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
Cellar Datacenter	No	No	No	Yes	Yes	Rack inlet/exhaust temps, humidity, leak, smoke, power (see 06-datacenter-spec Section 9)
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.

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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)

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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
Water Quality Index	TDS + pH sensors	At-a-glance water quality (see 05-water-system-spec)
RO Membrane Health	Post-RO TDS vs. feed TDS	Rejection rate %, replacement prediction
Water Consumption	Per-branch flow meters	Daily/weekly usage per zone
Leak Detection Map	Capacitive leak sensors	Green/red per zone, auto shut-off status
Hot Water Status	Tank temp + recirculation temp	Availability and efficiency
Datacenter Rack Temps	8x temperature sensors	Inlet/exhaust per rack, color-coded
Datacenter Power	Per-PDU metering	Total + per-rack kW, PUE metric
Datacenter Cooling	Cooling unit Modbus/SNMP	Compressor status, inlet/outlet temps
UPS Status	UPS SNMP	Battery %, load %, runtime remaining
Datacenter Smoke	VESDA / optical	Alert level (normal/pre-alarm/alarm)

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
Info	Dashboard notification	Water filter approaching change interval
Warning	Push notification	RO rejection < 95%, post-remin pH < 7.0
Critical	Push + audible alarm + auto shut-off	Water leak detected, RO rejection < 90%
Warning	Push notification	Datacenter inlet temp > 27 C, UPS on battery
Critical	Push + audible alarm	Datacenter inlet temp > 32 C, datacenter water leak, smoke pre-alarm
Emergency	Push + audible + auto-shutdown	Datacenter temp > 35 C, smoke alarm, UPS battery < 20%

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

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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
Water TDS/pH sensors	2 inline	Post-RO + post-remineralization	4-20mA / Modbus
Water flow meters	1 per branch + 1 total	At manifold in technical room	Pulse / KNX
Water leak sensors	1 per manifold + 1 per fixture + ceiling void	Under fixtures, ceiling low points	Capacitive / Zigbee
Motorized shut-off valve	1	Water entry point (POE)	KNX, fail-closed
Fiber backbone (OS2)	2 bundles (12-core each)	Cellar to ground floor + upper floor	Single-mode, 10G+
Datacenter temp sensors	8	Per-rack inlet + exhaust	Modbus / SNMP
Datacenter leak sensors	4	Under cooling units, low points	Capacitive / Zigbee
Datacenter smoke (VESDA)	1 system	Cellar ceiling	Relay / Modbus
Datacenter PDU metering	8 PDUs	2 per rack (A+B feeds)	SNMP
Datacenter door contact	1	Entry door	KNX / Zigbee

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).