How to install exhaust fan in skillion roof shed?

[Ritar]

I want to cool my shed in summer and reduce condensation under the corrugated colour bond roof. Shed made out of weathertex. Not insulated at all.

My shed:

- 6m long 1.6m wide 1.9 - 2.2m high

- there is a wall divide to separate the pool equipment section from tool storage section. The dividing wall is 5cm from the roof, so there is a gap between pool and tool sections. The tool section is about 5m in length

I thought a solar exhaust fan to circulate air about may be better than Foilboards under the roof, If you agree that would work, would one exhaust fan on the tool end of the shed do, and if so, what size? Will the air gaps from the colour bond corrugations allow enough air flow in or do I need a vent somewhere, if so, where do I place that?

[MitchellMc]

Hi @Ritar,

Installing a solar fan would undoubtedly assist with heat build-up in the shed, and I'd recommend a premium version like the Bradford CSR SolarXVENT 250mm Solar Powered Vent. Condensation forms due to warm, moisture-laden air hitting a cold surface. When the roof's temperature drops at night, the air inside the shed condenses on the underside of the roof. Adding a fan could potentially evacuate that warm air from the shed during the afternoon and reduce the condensation overnight. However, insulating the roof will likely prove to be a more effective solution.

Please let me know if you have any questions.

Mitchell

[Ritar]

Yes, I'm in Australia. Good reminder though about watching out for electrical wires, foil, nails....fraught with issues. 

[Ritar]

Please see some photos of the shed, inside and out.Potential position of foilboard sitting on top of the rafter5cm wall gap from top of wall to roof. Wall is between sections of the shed? enough air in from corrugationsNorthern side of shed, looking southSouthern side of shed looking northSouthern wall inside shed

[MikeTNZ]

Hi @Jewelleryrescue,

The reasoning behind the change in the Electricity Regulations 1995 mandating RCD's for Domestic Installations came about because of situations like this.

Mainly on lighting circuits, there was a 5 year old child that was killed in Rakaia when he climbed an Aluminium ladder put up against the house, no-one knew that the whole metal roof was live at 230V.

Some "electrician" had run a lighting cable with no Earth conductor to some outside lights, right under the roofing iron and screwed through it with a Tek Screw.

He never tested his work and the roof was live from there onwards.

The lights he had installed worked, so no issue with that.

An Insulation Resistance test would have picked this up and an RCD if it had have been installed at the time would have tripped every time, suggesting a serious fault.

That is a serious dropping of the ball, as it were.

Absolutely shameful.

Cheers,

Mike T.

[MitchellMc]

Hi @Ritar,

If you can place a wall vent down the far end of the shed away from the exhaust fan, that will assist in getting a nice flow of air through the structure. However, it looks like you have a reasonable amount of gaps the fans could draw air through.

Mitchell

[Ritar]

that sounds good. Thank you all for your suggestions and warnings. It's back off to Bunnings I go.

[Ritar]

Mitchell, just one more question- will this CSR Solar XVent just sit on the corrugated roof, or are you suggesting it go onto the northern end wall?

The sun disappears from this wall around 2pm so it may not be suitable to get enough heat out before the cooler evening. 

What would be a wired version you could also recommend for this space?

[Ritar]

Thanks Jewelleryrescue for the lead for EPE insulation rolls. It looks like it would be easier to install than stiffer foils boards.

When you say use builders glue, are you saying I glue it directly to the underside of the colour bond roof? Install it like a sheet, or follow the profile of the corrugated roof to minimise air gaps?

[Jewelleryrescue · Accepted solution]

Hi @Ritar 

Normally I would use foil  to the outside of frame before the cladding goes on as this serves many purposes. info for  new pre built shed owners

Such as a reasonably tight smooth fit and full insulation cover the  screws through the cladding and foil will ground the foil to outer shed if metal lights and wiring will never interfere with foil insultation An additional  Earth wire can be attached to foil back to the sheds sub fuse board. /so RCD can be in play.

@Ritar  Your retro fit.

The EPE foam is not 100% stiff and can be spanned short distances over the  roof,  sagging wont look good , I want your shed to look good for you, too. 

In the attached edited  photo it shows extra roof battens level with the top of the beam to sit any  insulation on flat.

OR  Ok  second thought you might as well put  the battens  on top of rafters as insulation will flex over the  bumps.   The more battens you have the  less the sag in the insulation you can put glue on after  foil is in place sqirt up on top of batton below insulation gravity will set it down to the batten . This wont look  perfect  but more industrial.  So  lets  explore ideas more.

Flat internal roof

You could even use 4-6mm ply cut sheets and make a internal roof lining (painted? your choice)  which will capture sandwich  the insulation between the roof (and can breath via side roof  corragations under the roof..  Screw the sheeting directly to the battons with the insulation on top with glue tack points just to stop it  moving,  See diagram blue roof panels Plus optional  blue insulated sidewall flat lining  or just insulation. 

You maybe able to attach all this to existing timber side rafters or just add more battons. Center battens do not screw directly below side wiring. in case some one later  uses  long screw hits the wire.

A cant estimate how much clearance you have  above the light fitting or if it is safe so probably best to cut around light fitting .

To be super safe contact a qualified electrician to verify your installation poses no risks.

Optional Static vents work 24/7 one at each end of the shed will cool as a though breeze and they are inexpesive  this may be enough not to need roof vent.

If you later use  roof vent place it as high as you can get in the ceiling in shed  centre.

Please use this as a guide only to formulate your own design

[MitchellMc]

The CSR solar vent would need to go on the roof, though I presumed you might be thinking of going with a powered unit on the wall, given your illustration, @Ritar.

Any of these slimline exhaust fans would work well for powered units.

I'll take this opportunity to remind our community members that a qualified electrician must complete all electrical work, including the installation of earth cables.

Mitchell