Greenhouse cooling fans

If you are in the horticulture trade and have greenhouses, greenhouse cooling fans could significantly reduce your business operating costs.

But there are different types of greenhouse cooling fans. The traditional axial type fans simply blow air horizontally along the greenhouse. Here is an introduction, by way of a story, into a completely new method of greenhouse cooling where there are far more benefits than just cooling.

This is the story of a Puravent customer who wanted some greenhouse cooling fans.

Some years ago supplied some destratification fans to a garden centre and nursery operation near Bradford. The initial enquiry came quite out of the blue and it transpired that our customer had brought a large second hand greenhouse and was planning to dismantle, move and rebuild it at their nursery.

Strangely, from our point of view, they were after destratification fans, not for their well understood impact lowering heating costs of the greenhouse, nor particularly for cooling, but mainly for the air movement pattern. Their idea was to get air movement through the soft leaves of bedding plants to prevent the lower leaves from rotting and to reduce plant losses.

We reckoned that for this type of application the best type of fan would be a ‘helecentrifugal’ destratification fan. Not only is this a bit of a mouthful it is also a type of fan that works in a completely different way to a normal destratification fan.....

Conventional destratification fans push air downwards from the ceiling to the floor

Helecentrifugal destratification fans pull air from above and underneath the fan and discharge it radially to the sides.

Conventional destratification fans push air to the floor Helecentrifugal destratification fans push the air radially to the sides

We thought that the up current from the floor level to the fan would be good to get air through the leaves, so anyway we finished up supplying 8 of these fans.

Greenhouse cooling fans - but this is all about destratification fans !

What happened? You may well ask!

The 1st thing that happened was after delivering the fans, we completely forgot all about it. At least that was until we got a phone call from our customer 6 months later. We work on the basis that 'no news' from a customer is 'good news', so our initial thought about this phone call was that maybe one of the fans has stopped working.

We were wrong! - in fact the customer was cock a hoop, delighted with the fans and told us all about it…

Turns out that the green house in this application had automatic roof vents and the reported practical benefits were;

• Destratification of heated air and reduced heating costs in winter (we kind of expected that one!)
• Noticeably faster internal distribution of solar gain on the inside surface of glass in the mornings
• Excellent cooling effect in warmer months, particularly when the roof vents are open (fresh air pulled in) and doors are open (warm air pushed out)
• Constant air movement proved excellent for reducing plant losses due to rot and disease, particularly effective if the plants are in pots on elevated mesh platforms

With roof vents and doors open these destratification fans change the air at a high rate, and the cooling effect is very evident.

With roof vents open the helecentrifugal fans bring in masses of fresh air through the vents and the over pressure (relatively warmer air) is expelled though open doors and vents to outside.

The economic benefits included;

• Significantly reduced heating costs
• Increased customer footfall in greenhouse in summer due to more comfortable temperature
• Plant losses due to scorching and drying out eliminated
• Lower irrigation costs
• Plant losses due to rot and disease virtually eradicated

“Whow” says us, “can we come and have a look?” We did visit on a warm spring day and it was quite extraordinary. The greenhouse with the fans was adjacent to another greenhouse without fans and as we walked from one to the other what hit us is the change in temperature. From hot muggy uncomfortable greenhouse to pleasant fresh greenhouse.

2 out of the 8 destratification fans supplied, in operation with the greenhouse roof vents open and pulling in huge quantities of cool fresh air.

Looking closely at the bedding plants being grown in pots and elevated on mesh platforms each one had moving leaves. As air current moves through the mesh it makes the foliage on each plant gently flutter. Our host is adamant that this airflow and fluttering is vital for growing stronger plants than would otherwise be the case, and keeps plant pathogens and rot at bay.

With all the realised benefits that these fans have brought to our hosts' business, he knows that these fans are important to the business. So much so that the fans are 'on' 24/7, 365 days a year. By and large a trusting chap, our host shows us a bunch of keys…”see that one?” he says “that’s for t' control box that runs t’ fans. I keep that key on my key ring so nob'dy can switch ‘em off!”

If any of this makes any sense and is of further interest, don’t hesitate to email or call us on 01729 824108.

You can have a gander at the fans on our website and/or read up on destratification with our online destratification guide.