“Healthy building” is one of the easiest claims to make and one of the hardest to verify. The difference is whether the project has explicit targets, sensors at the right locations, and a data model that survives handover.
This note sets out the framework we use: two performance tiers, a small set of parameters, and a clear separation between design targets and measured performance.
Two tiers, not one promise
We specify an acceptable tier and a high-performance tier. The acceptable tier is the floor a project should meet under normal operation. The high-performance tier is the target for premium spaces, or for projects pursuing a specific certification or tenant requirement.
Having two tiers prevents the common failure mode where a single aspirational number is written into the specification, never achieved in normal operation, and quietly ignored after handover.
The core parameters
| Parameter | Acceptable | High performance |
|---|---|---|
| CO₂ | < 1,000 ppm | < 600 ppm |
| PM2.5 | < 35 µg/m³ | < 15 µg/m³ |
| TVOC | < 0.5 mg/m³ | < 0.4 mg/m³ |
| Formaldehyde (HCHO) | < 0.4 mg/m³ | < 0.3 mg/m³ |
| Temperature | 18–24 °C | 20–21 °C |
| Relative humidity | 50–70 %RH | 60–65 %RH |
| Fresh air | 36 m³/h per person | 40 m³/h per person |
These values come from the Loxone Intelligent Building healthy-building standard. They are design targets, not a certification. Local code, the building use and the client brief always take precedence.
Where to measure
A single CO₂ sensor in the lobby tells you almost nothing about the meeting room at 14:00. Sensor location is a design decision:
- Occupied zones: at breathing height, away from diffusers and direct sunlight.
- Return air: useful for system-level control, not for occupant exposure.
- Outdoor reference: required to distinguish indoor generation from outdoor pollution.
- Critical rooms: conference rooms, classrooms, clinics and any space with variable occupancy.
Design targets versus measured performance
A design target is a number the system is engineered to achieve. Measured performance is what the building actually does. The gap between them is where most healthy-building claims fail.
We recommend three deliverables at handover:
- A sensor schedule with location, height, calibration date and the point name used by the platform.
- A trend baseline covering at least one normal week of operation, with occupancy context.
- An alarm philosophy that distinguishes a sensor fault from a genuine air-quality excursion.
If the building cannot show a week of trend data with sensor locations, it does not yet have a healthy-building specification. It has an intention.
Fresh air is a control problem
Fresh-air volume is usually specified per person and per hour. In operation, it is a control problem: occupancy changes, doors open, kitchens and bathrooms extract air, and the ventilation system has to respond without over-ventilating an empty building.
Demand-controlled ventilation uses CO₂ and occupancy to modulate fresh air. The control sequence should define the minimum fresh-air rate, the maximum rate, the deadband and the fault behaviour. That sequence belongs in the IBMS, not only in the AHU controller.
Water and thermal comfort
Air quality gets the attention, but water quality and thermal comfort are part of the same brief. The healthy-building standard also covers pH, bacteria, particles and dissolved solids for water, and air speed and heat load for thermal comfort.
For most projects, the practical first step is to agree which parameters are measured continuously, which are sampled periodically, and which are design assumptions. Pretending that every parameter is continuously monitored is a fast route to a dashboard nobody trusts.
A healthy building is not a certificate on the wall. It is a set of numbers a building can still produce a year after handover.
The takeaway
Specify two tiers. Put sensors where people actually breathe. Separate design targets from measured performance. And make the trend data part of the handover package, not an optional extra.
