What is a Passive House (Passivhaus)?

The Passive House (Passivhaus) standard was developed in Germany in the early 1990s. The core criteria are:

  • Specific heat demand below 15 kWh/(m²·yr)
  • Total primary energy demand below 120 kWh/(m²·yr)
  • Airtightness (Air Changes Per Hour at 50 Pa): ACH50 ≤ 0.6
  • Mandatory mechanical ventilation with heat recovery (MVHR)

Passive houses are typically built from concrete, brick, or steel with thick external insulation. Their main weakness is dependence on a mechanical ventilation system — without it, air quality in the airtight envelope deteriorates rapidly.

How Does Fachwerk Construction Work?

Fachwerk is a German architectural technique in which the load-bearing structure is formed from glulam timber beams (Leimholz), left exposed both inside and out. The spaces between the beams (Gefache) are filled with high-performance insulation.

Glulam (Leimholz) is manufactured from layers of pine and fir bonded under pressure. The result is a structural element with:

  • Exceptionally low thermal conductivity: λ ≈ 0.13 W/(m·K) — 8× lower than concrete (λ ≈ 1.1 W/(m·K))
  • Zero formaldehyde and benzene content
  • Natural release of phytoncides with an antibacterial effect
  • Longevity exceeding 100 years without major maintenance
Fachwerk house construction — glulam timber load-bearing beams (Leimholz)

Comparison: Passive House vs Fachwerk

Criterion Passive House Fachwerk (Natural Eco House)
Structural thermal conductivity λ ≈ 0.8–1.1 W/(m·K) (concrete/brick) λ ≈ 0.13 W/(m·K) (timber)
Insulation layer Thick external insulation (>25 cm) Insulation in Gefache + timber beam
Thermal mass High (concrete/brick) High (timber + insulation)
Airtightness Hermetic (ACH50 ≤ 0.6) High-quality airtight envelope
Ventilation Mandatory MVHR mechanics Natural air exchange + optional MVHR
Materials Concrete, brick, steel, synthetic insulation Natural timber, formaldehyde-free
Air quality Depends on MVHR system Natural — phytoncides from timber
Energy rating A / A+ A+
Longevity 30–60 years (typical build) 100+ years
Energy efficiency — Fachwerk A+ rating vs standard construction

Passive House or Fachwerk — Which Is Better?

Fachwerk construction achieves energy-efficient performance comparable to passive house standards — but without the limitations:

  1. No mandatory mechanical ventilation — timber breathes naturally, whereas airtight passive houses depend on MVHR machinery
  2. Healthier indoor environment — natural materials free of formaldehyde release phytoncides, not mechanically filtered air
  3. More beautiful solution — the exposed timber frame is a decorative feature, not a hidden structure
  4. Longer lifespan — a well-maintained fachwerk building lasts 150+ years (see medieval examples across Germany and Austria)
  5. More flexible layout — glulam beams allow wide open spaces with no load-bearing interior walls

Passive House on the Black Sea — Does It Make Sense?

In the Black Sea climate (mild winters, hot summers), the strict Passivhaus standard is an over-investment. A far more practical solution is a fachwerk house with A+ energy rating:

  • Superior thermal insulation cuts heating costs in winter
  • Natural timber stays pleasantly cool in summer (does not overheat like concrete)
  • Panoramic glazing enables passive solar heating without thermal loss
  • No MVHR maintenance costs
Natural Eco House fachwerk — panoramic Black Sea view

Fachwerk Houses in Kosharitsa — Technical Specifications

The German fachwerk houses by Natural Eco House in Kosharitsa, between Sunny Beach and Sveti Vlas, offer:

  • Glulam load-bearing beams (Leimholz) — formaldehyde-free
  • Double-layer insulation in Gefache
  • A+ energy rating
  • Panoramic glazing with low-emissivity glass
  • Smart Home system included
  • 200 m² built area, 4 bedrooms, 2 floors
  • Panoramic sea views over the Black Sea