house-spec/specs/02-sensor-automation-spec.md

Sensor & Automation Specification

1. Control Architecture

The air system is managed by a layered control architecture: local sensors feed data to a central controller, which modulates the MVHR, dampers, and humidifier. Home Assistant provides monitoring, logging, alerting, and override capability.

flowchart TD
    subgraph Sensors["Room Sensors (per zone)"]
        CO2["CO₂ Sensor"]
        VOC["TVOC Sensor"]
        PM["PM2.5 / PM10 Sensor"]
        TH["Temperature + Humidity"]
        RN["Radon Monitor\n(ground floor only)"]
    end

    subgraph FilterSensors["Filter Monitoring"]
        DP1["ΔP Sensor: Pre-filter"]
        DP2["ΔP Sensor: F7"]
        DP3["ΔP Sensor: Carbon"]
        DP4["ΔP Sensor: H13 HEPA"]
        DP5["ΔP Sensor: Exhaust F9"]
    end

    subgraph Controller["Central Controller"]
        KNX["KNX / Modbus Bus"]
        HA["Home Assistant"]
    end

    subgraph Actuators["Actuators"]
        MVHR["MVHR Fan Speed"]
        DAMP["Zone Dampers"]
        HUM["Steam Humidifier"]
        DEHUM["Dehumidifier"]
    end

    Sensors --> KNX
    FilterSensors --> KNX
    KNX --> HA
    HA --> Actuators

    style HA fill:#1a5e5e,color:#fff
    style KNX fill:#1a3d5e,color:#fff

---

2. Room Sensor Placement

Every occupied room requires a sensor unit. The following table defines sensor requirements per zone:

Zone	CO₂	TVOC	PM2.5	Temp/RH	Radon	Notes
Master Bedroom	Yes	Yes	Yes	Yes	No	Priority zone — sleep quality
Leo's Room	Yes	Yes	Yes	Yes	No	Priority zone — child health
Living Room	Yes	Yes	Yes	Yes	No	Largest volume, main gathering
Kitchen	Yes	No	No	Yes	No	Separate exhaust system
Office / Study	Yes	Yes	Yes	Yes	No	Cognitive performance critical
Bathroom(s)	No	No	No	Yes	No	Humidity control priority
Basement / Ground Floor	Yes	No	No	Yes	Yes	Radon monitoring mandatory
Technical Room	No	No	No	Yes	No	Equipment monitoring

2.1 Sensor Mounting Guidelines

• CO₂ sensors: Mount at breathing height (1.2–1.5 m), away from windows, doors, and supply diffusers. CO₂ reading at the diffuser is outdoor air, not room air.
• PM sensors: Mount away from direct airflow paths — measure room air, not supply air.
• Temperature/Humidity: Away from direct sunlight, heat sources, and exterior walls. With radiant ceiling heating and raised floor, mount sensors at 1.2–1.5 m wall height — away from both the heated ceiling surface above and the floor surface below (see 04-flooring-ceiling-spec Section 9.1).
• Radon monitors: Ground floor / basement only, placed in the lowest habitable room, away from windows and doors.

---

3. Sensor Hardware Recommendations

3.1 Multi-Sensor Units

Sensor	Recommended Model	Protocol	Parameters	Notes
CO₂ + Temp + RH	Aqara TVOC Air Quality Monitor or Senseair S8 (custom)	Zigbee / UART	CO₂, T, RH	NDIR sensor, ±30 ppm accuracy
TVOC	SGP41 (Sensirion)	I²C	TVOC, NOx index	Requires 24h conditioning
PM2.5/PM10	Sensirion SPS30	I²C / UART	PM1.0, PM2.5, PM4, PM10	Laser-based, long-life fan
Radon	Airthings Wave Plus or RadonEye RD200	BLE / WiFi	Radon (Bq/m³)	Continuous, hourly updates

3.2 Filter Differential Pressure Sensors

Sensor	Recommended Model	Range	Output
ΔP across each filter stage	Sensirion SDP810 or Dwyer MS-111	0–500 Pa	I²C / 4-20mA

One sensor per filter stage (5 total: G4, F7, Carbon, H13, Exhaust F9). Alerts when pressure drop exceeds threshold indicating filter loading.

3.3 Outdoor Reference Station

An outdoor sensor station provides baseline comparison:

• PM2.5 / PM10 (verify filtration effectiveness)
• Temperature + Humidity (MVHR efficiency calculation)
• Air pressure (positive pressure verification)

---

4. Automation Logic

4.1 Demand-Controlled Ventilation (DCV)

The MVHR operates in demand mode, modulating airflow based on sensor readings:

flowchart TD
    CO2{"CO₂ Level?"} -->|"< 600 ppm"| LOW["Minimum Flow\n0.5 ACH"]
    CO2 -->|"600–800 ppm"| MED["Standard Flow\n0.8 ACH"]
    CO2 -->|"800–1000 ppm"| HIGH["Boost Flow\n1.0 ACH"]
    CO2 -->|"> 1000 ppm"| MAX["Maximum Flow\n1.2+ ACH"]

