Solar Powered Roof ventilator myths and half truths

Solar powered roof ventilators are fantasy on a stick.
Fans are rated according to fan displacement at maximum speed in free air conditions.

That is a fan in a tube, with nothing on top and nothing below, at maximum speed which would be ostensibly driven by the solar panel accompanying the fan when presented to you as a product.

The minute the flow encounters resistance, like the cap on a solar fan roof ventilator or the free air available on the intake side, performance values are well short of those claimed.
Add the variances of light available on the day you can reduce those ratings further again.

Solar panel is the energy side of this equation so look at the life expectancy as claimed by the manufacturer or the marketing company.
There’s no point to going to the trouble of installing the unit just to find some months later that you have is a solar powered lemon, because if the warranty doesn’t cover the labour.
You’re going to be up for the same costs again and again….or until you, or someone else, falls off the roof.

Suitability

And after all of that, remember…if you don’t have a roof ventilator that works at night….which is when you really need it for the evening purge….then you don’t have the product that benefits you most.

Yes there are products out there that offer you solar during the day and switch over to 240vac at night through a transformer and a switching chip which are more things that will go wrong sooner than later.
So the question then becomes…what is the cost?…. and who is going to maintain it?… and at what cost?
However look on the bright side, you’ve acquired an education, albeit one you didn’t need.
This is where the calibre of guidance is important, whilst keeping an open mind.

There are, by design, solar powered products that use a fan during the day and revert to natural flow at night, albeit somewhat diminished.
The air entering the attic void (replacing that which is exhausted) needs to be able to enter freely through high flow eaves vents of minimal resistance such as the Condor type.

You can exhaust heat from the roof void using a fan….but not on the roof!

Warranty

No fan manufacturer in the world will guarantee their fans to operate continuously in temperatures above 60 degrees which means that there will be failures, especially with the cheaper products, that translate into repairs and/or replacement.

The question then is simple….is that what you want……or would you prefer a simpler approach to achieving a better result in ventilating your roof?

Sales are quick to tell you what types of ventilation systems they have in stock, and suggest you purchase one or the other with one or the other, be it for heat in the roof, moisture in the bathroom or venting the dreaded ‘mould’ in the roof’

And you find yourself with a whole lot of answers that don’t match up with the questions you may have.
Therein lays the secret, make sure they answer your question, and do not attempt to fit your question to their answer.
You may be ignorant to the principles involved, but it doesn’t mean you’re stupid!

Example:

Prospective purchaser asks, ‘Are they noisy?’
Salesman responds, these roof ventilators have now got nylon bearings.

Did the salesman say, this roof ventilator is not noisy?
No! he left it to you to presume what you wish without committing him/herself.

PP asks, ‘What is the warranty?’
Salesman says, ‘Haven’t heard of any not working’

Again did he/she answer your question?

Being in the business of selling and installing roof ventilators is not the same as having the expertise to know what is needed.

Mush like like going to the butcher to discuss impending open cut surgery

As with the wonder ventilation gimmick of the moment, the solar roof ventilator. That which is going to give you something for nothing….after you’ve installed the product.

The Roof Ventilation product of the decade……

A roof ventilator that has a 12v fan hooked up to a solar panel inside a plastic housing with the claim that it’s going to perform wonders because it’s a solar powered roof ventilator…

But doesn’t work at night when you need it most.

So, putting vague and evasive ventilator performance values aside,how long is the solar panel going to last?
And the fan, rated at ? in full sun of course because if there’s no sun…no workee,

How often do you plan to replace this wonder roof top ventilator?
And are you going to do periodical inspections up on the roof or are you going to pay someone to do it?

And the biggie….how is this going work regarding night time purging, the most critical time for venting the stored heat out of a house, or roof space?

On one occasion I asked a solar vent salesman just that.
What is going to happen of an evening when night time purging is critical…without skipping a beat his answer was…the solar vent is so efficient during the day that it doesn’t need to work at night….

Now to me, the ability to utter those words is a considerable feat, as that statement would have stuck in my throat had I attempted to offer it even in jest.
Now I ask you….how many poor schmucks believed him?….
Lots!, otherwise he would not be repeating it.

Take note…rocket science didn’t suffer any loss when the salesman or tradie chose this vocation….flim flam is alive and well, and when cornered will say ‘we’ve sold thousands’…… but were they thousands of satisfied customers?….I think not!