The HVAC Industry's Software Problem — And Why Engineers Are Building Their Own Tools

The State of MEP Software in 2025

Let me describe a typical day for an HVAC engineer in Germany.

You arrive at the office. You open Revit to work on the ventilation layout for a hospital project. You need to verify that your duct sizing meets the design airflow requirements from the ventilation concept. The concept was calculated in a different software — Solar Computer — so you open that too. The climate data comes from a DIN standard, which you reference from a PDF on your desktop. The architect just changed the room layout, so you need to update the room dimensions. You copy them from Revit, paste them into Solar Computer, re-run the calculation, and manually check if the duct sizes in your Revit model still match.

Then you get an email: the energy consultant needs the heating load calculation in Hottgenroth format, but your calculation was done in Solar Computer, and the two tools don't share data. So you re-enter the building parameters into Hottgenroth — the same U-values, the same room dimensions, the same climate data — for the third time today.

It's 11 AM. You haven't done any actual engineering.

This is not a caricature. This is the daily reality for thousands of MEP engineers across Germany, Austria, and Switzerland. And it's a problem that software should have solved a decade ago.

Why the Existing Tools Fall Short

The dominant MEP calculation tools in the DACH market haven't fundamentally changed since the early 2000s:

Solar Computer

Market leader for heating/cooling load calculations. The interface looks like it was designed for Windows XP — because it was. Competent calculation engine, but strictly desktop-bound, single-user, no API, no integration with BIM tools beyond basic IFC import.

Hottgenroth

Strong in energy consulting and KfW subsidy calculations. Similar vintage. Known for producing the exact report formats that building authorities expect — which is why consultants stick with it despite the UX.

Trimble Nova (formerly Plancal)

Integrated with Revit for MEP calculations. The closest thing to a modern tool, but expensive (€5,000+/year) and tightly coupled to the Trimble ecosystem.

The Common Problems

The result: mechanical engineers spend more time wrestling with software than doing engineering.

The Excel Problem

When the licensed software is too expensive or too rigid, engineers fall back to Excel. And Excel, for all its flexibility, is a terrible platform for engineering calculations:

• No version control. Which version of the spreadsheet has the latest climate data? The one in your email, the one on the server, or the one on your desktop?
• No validation. A mistyped U-value (0.28 vs 2.8) silently propagates through the entire calculation. No warnings, no bounds checking.
• No reusability. Every firm has its own Excel template for DIN EN 12831, each with slightly different assumptions, different cell layouts, and different bugs.
• No collaboration. Two engineers can't work on the same calculation simultaneously.
• No audit trail. Good luck explaining to a building authority reviewer which cells in your 47-tab workbook correspond to which clauses in the standard.

Excel is the default because it's accessible and flexible. But "accessible and flexible" shouldn't mean "error-prone and unmaintainable."

Why Now? What Changed?

Three trends are converging to make this the right time for cloud-native MEP tools:

1. The BIM Mandate

Germany's public sector increasingly requires BIM (Building Information Modeling) for construction projects. BIM means digital building models, standardized data exchange, and — crucially — the expectation that design data flows between tools without manual re-entry.

If the industry is mandating digital workflows, the calculation tools need to be digital-native too. A desktop application that can't read from a BIM model or write back to one is a dead end.

2. The Generational Shift

A new generation of engineers is entering the workforce. They grew up with web apps, cloud storage, and real-time collaboration (Google Docs, Figma, Notion). They expect their professional tools to work the same way.

When a 25-year-old engineer joins a firm and is handed a Windows XP-era desktop application with a 300-page PDF manual, the reaction is predictable: "There has to be a better way."

3. The Energy Transition

Germany's Gebäudeenergiegesetz (GEG) and the push for climate-neutral buildings mean more complex calculations: heat pump sizing, renewable energy integration, KfW subsidy optimization. These calculations cross multiple standards and require iteration — exactly the kind of workflow that benefits from automation and integration.

What Cloud-Native MEP Tools Could Look Like

Imagine a world where:

Your heating load calculation talks to your BIM model. You draw a room in Revit, and its heating load is automatically calculated in the cloud. Change a window U-value in the model, and the heating load updates in real time.

Standards are modular and composable. Need the heating load (DIN EN 12831), then the ventilation sizing (DIN 1946-6), then the heat pump dimensioning (VDI 4645)? Each calculation feeds into the next automatically — same building data, no re-entry.

Results are transparent and auditable. Every number links back to the specific clause in the standard that produced it. A reviewer can click on "Φ_T = 1,847 W" and see exactly which envelope components, U-values, and temperature differences went into that result.

Collaboration is built in. Multiple engineers work on the same project. The structural engineer updates the wall composition, and the MEP engineer's heating load calculation updates accordingly.

Reports generate themselves. The building authority gets a PDF that matches their expected format — not because the engineer spent two hours formatting it, but because the tool produces it automatically.

This isn't science fiction. This is what Mepbau is building.

Why Engineers — Not Software Companies — Will Build These Tools

The big AEC software companies (Autodesk, Trimble, Nemetschek) have the resources to build cloud-native MEP calculation tools. But they haven't. Why?

Incentive misalignment. Their revenue comes from desktop license renewals. Moving to cloud-based SaaS would cannibalize existing revenue streams and require entirely new product architectures.

Domain distance. Software companies hire software engineers, not HVAC engineers. Understanding how DIN EN 12831 works — really understanding it, including the edge cases and regional variations — requires years of domain experience.

Market fragmentation. The DACH MEP market is relatively small compared to, say, architectural design software. The ROI on building a cloud-native DIN EN 12831 tool doesn't justify a large company's investment.

This creates an opening for engineer-developers — people who understand both the domain and the technology. People who have spent years doing heating load calculations by hand and know exactly where the pain is. People who can read a DIN standard and write a Python implementation of it.

I don't think the next generation of MEP tools will come from Autodesk or Trimble. I think they'll come from engineers who taught themselves to code, got frustrated with the status quo, and decided to build something better.

The Hard Part: Trust

Technical implementation is the easy part. The hard part is earning the trust of an industry that's understandably conservative.

When an engineer stamps a calculation, they're personally liable. If the heating system is undersized and the building doesn't reach 20°C in January, the engineer — not the software vendor — faces consequences. No wonder they're reluctant to switch from a tool they've used for 15 years to a web app built by someone they've never heard of.

Earning that trust requires:

1. Transparency. Show every intermediate value. Reference every standard clause. Let the engineer follow the math.
2. Validation. Publish benchmark results against reference calculations and competing software. Don't just say your tool is accurate — prove it.
3. Compliance. Support the exact report formats that building authorities expect. A brilliant calculation engine is useless if the output doesn't match the required PDF template.
4. Community. Build in public. Share your methodology. Let engineers audit your approach before they trust it with their projects.

The Road Ahead

The HVAC industry's software problem isn't going to solve itself. The incumbents have no incentive to disrupt themselves. The standard bodies publish PDFs, not APIs. And the engineers who need better tools are too busy doing manual calculations to build them.

But the window is opening. BIM mandates are pushing the industry toward digital workflows. The energy transition is making calculations more complex and more frequent. And a generation of engineers who are comfortable with code is entering the workforce.

The tools that serve them need to be cloud-native, standards-compliant, transparent, and affordable. They need to be built by people who understand both the engineering and the technology.

I'm building one of them. If you see the same opportunity, I'd love to talk.

Working on software for the construction industry? Building tools for MEP engineers? Let's connect — hello@laborsam.com.