Advice: I want to remove hot air from garage

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duckDecoy

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#293192 5-Jan-2022 11:45

We have a stand alone garage that gets VERY hot in summer and I want to try and rectify this.

Tin roof A shaped, grooved plywood cladding, almost no gib lining except for a couple of places that I think was done for bracing purposes? But mainly on most walls I can see the building wrap paper. Its on poles and the floor is wooden slats with about 1cm gap between, so plenty of room for (hopefully) cooler air from the shaded underneath to flow up.

When its all shut up the temp rockets. If I open the side door or the main garage door it cools down pretty quick, so I think its just a matter of letting the hot air escape somewhere.

What are my options? I am guessing that some form of vent at the apex of the roof might help, but I don't know. It needs to not let water in when it rains and the wind is blowing.

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#2843524 5-Jan-2022 11:50

You would typically use something like this near the apex of the roof to exhaust hot air from a shed/garage.

https://www.bunnings.co.nz/bastion-300mm-mill-finish-aluminium-roof-vent_p0810899

timmmay

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#2843670 5-Jan-2022 13:23

I looked into greenhouse fans a few years ago. My conclusion there was fighting the sun would need a very large fan which is quite expensive. Passive is probably less effective but maybe effective enough.

Why do you need it cooler? So the car / contents aren't so hot?

Jase2985

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#2843846 5-Jan-2022 16:40

timmmay:

Why do you need it cooler? So the car / contents aren't so hot?

because people use their garages for more than just storing vehicles and/or stuff

duckDecoy

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#2843872 5-Jan-2022 17:28

timmmay:

Why do you need it cooler? So the car / contents aren't so hot?

We have replaced an old fridge in there and I am almost certainly shortening its life. We also store some food there after a big shop.

Goosey

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#2843885 5-Jan-2022 17:50

Ive started to keep the door a wee bit open where possible...

and try to avoid parking the car in the garage straight away.....afterall thats the heat source.

In the early evening, I on the odd occasion open the door for a few minutes to purge out the hot air as outside temp is cooler.

Seems to work... just cant store chocolate.

Jase2985

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#2843886 5-Jan-2022 17:54

instead of removing heat you want to prevent it getting in there in the first place if you can. can you line/insulate the garage?

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duckDecoy

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#2844239 6-Jan-2022 12:38

Jase2985:

instead of removing heat you want to prevent it getting in there in the first place if you can. can you line/insulate the garage?

Thats a good point, but I imagine its a bigger and more expensive job than trying to get the heat out. We don't even have a ceiling in.

KiwiME

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#2844324 6-Jan-2022 14:10

Check the temp of the ceiling with a radiant heat thermometer.

I'd suggest that both ventilation and ceiling insulation are the best options.

Jase2985

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#2844336 6-Jan-2022 14:32

duckDecoy:

Jase2985:

instead of removing heat you want to prevent it getting in there in the first place if you can. can you line/insulate the garage?

Thats a good point, but I imagine its a bigger and more expensive job than trying to get the heat out. We don't even have a ceiling in.

possibly short term.

elpenguino

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#2844340 6-Jan-2022 14:39

duckDecoy:

Jase2985:

instead of removing heat you want to prevent it getting in there in the first place if you can. can you line/insulate the garage?

Thats a good point, but I imagine its a bigger and more expensive job than trying to get the heat out. We don't even have a ceiling in.

If you've got a lot of heat gain from the metal cladding re-radiating heat into the garage, you can use a product more suited to that - the silver foil type of insulation.

Batts would be helpful for convective heat transfer via hot air.

Silver foily product could be applied between the roof framing but is probably a PITA to do with the roof in place.

Still, you don't have to remove the heat if it doesn't get there in the first place so a combination of prevention and treatment will probably be required.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

duckDecoy

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#2844346 6-Jan-2022 15:10

elpenguino:

If you've got a lot of heat gain from the metal cladding re-radiating heat into the garage, you can use a product more suited to that - the silver foil type of insulation.

I hadn't thought of that product, that could be well worth investigating.

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compound

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#2844647 6-Jan-2022 20:31

I thought silver foil insulation was banned in 2016 unless your garage is not electrically wired in any way.

SomeoneSomewhere

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#2844688 6-Jan-2022 23:17

There are some new non-conductive ones, but yes. The conductive aluminium ones are banned. A few too many people electrocuted themselves with it.

MikeAqua

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#2844736 7-Jan-2022 09:26

If it was me I'd get up on the roof pull the sheeting off and put down some insulating blanket/foil, and then put the roof back on using tec screws. Not actually a huge job. Probably a solid day's work for one person if it's a single garage. Tools needed are: Hammer, 600mm piece of wooden dowel (broom stick diameter), staple gun and cordless drill. I've done this on a garage and a house and it isn't difficult or complex if you're vaguely practical and don't mind heights.

I'd also look at a roof vent near the roof apex (job for a plumber) and some ventilation down low in the garage. Put the vents on the south wall if possible as that's where the coolest air is. if you have vents low and high you will get passive ventilation. If there is minimal internal cladding it should be easy to install vents in the wall. I've used this sort of vent before with no issues Airflo Aluminium Vent - Ventilation | Mitre 10™

You can also get insulation kits for tilting or sectional doors. We did that in our current house and it made a big difference.

Fans are an option too as others have suggested, but again you need to draw air in through vents for best results.

Mike

elpenguino

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#2844767 7-Jan-2022 10:22

compound:
I thought silver foil insulation was banned in 2016 unless your garage is not electrically wired in any way.

Have you got a reference for that ban?

Considering the roof and walls of sheds is commonly made of metal, such a ban would be a half measure.

One person I've spoken to had to earth his sheds wall cladding when electricity was installed.

You might be thinking of the use of foil insulation under floor. In that case yes, a few cases of electrocution occurred when staples were put through cables.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

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