Exhaust: Where do you pull air from?

Where do you get intake air from when its freezing outside?
My fans are creating negative pressure on my entire house. I have a 2300 sq. ft. home and its hard to close the doors. Where do people living up north get their intake air when its winter?
I want to pull from outside but my grow room would be freezing, what can I do?

That sounds pretty awesome. So its creating a vacumme affect that sucks the doors shut? What about pulling from the attic as heat usually rises it could have some nice temps up there. Check your spots with a high and low temp meter to see the variance in day and night temps in the location your pulling from. The title is a little misleading

Wasnt sure how to ask the question... I dont mind the negative pressure but I know its costing me alot of cfm's.
Where I live, outdoor temps in summer are around 90 F to 100 F. in the winter it can get down to the low 20's. As you can imagine, when its that hot outside the attic can get from 120 F to 140 F in summer and same temp as outside in winter. My attic is around 34 F right now. I was just wondering where people in Canada or Minnesota or New York get their intake air from.

I'm pulling my intake air from the crawlspace underneath the floor. Yep it's pretty cold sometimes..so I don't run the intake fan much..Right now, I'm only running my exhaust and my tent is running 72-73 deg at soil....varies up to 79 toward the top of plants. Passive intake is coming from a closet.

I am in my half story upstairs and My room is against my attic area. Well I just leave one flange of the hood open with no ducting on it, And pull the air threw the other flange where my ducting exhuasts into my attic. My theory is when the air volume is low in my room, it has to get air from somewhere correct? well it pulls warm house air underneath my door and gaps in my door and replinshes the air that way. So I get warm air and it dosen't have to run threw a fan which would cool the air. Just the suction alone brings in air from under the door. Another plus this way is I dont have to run a million fan and it clears my room quick. my room is 112 cubic feet, my fan moves 424cfm. My room is replinshed with warm air every 15 seconds... lol

Im about in the same situation... Im running total of just over 800 cfm. I have 50 cfm for clone chamber, 100 cfm for mother chamber, 100 cfm for veg. chamber and 600cfm for flower chamber. Right now I have transfer air ducts throughout the house pulling air from almost every room. I have a 4" duct ran to both of my bathrooms so I dont need bath exhaust..(bonus)... I have an 8" duct ran to a grille over my recliner so I can smoke in my living room. And I have 6 seperate 8" ducts running to grilles, I installed to look like return grilles for the A/C system, in the ceilings of my other rooms. That is where all the negative pressure is coming from... Normally, you would have a make-up air system to compensate for the air being drawn out of the home....The problem with that is it cost an arm and a leg, and you have to attach it to your A/C system for the house. Big headache!

I guess I could just use a little space heater instream with the air flow....I just didnt want to run that extra 1500 watts if its not absolutely necessary.

If you pulled cold air from outside, you could throttle your fans way down...

good point.....