house-spec/specs/03-baufritz-coordination-spec.md

# Baufritz Builder Coordination Specification

## 1. Overview

This document specifies requirements that must be communicated to and coordinated with Baufritz during the design and construction phases. Baufritz builds with excellent low-emission materials (no formaldehyde, no synthetic glues, tested for 300+ pollutants) and designs for airtight envelopes — this is the ideal foundation for our clean air system.

**The air system is not a retrofit. It must be designed into the structure from the beginning.**

---

## 2. Technical Room Requirements

A dedicated technical room is required for the air handling equipment. This is not a utility cupboard — it needs standing access for filter changes and equipment maintenance.

### 2.1 Minimum Specifications

| Parameter | Requirement |
|-----------|-------------|
| Floor area | 4–6 m² minimum (ideally 6–8 m²) |
| Ceiling height | ≥ 2.4 m |
| Access | Full-width door (≥ 900 mm), no obstructions |
| Floor | Waterproof, drainable (steam humidifier condensate) |
| Electrical | 3× dedicated 230V/16A circuits (MVHR, humidifier, controls) |
| Lighting | Bright, shadow-free (filter inspection) |
| Location | Central in building footprint (minimizes duct runs) |
| Noise isolation | Sound-insulated walls/door (MVHR generates 35–45 dB) |

### 2.2 Equipment Layout

```mermaid
block-beta
    columns 3

    block:row1:3
        A["G4/M5\nPre-filter\nHousing"] B["F7\nIntermediate\nHousing"] C["Activated\nCarbon\nHousing"]
    end

    block:row2:3
        D["H13 HEPA\nCassette Bank\n(600×600mm panels)"] space:1 E["MVHR Unit\n(Drexel & Weiss\nor Swegon)"]
    end

    block:row3:3
        F["Steam\nHumidifier\n(Condair/Hygromatik)"] G["Control\nPanel\n(KNX Gateway)"] H["Supply\nDuct\nManifold"]
    end

    style D fill:#1a5e1a,color:#fff
    style E fill:#1a3d5e,color:#fff
    style F fill:#1a5e5e,color:#fff
```

**All filter housings must be accessible from the front** with tool-free opening for filter changes. Minimum 800 mm clearance in front of each housing.

---

## 3. Duct Routing Requirements

### 3.1 Design Principles

| Requirement | Detail |
|------------|--------|
| Duct material | Rigid galvanized steel or aluminum — **no semi-rigid flex** |
| Exception | Final 0.5 m to each diffuser: flex for vibration isolation |
| Sealing | All joints mastic-sealed (not tape only) |
| Testing | Pressure-tested to Passivhaus duct leakage class after installation |
| Velocity: main trunk | ≤ 2.0 m/s |
| Velocity: branches | ≤ 1.5 m/s |
| Velocity: diffuser connection | ≤ 1.0 m/s |
| Main trunk diameter | 200–250 mm round (or equivalent rectangular) |
| Branch diameter | 125–160 mm round |

### 3.2 Routing Constraints

- **No ducts in exterior walls** — condensation risk and thermal bridging
- **Dedicated vertical risers** for multi-story distribution — coordinate with structural plan
- **Acoustic silencers** at MVHR outlets and before each room diffuser
- **Inspection/cleaning access points** at all bends > 45° and every 6 m of straight run
- **Fire dampers** at all floor/wall penetrations per DIN 4102

### 3.3 Duct Space Requirements

```mermaid
flowchart TD
    subgraph Ground["Ground Floor Ceiling Void"]
        GT["Main Supply Trunk\n200–250mm"]
        GB1["Branch: Living Room\n160mm"]
        GB2["Branch: Kitchen\n125mm (exhaust only)"]
        GB3["Branch: Office\n125mm"]
    end

    subgraph Upper["Upper Floor Ceiling Void"]
        UT["Main Supply Trunk\n200mm"]
        UB1["Branch: Master Bedroom\n160mm"]
        UB2["Branch: Leo's Room\n125mm"]
        UB3["Branch: Bathroom(s)\n100mm"]
    end

    TR["Technical Room"] --> GT
    TR --> UT

    style TR fill:#1a3d5e,color:#fff
```

**Baufritz must allocate ceiling void depth of ≥ 300 mm** in areas where main ducts run, or provide dedicated duct boxing. This must be shown on construction drawings.

