CRES flashcards

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

Stack effect

Buoyancy-driven air movement caused by indoor-outdoor temperature difference; warm air rises and exits high in the building while outdoor air enters low, driving winter infiltration and exfiltration.

Dew point temperature

The temperature at which air reaches saturation and water vapor begins to condense; surfaces at or below dew point collect moisture, which is why cold surfaces in humid spaces condense.

Thermal bridge

A localized path of higher thermal conductance through an assembly, such as framing, rim joists, or slab edges, that lowers the assembly's effective R-value below its nominal cavity value.

Latent versus sensible heat

Sensible heat changes dry-bulb temperature, while latent heat is energy absorbed or released during a phase change without a temperature change; dehumidification removes latent heat.

ACH50 calculation

Air changes per hour at 50 pascals equals CFM50 multiplied by 60, divided by conditioned volume in cubic feet; it normalizes blower door leakage across house sizes.

Blower door test purpose

Depressurizes the house to a reference pressure, typically 50 pascals, to quantify envelope air leakage and, with zonal pressure diagnostics, to locate the dominant leakage paths.

Pressure pan testing

With the house depressurized by a blower door, a pressure pan placed over a register reads the pressure difference; higher readings indicate a stronger leakage connection between the duct and an unconditioned zone.

Infrared thermography limits

Thermal imaging shows surface temperature differences only; it needs an adequate indoor-outdoor temperature difference and must be interpreted with emissivity, air leakage, and solar gain effects in mind.

Effective versus nominal R-value

Nominal R-value is the labeled product value; effective R-value is the installed performance after accounting for compression, gaps, convection within cavities, and thermal bridging.

Vapor retarder classes

Class I is 0.1 perm or less, Class II is 0.1 to 1.0 perm, and Class III is 1.0 to 10 perm; class selection depends on climate and assembly drying direction.

Window U-factor and SHGC

U-factor measures whole-window heat conductance, where lower is better; SHGC is the fraction of solar heat admitted, where lower values reduce cooling loads in warm climates.

Grade I insulation

A RESNET installation grade in which the cavity is completely filled, insulation contacts the air barrier on all six sides, and gaps and compression are minimal, allowing near-rated performance.

Manual J load calculation

A room-by-room heating and cooling load calculation using design conditions, envelope areas, and internal gains; equipment must be selected from this load, not from square footage rules of thumb.

External static pressure

The total resistance of the duct system and components measured at the air handler; it must stay within the blower's rated range or airflow drops and coils may ice or limits trip.

CFM per ton

The airflow delivered per ton of cooling capacity, typically targeted near 350 to 400 CFM per ton; too little airflow causes coil icing and low sensible capacity.

Heat pump balance point

The outdoor temperature at which heat pump capacity equals the building heating load; below this point, supplementary resistance heat operates to maintain indoor temperature.

Superheat and subcooling

Field measurements used to verify refrigerant charge; superheat is checked on fixed-orifice systems and subcooling on TXV systems, following the manufacturer's specified method and target values.

Air barrier continuity

The air barrier must be continuous, durable, and in contact with insulation across the entire envelope; gaps at rim joists, chases, and penetrations defeat the assembly.

Attic air sealing priority

The attic plane at the top of the house is a first-priority air sealing target because warm, moist indoor air rising into a cold attic can condense and cause decay.

Crawlspace encapsulation

Converting a vented crawlspace into a sealed, conditioned space by covering the ground with a vapor barrier, sealing foundation vents, and controlling humidity with a dehumidifier or conditioned air supply.

Bulk water management

Control of liquid water through roofing, flashing, drainage, and grading; it is the first defense in moisture management and takes priority over vapor control and air sealing.

Exhaust fan termination

Bath and kitchen exhaust must discharge outdoors through short, smooth duct with a backdraft damper; terminating into an attic or crawlspace adds moisture and can cause mold and decay.

Carbon monoxide hazards

CO is a colorless, odorless product of incomplete combustion; exposure causes headache, nausea, dizziness, and can be fatal, so CO testing and alarms are life-safety measures.

Combustion appliance zone test

A test that operates exhaust fans and the air handler to see whether the combustion appliance zone depressurizes enough to backdraft natural-draft appliances, causing spillage of flue gases.

Flue gas spillage

Combustion products escaping from the draft hood or flue connector into the living space rather than venting outdoors; it is a fail condition that requires correction before other work.

Radon entry and mitigation

Radon is a radioactive soil gas that enters through foundation cracks and openings; testing is required, and mitigation typically uses sub-slab depressurization with a vented fan.

HERS Index

A score where 100 represents a reference new home of the same size and shape; lower scores mean greater efficiency, and a score of zero indicates a net-zero-energy home.

Model calibration

Adjusting energy model inputs so predicted annual consumption matches actual utility bills, commonly aiming to be within about ten percent of measured annual use.

Degree-day method

An estimation technique that integrates the difference between a base temperature and outdoor temperature over a season to approximate heating or cooling energy use.

IECC performance path

A code compliance route that uses whole-building energy modeling to demonstrate the proposed design meets or beats the prescriptive package, allowing trade-offs among measures.

Simple payback

Installed measure cost divided by annual energy savings, expressed in years; it is a screening metric that ignores measure life, financing, and non-energy benefits.

Scope of work elements

A written scope lists each measure, quantity, location, expected outcome, exclusions, assumptions, and who obtains permits, so the customer and contractor share the same expectations.