Thread: Whirlybirds - is 3 enough?

I have a small AC in my 42m^2 shed which is also sealed and insulated. If we have series of hot days the whole thing gets and stays really hot so if I want to do shed work after not using it for a while I go down about 5:30 - 6am and open the doors and turn on the ventilators - this at least gets the whole thing down to ambient by the time I go down at around 7:30m.

By about 8:30am the Solar PV system is producing something and depending on the external temp I'll turn on the AC.
If I try to cool down the shed without any ventilation it can take up to an hr to cool the shed using the AC but if I do this with the solar it's not costing me much.
If I go down in the afternoon and its been 40C outside it takes as much as double that to cool the insides down, although usually within half an hr its bearable in there.

This morning I worked in there for about 3 hours during which the outside temp went from ~32 to now 39ºC during which I had a a fairly constant 24-25C. Of course this only works if I don't use dust extraction but even then I can still use the DC for a short burst (a few mins) if I really need to as once the shed has cooled down the AC recovers that lost coolth in about 15 minutes.

Please read my post above. Brisbane is incredibly humid. Unless very carefully engineered evaporative air conditioners will make the situation worse, not better.


When you are making absolute statements based on your experience please remember we are solving different problems. The shed in question is in Brisbane, which has very different issues to say Melbourne for example.

I hear what you are saying about the height. My eves are at 3.5m. This is a problem for the mezzanine store and also for any stairs up to it. However apparently there is a cost jump if we raise the eves above this.

3.5 is good. What about increasing roof pitch ?

You can get second hand solar panels for about $10 each. It'd be funny to cover the roof, add an inverter and only connect it to a huge air con. Not connected to mains so maybe less regs to deal with. You might even be able to set it up to auto start/stop as solar permits.

Originally Posted by damian

. . . . .You might even be able to set it up to auto start/stop as solar permits.

I thought for a moment you were referring to and electric vehicle charging station

Originally Posted by damian;[URL="tel:2268935"

2268935[/URL]]Please read my post above. Brisbane is incredibly humid. Unless very carefully engineered evaporative air conditioners will make the situation worse, not better.


When you are making absolute statements based on your experience please remember we are solving different problems. The shed in question is in Brisbane, which has very different issues to say Melbourne for example.

Who is making “absolute statements” ?

Quite a few of the previous replies related experience in southern states but made absolute statements about how the OP should proceed.


I've not lived in Melbourne but I did live in Sydney for 30+ years. A shed there requires a very different approach.

Originally Posted by damian;[URL="tel:2269191"

2269191[/URL]]Quite a few of the previous replies related experience in southern states but made absolute statements about how the OP should proceed.


I've not lived in Melbourne but I did live in Sydney for 30+ years. A shed there requires a very different approach.

you must be reading something that I am not seeing, a look through the thread again and I only saw one comment that suggested what the OP should do, and I wouldn’t have described that as an absolute statement and the OP agreed it was a good idea. Other than that what I see is a wide variety of opinions and experiences with no real trend based on location.

like most things in life I suspect there are many variables that determine if whirlybirds will work in any given scenario, I highly doubt location is the only one.

I also take a different view on threads like this, yes it’s main purpose is to help the OP, but I would suggest much of the discussion and opinions here would interest many other members in various states and may well answer questions others hadn’t thought to ask.

Cheers Andrew

Only a few years ago I went through this whole thing to cool down a tiny workspace (5x5).

Whirlybirds are useless. The solar ones are useless.

They sound good on paper, but in practice they make not one iota of difference. I spent a long time talking with various roofing people discussing the reality of on-the-ground (roof!) experience. Adding them to a roof to remove heat simply does not work in any meaningful way. I found a scientific paper which looked at exactly this issue and the use of a whirly is PURE MYTH.

I ended up with insulating as best I could and adding a 2kw high efficiency inverter reverse cycle aircon. Bloody MAGIC!

The whole area was cooled and heated to perfection. On humid days it sucked the air dry.

This is in Canberra where it can easily hit 40 in summer and -5 in winter. Nights are hot and cold. The environment here is all over the place.


If I were to do it again, I'd absolutely run the unit with a solar panel bank and leave the space at 22 all year, day and night.

I'd reckon setting up a bunch of second hand panels with a decent battery bank would be entirely doable. One can of course BUY such a solution off the shelf, but that's no fun! There was a thread on the forum about a house in Tassie that was way off grid and the poster did exactly this....

Theres a major problem with putting solar panels on my shed - it’s surrounded by 3 shady trees plus the dreaded Bouganvillia. SWMBO is super protective of these plus it cost me two cartons and a lot of talking to get the shed builders to not damage the trees whilst enlarging the shed. Fortunately there’s plenty of capacity for the house solar to run the shed AC

As someone has already commented there are various results depending on your location, here's my experience.
In Karratha, which is in the Norwest of WA and gets extremely hot in summer, we owned an 20m x 12m industrial shed which was leased to a machinery engineering company. One day the manager contacted me to discuss ways of trying to cool the shed, I dropped in and it was like stepping into an oven. We decided to put two large whirly birds on the roof. After they were fitted I poked my nose in to see how things were and the manager assured me that they had made a huge difference to lowering the heat in the building.
My shed where I am now, similar in size to the Karratha shed, has two whirlybirds since new so I wouldn't know if they make a difference or not, but in recent 40 degree days it has been quite comfortable in there.
Cheers,
Geoff.

As I said previously whirlybirds like most "solutions" can work if properly deployed and won't if not.

They are inefficient pumps, so unless there is easy ingress of air they won't cool.

If the air outside is as hot as the air inside they won't cool.

If humidity is the main problem they won't help as much.

I'd love to see this scientific paper referred to. I spent most of my working life doing research and know from experience most PhD's are f idiots. I really wish I'd done temp measurements before and after as I did with the house insulation. Venting my shed with whirlybirds made an incredible difference.