**Note**: The ceiling void is shared with the Lindner Plafotherm radiant ceiling system (see 04-flooring-ceiling-spec Section 4). On the ground floor, branch supply ducts may route through the raised floor cavity instead (see 04-flooring-ceiling-spec Section 6), potentially reducing ceiling void requirements. However, the main supply trunk and Plafotherm pipes still require adequate ceiling void depth. **Floor-to-floor structural height must be ≥ 3000 mm** to accommodate both the raised floor and ceiling system while maintaining ≥ 2500 mm usable room height (see 04-flooring-ceiling-spec Section 2).

---

## 4. Building Envelope Requirements

### 4.1 Airtightness

| Parameter | Requirement |
|-----------|-------------|
| Blower door test (n50) | ≤ 0.6 ACH (Passivhaus standard) |
| Target | 0.3 ACH if achievable |
| Testing | Blower door test during construction (before interior finishing) AND after completion |

Baufritz typically achieves excellent airtightness. This is critical — the air system only works if 100% of air passes through the filter stack. Every uncontrolled leak bypasses the entire system.

### 4.2 Radon Protection

| Item | Specification |
|------|--------------|
| Radon membrane | Continuous radon-proof membrane at foundation/ground slab |
| Membrane type | HDPE or bituminous, radon-tested per DIN/ISO |
| Sealing | All penetrations (pipes, cables) sealed with radon-rated sealant |
| Sub-slab ventilation | Provision for passive sub-slab depressurization (can be activated later if needed) |
| Monitoring | Radon sensor in lowest habitable room, connected to Home Assistant |

**Note**: The Bremen/Grasberg area is generally low radon risk per BfS (Federal Office for Radiation Protection) maps, but radon protection is inexpensive at construction stage and expensive to retrofit. Specify it regardless.

**Raised floor compatibility**: The Lindner NORTEC Doppelboden pedestal system must be anchored with adhesive bonding only — no mechanical fixings that penetrate the radon membrane. Verify adhesive compatibility with the membrane material (see 04-flooring-ceiling-spec Section 7.5).

### 4.3 Thermal Bridge Prevention

Baufritz excels at thermal-bridge-free construction. Verify:
- No thermal bridges at window reveals, sills, lintels
- No thermal bridges at floor/wall junctions
- No thermal bridges at balcony connections (if any)
- Surface temperatures never below dewpoint at any point (prevents condensation → mold)

---

## 5. MVHR Specification for Baufritz

### 5.1 Unit Selection

Specify to Baufritz that the MVHR unit must meet:

| Parameter | Minimum | Preferred |
|-----------|---------|-----------|
| Available static pressure | 450 Pa | ≥ 500 Pa |
| Airflow capacity | 400 m³/h | 450 m³/h |
| Heat recovery | 85% | ≥ 90% |
| Fan motor | EC variable speed | EC variable speed |
| Bypass | Summer bypass with motorized flap | Automatic |
| Controls interface | Modbus | KNX native |
| External filter box | Compatible | Designed for |

### 5.2 Baufritz-Typical vs. Our Requirements

Baufritz typically installs standard residential MVHR units (e.g., Zehnder ComfoAir Q350, Paul Novus 300). These are excellent units but designed for F7/F9 filtration with ~200–250 Pa system pressure.

**Our H13 whole-house requirement means upgrading to a higher-pressure unit.** This must be specified early because:
- The MVHR unit dimensions affect technical room layout
- Higher-pressure units may have different duct connection sizes
- Electrical requirements may differ (larger EC motors)
- Noise characteristics change — sound insulation may need upgrading

---

## 6. Garage Separation

If the house includes an attached garage:

| Requirement | Detail |
|------------|--------|
| Pressure separation | Garage at negative pressure relative to house |
| No shared air volume | No door directly from garage to conditioned space without airlock |
| Separate exhaust | Garage has its own exhaust fan with timer/CO sensor |
| Sealing | All wall/ceiling penetrations between garage and house fully sealed |
| CO sensor | In garage, interlocked with garage exhaust fan |

**Garage exhaust fumes (CO, NOx, PM, benzene) are extremely hazardous. Zero tolerance for garage air entering the conditioned space.**

