Underflow Grain Ventilation systems
Underflow
Underflow grain ventilation is a specialised underfloor ventilation system that transforms how grain stores handle crop cooling. Unlike standard pedestal ventilation where fans sit inside grain stores, Underflow grain ventilation draws air through pedestals into below-floor ducts, positioning fans externally for maximum safety and efficiency.
Pedestal more secure when filling and no top pipe to protect
Great for new build stores
Warm Air expelled outside of store – fans outside so simple to move
Pedestal Ventilation via below the floor ducts
Available with PV250, PV400, or Evolution fans, Evans & Pearce Underflow systems deliver professional-grade grain store ventilation for new build or retrofit installations.
Product Details
Specifications
Underflow suits overhead conveyor filled stores. Pedestals remain more secure when filling. All warm air is expelled outside of the store. Moving fans between pedestals is simple.
Polycool Standard
Part No: PED-UF120BASE
Type: Polycool Pedestal with Cap and Transition Piece
Base unit: 1.2m x 450mm perforated base unit
Suggested crop storage depth: 3m – 5.5m
Fan Recommendation (not included): PV250 or Evolution
Polycool
Maxi
Part No: PED-UF200BASE
Type: Polycool Pedestal with Cap and Transition Piece
Base unit: 2m x 450mm perforated base unit
Suggested crop storage depth: 5m – 9m
Fan Recommendation (not included): PV400
Metalcool Standard
Part No: PED-UF250MET
Type: Metal Louvred Pedestal with Cap and Transition Piece
Height: 3.5m
Base unit: 1.2m x 250mm louvred, perforated base unit
Base plate: 400mm x 400mm
Suggested crop storage depth: 3m – 5.5m
Fan Recommendation (not included): PV250 or Evolution
Metalcool
Maxi
Part No: PED-UF300MET
Type:Metal Louvred Pedestal with Cap and Transition Piece
Base unit: 1.2m x 300mm louvred, perforated base unit
Base plate: 400mm x 400mm
Suggested crop storage depth: 5m – 9m
Fan Recommendation (not included): PV400
Underflow Pedestal Options
Two options and sizes of pedestals
Improved pedestal ventilation for new build grain stores
Use PolyCool or MetalCool Pedestals – Maxi or Standard Bases
Underflow
Vent from air ducts positioned below store floor
Moving fans between pedestals is simple
Use with PV250 or PV400 Fans
Easy to move and position fans outside the store
Warm air removed from store
Overhead filled store
Pedestals more secure when filling
No ‘top pipe’ to protect
How to space pedestals in your grain store
| STORAGE DEPTH | PEDESTAL SPACING |
|---|---|
| 2.5-3.5m | Storage depth plus 100% |
| 3.6-5.0m | Storage depth plus 75% |
| 5.1m and above | Storage depth plus 50% |
What is Underflow Grain Ventilation?
Underflow grain ventilation represents a specialised approach to grain store ventilation where air movement follows a fundamentally different path than traditional pedestal systems. Rather than fans positioned inside grain stores pushing air upward through pedestal structures, Underflow grain ventilation draws ambient air down through pedestals into interconnected below-floor ductwork.
This underfloor ventilation configuration positions ventilation fans externally to the grain storage area, typically outside the building or in dedicated equipment spaces. The below-floor ducts connect multiple pedestals, creating an efficient underfloor ventilation grain network that distributes conditioned air evenly throughout the stored crop.
Benefits of Underflow Ventilation for Grain Stores
Underflow grain ventilation delivers distinct advantages that make this underfloor ventilation system the preferred choice for specific grain storage applications:
External Fan Positioning: By moving fans outside grain stores, underflow grain ventilation eliminates internal equipment that workers must navigate around. This proves particularly valuable in facilities where grain pedestals already occupy floor space.
Enhanced Safety for Overhead Filling: Grain stores using overhead conveyor systems benefit significantly from underfloor ventilation grain approaches. With no fans positioned at floor level, falling grain encounters no obstructions, reducing damage risks to expensive ventilation equipment.
