Ridge vents vs. roof (box) vents vs. soffit vents in Vancouver — what actually works

In Vancouver’s rain and wind, the most reliable system is continuous soffit intake paired with continuous ridge exhaust, sized to code (typically 1/300 of insulated ceiling area; 1/150 on lower slopes/joist roofs), with clear baffles at eaves. Box “roof” vents are a fallback for chopped ridgelines; powered fans rarely pencil. ( BC Publications ^[1] , RCABC ^[2] )

• Balance intake and exhaust by area; don’t starve the soffits. ( National Roofing Contractors Association ^[3] )
• Keep a 63 mm clear air channel above insulation; add baffles at eaves. ( BC Publications ^[1] )
• Prefer continuous ridge vents with rain-baffled designs and proper metal flanges. ( RCABC ^[2] )
• Use box vents only when ridges are short or interrupted—place them high and distribute. ( National Roofing Contractors Association ^[3] )
• Avoid powered attic fans; they depressurize and can pull house air and moisture. ( GreenBuildingAdvisor ^[4] , Energy Vanguard ^[5] )

I’m Harman at Paragon Roofing BC. I spend my seasons on ladders across Metro Vancouver—from sea-breeze corridors to shaded North Shore ravines—tuning roofs to our climate’s one-two punch: wind-driven rain and long time-of-wetness. Here’s the honest breakdown of ridge vents vs. roof (box) vents vs. soffit vents —what works, what fails, and how to size and detail the system so your attic stays dry year-round and your roof quietly lasts.

The physics Vancouver cares about

Vancouver’s normals (1991–2020) show persistent cool-season precipitation and frequent storm cycles; roofs get short drying windows between events. Venting isn’t decoration—it’s the safety valve that dries the deck and keeps shingle temperatures in check. The code formalizes that reality by requiring a vent area ratio and clear air pathways above insulation. ( Climate Data Canada ^[6] , BC Publications ^[1] )

Two field truths follow:

1. Air wants a low-to-high path. Intake down low (soffits) and exhaust up high (ridge). Get the path wrong—or block it—and the system stalls. ( National Roofing Contractors Association ^[3] )
2. Edges and clearances decide everything. You need a 63 mm(2½″) airway above insulation, and at eaves you must install baffles that maintain at least 25 mm of continuous, unobstructed passage into that airway. ( BC Publications ^[1] )

The contenders, Vancouver-style

Soffit vents (intake): the unsung heroes

If you forget everything else, remember this: intake is the system’s throttle. Starved soffits doom any exhaust you choose. Best practice in our climate is continuous aluminum or polymer soffit venting(not a few token grills), verifying that baffles keep the channel open over insulation and that bird blocks or paint haven’t sealed the louvers. The code requires both net free area(NFA) and distribution —not less than 25% of the openings low and 25% high. Translation: you can’t “all-ridge, no-soffit” your way to a working roof. ( BC Publications ^[1] , Province of British Columbia ^[7] )

When I upgrade soffits:

• Older houses with solid soffits and no continuous intake.
• Homes with “spot” soffit vents that don’t add up to the math.
• Any attic where insulation has crept over the top plates—baffles re-establish the airway. ( BC Publications ^[1] )

Ridge vents (exhaust): the quiet, continuous finish line

Continuous ridge exhaust is my first choice on most Vancouver steep-slope roofs if(and only if) you give it healthy soffit intake. It has three advantages: it sits at the highest point where warm, moist air collects; it is continuous (not points); and when properly designed it resists wind-driven rain. The RCABC Roofing Practices Manual also sets dimensional guardrails—ridge vents should provide ≥ 50 mm flanges to overlap roofing, with metal vent flanges ≥ 100 mm and minimum vertical sealed heights ≥ 75 mm on accepted metal vents. Those aren’t trivia; big flanges and raised throats keep water out when the wind leans in. ( RCABC ^[2] )

Where ridge shines:

