problem with ventilation in the winter

i have a 8X8X10 setup with 1 1000w hps air cooled lap and i was wondering how to bring fresh air in during the winter time. during the summer the fresh air intake is fine but as soon as winter comes around my rooms temperature drops. how else can i get fresh air to my plants. please help

Why not take it from inside your house?

if i dont use air from outside dont i haveto use co2?

There's more CO2 in your house, probably. The air quality might also suffer slightly to greatly(or could be better). Could air filter it first....