CRES key terms

The continuous layer of insulation and air control that separates conditioned interior space from unconditioned or outdoor space; its location determines where heat loss is calculated in modeling and where field inspection focuses.

Heat flow that bypasses insulation through framing, fasteners, or structural penetrations with higher conductance; it lowers effective assembly performance below the nominal cavity R-value and appears as cold stripes on infrared scans.

Buoyancy-driven air movement caused by indoor-outdoor temperature and density differences, producing upward flow in tall buildings and drawing air in low and pushing it out high.

The air control layer that resists air leakage between conditioned and unconditioned zones; it may coincide with the thermal boundary or be located elsewhere, and leakage at it drives moisture and energy problems.

The fraction of total equipment cooling capacity used to remove sensible heat rather than latent heat; a mismatch with the building load leaves homes either humid or overcooled.

A measure of steady-state thermal resistance per unit area, expressed in ft2·h·°F/Btu in US practice; higher values mean slower conductive heat flow through a material or assembly.

The overall conductance of an assembly such as a window or wall, equal to the reciprocal of its total R-value; codes and programs set maximum U-factors for fenestration and envelope components.

The fraction of incident solar radiation admitted through fenestration as heat, combining directly transmitted and absorbed-then-inward-released energy; lower values reduce cooling loads in sunny orientations.

A diagnostic procedure using a calibrated fan in a temporary doorway panel to depressurize or pressurize a building while measuring airflow, yielding envelope leakage at a reference pressure.

Leakage airflow measured at a 50-pascal pressure difference, divided by conditioned volume; it normalizes blower door results so homes of different sizes can be compared against program thresholds.

The hypothetical open area that would produce the same leakage as the measured envelope at a specified reference pressure; it is often reported alongside ACH50 to convey hole size in familiar units.

Use of a thermal camera to visualize surface temperature differences that reveal insulation gaps, thermal bridging, air leakage paths, and hidden moisture, always interpreted with knowledge of interior and exterior conditions.

The temperature difference between two environments, such as indoors and outdoors or supply and return air; adequate delta-T is required for meaningful blower door, duct leakage, and infrared diagnostics.

A procedure that pressurizes the duct system with a calibrated fan and measures leakage to outside or to unconditioned space, typically reported as cubic feet per minute at 25 pascals.

Permanent closure of duct joints, seams, and penetrations using mastic, mesh, or listed tape to reduce conditioned air loss and prevent pressure imbalances between rooms.

A sustained difference between supply and return airflow in a zone or between indoors and outdoors, which can drive backdrafting, moisture migration, and comfort complaints.

The continuous material system that controls unintended air movement through the envelope; it must be sealed at joints, penetrations, and transitions to be effective.

Field work that closes gaps, cracks, and penetrations in the building envelope and interior pressure boundary with caulk, foam, gaskets, or weatherstripping to cut infiltration and exfiltration.

Unintentional outdoor air entering a building through leaks driven by wind, stack effect, and mechanical pressure differences; it carries both energy and moisture consequences.

A material class that slows diffusion of water vapor through an assembly; its placement and permeance must suit the climate so the assembly can dry rather than accumulate moisture.

The temperature at which air reaches saturation and water vapor begins to condense; locating the dew point within an assembly identifies where wetting risk is greatest.

Change of water vapor into liquid on a surface or within a material when vapor pressure and temperature conditions reach saturation, a common cause of hidden envelope damage.

The space containing fuel-burning equipment and its combustion air supply; testing and sealing work must not create depressurization that starves appliances or reverses vent flow.

Reversal of flue gas flow caused by depressurization, blocked flues, or poor vent design, allowing combustion byproducts to enter occupied space; it is a serious safety hazard requiring immediate action.

Combustion gases escaping from an appliance draft hood or flue connector into the room instead of venting outdoors, detected with a mirror, smoke, or electronic probe during safety inspection.

A colorless, odorless gas produced by incomplete combustion that binds hemoglobin and can be fatal; assessment work includes testing, source identification, and installing alarms per standards.

An industry method for sizing heating and cooling equipment from room-by-room envelope and internal load estimates, forming the basis for correct equipment selection and distribution design.

An industry procedure for sizing ducts and selecting fittings based on airflow and available static pressure, ensuring each room receives its calculated airflow.

The resistance to airflow measured in a duct system or across equipment, expressed in inches of water column; excessive values indicate undersized ducts, restrictive filters, or coil problems.

The volume of air moved per unit time, usually cubic feet per minute; verifying it at equipment and registers confirms whether delivered capacity matches design intent.

The rate of heat that must be removed to maintain design indoor conditions, combining envelope gains, internal gains, and solar and latent contributions.

The portion of a load associated with removing moisture from air through dehumidification; it is driven by infiltration, occupancy, and vapor sources rather than temperature alone.

A mathematical representation of envelope leakage used in energy simulation, often derived from blower door data and combined with weather and pressure assumptions to estimate annual infiltration.

Adjustment of model inputs so predicted energy use reasonably matches utility bills or monitored data, improving confidence in savings estimates for proposed measures.

The documented pre-retrofit condition or reference case against which savings from proposed measures are measured; it must be defined consistently with the post-work conditions.

A structured process for quantifying actual energy savings after an upgrade by comparing measured post-installation use with an adjusted baseline, reducing reliance on predictions.

A written description of the specific measures, materials, quantities, and responsibilities agreed for a project; it defines boundaries so contractors and customers share the same expectations.

A documented, mutually approved modification to the original work scope that records added or removed measures, cost adjustments, and schedule effects before the work proceeds.

A structured pre-work check of combustion appliances, venting, carbon monoxide, moisture, electrical hazards, and air quality conditions that must be resolved or addressed before weatherization proceeds.