Juergen Kunz
6172e6c79c
- 01: H13 HEPA whole-house air filtration, MVHR, duct design, pressure management - 02: Sensor placement, automation logic, Home Assistant integration, wiring - 03: Baufritz builder coordination, construction checkpoints, timeline - 04: Lindner NORTEC Doppelboden with WOODline parquet + Plafotherm AirHybrid radiant ceiling - Build system: tsx + marked + puppeteer, renders Mermaid diagrams to PDF
204 lines
9.2 KiB
Markdown
204 lines
9.2 KiB
Markdown
# Air System Specification
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## 1. Design Philosophy
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In a well-sealed Baufritz home, 100% of incoming air passes through the ventilation system. The goal is to engineer indoor air that is **measurably superior to outdoor air** across every parameter — not merely acceptable, but actively health-positive.
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**Target: Whole-house H13 HEPA filtration (ISO Class 7–8 equivalent), with full control over particulates, gases, humidity, CO₂, and pressure.**
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---
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## 2. Filter Cascade — Corrected Sequence
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The filter stages are ordered so that **every upstream stage's potential contaminants are caught by the next downstream stage**. The H13 HEPA is always the final particle barrier before air enters the living space.
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```mermaid
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flowchart TD
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A["Outdoor Air Intake\n weather-protected, north-facing preferred"] --> B
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B["Stage 1: G4/M5 Pre-filter\nCoarse particles, pollen, insects"] --> C
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C["Stage 2: F7 Intermediate Filter\nFine dust, mold spores"] --> D
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D["Stage 3: Activated Carbon\nVOC, NO2, ozone removal"] --> E
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E["Stage 4: H13 HEPA - FINAL BARRIER\n99.95% efficiency at 0.3um\nCatches everything incl. carbon fines"] --> F
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F["MVHR Unit\nCounterflow heat recovery 80-95%"] --> G
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G["Steam Humidifier\nelectrode or resistive, inherently sterile"] --> H
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H["Motorized Zone Dampers"] --> I
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I["Room Distribution"]
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style E fill:#1a5e1a,color:#fff,stroke:#0d3d0d
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style D fill:#4a4a00,color:#fff,stroke:#333
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style F fill:#1a3d5e,color:#fff,stroke:#0d2840
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```
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### 2.1 Stage Details
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| Stage | Filter Class | Function | Face Velocity | Initial ΔP | Change Interval |
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|-------|-------------|----------|---------------|------------|-----------------|
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| 1 | G4 / M5 | Coarse protection — pollen, insects, large dust | < 2.5 m/s | 30–50 Pa | Every 3 months |
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| 2 | F7 (ePM2.5 ≥ 65%) | Fine particulates, mold spores, extends H13 life | < 2.0 m/s | 40–60 Pa | Every 6 months |
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| 3 | Activated Carbon | VOC, NO₂, ozone adsorption | < 1.5 m/s | 30–50 Pa | Every 12 months |
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| 4 | H13 HEPA | Final barrier — 99.95% @ MPPS (0.3 µm) | **< 1.0 m/s** | 80–150 Pa | Every 12–18 months |
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### 2.2 Critical Design Rules
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- **Carbon BEFORE HEPA**: Carbon filters shed microscopic activated carbon fines. The H13 HEPA downstream catches these. Never reverse this order.
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- **Face velocity across H13 panels must stay below 1.0–1.5 m/s**: This requires filter housings 2–4× larger than the duct cross-section. At low face velocity, pressure drop drops to 80–100 Pa initial, noise disappears, and filter life doubles.
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- **Filter housing must accommodate 600×600 mm panel filters** (or larger) — not inline cylindrical filters.
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- **Differential pressure sensors across each stage**: Electronic, connected to Home Assistant. Change filters based on actual loading, not calendar time. Spring pollen will load pre-filters in weeks.
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---
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## 3. Exhaust Side Filtration
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The exhaust path also requires filtration to protect the MVHR heat exchanger:
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```mermaid
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flowchart LR
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R["All Rooms\n(except kitchen)"] --> EF["F9 Exhaust Filter\nProtects heat exchanger"]
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EF --> MVHR["MVHR Exhaust Side"]
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MVHR --> OUT["Outdoor Exhaust"]
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K["Kitchen"] --> KE["Dedicated Kitchen Exhaust\nNEVER recirculated into MVHR"]
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KE --> KOUT["Separate Outdoor Exhaust"]
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style K fill:#8b0000,color:#fff
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style KE fill:#8b0000,color:#fff
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```
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- **Minimum F9 on exhaust** before the MVHR heat exchanger
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- **Kitchen exhaust is entirely separate** — cooking aerosols, grease particles, and combustion byproducts must never enter the MVHR system
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- Kitchen hood: ducted directly outside through a dedicated penetration with backdraft damper
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---
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## 4. MVHR Unit Requirements
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For whole-house H13, the MVHR must handle significantly higher system pressure than standard residential units.
