Ventilation methods

Hi,

In a small greenhouse ventilation is typically one or two top openers with a bottom louver etc.

Wondered if using a temperature controlled extractor fan would offer any benefits or possibly have some downsides ?

 

How small is small?

Perhaps a fan stirring up the works would ensure the plants get good circulation and maybe bit of shade cloth?

 

Here's a few ...

Downsides:

Requires expensive electrical supply and temperature contoller.

If not set up correctley, used in conjunction with thermostatic heating the extract fan can be blasting out warm air whilst the heater below turns itself on/up to make good heat loss.

Benefits:

Extra ventilation for when autovent controlled roof windows aren't adequate.

Allows door to be left closed keeping birds and cats out (if no mesh screen), also wind and rain.

Improves air circulation.



For a small greenhouse you might get away with something like an (Artic) computer fan, a mains adapter (ex-mobile phone charger will do) and a temperature controller with a cooling function. Using a timer can help prevent it coming on when the heating's on. A fan speed contoller is usefull to adjust the fan speed, I use a Zalman Fanmate to slow down the fan in my big growbox.

 

Thanks all,

Have got an Arduino based temp controller to easy enough to add a pwm variable fan control; will give it a try as keeping the west facing door shut will also help keep the flying bugs out.

 

That reminds me, place some mesh over the inside of the fan to prevent any butterflies or bees that get inside from being shredded.

 

Hi,

Did not want to complicate the original question, but the 'greenhouse' in question is actually a 4x2x3ft mini greenhouse / frame within my 8x6 lean to.

Its specifically to year round grow small orchids, paphs and phals, along with other shade loving filler plants like ferns etc.

As you can see just starting to place the plants, and the ventilation is just a string from the main greenhouse auto top vent pulling up the lid and, when connected, to a flap on the bottom of the side.
While it does work think using some temperature controlled fans might give better results.

 

Hi ricky, something like this might be suitable, also on eBay list cheap solar fans for around £4,

I've never used any so I cant comment just a suggestion.
Solar Powered Fan|Vent for ventilation and extraction from SolarShop

 

I have a dc fan that would normally be in a server - it moves a lot of air. Smaller pc fans can be run off of a little solar panel. Done it, still have then running and darn cheap to set up too

 

Something that small looks perfect for a computer fan setup, it's probably smaller than my growbox with lights and propagators all generating heat, and using a speed controller gave me the peace of mind that the fan wouldn't blast every bit of heat outside in seconds

 

Have got some 120mm fans on order to supplement the one I already have in there purely as a circulation fan.

Also took a pun and ordered a little £5 12v dc humidifier thats on ebay as no idea how good or bad they really are; have used a full size domestic one before but way too big for this little enclosure.

 

And if you use a small solar panel, the fan operates when the sun shines. Just when you need it!

 

Looking back at what I paid, I got that speed controller for £2.99 delivered (part of larger order) Zalman FAN MATE 2 (3-pin fan Speed Controller) £2.99 @ amazon (Add-on item) Alwsys worth knowing what you're going to need and snapping up stuff when cheap.

And this was the fan I bought Arctic Cooling F8 @ Amazon £2.59 with orders over £10

 

Just an update that might be useful to others..

Tried various PC fans but just not enough flow to cover my small housing and their output/flow was very narrow; seems many of the 120mm fans are low speed these days, something like a Arctic F12 is quoted as twice the rpm / airflow, but twice the price.

One of these arrived today and it really does the job with its big blades really giving a wide and big flow but without being overly forceful, just what the plants need.

Its from £6 , depending who you buy from /postage, so its seem ideal, just a case of how it stands up to running 24/7 in a humid area, but at that price can afford to have a spare ready.

Seems they do a similar plastic version which might withstand the moisture better, but the airflow looks a little bit restricted to the one I have.

Prem-i-air 6" USB Desk Fan

 

Have you looked at bathroom/shower extract fans? N.B. the over-run timer might need reducing.

For example £13 on clearance at Wickes Wickes Extractor Fan with Timer 100mm | Wickes.co.uk