Cavity batt in a steel stud is not the envelope. Steel is a thermal short. IECC and ASHRAE 90.1 name continuous insulation (ci) as insulating material continuous across structural members, uncompressed, with no thermal bridges other than fasteners and service openings — outboard, inboard, or integral to the opaque wall. That is the definition. It is not an EIFS cladding manual, and not a license to treat every foam board on the elevation as the drywall sub’s free extra.
This page is for the wall-and-ceiling shop that hangs sheathing, hangs or coordinates the ci, or fastens through it into exterior CFS or masonry. Member selection, cladding attachment, and U-factor belong to the documents and the design professional. Do not invent an R-value onto a bid. Directory: Insulation, Exterior sheathing, Products.
What ci is — and what it is not
Cavity insulation lives between studs. On interior partitions that is the batt the commercial drywall number often already carries. On an exterior CFS backup it is still cavity. It does not break the stud flange.
Continuous insulation runs across those flanges. Rigid foam (ASTM C578 polystyrene class or C1289 polyiso class) and mineral-wool board are the usual commercial products. The energy-code definition is picky: a linear metal Z that slices through the foam so the Z is the thermal bridge is not ci. It is a furr with insulation stuffed around it. Point fasteners through uncompressed foam, or thermally broken clips that the envelope engineer actually named, are how cladding and furring stay on without turning the ci into Swiss cheese.
Thermal break in this trade is the ci (or a listed clip/pad) interrupting the steel path. It is not a marketing sticker on a 25-ga interior stud. Interior light-gauge still sees 5 psf partition load, not a wind-bearing envelope.
Not this page: EIFS lamina, finish coats, or mesh. EIFS is a cladding system that often includes ci. If the bid invitation is EIFS, that is a different specialty. If the bid is CFS backup, glass-mat sheathing, rigid ci, and rails, that is the wall-and-ceiling / envelope split this guide is about.
Who owns the package
On a typical commercial job the split is messy. Read the invitation.
- Interior metal stud, board, finish, cavity insulation — usually the drywall / W&C number. See steel stud framing basics.
- Exterior CFS — sometimes the same W&C number, sometimes a CFS sub, sometimes the GC’s skin. Exterior CFS vs interior light-gauge and Exterior cold-formed framing.
- Glass-mat or gypsum sheathing — often W&C. Application is ASTM C1280 / GA-253, not interior C840 / GA-216. Exterior sheathing and WRB.
- ci board — insulation contractor, W&C, or envelope. If you hang it, you also own fastener length, compression, and the edge at openings.
- WRB and cladding rails — envelope, GC, or you. Fasteners through ci into CFS still have to hit the member the engineer sized.
Residential production meets ci as foam sheathing on wood more often than as CFS backup. That foam is usually the framer or the insulation contractor, not the hang crew — unless the shop sold a full envelope. Mixed-use and townhome CFS is the commercial rule set, not the 2×4 habit.
Fastening through ci
The hang problem is length and engagement, not a new screw type invented on the lift.
Interior gypsum into light-gauge is still ASTM C1002 Type S. Heavier exterior and structural steel wants ASTM C954 (Type S-12 class) self-drilling points. Sheathing screws are a third data sheet. ci does not change the family; it adds the foam (and any outboard sheathing or drainage layer) the screw must pass before it finds steel or wood. See Type S vs Type W and Fasteners. Lengths come from the fastener house — Grabber and peers — plus the cladding and ci through-insulation tables and the IBC/IRC cladding-through-foam sections (edition-dependent). Do not guess a length from last year’s foam.
Compression. ci is specified uncompressed. Over-driving a long screw into 25-ga or crushing foam under a rail is how you lose thickness and create a dish the cladding will telegraph. Snug to the connected materials; do not use the gun as a clamp.
Point vs line. Fasteners are the thermal bridges the energy definition allows. A continuous metal Z through the ci is a line bridge. If the drawing shows Z-furring as the ci attachment, that is an engineering / U-factor problem, not a production upgrade. Thermally isolated clip systems exist as a class; use only the clip the documents named.
Sheathing vs ci order. Some walls: CFS, glass-mat sheathing, then ci, then rails. Some: ci as insulating sheathing, gypsum on the interior only. Some masonry: ci or Z-furr inboard for the interior gypsum. Hang sequence follows the wall type. Interior paper-faced C1396 board still wants a closed, conditioned box — how to hang drywall. Exterior glass-mat is a substrate, not a Level 4 wall.
Thermal breaks the field actually sees
Stud flanges. Bare CFS with cavity batt only is the textbook bridge. ci outboard of sheathing is how commercial envelopes recover. Interior drywall stud is still not exterior backup; mils, coating, and C955 / AISI S240 vs C645 / S220 stay in the exterior CFS guide.
Tracks, clips, and shelf angles. Floor and head tracks, bypass clips, and masonry shelf angles are linear bridges unless the detail lets ci pass or a thermal pad/clip is in the design. Do not copy a TI deflection-track habit onto a curtain-wall bypass and call it ci.
Openings. Windows and doors are where ci dies if the return is all metal. That is a flashing and buck detail, not a drywall taping detail. Coordinate; do not foam the gap with leftover batt and move on.
Interior Z-furr on masonry. Classic W&C work: hat channel or Z on the block, then gypsum. If the spec also wants ci, the Z cannot pretend to be the ci. Either the foam is continuous and the furr is point-fastened through it, or the assembly is a U-factor wall. Price the fasteners and the plane.
Bid notes that keep ci from eating the number
Split the takeoff even if one contract holds it: CFS, sheathing, ci, cavity, WRB-adjacent board, interior hang. Different screws, different labor, different punch.
Qualify exposure. Glass-mat sheathing and rigid ci both have manufacturer weather windows. Paper-faced gypsum sheathing is the short window. See choosing drywall type and Georgia-Pacific Gypsum as the DensGlass-class example — then read the product you actually submitted.
Fire and ci are not automatic friends. A UL / GA-600 exterior wall that names gypsum sheathing, a mineral-wool cavity, and a cladding does not silently accept a foam thickness you added for energy. Substitutions go through the design professional and the AHJ.
Interior finish still cares about plane. Long screws through crushed foam will oil-can a rail. A Level 5 interior on the other side of a wavy backup is still your photograph if you framed it.
Steel mills: ClarkDietrich, MarinoWARE. Sheathing hang is not interior production — exterior sheathing and WRB.
Related directory
Envelope board: Exterior sheathing. Steel: Exterior cold-formed framing, Steel stud / framing. Batts and boards: Insulation. Screws: Fasteners. Product door: Products.
FAQ
Is continuous insulation in the drywall sub’s number?
Sometimes. Interior cavity insulation often is. Exterior ci is a package question on every bid. Confirm it in writing.
Does Z-furring through foam count as ci?
Not under the IECC / ASHRAE 90.1 definition. Linear metal through the insulation is a thermal bridge. Point fasteners (and listed thermal clips) are the allowed class of penetration.
Can I use interior Type S screws through ci into exterior studs?
Length and point follow the steel thickness and the through-insulation table, not the interior hang gun. Light-gauge interiors are C1002 Type S; heavier exterior steel is C954 class. ci only adds the stack the screw has to pass.
Is this an EIFS install guide?
No. EIFS is a cladding system. This page is ci, thermal break, and fastening the W&C shop hangs or coordinates on CFS and masonry.
Does ci replace glass-mat sheathing?
Only if the wall type says the foam is the sheathing and the fire / WRB / cladding documents agree. Many commercial CFS walls still want gypsum or glass-mat plus ci outboard.