How to install exhaust fan in skillion roof shed?

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

All comments

Hi @Ritar

Every step you take will help reduce heat and condensation so try your prefered steps first.

My stages I am in to free cooling passive stuff just so you know my adgenda.

1 foil roof insulation

2 static (non powered roof vents 300mm) start at the highest pitch of the roof that gets the most 3 pm sun you can also install a 2nd one so think about 2 high locations ( 2 for MOSTLY FOR CONDENSATION reduction.) (If you thinking solar: Not all solar powered roof fans are strong enough so beware not to get a puny one.)

3 Big fan 450 for use while your in the shed ,

Try passive insulation and cooling in stages. OR put in a big ass fan 450mm- 700mm, Bunning has huge fan selection of industrial fans.

Insulation Fixed or ocilating

On ebay type "Garage Insulation" (This insulation is like a roll where as foil boards may leak more at edges if not a tight fit.) look for double foil +EPE foam 4-6mm tack with builders glue to the inside of your shed. roof and wall this is similar to how space craft are insulated you know they dont have room in there for pink batts lol. The double foil will greatly reduce heat the foam layer forms a thermal break and the foam will trap warmer air in winter. Cost for your shed roof approx $200 with the left overs use it on sun side walls.

If the condensation persists and there will still be some heat try using a static vent. Some also have clear lids to let light in so its a vent/solar light tube. Heat goes up out of the roof naturealy pulling in cooler air at door way mostly or under edges

You can also use whirly birds just make sure it is made to fit your corregeted roof profile ask the staff to help you pick the right one to match your roof,

AS a static guide make sure it is fit for corregated roof you choose another.

Ezylite Black DIY Static Roof Vent I/N: 0820197 $69

good luck in your search for coolness

Jason

Hi @Ritar,

Great to see you receive a prompt and helpful reply from @Jewelleryrescue. I'm sure @MitchellMc will be happy to share his thoughts when he's back on the site tomorrow, and @MikeTNZ and @CSParnell might also like to add their electrical expertise.

In the meantime, you might be interested in the advice community members shared for this article - How do you add insulation to a garage or shed?

Are you based in Australia? I should point out that the New Zealand Ministry of Business, Innovation and Employment (MBIE) issued a ban on the use of foil insulation in July 2016. The ban applies to the installation and/or repair of foil insulation in residential buildings. More information is available here: Foil insulation ban | Building Performance.

Jason

Yes @Jason I can see the poor use of foil being a shock hazzard mainly during installation.

But any electrician who left exposed wirers or the potential for exposed wires on lights etc like that for the foil to touch really is the real danger.

But in NZ you cant fight city hall. Thanks for the information.

Hi @Ritar

I havent seen any half decent solar powered vents around most of them have only 100mm vent holes and is a bit restrictive.

I do like the whirybirds as some of them turn with an additional wind powered fan in the throat of the vent .But when there is no sun or wind the heat under the roof will still vent out.

There is the static vents to at approx 300mm dia I like the clearcover versions acting like a bonus skylight.

To properly address your concern re instalation different vents have there own normally included kits and instructions for your corrugate roof. Grab a tube of roofing silicon too it cant hurt, JUST make sure its the right one with the correct roof kit mounting for your shed.

CSParnell

Thanks @Jason I think this one comes best to natural airflow be it by solar fan and enough intake through gaps or addition of vents.

Addining of electrical exhaust fans would be an over kill.

Hi @Ritar,

Thanks for contacting us in this respect.

Is there any chance that you could provide us with some pictures of your current building?

Possibly with annotations to where you want to put the fan?

This would make it so much easier to visualise.

Thanks,

Mike T.

Hi @Jason,

Yes there have been issues with foil insulation, mainly with homeowners installing foil sheet.

When they staple this to the timber in the roof or under the floor, there is a risk that a staple could go through a power cable feeding either lights or socket-outlets and hence livening the entire metal foil, which causes a shock hazard if there is no RCD protection in the house.

By rights, things like this should not happen, the duty of care is on the person installing this material.

Where cables might be damaged by staples, the homeowner is required to have the cables fitted with extra mechanical protection (either flexible or rigid PVC conduit) over the cables themselves, by an Electrician.

Hi @Jewelleryrescue,

We aren't talking about exposed wires, what we are talking about is homeowners that don't check cabling before they start stapling foil to joists and the like.

The Electricity Regulations and common trade practice dictates that you always run your cables on the side of a timber member in a domestic building.

Regardless of this, this does not stop Joe Homeowner from using nails, screws or whatever fixings to hold the foil up.

Also, there is no City Hall in New Zealand, we all have to comply with the Building and Electricity Regulations here and also ECP 51, that pertains to

Domestic Electrical Installations.

Maybe you should have a read of this ECP, it could explain a lot.

Cheers,

Mike T.

Hi @MikeTNZ Good to talk again. 🙂

The foil to my mind runs under the sheeting on top of the rafters like sarking. But if they pin foil to the underside of same rafter they should miss all power given you said power is supposed to be pinned to the side of the rafter.

No city hall? that explains a lot. No batman for Christchurch

I dont think I will be building in NZ to soon to much work to do here.

Your country will have a whole bunch of extra earth quake building codes too I would hope If they are sensible it would be good to know some new approaches to make structures safer.

In Oz most houses built on a timber frame supporting the roof the brick walls are all but decorations and will fail and crack if the earth moved but house wont fall down as the timber is doing all the load bearing.

Dosnt NZ use RCD? re the fools drilling into power cables.

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

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

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

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

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

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?

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?

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

@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.

Flat internal roof

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

Thanks @MikeTNZ

From now on I am going to think earth wire to roofs and sarking. For $1 wire not good situation I have being hit by 240v and it no picnic due to a failed earth.

Hi @Ritar,

As long as you have a registered Electrician run the cabling for your fan, I can't see an issue with it.

If you wanted to go the whole hog, you could put another fan at the other end of the building that will allow through ventilation.

As in, one fan draughting air into the shed and the other pulling waste air out, fans these days are so cheap and it makes sense to have an arrangement like this, especially if you do work that is quite dusty or you need lots of free air when working with adhesives and what-not.

Have a think about that, your Electrician will install a single switch that will turn both fans on at once.

Any further questions,

Let me know.

Cheers,

Mike T.

Thank you everyone for your great suggestions. I'll mull it over and speak with an electrician firstly. I want to do it right, and safely. No value in skimping when electricity is involved that's for sure.

Hi @Ritar,

Damn sorry, do you have someone like a Heating/Ventilation Technician that you could call?

They would be your best bet, if anything, they do this stuff day in, day out and would give you better advice than an Electrician.

Cheers,

Mike T.