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.

```mermaid
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:

```mermaid
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

```mermaid
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

```mermaid
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).