Passivhaus Certification: PHI Building Criteria, Version 10c (January 2023)

The Passive House Institute (PHI) certifies buildings against its “Criteria for Buildings”, currently Version 10c of January 2023, valid with PHPP Version 10. This article summarises the Passive House, EnerPHit and PHI Low Energy Building criteria from that document (PHI, Criteria for Buildings, Version 10c; Table numbers below refer to it). Certification projects follow the criteria in force when the certification process started, so check which version applies to your project.

What are the Passivhaus criteria in Version 10c?

A Passive House is classified Classic, Plus or Premium depending on its renewable primary energy (PER) demand and renewable energy generation. The heating, cooling and airtightness criteria are the same for all three (Table 1). The limits apply in all climates worldwide, and the reference area is the treated floor area (TFA) from the PHPP manual, except for generation (projected building footprint) and airtightness (net air volume).

Heating demand (15 kWh/(m²a)) and heating load (10 W/m²) are alternatives to each other, not two limits that must both be met.

PER demand includes all energy uses in the building. A deviation of up to 15 kWh/(m²a) from the PER or generation criterion is allowed if it is compensated by a different amount of generation or demand; the compensation is calculated in kWh/a because the two criteria use different reference areas. Source: Table 1 and footnotes 6 to 8.

What other requirements does the certifier check?

Version 10c also sets comfort limits: for buildings without active cooling, no more than 10% of hours in a year with indoor temperatures above 25 °C (with active cooling, the cooling system must be adequately dimensioned), and no more than 20% of hours above 12 g/kg absolute humidity (10% with active cooling) (sections 2.4.1 and 2.4.2). All rooms within the thermal envelope must be ventilated directly or indirectly (section 2.4.3).

Airtightness is measured to ISO 9972 (method 1) with PHI’s deviations: a series of measurements at both positive and negative pressure, with the average of both used for the n50 limit. The test covers the whole heated or cooled volume, and spot tests of building parts or results from identical buildings are not accepted (section 3.2.10). PHI recommends testing while the airtight layer is still accessible.

What are the five core principles?

PHI states that the Passive House and EnerPHit standards rest on five principles: very good thermal insulation, highly energy-efficient windows, controlled mechanical ventilation with heat recovery, no thermal bridges, and airtightness (PHI building certification page). The criteria above are the limits; the component values (U-values, window data, heat recovery efficiency) are not Passive House criteria but come out of the PHPP calculation for the climate and building. PHI publishes certified component data sheets, and Table 2 of the criteria lists component values for EnerPHit.

How does EnerPHit differ?

EnerPHit is the PHI standard for retrofits using Passive House components. It can be proved either by the component method (Table 2, with climate-zone U-values, window values and minimum heat recovery) or by the energy demand method (Table 3). Compliance with only one method is needed, and the general criteria in Table 4 always apply.

The cooling and dehumidification demand equals the Passive House requirement (with n50 taken as 1.0 1/h for the building-specific limit). The general criteria (Table 4) are airtightness n50 of 1.0 1/h or less, and the same Classic, Plus and Premium PER demand (60, 45, 30, with an allowance for larger heating or cooling demand compared with Passive House) and generation (none, 60, 120) classes. EnerPHit therefore has no single 25 kWh/(m²a) limit: the heating limit depends on the climate zone. Partial renovations may be pre-certified under an EnerPHit Retrofit Plan, which requires the first modernisation step to be completed and a significant reduction in energy demand against the initial state, shown by one of four cases (section 3.3.1): (a) at least a 20% reduction of PER or PE demand; (b) at least a 20% or 40 kWh/(m²a) reduction of the heating demand or of the cooling and dehumidification demand, for whichever had the higher useful energy demand initially; (c) at least one housing unit almost entirely modernised in a building with several owners; or (d) a new extension built in accordance with the plan. Air infiltration leak detection is also required. EnerPHit Unit, for single retrofitted units, was in development in the source consulted, with qE50 of 1.0 m³/(h m²) or less as its airtightness requirement.

What is the PHI Low Energy Building standard?

For buildings that miss the Passive House or EnerPHit criteria, the PHI Low Energy Building standard (Table 5) requires heating demand of 30 kWh/(m²a) or less, cooling and dehumidification demand equal to the Passive House requirement plus 15, n50 of 1.0 1/h or less, and PER demand of 75 kWh/(m²a) or less (exceeding by up to 15 allowed with compensating generation).

How is compliance verified?

Evidence is prepared in the Passive House Planning Package (PHPP) and reviewed by a PHI-accredited certifier. The certifier checks the energy balance calculation and also requires construction-stage evidence: the airtightness test, the ventilation adjustment protocol and a site manager’s declaration. Certification is possible after completion if the criteria are met. The certifier need not visit the building, so it can be chosen regardless of location (PHI building certification page).

Which mistakes delay certification?

• Treating heating demand and heating load as two limits. The criteria are 15 kWh/(m²a) heating demand, or 10 W/m² heating load as the alternative.
• Assuming one threshold set for all classes. Classic, Plus and Premium differ in PER demand (60, 45, 30) and generation (none, 60, 120 kWh/(m²a) of footprint).
• Applying the 15 kWh/(m²a) cooling limit as fixed. It is 15 plus a variable allowance calculated in PHPP.
• Testing airtightness after the airtight layer is covered. The 0.6 1/h limit is judged on the average of positive and negative pressure tests of the whole envelope volume.
• Using EnerPHit with a fixed limit. The heating limit depends on the climate zone, or the component table applies.
• Designing to an outdated version. Confirm the criteria version that applies when certification starts.