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Solar Whiz...or not?

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Started 3 years ago by AJB
Latest reply from jdaley

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AJB
Member

We are considering installing a Solar Whiz (solar roof ventilation whirlybird) to help extract hot air directly from a bedroom on the third floor of our West-facing townhouse in Melbourne. The only window in the room (and the entire East side of our house) is a small wind-out one in the skylight. It's our baby's room and simply leaving the window open at night isn't feasible. The roof is tin and relatively flat with little roof space. Thus the fan would extract air directly from the roof.

We'd greatly appreciate the thoughts of any people with knowledge/experience of Solar Whiz products in a similar situation.

Posted Wednesday 6 Dec 2017 @ 7:52:37 am from IP #
Lance
Key Master

The solar Whiz is a whirlybird alternative, forced air ventilation, would work a lot better than a whirlybird, which don't do a lot at all when you have hot but relatively still days. Given that you may want this extracting hot air at night, a solar vent isn't ideal, a decent regular exhaust fan is probably the better option.

Posted Wednesday 6 Dec 2017 @ 8:56:53 am from IP #
AJB
Member

Thanks Lance. I hadn't really considered that. Do you mean the sort of exhaust fan more commonly found in kitchens, laundries and bathrooms? Would noise be an issue, given that we have a sleeping baby in the room in question? Do such fans have thermostats?

Posted Wednesday 6 Dec 2017 @ 9:39:59 am from IP #
Lance
Key Master

Some are noisier than others, but continuous low level noises tend not to wake humans, it's short, sharp, unusual noises we usually respond to, although I've not had a baby in the house so can't say for sure.

A thermostat would simply be added at the switch that controls the fan, or elsewhere if you want to monitor the air temp at a different height.

Posted Wednesday 6 Dec 2017 @ 8:54:52 pm from IP #
Benny
Member

I'd second what Lance says AJB. What does a solar Whiz cost to buy and install ? What would a standard extractor fan cost ? Is there a wall high up where you could install an extractor fan ? Putting it through the ceiling/roof is probably a lot more expensive and more potential for problems with leaks.
Just keep in mind that if you install a say 25W fan, it will only use 0.2kWh over 8hours, which will cost about 5c in electricity use. 100 days a year, would be $5.

Also keep in mind that when you say you want to extract the hot air - where is the replacement air going to come from ? Are you planning to open windows and bring in fresh, cool, night-time air or bring the cooler air up from downstairs ?

Posted Thursday 7 Dec 2017 @ 7:30:33 am from IP #
AJB
Member

Hi Benny. Thanks for the input, you've raised some good points.

They cost around $1,500-$1,800 installed. I'll look into a standard fan.

Yes, the air is much cooler downstairs, so the idea would be to draw it up. This would probably involve leaving the door to the (baby) room open, which isn't ideal.

Posted Thursday 7 Dec 2017 @ 10:18:15 am from IP #
AJB
Member

Update. I went to the Solar Whiz office in Melbourne last week. Things got off to a bad start when the first guy I spoke to told an outright lie (claiming they'd installed a system in my suburb recently when the reality was that my partner had simply made an inquiry) and asked them in person how it worked and if they had any evidence to prove this, or even an independent review. Long story short: zero evidence and a lot of double talking by the salespeople about testimonials, satisfied customers, the time they installed one here or there, etc.

These things have been on the market for something like 9 years and, it seems, they've never run a simple test to see if they are effective at actually cooling a building! They were quick to point out how much air they can move, but to me that's like asking a car salesperson if a vehicle will do 100 mph and only being told about how aerodynamic it is compared to a bus.

They may well work and Solar Whiz be a fantastic product, but I'm not shelling out the best part of $2,000 to find out. The logic and performance of the two guys (who seemed well-intentioned) I spoke with was borderline embarrassing.

Posted Sunday 10 Dec 2017 @ 3:39:16 am from IP #
Benny
Member

Well done AJB. Thanks a lot for following up and reporting here. As you say - if they're so good why not a simple test to show it ? All you hear is people saying they make a big difference - which as many other tests show, people will always do when they have spent so much money on such a device.
If you have ducted AC AND a very hot roof space AND thin duct insulation AND the exhaust fan only cost $100 I could understand it. But $2000 !!

