Passive House Calculator

About the Passive House Calculator

The Passive House (Passivhaus) standard is the world's most rigorous energy efficiency standard for buildings. Developed in Germany in 1990 by Dr. Wolfgang Feist, it specifies that a building's heating demand must not exceed 15 kWh/m²/year—approximately 90% less than a typical building. This is achieved through five key principles: superinsulation, airtight construction, thermal bridge-free design, high-performance windows, and heat recovery ventilation.

A certified Passive House in a cold climate uses so little energy for heating that a small electric heater could warm the entire building. In Germany, the average Passive House uses about 1.5 liters of heating oil equivalent per square meter per year—versus 15+ liters for a standard new building and 20-25 liters for existing stock. The total primary energy demand (heating, cooling, hot water, electricity) must not exceed 120 kWh/m²/year.

This calculator models a building's energy balance using simplified Passivhaus methodology. Enter your building dimensions, insulation levels, window specifications, airtightness, and climate data to estimate heating demand and determine whether your design meets Passive House criteria.

When This Page Helps

Building construction and operation account for 40% of global CO₂ emissions. Passive House design can reduce operational energy by 80-90%. Use this calculator to check whether your envelope, airtightness, glazing, and ventilation assumptions are enough to meet Passivhaus-style heating targets.

How to Use the Inputs

1. Enter your building's floor area and wall/roof/floor dimensions.
2. Specify insulation R-values for walls, roof, floor, and windows.
3. Input the air changes per hour at 50 Pa (blower door result).
4. Set the heat recovery ventilation efficiency.
5. Choose your climate zone or enter heating degree days.
6. Review the annual heating demand and Passivhaus compliance.
7. Explore how changing each parameter affects the energy balance.

Example Calculation

Tips & Best Practices

• Windows are the weakest link — triple-glazed with U-value ≤ 0.8 W/m²K is essential for cold climates.
• South-facing windows (northern hemisphere) provide free solar heating — optimize their size and orientation.
• Airtightness is about construction quality, not expensive materials — tape, sealant, and attention to detail.
• The HRV efficiency matters enormously — going from 75% to 90% recovery halves ventilation heat loss.
• Thermal bridges at junctions (wall-floor, wall-roof) can undermine even thick insulation — detail carefully.
• Internal gains (people, appliances, lighting) contribute 2-5 kWh/m²/yr — they're significant in super-insulated buildings.

The Five Principles of Passive House

The Passive House standard rests on five synergistic principles that work together to virtually eliminate heating and cooling demand:

**1. Superinsulation** — Walls, roof, and floor typically achieve R-40 to R-60 (U-values of 0.10-0.15 W/m²K), versus R-13 to R-30 in standard construction. The extra insulation costs relatively little but dramatically reduces conductive heat loss.

**2. Airtightness** — The building envelope is sealed to ≤ 0.6 air changes per hour at 50 Pa pressure difference (ACH50). This eliminates uncontrolled air leakage, which in conventional buildings accounts for 25-40% of heat loss. Airtightness is verified by blower door testing.

**3. Thermal Bridge-Free Design** — Every junction (wall-floor, wall-roof, window frame) is detailed to prevent "thermal bridges" where heat short-circuits through the insulation. Even small thermal bridges can increase heat loss by 10-30% if uncorrected.

**4. High-Performance Windows** — Triple-glazed, argon or krypton-filled, low-e coated windows with insulated frames achieving U ≤ 0.80 W/m²K. Windows are simultaneously the weakest thermal element and a source of solar heat gain — orientation and sizing are critical design decisions.

**5. Heat Recovery Ventilation** — Mechanical ventilation with ≥ 75% heat recovery (ideally 85-95%) provides continuous fresh air while recapturing most of the heat from exhaust air. This is the technology that makes airtight buildings healthy and comfortable.

Economics and Comfort

The economic case for Passive House is compelling when viewed over a building's lifetime. A typical Passive House costs 5-15% more to build but saves 80-90% on energy costs annually. With energy prices rising and building lifetimes of 50-100 years, the net present value is strongly positive in most markets.

Beyond economics, Passive Houses are exceptionally comfortable. The superinsulation and airtightness eliminate drafts, cold spots, and temperature fluctuations. Interior surface temperatures are uniform (no cold walls), and the HRV provides consistently fresh air without the noise and maintenance of conventional HVAC systems.

Global Adoption

As of 2024, over 100,000 Passive House-certified buildings exist worldwide. Germany and Austria lead in absolute numbers, but the standard has been adapted to every climate from subarctic Finland to subtropical China. Several jurisdictions (Brussels, Luxembourg) have adopted Passive House as the default building standard for new construction. The EU's "nearly zero-energy building" (nZEB) requirement, mandatory since 2021, closely approximates Passive House performance levels.

Frequently Asked Questions

• What qualifies as a Passive House?

  The Passivhaus Institut (PHI) certification requires: (1) Heating demand ≤ 15 kWh/m²/year, (2) Cooling demand ≤ 15 kWh/m²/year, (3) Total primary energy ≤ 120 kWh/m²/year, (4) Airtightness ≤ 0.6 ACH at 50 Pa, (5) No thermal bridging. These are verified through energy modeling (PHPP software) and blower door testing.

• How much more does a Passive House cost?

  Typically 5-15% more than conventional construction, depending on climate and local building standards. The premium covers: thicker insulation, high-performance windows (triple-glazed), HRV system, airtight membrane, and careful detailing. The extra cost is recovered in 7-15 years through 80-90% lower energy bills—and the building is far more comfortable.

• What is a heat recovery ventilator (HRV)?

  An HRV exchanges stale indoor air with fresh outdoor air while recovering 75-95% of the heat from the outgoing air. This is essential in airtight buildings: you need mechanical ventilation for air quality, but without heat recovery, ventilation would lose most of the heat you're trying to conserve. A good HRV provides fresh air continuously while losing minimal energy.

• Can Passive Houses work in hot climates?

  Yes, but the strategy shifts. In hot climates, the focus is on: high thermal mass (stores cool), excellent shading (blocks solar gain), reflective roofing, and cooling via nighttime ventilation or minimal air conditioning. The Passivhaus Institut has a "PHI Low Energy Building" class for climates where the standard is hard to achieve conventionally.

• Is 0.6 ACH50 airtightness achievable?

  Yes, with careful construction. Standard new construction achieves 3-7 ACH50, energy-efficient buildings 1-3 ACH50, and Passive Houses must achieve ≤ 0.6 ACH50. This requires: continuous airtight membrane, taped seams, sealed penetrations (pipes, wires), and pre-compressed sealing tape at window frames. It's a construction quality issue, not a technology barrier.

• Do Passive Houses need a furnace?

  In most climates, no traditional furnace is needed. The heating demand is so low (typically 1-2 kW peak for an entire house) that it can be met by: a small electric heater, a heat pump, or even post-heating the ventilation air supply. Many Passive Houses use a combined HRV + small heat pump unit as their entire HVAC system. No radiators or ductwork needed.