Why the choice carries so much weight
Building services account for a substantial share of construction cost in modern buildings — and for practically all energy consumption in operation. Buildings represent around 40 per cent of Swiss energy consumption and roughly a quarter of national CO₂ emissions. Whoever decides on the building services co-decides decades of operating cost.
At the same time, building services are a black box for most clients. That is why they are often awarded on the one criterion that can be compared without technical knowledge: the fee. Understandable — and expensive, because cheap proposals usually economise precisely where the effect would be greatest: concept work, trade coordination and site supervision.
1. Is the scope clearly delimited under SIA 108?
SIA 108:2020 defines the project phases — strategic planning, preliminary studies, design, tendering, realisation and operation — and the associated part-services. A sound proposal states exactly which of these are included and which are not.
Without that delimitation you are comparing apples with pears. The cheapest proposal is then frequently the one that omits the most, and the difference returns later as a variation. If in doubt, ask for the scope to be shown phase by phase in a table.
2. Is trade coordination explicitly included?
The most expensive errors do not arise within a discipline but between disciplines: a duct clashes with a downstand beam, a riser is undersized, a penetration is missing. Trade coordination means somebody owns the spatial alignment of every technical discipline with architecture and structure.
It is a service in its own right with its own effort. If it is not mentioned in the proposal it is usually not included — and on site it ends up belonging to nobody.
3. Does one office cover every discipline?
HLKS covers heating, ventilation, air conditioning and plumbing; HLKKSE adds refrigeration and electrical services. The more disciplines an office designs itself, the fewer interfaces you have to manage. Where packages are split, you need a named party responsible for overall coordination — otherwise everyone waits for everyone else.
4. Do the references genuinely match your project?
A reference list impresses quickly. What counts is the fit: building category, plant complexity and above all new build versus existing stock. Refurbishing an occupied apartment building demands entirely different skills from a greenfield office building — phasing, temporary services, noise windows and tenant communication are disciplines of their own.
Ask for two or three comparable projects and whether you may speak to the client. An office that did good work will make that introduction gladly.
5. Is site supervision on offer?
Design defines what gets built. Site supervision checks that exactly that is delivered — including programme and cost control, invoice verification, commissioning and handover under SIA 118. Where both sit with one office, the classic blame exchange between design and delivery disappears.
An office that does not offer supervision at all leaves quality assurance to you. In that case, ask who will take it on.
6. How is commissioning handled?
Air volume balancing, hydraulic adjustment, control parameterisation and measurement records determine whether a technically correct system also runs efficiently. With heat pumps in particular, every degree of flow temperature acts directly on electricity consumption.
Ask concretely: who carries out the hydraulic balancing, who documents it, and who re-checks the system after the first heating season?
7. How digital is the office — and why?
BIM is not an end in itself. Its benefit scales with installation density and the number of parties involved. The governing framework today is the SN EN ISO 19650 series; the Swiss SIA 2051 bulletin was withdrawn at the end of 2024. A good office will explain when the modelling effort pays for itself — and will also say when conventional 2D design is more economical.
8. Does the office know the cantonal regulation?
In the Canton of Zurich, replacing a heat generator requires renewable energy where technically feasible and adding no more than five per cent over the life cycle. Electric resistance heating and central electric water heaters must be replaced by 2030. An office that does not know these rules cold will design past the deadlines — and miss the subsidies.
9. Do you understand what you are being told?
An underrated criterion. You need to defend decisions in an owners' meeting, before a foundation board or a supervisory board. If you cannot restate a concept in three sentences after the first meeting, that is rarely your fault.
Watch whether reports contain recommendations or merely list options. A reasoned recommendation is precisely what you are appointing an engineer for.
10. Is the fee model transparent?
Fees are usually derived from SIA 108 — either from the cost-determining construction value or from time actually spent at agreed rates. Both are legitimate; what matters is that the basis is transparent and that variations are governed.
Be careful with lump sums that lack a defined scope: they are only as good as the delimitation behind them.
Conclusion: ask about what the proposal does not say
The most revealing answers come from questions a proposal does not address: who coordinates the trades? Who stands on site? Who checks the system after the first winter? An office with clear answers has understood the roles in the project — and that is exactly what you need.
We are happy to answer these questions for your specific project. Write to us or call +41 56 441 22 23.