Posted Sunday 10 Dec 2017 @ 1:16:14 pm from IP #
Morbo
Member

for 2k youcan get your roof painted white or sisalation put in, result is guaranteed

Posted Sunday 10 Dec 2017 @ 8:14:17 pm from IP #
Phil A
Member

If you do a search on this site you will find pages of discussion on this subject.
While ever you have people building flat rooved houses with little roof space you will always have this problem until the technology to fix it becomes affordable.
Don't forget, the sun provides 800watts to 1000watts PER SQUARE METRE heating on your roof. ie above one room you may have 4 to 8 kw of HEATING.
If you put a 4kw heater inside your room in the middle of summer, how big of a fan would you need to remove all of that heat? A whirly gig? I don't think so.
If I somehow ended up in a flat rooved house I would immediately put a safari roof on it.

Posted Saturday 16 Dec 2017 @ 2:06:44 am from IP #
AJB
Member

Thanks Morbo. The roof is silver colored, so I'm not sure how much difference white would make.

Thanks Phil. Interesting about the heater equivalent.

Posted Sunday 17 Dec 2017 @ 7:43:07 am from IP #
AJB
Member

Update. We ended up spending $205 on a 10m roll of Renshade. This was enough to cover all the West and North facing windows on the 3rd floor. Only been up for a few days, but noticeably cooler in the rooms. Ugly, but acceptable and when you have a baby and a stressed new mother....small price to pay.

Posted Sunday 17 Dec 2017 @ 7:45:18 am from IP #
Morbo
Member

by silver you mean galvanised? This would have a higher heat absorption than white

Posted Sunday 17 Dec 2017 @ 7:50:12 am from IP #
AJB
Member

Yes, galvanised. Is there a way of calculating the cost benefit ratio of white vs galvanised? And would I then have a cooler house in Winter? I'm in Melb, so there aren't that many hot days.

Posted Sunday 17 Dec 2017 @ 7:59:29 am from IP #
Morbo
Member

$2000 for that whirly and you have a hole in the roof. It has to save you 6700 kWh to pay itself off. This is more than 3 years of my total power consumption. So, unlikely it will ever pay itself. But chances are bigger that on a rainy day the lights go out.
Overall I guess my house is 2-3 deg cooler with all that insulation in the roof. So its more a comfort thing than a money thing. Essentially with all the things I did my weatherboard outperforms standard brick veneer. But still, its more a sport than the faint chance to ever get that money back. Plus trial for off grid one day.

Posted Monday 18 Dec 2017 @ 10:58:56 am from IP #
Sunshine
Member

AJB,
The Solarwhiz also includes as an option an AC plugpack for night time running after the sun goes down.

Posted Wednesday 20 Dec 2017 @ 1:54:13 pm from IP #
AJB
Member

Yes, I know. Still yet to be convinced that it'll lower the temp in the room in question though. Running it at night would also entail leaving the door to that room open, which wouldn't be idea for a sleeping baby.

Posted Wednesday 20 Dec 2017 @ 8:53:26 pm from IP #
Sunshine
Member

the Solarwhiz has lowered our upper level temperature by three degrees and lowered our lower level by one degree.. we don't use the AC plugpack option eventhough it is installed.

Posted Thursday 21 Dec 2017 @ 1:44:56 pm from IP #
Benny
Member

Sunshine - is your solarwhiz just venting the attic space or connected to upper floor ceiling to pull air from there ? Do you think it works by reducing attic temp and so reducing inflow of heat through ceiling to upper floor ?

Posted Friday 22 Dec 2017 @ 6:49:11 am from IP #
AJB
Member

Sunshine - also be interested in the answer to Benny's question. And also how you conclude that it's made three degrees of difference. It would be super easy for the company (or any independent tester) to measure the efficacy of Solarwhiz with a controlled experiment, but no one seems to have. Why not? They have my details and my offer to buy if they can show me evidence that it works....they never got back to me.

Posted Friday 22 Dec 2017 @ 7:38:33 am from IP #
Sunshine
Member

AJB,
used a simple thermometer..upstairs in summer in a high set home in SE Qld heat is now great compared with before.. not sure why you think that extracting hot air in the attic and upper level doesn't work?

Posted Friday 29 Dec 2017 @ 3:09:44 am from IP #
Sunshine
Member

Benny,
Have ducted air con vents in each room on upper level, so attic and upper level has the heat removed.. the attic is actually quite okay to be in, in the middle of the day in summer..

Posted Friday 29 Dec 2017 @ 3:12:03 am from IP #
Sunshine
Member

AJB,
"Yes, I know. Still yet to be convinced that it'll lower the temp in the room in question though. Running it at night would also entail leaving the door to that room open, which wouldn't be idea for a sleeping baby."
Ducted air con vents without the ducting ensures that the hot air in the room escapes without needing a door to be open.

