Phius Certified Passive House Consultant (CPHC) key terms

A design approach that keeps indoor comfort mostly through envelope quality, solar gain control, and fresh-air ventilation, so heating and cooling loads shrink to the point where conventional mechanical systems become unnecessary.

A performance-based building standard originating in Germany that sets limits on space heating and cooling demand, primary energy use, and airtightness, verified by modeling and on-site testing rather than prescriptive construction rules.

A nonprofit organization that maintains and certifies a North American adaptation of the Passive House standard, offering climate-specific targets, certification of buildings and professionals, and quality assurance review of projects.

A professional credential issued by Phius after training and examination, showing competence in passive building design, WUFI Passive modeling, mechanical system design, and the Phius certification process.

The baseline Phius certification path, requiring projects to meet climate-specific limits on heating and cooling demand, source energy, and airtightness while demonstrating cost-optimized envelope and system choices.

A stricter Phius certification tier requiring all annual operational energy, including plug loads and appliances, to be offset by on-site renewable generation, on top of the CORE performance requirements.

The controlling document that defines Phius program requirements, submission stages, modeling conventions, documentation, and quality assurance obligations for a certified project or consultant.

Whole-building energy and hygrothermal modeling software used for Phius projects, combining a monthly or dynamic energy balance with moisture transport analysis and reporting formatted for certification review.

Annual space heating energy per unit of treated floor area, usually expressed in kWh per square meter per year; a headline metric compared against a climate-specific limit for certification.

Annual space cooling energy divided by treated floor area, reported in kWh per square meter per year and compared with a climate-specific cap that accounts for local dehumidification and solar loads.

The conditioned floor area used as the denominator for intensity metrics, calculated by a defined rule set that excludes some unconditioned or unfinished spaces and includes interior wall footprints.

Energy consumed at the source, including generation and delivery losses, calculated by multiplying delivered energy carriers by conversion factors; used to judge total building efficiency beyond heating and cooling alone.

A Phius metric that sums delivered energy across all end uses after applying site-to-source multipliers, allowing comparison of buildings that use different fuels or electricity grids.

An energy balance method that credits on-site or off-site renewable supply against demand, accounting for the timing and conversion losses of renewable generation and storage.

Energy generated on the project site or procured from qualifying renewable sources, which may be credited against building demand under defined rules, typically limited to annual consumption.

A localized path where heat flows more readily through the envelope than in adjacent assemblies, such as a slab edge or balcony penetration, raising heating demand and creating cold interior surfaces.

A design goal in which structural penetrations and geometric junctions are detailed so that heat flow at those locations stays close to the surrounding assembly, eliminating condensation risk and demand penalties.

The linear thermal transmittance of a junction, reported in watts per meter per kelvin, quantifying the extra heat flow per unit length of a thermal bridge beyond the clear wall area.

The point thermal transmittance of a discrete penetration such as a bracket or bolt, expressed in watts per kelvin, used in modeling to account for localized heat flow that linear values miss.

Insulation installed as an uninterrupted layer outside or around structural framing, reducing repeated thermal bridges and improving effective assembly performance compared with insulation placed only between studs.

A material's resistance to conductive heat flow, expressed in area times temperature difference divided by heat flow; higher values mean better insulation, and assembly values must be adjusted for framing.

The overall heat transfer coefficient of an assembly, equal to the inverse of its total resistance, describing how much heat passes per unit area and temperature difference.

The rate of heat loss through a whole window unit including frame, spacer, and glass, typically reported for a standard size and used as a primary input to envelope heat loss calculations.

The fraction of incident solar radiation admitted through a window as heat, combining directly transmitted and absorbed-then-released energy; it drives overheating risk and useful winter solar gains.

The share of a wall or building facade area occupied by windows, used to balance useful daylight and winter solar gains against heat loss and summer overheating.

The likelihood that indoor temperatures exceed comfort thresholds during warm periods, assessed in modeling from solar gains, internal gains, ventilation rates, and the ability to purge heat.

The measured air change rate of a building at a 50 pascal pressure difference, determined by blower door testing, used to limit infiltration heat loss and moisture-laden air movement.

A field test that pressurizes or depressurizes a building and measures leakage airflow, producing the n50 value and locating leaks for correction before certification.

A material or coating that limits water vapor diffusion into an assembly, positioned by climate and assembly type so moisture can dry out and condensation stays within acceptable limits.

Simulation of heat and moisture transport through building assemblies over time, used to verify that condensation, mold growth, and freeze-thaw damage are avoided under real climate loads.

A balanced mechanical ventilation system that transfers sensible heat from exhaust air to incoming outdoor air, providing fresh air without excessive heating energy in cold conditions.

A balanced ventilation system that transfers both sensible heat and moisture between exhaust and supply air, useful in humid climates where dehumidifying incoming air is costly.

The fraction of heat in exhaust air that the recovery unit transfers to supply air, net of fan energy and defrost effects, used in modeling to compute ventilation heat loss.

A ventilation strategy that supplies and exhausts equal air volumes through ducted fans, controlling where air enters and leaves so that fresh air reaches occupied rooms and moisture is removed at source.

Outdoor air supplied to replace air removed by exhaust systems such as kitchen or bath fans, which must be planned so pressure imbalances and backdrafting do not undermine ventilation and combustion safety.

The energy needed to remove moisture from air through condensation or desiccant processes, distinct from sensible cooling, and a major design driver in humid climates.

The part of a building intentionally heated or cooled to stay within comfort ranges, defining the boundary of the thermal envelope and the area counted in energy metrics.

The Phius process in which submitted models, drawings, and test results are checked against program requirements by reviewers, with corrections required before certification is granted.