Glossary

The vocabulary, defined

40 terms from the Shield™ system and from building science generally, each defined in a sentence or two rather than a paragraph of jargon.

A

ADU: Accessory dwelling unit: a secondary home on a lot with an existing house. One of the residential markets Guardian's material identifies.
Air barrier: The layer that stops air moving through the envelope. It is tested at the building level, for example by the US Army Corps protocol at 0.25 cfm per square foot at 75 pascals.
Air infiltration: Uncontrolled air leaking through the envelope. Up to 40 percent of a home's heat loss is due to air leakage, which is why an airtight envelope saves more than added insulation alone.
Axial load: Load acting straight down the wall. Standard 9-foot Shield™ walls have a design axial load of 2,250 pounds per lineal foot.

C

Cold-formed steel (CFS): Structural members shaped from sheet steel at room temperature rather than rolled hot. Light, dimensionally stable, non-combustible and infinitely recyclable, with a minimum of 25 percent recycled content. Designed to the AISI North American Specification.
Curtain wall: An exterior non-load-bearing cladding panel that carries only its own weight and wind load, attached to a steel frame or masonry structure. Shield™ curtain walls run to 33 feet standard length, 3½ to 12 inches thick, R-16 to R-75.

D

Demising wall: The wall separating one tenancy or dwelling from another. Shield™ demising and corridor walls can carry multiple floors, can be classified as non-combustible, and come in sections up to 10 feet high by 38 feet long.
Design wind load: The pressure a wall is engineered to resist. Standard 9-foot Shield™ walls are designed for up to 40 psf, and the system can be engineered to 20-foot heights at the same load.

E

E3 Quotient: The mortgage savings programme Guardian publishes, tying an energy-efficient envelope to the cost of owning the building.
Energy Wise® certification: The certification under which the Federal Social Security Administration facility's 81 percent HVAC saving was established.
Expanded polystyrene (EPS): A rigid closed-cell foam that is about 98 percent air, non-toxic, inert and free of CFCs and HCFCs. In a Shield™ panel it is both the insulation and the structural web. Graded to ASTM C578; Guardian uses UL certified modified EPS at a minimum density of 0.90 pcf, Type I.

F

Fire-resistance rating: The time an assembly keeps carrying load and blocking fire in an ASTM E119 furnace test, usually expressed in hours. It rates the assembly, so the drywall layer is part of it.
Flame spread index: How fast flame travels across a material's surface in the ASTM E84 tunnel test, scaled against red oak at 100. EPS rigid foam tests at 5 to 20.

H

High-velocity hurricane zone: The strictest US wind design category, applied in parts of South Florida. Guardian states the system can be designed to meet those requirements.
Hose stream test: ASTM E2226, applied after a fire test to prove the assembly does not disintegrate under fire-fighting water. A rating quoted without it is incomplete.

I

ICC-700: The National Green Building Standard for residential buildings, one of the major programmes cold-formed steel framing satisfies.

L

LEED: Leadership in Energy and Environmental Design, the USGBC's green building rating system. Cold-formed steel meets its sustainability requirements and Guardian states the panels are LEED capable.
Live load: The variable load on a structure — occupants, snow, equipment — as opposed to the permanent dead load. Shield™ roof panels span 8 to 15 feet at 30 to 50 psf live load.
Load-bearing wall: A wall that carries floors or roof above it. Shield™ load-bearing walls can carry multiple floors and eliminate some or all of the red iron framing; 3½ to 12 inches thick, R-16 to R-50.

N

Net zero: A building that produces as much energy as it uses over a year. Guardian states the panels are net-zero capable designs.
Non-combustible: A code classification for materials that do not contribute fuel to a fire. Shield™ demising and corridor walls can be classified as non-combustible.

O

Offsite construction: The broader practice of manufacturing building elements away from the site. McKinsey put the productivity gap between construction and manufacturing at 170 percent, which is the gap panelization closes.

P

Panelization: Building wall and roof elements in a factory and assembling them on site. It brings minimal waste, improved quality, reduced cycle time, reduced trade work, less rework and lower cost at scale.
Parallel path: Manufacturing panels while the foundation is being completed, so factory and site work run at the same time rather than in sequence.
Passive house: A performance standard for very low energy buildings built on five principles: continuous insulation with no thermal bridging, an extremely airtight envelope, high-performance windows and doors with managed solar gain, balanced heat- and moisture-recovery ventilation, and a minimal space conditioning season.
PHIUS: Passive House Institute US, which certifies buildings and products to a climate-specific passive standard. Guardian states Shield™ is the first and currently only PHIUS-certified panel system in the US.

R

R-value: Thermal resistance: how well an assembly resists heat flow. It varies with temperature, which is why Guardian publishes values at both 40 °F and 75 °F mean temperature.
Red iron: Hot-rolled structural steel framing, named for its oxide primer. Shield™ load-bearing panels can eliminate some or all of it.
Rough opening: The framed opening left for a window or door. Shield™ panels arrive with rough openings and integrated structural headers per the architectural drawings.

S

Shear wall: A wall that resists lateral load from wind or earthquake. Shear structure can be integrated into Shield™ bearing wall panels per the engineering drawings.
Shield™ panel: The Guardian building system's panel: cold-formed galvanized steel studs embedded flush into an expanded polystyrene core on both sides and mechanically fastened, acting as an I-beam with the steel as flanges and the foam as the web.
Smoke developed index: How much smoke a material produces in the same ASTM E84 test. EPS rigid foam tests at 95 to 300.
Sound absorption coefficient: How much sound energy a surface absorbs rather than reflects, from 0 to 1. Shield™ measures 0.36 at 1 kHz, 0.54 at 2 kHz and 0.38 at 4 kHz.
Sound Transmission Class (STC): A single number for how much airborne sound a partition stops, derived from an ASTM E90 test. Shield™ assemblies reach STC 59.
Structural header: The member that carries load over an opening. In Shield™ panels headers are integrated at the factory; the industry reference is the NASFA L-shaped header guide.

T

TEK screw: A self-drilling screw used to fasten sheet steel without a pilot hole. Shield™ panels are connected with 20-gauge minimum galvanized angle or track fastened with TEK screws.
Thermal bridging: A conductive path that bypasses the insulation, typically the studs and plates of a framed wall, lowering the whole-wall R-value well below the insulation's rated value. The Shield™ steel is set into the EPS opposed inside and outside specifically to eliminate it.
Thermal envelope: The continuous barrier of insulation and air sealing that separates conditioned space from outside. A Shield™ panel is a structural thermal envelope: it carries load and forms the envelope in one element.

V

Vapor permeance: How readily water vapour passes through a material, measured in perms under ASTM E96. It decides which way a wall assembly can dry.

W

Whole-wall R-value: The effective R-value of a wall including its framing, corners and openings, as opposed to the R-value of the insulation alone. The gap between the two is the cost of thermal bridging.

Written by Data Subsystems, for Guardian Structural Technologies. Last updated 6 September 2026.

Drafted from Guardian Structural product literature and published building-science sources. Awaiting Guardian technical review. Confirm any figure against the current product documents or ask us before you rely on it in a design.

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