• Long, clean ridgelines over connected attic volumes.
• Houses where exterior looks matter (continuous ridge is visually calm).
• Rainy sites; modern ridge products include exterior baffles that increase Bernoulli-assisted pull while blocking blow-in. ( National Roofing Contractors Association ^[3] )

Where I hesitate:

• Short, chopped ridges with dormers everywhere—too little linear footage.
• Cathedral ceilings with multiple isolated rafter bays (you may need over-deck venting or purlins; see code notes below). ( BC Publications ^[1] )

Roof (box/turtle) vents: point exhaust that still works—if you respect placement and math

Roof vents can be excellent when you don’t have a continuous ridge or need to supplement ridge on a complex plan. I distribute them near the peak, on each plane, keeping their combined NFA equal to the exhaust target and matching intake NFA down low. The NRCA ’s balanced system concept—about half of total NFA down low and half up high—remains the simplest sanity check. What doesn’t work: two lonely boxes on a big attic and a dozen painted-shut soffits. ( National Roofing Contractors Association ^[8] )

Box-vent gotchas I see:

• Set too low on the slope: they dump pressurized, wet air back into the attic path.
• Clumped on one plane: starves other planes of exhaust.
• No rain baffles: in a southeaster, you’ll see blow-in around cheap caps. Use quality hoods with raised throats per RCABC acceptance. ( RCABC ^[2] )

Gable vents (legacy): use with intent, not by default

Gable vents can add cross-flow in simple, rectangular attics, but mixing gable with ridge/box exhaust can short-circuit the low-to-high path, especially if soffit intake is weak. In Vancouver’s wind-driven rain, gable faces are also splash zones. I’ll keep or add them only when the geometry supports true cross-vent and rain entry can be managed; otherwise, I lean on soffit+ridges/boxes. Building-science literature backs the caution that “more vents” isn’t automatically “more drying.” Design the path first. ( buildingscience.com ^[9] )

Powered attic fans: almost never my answer here

They depressurize the attic and can pull conditioned, moist house air through ceiling leaks, worsening moisture and energy bills. Case studies and industry analyses document back-drafting and CO risks around atmospherically vented appliances. In our cool-marine climate, dollars are better spent on air-sealing the ceiling, real intake, and passive exhaust. ( Energy Vanguard ^[5] , ACEEE ^[10] , GreenBuildingAdvisor ^[4] )

The numbers (made simple) — and how to size vents for Vancouver

Code ratios:

• 1/300 of insulated ceiling area as unobstructed vent area (NFA) is the baseline.
• 1/150 if the slope is < 1:6 (≈ 2:12) or where joist roofs apply (think low-slope/roof-joist assemblies).
• Distribution: not less than 25% of openings high and 25% low —balanced is best.
• Clearance: maintain 63 mm above insulation; eave baffles must provide ≥ 25 mm unobstructed air space and extend ≥ 50 mm above insulation. ( BC Publications ^[1] )

Quick calculator (rule-of-thumb):

• For 2,000 ft² of insulated ceiling, 1/300= 6.67 ft² NFA total(≈ 960 in²). Target ~480 in² intake and 480 in² exhaust —then round up to account for bug screens and product tolerances. NRCA/ARMA shortcuts support balancing intake and exhaust by equal NFA. ( Asphalt Roofing ^[11] , National Roofing Contractors Association ^[3] )

Product labels:
Every vent lists NFA per unit. Continuous ridge products show NFA/linear-foot; soffit strips list NFA/linear-foot; box vents list NFA each. Add them up—don’t guess.

Detailing that makes vents “Vancouver-proof”

At eaves:

• Insert baffles above the top plate so insulation can’t slump into the airway. Keep the channel open at least 25 mm, ideally more, and extend the baffle 50 mm above insulation to stop drift. ( BC Publications ^[1] )
• Confirm soffit panels are truly vented and not painted shut.

