past performance does not guarantee future results. All investments involve risk, including loss of principal.