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Unvented attic as a wildfire path
An unvented attic is a legal path when you have no attic ventilation openings to protect. Deschutes County’s R327 FAQ lists it next to two other options. Put the vents 12 feet or more above grade, or use a manufactured ember-resistant vent. Mesh and listings apply to openings that remain. An unvented attic does not make the roof fireproof. It does not replace crawlspace, dryer, or mechanical vent rules.
You are choosing whether the attic has holes. An unvented attic is a path when you have no attic vents to protect. Put that choice on the drawings.
Why it matters
Embers enter attics through gable, ridge, soffit, and eave vents. Where R327 is adopted, vents on the underside of eaves, soffits, and cornices are restricted. Removing the attic openings is one way off that detail. It is a construction choice, not a product listing.
CAL FIRE and IBHS still tell you to cover or replace vents you keep. See vents and mesh versus listed.
How it works
A ventilation opening is a hole. Embers go through holes larger than the screen, and through gaps beside the frame. If the attic is built without those openings, that ember path is gone.
The roof still has to stay dry. Insulation still has to match the rest of the adopted code. That is a different chapter from R327. An unvented attic is a designed roof assembly. This page does not spec foam, vapor control, or net free area.
An unvented crawlspace is a sibling option on the Deschutes FAQ. Decide it separately. Closing the attic does not close the crawl.
The three paths
Deschutes County names attic and crawlspace ventilation as one of the largest R327 changes. It lists three options. Other departments that adopted R327 still apply the same code text. Confirm with the authority having jurisdiction.
| Path | What you do | What it does not do |
|---|---|---|
| 1. Unvented attic (or unvented crawlspace) | Design the assembly with no attic (or crawl) ventilation openings. | Does not protect dryer, mechanical, or leftover gable and ridge vents. Does not replace moisture and insulation rules. |
| 2. Height | Place allowed ventilation openings 12 feet or more above grade. See the 12-foot rule. | Does not help a soffit vent below that line. Deschutes notes there is no 12-foot exception for the underside of elevated decks. |
| 3. Manufactured ember-resistant vent, or mesh where the opening is allowed | Use a model designed to resist ember and flame, or 1/16–1/8 inch noncombustible metal mesh on openings R327 still allows. | Hardware-store 1/4 inch animal screen is not this path. Perforated soffit is not this path. |
Path 3 is two sub-paths. The prescriptive path is mesh. The performance path is an ASTM E2886 listed assembly, often in OSFM category 8165. Deschutes County says it will accept OSFM handbook products when they are shown on the drawings. See show the product on the drawings. Listing is still voluntary for most WUI products. See listed is voluntary.
Example records: BrandGuard gable vents, BrandGuard soffit and undereave vents, Vulcan gable vents. Confirm the live listing and the model. See how to read a listing.
IBHS Wildfire Prepared Essential accepts mesh or a listed vent on openings that exist. It does not require you to invent openings.
What people mix up
- Taping or foaming existing vents and calling the attic unvented.
- Leaving gable or ridge vents open after you “close the eaves.”
- Treating perforated fiber-cement soffit as either an unvented eave or an ember-rated vent. See Findings.
- Treating enclosed eaves (a soffit under the overhang) as the same thing as an unvented attic. You can enclose eaves and still vent the attic at the gable or ridge. See eaves and ember versus flame versus radiant heat.
- Forgetting the crawlspace, dryer, and bath-fan outlets. Do not put ember mesh on the dryer. See dryer vents versus mesh.
- Treating the 12-foot exception as an unvented attic. Height is a measurement on an opening that still exists.
- Importing California “listed vents only” onto an Oregon drawing when the official will accept mesh or unvented. CWUIC is California construction code. See Oregon R327 versus California CWUIC.
How to check
- Read the adopted code for the lot. If R327 is not adopted, this is voluntary hardening or an insurer checklist.
- Count every opening. Attic, gable, ridge, soffit, eave, crawl, dryer, mechanical.
- If the drawing claims unvented attic, there should be no attic ventilation openings on that drawing. Ask how moisture and insulation are met.
- If vents remain under 12 feet on an eave, soffit, or cornice, R327 wants a manufactured ember- and flame-resistant vent, not ordinary mesh on a louver, unless the official says otherwise.
- If you spec a listed vent, put the listing ID and the model on the drawing. Match the OSFM record or the ICC report.
- Size any remaining vents so the building still meets ventilation code. Fine mesh reduces net free area.
Limits
This page is not a spray-foam specification. It does not rate roofs, snow, or solar. It does not decide what your building official will stamp. FireApproved is not the authority having jurisdiction. An unvented attic does not make the house fireproof. Embers can still attack the covering, the gutter, and Zone 0. See gutters and debris.
Related records
Questions
Can I skip ember-resistant vents if the attic is unvented?
You can skip attic ventilation openings you do not have. Dryer vents, mechanical outlets, and crawlspace vents are separate. If any attic, gable, ridge, or soffit opening remains, it still needs 1/16–1/8 inch metal mesh or a manufactured ember- and flame-resistant vent, as the adopted code requires.
Is stuffing the vents or spraying foam the same path?
No. An unvented attic is a designed roof assembly that meets the rest of the adopted residential code, including moisture and insulation rules. Blocking existing vents with tape, foam, or plastic is not that assembly. Confirm the detail with the building official.
Does an unvented attic satisfy IBHS or Safer from Wildfires?
Those checklists care that ember entry points are controlled. No attic vent is one way to do that. They still look at other vents, the roof, eaves, and Zone 0. Do not treat unvented as a substitute for the rest of the checklist or for adopted code.
Is putting vents 12 feet up the same as an unvented attic?
No. Height is a separate R327 exception for allowed openings. Unvented means those attic openings do not exist. See the 12-foot rule. Remaining openings still need mesh or a listed vent.