At ridge:

• Choose externally baffled ridge vents with rain deflectors; verify flanges give you ≥ 50 mm coverage each side.
• Stop the vent short of hips and returns to avoid dead-end pockets; tie multiple ridges together under the sheathing where possible. ( RCABC ^[2] )

For box vents:

• Place within the top 24–36″ of slope.
• Distribute by plane; keep spacing even; avoid “one plane loaded, the other starved.”
• Use hoods with raised throats and proper flanges; cheap caps are an invitation in a southeaster. ( RCABC ^[2] )

For tricky assemblies (cathedral, compact roofs):

• The BC code allows purlins to interconnect rafter spaces and maintain continuous airflow; otherwise, consider vented over-deck systems. The point is continuity: the air path must run unbroken from eave to ridge. ( BC Publications ^[1] )

Common Vancouver attic problems I fix—and the ventilation cure

Blackened sheathing near eaves
Cause: blocked soffits and no baffles; moist interior air condenses at the cold edge.
Fix: cut continuous intake, install baffles, and verify ridge/box NFA matches. (Air-sealing the ceiling helps as much as vents.) ( BC Publications ^[1] )

Winter “musty” odour after storms
Cause: low intake + point exhaust pulling house air into the attic.
Fix: add soffit NFA, rebalance exhaust, and air-seal the top floor penetrations; do not add a powered fan. ( GreenBuildingAdvisor ^[4] )

Wind-driven rain traces under ridge or box vents
Cause: low-profile caps without external baffles; minimal flange/height.
Fix: swap to RCABC-accepted, raised-throat vents; ensure shingles and underlayment shingle-fashion the vent flanges. ( RCABC ^[2] )

Hot bonus room below a split gable
Cause: chopped ridges; no cross-ties; two isolated attics.
Fix: interconnect bays with purlins or add high exhaust on each isolated volume; ensure equal intake to each. ( BC Publications ^[1] )

“Which should I pick?” — My decision tree

1. Do you have continuous, ventilated soffits?
   If no, fix intake first. Nothing else works until you do. ( National Roofing Contractors Association ^[3] )
2. Do you have a long, clean ridge over one connected attic?
   If yes, choose continuous ridge exhaust and size to NFA; it’s quiet, effective, and looks right. ( National Roofing Contractors Association ^[3] )
3. Ridge chopped by hips/dormers or multiple isolated volumes?
   Use distributed box vents at the high points of each volume; match totals to the math and to intake. ( National Roofing Contractors Association ^[8] )
4. Thinking about a powered fan?
   In our climate, don’t —unless an engineer designs it, the ceiling plane is airtight, and combustion safety is verified. Even then, savings are dubious. ( Energy Vanguard ^[5] )
5. Cathedral or compact roofs?
   Provide a continuous airway per code (purlins/vent chutes), or use over-deck venting. Don’t pepper isolated rafter bays with vents that don’t connect. ( BC Publications ^[1] )

Ridge vs. roof vs. soffit — quick comparison for Metro Vancouver

(Standards notes: NFA ratio 1/300 typical; 1/150 for low-slope/joist roofs; maintain 63 mm air channel and 25 mm+ baffle space; distribute vents— ≥25% high and ≥25% low.) ( BC Publications ^[1] )

Codes, standards, and why they matter for warranties

• Vancouver Building By-law / BCBC 9.19 set the minimum: vent ratios, distribution, clearances, and baffles. If you size to those numbers and actually provide the pathway, you’ll meet the legal floor and the physics. ( BC Publications ^[1] )
• RCABC Roofing Practices Manual adds execution detail (vent flange dimensions, acceptable designs, and integration with roofing)—the manual local inspectors and specifiers treat as the playbook. Following it isn't just about passing inspection; it makes November weather boring. ( RCABC ^[2] )
• NRCA/IIBEC guidance backs balanced intake/exhaust and locating exhaust at or near the ridge, with intake down low. When you align code + RCABC + NRCA, warranties and inspectors stop asking questions. ( National Roofing Contractors Association ^[8] , IIBEC ^[12] )

Worked example — sizing a real Vancouver attic (and avoiding gotchas)

House: 1½-storey, 1,800 ft² insulated ceiling, 6:12 main gable with two short hips, continuous soffits, medium tree cover.

