Constructing Passive Houses with Cold-Formed Steel: The 5 Core Principles & Implementation Guide
The Passive House (Passivhaus] standard, established by the Passive House Institute (PHI] in Darmstadt, is the world's leading standard in energy-efficient construction. It slashes space heating and cooling energy demand by up to 90% compared to conventional building stock without compromising thermal comfort or indoor air hygiene. Cold-formed steel (CFS] provides an ideal structural substrate due to its immutable dimensional stability and CNC precision.
The 5 Foundational Building Physics Pillars
- Continuous Super-Insulated Thermal Envelope: External walls, roof, and foundation slab interfaces are engineered to achieve U ≤ 0.11 - 0.14 W/m²K.
- Thermal Bridge Free Construction: Structural linear thermal bridges must satisfy Ψ ≤ 0.010 W/mK throughout all building junctions, maintaining an internal surface temperature factor fRsi ≥ 0.75 to eliminate condensation and mold growth permanently.
- Triple-Glazed Passive Certified Fenestration: Windows and doors achieve installed Uw ≤ 0.80 W/m²K using argon-filled triple glass (Ug = 0.50 - 0.60 W/m²K], composite warm-edge spacers, and external solar shading (Raffstores].
- Rigorous Building Airtightness: Envelope air exchange rate under 50 Pa differential pressure must not exceed n50 ≤ 0.60 h⁻¹ (SerVilla typically delivers 0.35 h⁻¹].
- Mechanical Ventilation with Heat Recovery (MVHR]: Balanced continuous ventilation recovering ≥ 85\% of sensible heat from extract air, equipped with F7/ePM1 fine pollen filtration.
Moisture and Condensation Control in Steel Envelopes
Because steel conducts heat efficiently, the governing rule for passive steel construction is continuous exterior insulation encapsulation.
- Structural CFS studs are continuously wrapped externally by 120–160 mm of high-density basalt mineral wool. This keeps the structural steel envelope at stable room temperatures year-round.
- Inboard variable vapor retarders (Sd = 0.2m to 20m] block interior humidity migration during winter while facilitating inward drying during summer.
- An internal 50 mm service installation cavity ensures all electrical boxes, switches, and water pipes run inboard of the airtight plane without piercing membranes.
Editorial Disclosure & Engineering Note:
Analysis presented in this guide reflects Eurocode structural benchmarks, Passive House Institute physics, and over two decades of SerVilla international cold-formed steel manufacturing experience. Custom statutory site verification is conducted for every individual plot.
