Is it better to exhaust out or intake from outside?

Dilemma I'm having for my 5x5, I'm not sure if I should intake from outside with a 4 inch going over my 1000w HPS and exhaust into the room for free heating. This would be ideal as I live in the UK, temps can be quite chilly at times so the free heat is welcome. But will this not cause humidity and temp issues?

The other option is to have the carbon filter attached to one end of my HPS sucking air in and venting it outside, and either using the 4inch to intake or just intake passively. I might be overthinking it but I feel this won't be as effective.

The first option wouldn't exchange air in your tent to keep co2 levels up.
You will likely need more than a 4" fan to keep a 5x5 cool running a 1000w hps.
Yes without exchanging air your humidity will rise.
Stick to whats common, filter> fan> hood> outside. Or filter>hood>fan>outside. The latter you want to make sure your hood is sealed perfectly of your fan will suck stinky air through your hood and you will lose stealth.

Passive intake is fine with that tent size.

Vent your lights from outside to outside, vent the room from inside to carbon scrubber outside.

i vent lights from outside to outside. i also have a fan pulling from outside to inside the room. both are set on a temprature controller. it turns on the fans at 79f and shuts off at 74f. its cold so they only run around 2-5 minutes to drop the temp and stay off about 15-20 minutes.

coreywebster said:

The first option wouldn't exchange air in your tent to keep co2 levels up.
You will likely need more than a 4" fan to keep a 5x5 cool running a 1000w hps.
Yes without exchanging air your humidity will rise.
Stick to whats common, filter> fan> hood> outside. Or filter>hood>fan>outside. The latter you want to make sure your hood is sealed perfectly of your fan will suck stinky air through your hood and you will lose stealth.

Passive intake is fine with that tent size.

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Thanks for the replies. The 4" was actually gifted to me by a friend and would've only been used as an intake; I have a 6 inch 1500cfm box fan that I'll leave running at half speed for extraction. So just to clarify Carbon filter > Hood > ducting > Fan > Outside should be fine with a passive draw for intake? Will this cause an increase in temps as opposed to using separate ventilation for the light?

I would run filter>fan> ducting to hood> then ducting from hood outside.
Putting your fan after the hood makes the fan suck smelly air through any small holes at your connections or hood. Plus you are pulling hot air directly into your fan.
I also have never used an intake fan. Just have intake opening and the suction of the exhaust fan does the rest.
Cheers

GreenHighlander said:

I would run filter>fan> ducting to hood> then ducting from hood outside.
Putting your fan after the hood makes the fan suck smelly air through any small holes at your connections or hood. Plus you are pulling hot air directly into your fan.
I also have never used an intake fan. Just have intake opening and the suction of the exhaust fan does the rest.
Cheers

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I would want to do that, but the box fan is large and too heavy to fit into the tent feasibly. I can hardly hear it though...

You never want to suck on flexible ducting.

xhexk said:

I would want to do that, but the box fan is large and too heavy to fit into the tent feasibly. I can hardly hear it though...

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Well that is also an important indoor growing skill. Adversity and making what you have to work with work.
Cheers