Phius Certified Passive House Consultant (CPHC) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Treated floor area (TFA)

The conditioned floor area used to normalize all Phius demand and load metrics. Only spaces inside the thermal and airtight boundary count, so zone boundaries must be drawn deliberately.

Specific space heat demand

Annual space-heating energy divided by treated floor area, in kWh/(m²·yr). It is a certification metric, distinct from peak load, and both must pass.

Peak heating load

The maximum heating power needed at design conditions, in W or W/m². A low peak load is what allows a passive building to omit a conventional central heating distribution system.

n50 airtightness

The air change rate at 50 Pa pressure difference, measured by blower door. Passive targets are typically n50 ≤ 0.6 h⁻¹ for the whole building.

Linear thermal transmittance psi

The heat loss per unit length per kelvin at a junction, in W/(m·K). Junction penalty equals psi times junction length and is added to the assembly UA.

Continuous exterior insulation

Insulation outside the structure that limits thermal bridging at studs and slabs and keeps the structural layer warm, raising the condensing surface above the interior dew point.

Whole-window U-value

The U-value of frame, spacer, edge, and glazing combined, not center-of-glass. It governs both heat loss and interior surface temperature, so it predicts condensation risk.

Solar heat gain coefficient

The fraction of incident solar radiation admitted through a window as heat. High values help in heating climates; low values with shading are needed to control cooling demand.

Vapor retarder placement

In cold climates the vapor retarder goes on the warm side; in mixed and warm-humid climates vapor-open assemblies control inward vapor drive from wet cladding.

Slab edge thermal bridge

The junction where a slab meets the foundation wall and exterior. Insulating the slab edge continuously reduces a bridge that can otherwise dominate the envelope UA.

WUFI Passive assembly model

A layered hygrothermal model of each envelope assembly, built from materials with thermal and moisture properties, then referenced by area in the whole-building energy balance.

Zone classification

Each modeled space is conditioned, unconditioned, or adjacent. Only conditioned treated floor area enters the demand metrics, so misclassification directly distorts results.

Heat recovery efficiency

The fraction of heat in exhaust air transferred to supply air, typically 75-85% for certified units. It is entered in the model and reduces ventilation heat loss.

Shading factor

A multiplier reducing solar gain through a window for overhangs, fins, and horizon obstructions. It is applied with the glazing g-value, not instead of it.

Model sanity check

Comparing predicted specific demand against assembly U-values and glazing area. An implausibly low result usually means an unmodeled zone or an incorrect area.

As-built model update

The certified model must match the constructed envelope, ventilation, and systems. Deviations found during construction require a documented model revision and resubmission.

Balanced ventilation

Supply and exhaust air volumes are equal, avoiding pressure differences that drive moist interior air into assemblies and increase infiltration losses through the envelope.

Frost protection strategy

A preheater, recirculating defrost damper, or supply-air tempering that prevents core icing in cold weather. The chosen strategy must be represented in the energy model.

Duct location

Ducts inside the conditioned envelope retain recovered heat. Ducts in attics or garages lose it, so they must be sealed and heavily insulated if unavoidable.

Post-heater energy

Energy used to temper ventilation supply air after recovery. It is allowed but counts against demand metrics, so the design aims to minimize it.

Drain-water heat recovery

A device recovering heat from warm wastewater to preheat domestic hot water. It reduces a load that becomes dominant once space conditioning is minimized.

Cooking exhaust interlock

A damper or control that balances high-rate kitchen exhaust against the HRV so the building does not depressurize and pull humid air into the envelope.

Phius climate-specific limits

Source energy and demand limits vary by climate zone. A design that passes in one location may fail in another because the limits change with climate.

Source energy limit

A cap on primary energy including grid and generation efficiency. All-electric heat-pump designs are favored, and on-site renewables can be credited against the limit.

Certified passive house consultant

A credentialed professional who prepares and submits the Phius energy model. The credential requires continuing education and cannot submit projects once lapsed.

Performance versus prescriptive path

The performance path uses the WUFI Passive model against numeric limits; prescriptive paths constrain assemblies and systems directly. Both can reach certification.

Certificate issued to building

Phius certification belongs to the specific constructed building, not to the designer. It follows verified airtightness and commissioning, not just a passing model.

Blower-door test timing

The test is run after the air barrier is complete but before finishes conceal it, so a failed result can still be corrected by sealing accessible leaks.

Thermal imaging survey

Infrared imaging during a blower-door test reveals missing insulation and air leaks. A temperature difference of at least about 10 K between inside and outside is needed.

Ventilation commissioning

Verification of design airflow at each terminal, supply-exhaust balance, and measured heat recovery efficiency. Results are recorded as part of the certification documentation.

QA checklist sign-off

A trade-by-trade record of envelope continuity, window installation, penetration sealing, and system commissioning, signed off before the work is concealed.

Independent QA reviewer

A reviewer separate from the design team who confirms the built building matches the certified model, using test reports, commissioning records, and photographs of concealed work.