Ridge vents, gable louvers, exhaust fans and thermostat-controlled packages — engineered into every MegaDome to control condensation, protect equipment and extend membrane life across Ontario's cold-winter, humid-summer climate.
An engineered fabric building encloses a very large volume of air over materials that release moisture — stored salt, aggregate, feed, livestock, freshly welded steel, running vehicles, hot process equipment. When that warm, saturated air rises and contacts the underside of a cool PVC membrane, it condenses. Condensation drips onto stored product, wets the steel frame at its base connections, and drives ammonia and chloride vapours into the membrane surface where they accelerate hydrolysis.
Ventilation is the answer, and it is not an afterthought. Building Depot engineers the ventilation package into the structure itself — continuous ridge exhaust, sized gable intake, mechanical exhaust for peak loads, and control logic that responds to interior temperature and humidity. The result is a building that stays dry inside, protects what's stored in it, and holds its 25-year membrane and 50-year frame life.
Every ventilation package is sized to your building's volume, use-case and Ontario climate zone. The physics of stack-effect exchange, dew-point control and required air-changes-per-hour are engineered into the shop drawings before your MegaDome ever leaves the fabrication plant.
A full-length weather-hooded opening running the entire ridge of the dome. Warm, moist interior air rises by natural convection and exhausts continuously along the peak. Zero power, zero moving parts, engineered for driving rain and snow.
Fixed or motorized louvers cut into the gable end walls and low sidewalls. Draws cool, dry make-up air in low so it can rise through the building and exhaust at the ridge — the intake half of the stack-effect loop.
Belt-drive or direct-drive sidewall exhaust fans sized against building volume. Delivers active air exchange when passive ventilation can't keep up with summer heat, process load, welding fumes or livestock ammonia.
Fans and motorized dampers are staged by interior temperature, relative humidity, CO₂ or CO sensors. The building ventilates on demand — quiet and efficient in winter, aggressive in summer or during process peaks.
Long, narrow buildings — dairy barns, horse-riding arenas, indoor sports — use cross or tunnel ventilation: banks of intake louvers at one end, banks of exhaust fans at the other. Delivers uniform 400–500 fpm air velocity across the animals or occupants.
Manufacturing, welding shops, mining process buildings, aircraft hangars and hazardous-vapour storage each get a purpose-engineered package — combining ridge, wall, roof and floor-level ventilation with make-up air heaters, spark-resistant fans and explosion-rated components where required.
Building Depot supplies and installs only ventilation components that meet or exceed MegaDome's factory accessory specifications — so the ventilation package integrates directly into the arched steel frame and does not affect the structural, membrane or warranty rating of the building.
| Component | MegaDome Specification | Typical Sizing |
|---|---|---|
| Continuous Ridge Vent | Weather-hooded aluminum extrusion, hot-dip galvanized structural supports, integrated with MegaDome ridge cap and PVC membrane keder attachment. | Full building length · 12" – 24" throat |
| Gable / Sidewall Louvers | Galvanized storm-proof blades, insect and bird screen, gasketed motorized damper option, insulated blade option for cold storage. | 3'×3' to 6'×6' — sized 1:1 to ridge exhaust |
| Sidewall Exhaust Fans | Belt- or direct-drive axial, galvanized housing, AMCA-rated, TEFC motor, motorized or gravity shutters, CSA / cUL listed. | 24" – 55" · 5,000 – 30,000 CFM per unit |
| Controls | Multi-stage thermostat, humidistat, CO / CO₂ / NO₂ sensor input, VFD for variable-speed fans, NEMA 4X enclosure. | 120 / 240 / 600 V single or 3-phase |
| Curtain Sidewalls | PVC / mesh curtain on gear-drive winch, integrated with MegaDome sidewall extrusion — matches roof membrane for uniform envelope. | 4' – 16' drop · full building length |
| Make-Up Air / HVLS | Direct-fired make-up air heater or high-volume low-speed circulation fan, ceiling-mounted from arch web with engineered rigging. | 100,000 – 2,000,000 BTU/h · 8' – 24' HVLS |
All components are integrated into the MegaDome shop drawings by Building Depot engineering and stamped by a P.Eng licensed in Ontario. Ventilation cut-outs are engineered into the arch spacing before fabrication — no field modifications to the primary steel or membrane.
Warm interior air is less dense than cool outside air. It rises, exits through the continuous ridge vent, and pulls cooler make-up air in through low gable and sidewall louvers. The larger the temperature differential and the taller the building, the stronger the drive — which is why MegaDome's tall arched profile ventilates passively better than a low-slope steel building.
The number of times the building's entire air volume is replaced per hour. Cold storage: 1–2 ACH. Warehousing and equipment: 2–4 ACH. Manufacturing: 4–6 ACH. Livestock summer: 40–60 ACH. We calculate volume (L × W × avg. height) and specify vent area and fan CFM to hit the target.
Cross-ventilation moves air across the short axis of the building — used for wide, shallow footprints. Tunnel ventilation moves air end-to-end at 400–500 fpm — used for long, narrow buildings like dairy free-stalls and indoor sports domes where uniform velocity over the occupants matters.
Condensation forms when the interior dew-point rises above the membrane's surface temperature. Ventilation removes moisture (lowering dew-point) faster than the process inside generates it. We size the package against the worst-case Ontario winter delta — outside -25 °C, inside +5 °C at 70% RH — to guarantee zero interior drip.
Positive pressure (supply fans) is used to keep dust, insects and outside contaminants out — common in food processing. Negative pressure (exhaust fans) is used to contain odours and fumes — common in waste transfer, foundries and livestock. Building Depot specifies the pressure regime with your operations lead.
Winter: passive stack ventilation, minimum-position dampers, insulated inlets to protect against -30 °C in Sudbury, North Bay and Thunder Bay. Summer: full mechanical exhaust, opened curtains and boost fans to hold interior temperature within 8–15 °C of ambient during 30 °C+ GTA / London / Windsor peaks.
Continuous ridge + curtain sidewalls. 4–8 ACH in summer for dairy, livestock and horse-riding arenas.
ExploreRidge vents + thermostat-controlled sidewall exhaust for welding, forklift and process load.
ExplorePassive ridge ventilation strips chloride vapours from salt storage — no power required.
ExploreHeavy-duty exhaust and make-up air packages for haul-truck maintenance and process cover.
ExploreHigh-volume passive + mechanical ventilation for fuel vapour management and humidity control.
ExplorePassive stack ventilation only — no motors to corrode. Standard on every DB series salt shed.
ExploreLow-CFM continuous exchange keeps stored fleet condensation-free through winter cycles.
ExploreHigh-CFM exhaust with odour management and negative-pressure containment options.
ExploreCombined vehicle-bay CO monitoring and thermostatic exhaust for municipal yards.
ExploreTunnel or cross ventilation delivering uniform air over players in domes and arenas.
ExploreRidge + gable louvers keep humidity low and pallet-stored goods dry year-round.
ExploreCO/NO₂-triggered exhaust with make-up air heaters for winter shop operation.
ExploreProduct specification sheets, technical data, maintenance guides and Building Depot's Ventilation Design Guide are available on request or from our downloads library.
Serving fabric building projects across Ontario
Ontario engineering, foundation and installation on a single contract. No obligation.
Tell us building size, use-case and Ontario site. We'll size ridge, gable and mechanical ventilation and return a fixed quote within 24 business hours.
Ontario engineers on the line · quote returned within 24 business hours