Code target:

• 1/300 → 1,800 ÷ 300 = 6.0 ft² NFA total (864 in²).
• Split evenly → 432 in² intake, 432 in² exhaust(or better, intake ≥ exhaust to avoid depressurization). ( National Roofing Contractors Association ^[3] )

Soffit plan:

• Continuous strip vents rated 9 in²/lf → need 48 lf each side overall. Confirm baffles in every cavity, 25 mm minimum channel, and that paint hasn’t sealed louvers. ( BC Publications ^[1] )

Exhaust plan (ridge + boxes):

• Ridge length is short due to hips; we can get 240 in² from ridge (say 12 in²/lf × 20 lf).
• Make up the remaining ~190 in² with two box vents(100 in² each) placed high on opposite planes, not clustered.
• Verify total exhaust ≤ intake; if intake is tight, add soffit length rather than more boxes.

Final check:
Eave baffles all in; 63 mm clearance everywhere; attic hatches weather-stripped; bath fans vented outside, not into soffits. Code satisfied, physics respected. ( BC Publications ^[1] )

What not to do (Vancouver edition)

• All ridge, no soffit. The ridge will pull from the easiest opening—often your house. That’s bad air, moisture, and heat leaving through the ceiling. ( buildingscience.com ^[13] )
• Mix gables with ridge/boxes haphazardly. You’ll short-circuit the pathway and stall low-to-high flow. Design the route, then pick vents. ( buildingscience.com ^[9] )
• Add a powered fan to “fix” weak intake. You’ll depressurize and risk back-drafting appliances. Solve the intake first; seal the ceiling plane. ( Energy Vanguard ^[5] )
• Skip baffles. Insulation drifts, storms flex soffits, and the airway closes. Baffles lock the passage. ( BC Publications ^[1] )
• Ignore rain entry. Choose ridge/box vents with proper baffles, flanges, and raised throats per RCABC dimensions. Cheap caps leak sideways. ( RCABC ^[2] )

Final take (from a ladder in November)

Vancouver roofs don’t need gimmicks; they need a clear airway from cool, continuous soffit intake to high, rain-resistant ridge (or well-placed box) exhaust, sized to code and balanced by area, with baffles locking the path open over insulation. Do that, and storms become nonevents; don’t, and the attic writes its own story in stains and smells.

Written by Harman, Roofer, Paragon Roofing BC (Vancouver).
I design, install, and troubleshoot roofs across Metro Vancouver’s wet, windy microclimates. My vent specs start with physics, then code, then craft—so decks dry fast, shingles run cool, and November passes quietly. roof ventilation Vancouver

References (not included in word count)

• Vancouver/BC Code—Roof Spaces Venting: BCBC/BC-adopted Section 9.19: ratios (1/300, 1/150), distribution (≥25% high/low), 63 mm clearances, and eave baffle details. ( BC Publications ^[1] )
• RCABC Roofing Practices Manual: Building Ventilation page (vent distribution; flange and height requirements for accepted ridge/roof vents). ( RCABC ^[2] )
• NRCA/IIBEC attic ventilation primers: balanced intake/exhaust concept; high-point exhaust and low-point intake guidance. ( National Roofing Contractors Association ^[8] , IIBEC ^[12] )
• Building Science (BSD-102 & Crash Course): purpose and limits of attic ventilation; cautions about wind-driven rain and vent placement. ( buildingscience.com ^[9] )
• Powered attic fans—risks: energy and safety concerns; depressurization, moisture, and back-drafting cautions. ( Energy Vanguard ^[5] , GreenBuildingAdvisor ^[4] , ACEEE ^[10] )
• Climate context: Environment and Climate Change Canada—1991–2020 climate normals for Vancouver. ( Climate Data Canada ^[6] )

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