---

## 7. Kitchen Exhaust Specification

| Requirement | Detail |
|------------|--------|
| Type | Ducted to outside — NOT recirculating |
| Backdraft damper | Motorized, closes when hood is off |
| Duct material | Stainless steel or galvanized (grease-rated) |
| Interlock | Activates MVHR boost mode for make-up air |
| Separation | Never connected to the MVHR system |
| Fire safety | Fire damper at wall penetration |

---

## 8. Electrical & Wiring Coordination

### 8.1 Technical Room Electrical

| Circuit | Rating | Purpose |
|---------|--------|---------|
| MVHR dedicated | 230V / 16A | MVHR unit power |
| Humidifier dedicated | 230V / 16A (or 400V / 3-phase) | Steam humidifier (high wattage) |
| Controls | 230V / 10A | KNX power supply, gateway, sensors |
| Backup/spare | 230V / 16A | Future expansion |

### 8.2 Building-Wide Wiring

| Item | Specification |
|------|--------------|
| KNX bus cable | To every zone (MVHR dampers, sensors) |
| Cat6a shielded | To every room (sensor data, future-proofing) |
| 230V at sensor points | USB power for sensor units |
| Outdoor sensor cable | Weatherproof, north wall |
| ΔP sensor cabling | 5× runs from filter housing to control panel |

**All wiring for the air system must be specified on Baufritz's electrical plan before wall construction begins.** Retrofit wiring in a sealed timber-frame house is extremely difficult and expensive.

---

## 9. Construction Phase Checkpoints

### 9.1 During Construction

| Phase | Checkpoint |
|-------|-----------|
| Foundation | Radon membrane installed and sealed at all penetrations |
| Framing | Duct routing voids verified, vertical risers in place |
| Framing | Ceiling void dimensions verified for Plafotherm + MVHR trunk |
| Pre-close | First blower door test (target ≤ 0.6 n50) |
| Pre-close | All duct runs installed, mastic-sealed, pressure-tested |
| Pre-close | All KNX/Cat6 wiring installed and tested |
| Interior finishing | Plafotherm ceiling suspension and panels installed |
| Interior finishing | Ceiling heating circuit pressure-tested |
| Interior finishing | Raised floor pedestals installed, subfloor leveling verified |
| Interior finishing | Under-floor services (ducts, wiring) installed and pressure-tested |
| Interior finishing | Floor panels and WOODline parquet tiles installed |
| Interior finishing | Verify no ducts compressed or kinked by finishing work |
| Completion | Final blower door test |
| Completion | Commission MVHR, set airflows, balance dampers / AirHybrid panels |
| Completion | Commission ceiling heating/cooling, verify surface temperatures |
| Completion | Commission sensors, verify readings, connect to Home Assistant |

### 9.2 Commissioning Verification

| Test | Acceptance Criteria |
|------|-------------------|
| Blower door (n50) | ≤ 0.6 ACH |
| Duct leakage | Passivhaus class |
| Room-by-room airflow | Within ±10% of design spec |
| House positive pressure | +3 to +5 Pa vs. outside |
| CO₂ decay test | < 800 ppm within 30 min of occupancy end |
| PM2.5 indoor vs. outdoor | Indoor < 10% of outdoor |
| Noise at diffusers | < 25 dB(A) per diffuser |

---

## 10. Timeline Integration

| Baufritz Phase | Air System Action | Lindner Floor/Ceiling Action |
|----------------|-------------------|------------------------------|
| Initial design | Specify MVHR unit, technical room size, duct routing | Confirm raised floor + Plafotherm, specify cavity heights and floor-to-floor height (≥ 3000 mm) |
| Detailed planning | Approve duct routing on drawings, specify all penetrations | Lindner layout drawings for floor and ceiling, coordinate with MVHR plan |
| Pre-fabrication | Confirm radon membrane spec, duct void dimensions | Verify subfloor level tolerance and ceiling anchor points in prefab panels |
| Factory build | Verify duct voids in prefab wall/floor panels | No impact (Lindner systems installed on-site) |
| On-site assembly | Supervise duct installation, first blower door test | Install ceiling system, then floor pedestals and cavity services |
| Finishing | Sensor wiring, diffuser installation | Parquet tile installation, floor and ceiling commissioning |
| Handover | Full commissioning, sensor calibration, HA setup | Heating/cooling commissioning, AirHybrid airflow verification |