    VOC{"TVOC Level?"} -->|"> 500 µg/m³"| PURGE["Purge Mode\nMax flow + alert"]
    PM{"PM2.5 Indoor?"} -->|"> 15 µg/m³"| CHECK["Check Filters\nAlert if ΔP normal"]

    style MAX fill:#8b0000,color:#fff
    style PURGE fill:#8b0000,color:#fff

4.2 Humidity Control

flowchart TD
    RH{"Room RH?"} -->|"< 35%"| HUMON["Activate Steam Humidifier"]
    RH -->|"35–40%"| HUMLOW["Low Steam Output"]
    RH -->|"40–60%"| OKAY["Optimal — No Action"]
    RH -->|"60–65%"| DEHUMLOW["Reduce Humidifier / Light Dehumid"]
    RH -->|"> 65%"| DEHUMON["Active Dehumidification + Alert"]

    style HUMON fill:#1a5e5e,color:#fff
    style DEHUMON fill:#8b0000,color:#fff

4.3 Filter Maintenance Alerts

Condition	Action
ΔP across any stage > 1.5× initial value	Warning: filter loading, plan change
ΔP across any stage > 2.0× initial value	Critical: change filter immediately
ΔP drops suddenly	Warning: possible filter seal failure
Indoor PM2.5 > outdoor PM2.5	Critical: filter bypass or seal failure

4.4 Night Mode (Bedrooms)

• Between 22:00–07:00, bedroom zones get priority airflow
• CO₂ target tightened to < 600 ppm (sleep quality)
• Fan speed profile optimized for minimum noise
• Living room / kitchen dampers partially closed to redirect airflow

4.5 Cooking Mode

• Kitchen hood activation triggers:
  • Kitchen zone damper closes (prevents pulling kitchen air into MVHR)
  • Dedicated kitchen exhaust activates
  • MVHR boost mode engages to compensate for exhaust pressure
  • 30-minute timer to return to normal after cooking ends

---

5. Home Assistant Integration

5.1 Dashboard Elements

Widget	Data Source	Purpose
Air Quality Index (per room)	CO₂ + PM2.5 + TVOC composite	At-a-glance air quality
Filter Status (5 stages)	ΔP sensors	Remaining filter life %
MVHR Status	MVHR controller	Fan speed, mode, heat recovery %
Humidity Map	Room RH sensors	Whole-house humidity overview
Radon Trend	Radon monitor	24h / 7d / 30d trends
Indoor vs. Outdoor	Outdoor station vs. indoor	Filtration effectiveness proof
Energy Dashboard	MVHR + humidifier power	Running cost tracking
Ceiling Heating/Cooling	Manifold actuators + surface temp	Per-zone heating/cooling status
Ceiling Surface Temp	Embedded ceiling sensors	Condensation risk indicator (vs. dewpoint)
Floor Surface Temp	Embedded floor sensors (if cooling)	Comfort limit monitoring

5.2 Alerting

Alert Level	Channel	Examples
Info	Dashboard notification	Filter approaching change interval
Warning	Push notification	CO₂ > 1000 ppm, RH > 65%
Critical	Push + audible alarm	Filter failure, PM2.5 spike, radon > 300 Bq/m³

5.3 Data Logging

All sensor data logged to InfluxDB via Home Assistant for long-term trend analysis:

• 1-minute resolution for CO₂, PM, TVOC
• 5-minute resolution for temperature, humidity
• 1-hour resolution for radon
• Retention: minimum 2 years

---

6. Communication Protocols

flowchart LR
    subgraph Field["Field Level"]
        S1["Room Sensors\n(Zigbee / WiFi)"]
        S2["ΔP Sensors\n(I²C / 4-20mA)"]
        S3["Outdoor Station\n(WiFi)"]
    end

    subgraph Bus["Bus Level"]
        KNX["KNX Bus\n(MVHR, Dampers, Humidifier)"]
        ZB["Zigbee Coordinator\n(Room Sensors)"]
    end

    subgraph Server["Server Level"]
        HA["Home Assistant\n+ InfluxDB"]
    end

    S1 --> ZB
    S2 --> KNX
    S3 --> HA
    ZB --> HA
    KNX --> HA
    HA --> KNX

    style HA fill:#1a5e5e,color:#fff

• KNX: Primary bus for MVHR control, motorized dampers, humidifier — wired, deterministic, reliable
• Zigbee: Room sensor network — mesh, low power, well-supported in Home Assistant
• WiFi: Outdoor station, radon monitors — direct to Home Assistant
• InfluxDB: Time-series database for long-term data retention and Grafana dashboards

---

7. Wiring Requirements for Baufritz

The following must be specified at construction stage:

Item	Quantity	Location	Cable
KNX bus cable	1 run per zone	All zones + technical room	KNX TP (green, 2×2×0.8mm)
230V outlet for room sensor	1 per room	At sensor mounting point	Standard NYM
Cat6 network drop	1 per room	Near sensor location	Cat6a shielded
Dedicated circuit: MVHR	1	Technical room	3×2.5mm²
Dedicated circuit: humidifier	1	Technical room	3×2.5mm² (steam = high draw)
ΔP sensor cable runs	5	Filter housing to technical room	4-wire shielded
Outdoor sensor power + data	1	North-facing exterior	Weatherproof outlet + Cat6
Ceiling surface temp sensors	1 per zone	Embedded in Plafotherm panels	4-wire shielded
Floor surface temp sensors	2-3 per zone	On/in parquet surface	4-wire shielded

Note: On the ground floor, KNX bus cable and Cat6 runs can be routed through the Lindner NORTEC Doppelboden cavity instead of wall chases, simplifying installation (see 04-flooring-ceiling-spec Section 6.1).