Posted Friday 29 Dec 2017 @ 3:21:40 am from IP #
jdaley
Member

I have been doing experiments with getting heat out and preventing it coming in at home in Bendigo.
With 16 ft ceilings radiant heat off the ceiling is not noticeable, but when measured with Temp gun it can be as high as 46 degrees inside on 45 degree days.
My solutions are;
Installed a safari roof with a membrane to reflect additional heat.
Installed a thermostatically operated solar fan that kicks in at 20 degrees.
Now thinking about a separate fan for night time, or a light glowing on the solar fan to remove residual built up heat, or draw in cooler night time air.
Measurements of Temp in degrees
Exposed to direct sun - Roof iron 76 Cost zero
Under solar PV cell 56 Cost nil in terms of intentional heat reduction planning
under safari roof 46 Cost about $35 per squ Metre
Inside high ceiling 36 before solar fan installed Cost zero
inside high ceiling 29 after solar fan installed. Cost $320
Extra night time fan not installed yet, through the wall Cost $70

I also have a ceiling fan in each room as well.

Posted Friday 29 Dec 2017 @ 4:53:16 am from IP #
mboy
Member

Thanks for sharing your measurements. I presume the temp measurements before and after solar fan installed was taken using the temp gun taken at the ceiling wall?

The drop of 7 degrees is impressive but how does that translate to the ambient room temperature?

Posted Friday 29 Dec 2017 @ 4:59:55 am from IP #
jdaley
Member

I use the temp gun all over.
For ambient temp I just measure the temp of a glass on a shelf at head height.
Standard beer stein unit perhaps
With the solar fan operating, the room never comes oppressingly hot anymore.
On hot days the heat build up 'layer or base' crept closer to the floor, now it is noticeably
cooler at head height, using the beer stein standard method.

Posted Friday 29 Dec 2017 @ 5:07:31 am from IP #
AJB
Member

jdaley - what is a safari roof? Please tell us a little more about your solar fan. I presume it isn't some sort of ceiling fan.

Sunshine - it's not that I don't think extracting hot air won't work, it's just that I'd like something quantifiable so that I can weigh up whether it would be worth the investment.

Posted Friday 29 Dec 2017 @ 5:21:39 am from IP #
mboy
Member

JD: this is great information. It would be good to see more of these experiments/measurements by the others and the makers of roof exhaust fans.
Give me some reassurance that roof ventilation is important for summer: and solar based exhaust fans makes sense compared to whirlybirds

Posted Friday 29 Dec 2017 @ 5:33:40 am from IP #
jdaley
Member

A safari roof is a second layer above an existing roof.
I used the term because the Land Rover company used them on vehicles that went to Africa, in an attempt to keep the occupants a bit cooler from the radiant heat through the roof.
Shade cloth stretched across any roof, with an air gap will also work, and does so very well with flat rooves and about a 300mm gap.
Essentially it is the air gap that shades the under roof.
I insert a good quality membrane, one used for steel framed buildings between the structural parts.
Its built as follows;
Assuming a standard Corrugated Iron [CI] roof
Top hat sections are fitted vertically up the slope of the roof, height of the section can be 50mm or 100mm what ever you have in mind or get at an economical price. I have not seen or done any research about an optimal gap.
Across those sections I install the new roof purlins, horizontally, sandwiching the membrane between the steel sections.
I have started looking at fitting panels of insulation into the frame created by the sections.
The roof is then attached to the new purlins.
It's not weather proof and that is so the warmed air can move up the roof inside the safari gap and escape out the top using traditional thermo syphoning principles.[ hot air rises ] and cooler air is drawn into the gap, preventing heat build up in the rood skin etc.
A specially made ventilated ridge cap can be installed [cost 2016 $75 a Metre] to keep birds and debris out.

Posted Friday 29 Dec 2017 @ 6:23:52 am from IP #
jdaley
Member

AJB,
The roof fan I use was purchased from a Home and Garden hardware in Bendigo, I have forgotten its name. But it was reviewed on this site as having too much noise.
I don't agree it hums when its running and I find that useful since I know its drawing air from the high ceiling space.
Because its solar powered it does not make any noise at night to disturb the 'possums'.
You need to purchase a different model for CI [ corrugated Iron ] or tiled rooves.

It kicks in at 20 degrees which the 'possums' complained about also, but I have found no issue with that and 16 foot ceilings.Most people seem to use them inside roof spaces.
Cost about $300 from memory but I have seen them on super special from time to time, particularly when Masters closed down.

I am now looking at fitting something, or modifying the solar one so I can power it at night to drawn cooler night air through the building.

Posted Friday 29 Dec 2017 @ 6:36:32 am from IP #

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