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### 4.1 Minimum Specifications
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| Parameter | Requirement |
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|-----------|-------------|
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| Available static pressure | ≥ 450 Pa (preferably ≥ 500 Pa) |
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| Airflow capacity | ≥ 400 m³/h (for ~150–200 m² at 0.8 ACH) |
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| Heat recovery efficiency | ≥ 85% (counterflow plate, no enthalpy wheel) |
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| Fan type | EC (electronically commutated), variable speed |
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| Filter bay | External filter box connection, or large internal bay |
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| Controls | KNX or Modbus interface for building automation |
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| Noise at rated flow | ≤ 35 dB(A) at 1 m |
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### 4.2 Recommended Units
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| Unit | Max Static Pressure | H13 Support | Notes |
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|------|---------------------|-------------|-------|
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| Drexel & Weiss aerosilent | ~600 Pa | Native options | Austrian, Passivhaus standard |
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| Swegon CASA R5 | ~600 Pa+ | Via external box | Semi-commercial, bridges residential/commercial |
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| Zehnder ComfoAir Q600 | ~500 Pa | Via external box | Largest residential Zehnder, KNX native |
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| Paul Novus 450 | ~450 Pa | Via external box | Very quiet, excellent German engineering |
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| Hoval HomeVent FR | ~500 Pa | Via external box | Commercial-grade residential |
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**Recommendation**: Drexel & Weiss aerosilent or Swegon CASA — both designed for the pressure demands of H13 whole-house filtration.
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---
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## 5. Humidification
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### 5.1 Requirements
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| Parameter | Target |
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|-----------|--------|
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| Relative humidity | 40–60% year-round |
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| Humidifier type | **Steam ONLY** (electrode or resistive) |
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| Position | Downstream of MVHR, in supply duct |
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| Control | Hygrostat per zone, integrated with central controller |
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### 5.2 Why Steam Only
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Since the H13 HEPA is the final particle barrier upstream of the MVHR, anything added to the airstream after the HEPA must be inherently sterile:
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- **Steam humidifiers**: Water boiled to 100°C — output is sterile vapor, no mineral dust, no biofilm
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- **Ultrasonic**: Creates aerosols containing dissolved minerals and bacteria from reservoir — **PROHIBITED**
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- **Evaporative (unsterilized)**: Biofilm grows on wetted media within days — **PROHIBITED**
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**Recommended brands**: Condair, Hygromatik — industrial-grade steam humidifiers designed for duct integration, commonly used in German clean rooms and hospitals.
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### 5.3 Dehumidification
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In summer, dehumidification is handled by:
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- The MVHR cooling bypass (partial)
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- Optional: small split heat pump unit on the supply duct, or dedicated dehumidifier in the technical room
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- Target: never exceed 60% RH at any surface
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---
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## 6. Duct Design
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### 6.1 Velocity Requirements
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| Duct Section | Max Velocity | Typical Diameter |
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|-------------|-------------|-----------------|
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| Main supply/extract trunk | ≤ 2.0 m/s | 200–250 mm round |
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| Branch ducts to rooms | ≤ 1.5 m/s | 125–160 mm round |
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| Final connection to diffuser | ≤ 1.0 m/s | 100–125 mm round |
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At 0.8 ACH for 150 m² with 3 m ceilings = **~360 m³/h airflow**. Main duct at 2.0 m/s → ~250 cm² cross section → **200 mm round duct minimum**.
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### 6.2 Material and Sealing
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- **Rigid steel or aluminum ducts throughout** — no semi-rigid flex (adds resistance, collects contamination)
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- **Exception**: final 0.5 m connection to each diffuser may use flex for vibration isolation
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- **All joints sealed with mastic** (not just tape) — Passivhaus duct leakage class
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- **Pressure-tested after installation** before walls are closed
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### 6.3 Duct Routing
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Must be coordinated with Baufritz at structural design stage:
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- Duct runs in ceilings and walls need to be planned and boxed in
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- Dedicated vertical risers for multi-story distribution
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- No ducts in exterior walls (condensation risk, thermal bridge)
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- Acoustic silencers at MVHR outlets and before each room diffuser
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- **Ground floor alternative**: branch ducts may route through the Lindner NORTEC Doppelboden cavity (see 04-flooring-ceiling-spec Section 6). Supply air may be distributed via Plafotherm AirHybrid ceiling panels (see 04-flooring-ceiling-spec Section 5), potentially replacing conventional wall/ceiling diffusers
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---
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## 7. Pressure Management
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| Parameter | Target |
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|-----------|--------|
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| House pressure vs. outside | **+3 to +5 Pa** (slight positive) |
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| Supply vs. exhaust airflow | Supply 5–10% greater than exhaust |
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| Kitchen exhaust compensation | Dedicated make-up air or interlock with MVHR boost |
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Positive pressure ensures:
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- All infiltration passes through the filter stack
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- Radon and soil gases cannot infiltrate from below
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- Garage pollutants cannot enter (garage must be entirely pressure-separated)
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---
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## 8. Air Quality Targets
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| Parameter | Target | Danger Threshold |
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|-----------|--------|-----------------|
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| PM2.5 | < 5 µg/m³ | > 15 µg/m³ |
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| PM10 | < 10 µg/m³ | > 25 µg/m³ |
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| CO₂ | < 800 ppm | > 1000 ppm |
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| TVOC | < 200 µg/m³ | > 500 µg/m³ |
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| Relative Humidity | 40–60% | < 30% or > 70% |
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| Radon | < 100 Bq/m³ | > 300 Bq/m³ |
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| Temperature uniformity | ± 1.5°C between rooms | > 3°C delta |
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| Formaldehyde | < 30 µg/m³ | > 100 µg/m³ |
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---
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## 9. Estimated Filter Costs (Annual)
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| Stage | Interval | Cost per Change | Annual Cost |
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|-------|----------|----------------|-------------|
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| G4/M5 pre-filter | 3 months | 10–20 EUR | 40–80 EUR |
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| F7 intermediate | 6 months | 20–40 EUR | 40–80 EUR |
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| Activated carbon | 12 months | 50–100 EUR | 50–100 EUR |
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| H13 HEPA panels | 12–18 months | 80–200 EUR per panel | 80–200 EUR |
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| **Total** | | | **210–460 EUR/year** |
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This is the cost of breathing clean air. For context, this is less than a monthly gym membership.
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