Improved Grain Store Stability: Underflow grain ventilation systems create more stable grain stores during filling operations. External fan positioning means no internal equipment to work around when levelling grain or operating machinery inside storage facilities.
Cost-Effective for New Builds: When designing new build grain stores, incorporating underfloor ventilation systems during construction proves more economical than retrofitting. The below-floor ductwork integrates cleanly into foundation plans.
Underflow Installation: New Build vs Retrofit
Underflow grain ventilation adapts to both new construction and existing grain stores, though each scenario presents distinct considerations:
New Build Grain Stores: New build grain stores offer the ideal opportunity for underfloor ventilation systems. During foundation construction, below-floor ducts integrate seamlessly into the concrete floor design. This allows precise positioning of Underflow grain ventilation ductwork to optimise air distribution patterns. Planning underfloor ventilation grain systems from the outset ensures proper fan sizing, duct dimensions, and pedestal spacing without retrofit compromises.
Retrofitting Existing Stores: Adding Underflow grain ventilation to existing grain stores requires floor cutting to install below-floor ductwork – a significant undertaking compared to standard pedestal installation. However, for grain stores with overhead filling systems or other operational constraints that make traditional fan positioning problematic, the benefits of external fan location justify the installation investment. The key lies in careful planning to minimise floor disruption while achieving effective grain store ventilation coverage.
Frequently asked questions
Underflow grain ventilation is an underfloor ventilation system where air moves downward through grain pedestals into below-floor connected ducts rather than upward through fans inside grain stores. This Underflow grain ventilation design positions fans externally, drawing air through the stored crop and into underground ductwork. The system works particularly well for overhead conveyor filled grain stores where traditional internal fans would obstruct filling operations.
Underflow grain ventilation eliminates internal fans from grain stores, improving safety during overhead filling operations and simplifying floor-level operations. With fans positioned outside the storage area, underfloor ventilation systems reduce equipment damage risks from falling grain and eliminate obstacles that workers must navigate around. This underflow grain ventilation approach proves especially valuable in grain stores where space optimisation matters, or overhead conveyor systems require unobstructed floor areas.
Yes, though retrofitting Underflow grain ventilation requires cutting existing floors to install below-floor ductwork. While this represents more work than adding standard pedestals, the grain store ventilation benefits justify the investment for facilities with overhead filling systems or operational constraints that make internal fan positioning problematic. New build grain stores integrate underfloor ventilation more easily during initial construction.
Underflow grain ventilation systems integrate with both Polycool and Metalcool pedestals fitted with 150mm spigot connections. This flexibility means you can choose pedestals based on your grain stores’ specific requirements while maintaining the underfloor ventilation advantages. Both pedestal types deliver proven performance when configured for underflow grain ventilation applications.
Evans & Pearce Underflow grain ventilation works with PV250, PV400, or Evolution fans depending on your grain store size and airflow requirements. These fans position externally to grain stores, connecting to the underfloor ventilation ductwork. Fan selection depends on storage volume, desired air change rates, and the number of pedestals in your grain store ventilation system.
Absolutely – Underflow grain ventilation is particularly well-suited to overhead conveyor filled grain stores. By positioning fans externally rather than at floor level, this underfloor ventilation approach eliminates equipment in the path of falling grain during filling operations. This reduces damage risks to expensive fans while maintaining effective grain store ventilation throughout your storage depth.
Underflow grain ventilation typically costs less than full underfloor ventilation systems because it requires targeted below-floor ductwork connecting pedestals rather than extensive plenum chambers across entire grain store floors. While more complex than standard pedestal installation, underflow grain ventilation delivers external fan positioning benefits at lower cost than comprehensive underfloor ventilation grain systems.
Underflow grain ventilation handles the same storage depths as standard pedestal systems – typically 3m to 9m depending on pedestal selection. Using Polycool Standard pedestals suits grain stores up to 5.5m depth, while Polycool Maxi extends underfloor ventilation capabilities to 9m depths. The underflow configuration doesn’t limit storage depth; fan selection and pedestal spacing determine effective grain store ventilation coverage.
