This is one of the bigger issues and questions we have to address so we've created a page dedicated to the issue! If were given a link to this page instead of a more personal response please do not be offended, after 15 years we just had to pursue a little more efficiency in addressing the issue!
In looking at options for venting systems often times it seems like the easiest solution is just to vent to the attic or to the outside of the home. We very strongly advise not to do this unless it is a done in a very mild year round climate.
But the Air is Hot and Should Be Removed. Well, not really, in reality the air from cabinets and closets may be hot from an electronics standpoint but not for the HVAC system.
Conditioned Air. In reality the air that's been heated by electronics has already been conditioned which means humidity removed and has been filtered... What venting
Lets Do Some Math. Lets just say are exhausting 100cfm and have a 20x20 room with 10' ceiling so that's 4000 cubic feet so in 40 minutes you're completely removing all of the air in that room and replacing it with outside air. Now lets be more realistic and do calculations for 120 or 150 cfm, bigger IDF fans 250 to 300cfm and then consider the whole house, you can realistically be cycling the air in the entire house within a day and that's no good.
But my bathroom and cooktop fans exhaust air! This is not comparing apples to apples as that is undesirable air that should be exhausted as it can be not only hot but also humid and smelly, it's a whole different ballgame but at the same time is it also important to not run those fans unless necessary. This is why often times bathroom fans are used with a timer.
Winter vs Summer. Lets also not forget that in climates where it's cold in the winter that this air quickly becomes very desirable and helps the HVAC system.
Where to Vent To!?!?!?
Return Vent. The best place to vent to is the HVAC return vent which if have access to the attic and the HVAC system is in the attic, or a return duct runs through the attic, then connecting to it is hands down the best option. This means the air will be distributed throughout the system and when the system is running it actually helps to pull air through the area being vented. Typically this connection would be made by an HVAC professional but can be done DIY using a standard duct collar and cutting it into the duct board associated with the return airflow. The duct collar is available at most home stores or HVAC supply houses.Another Area. If can't reach the HVAC return then simply vent back into the home or business but preferably to a larger room or hallway, somewhere that the air will mix and more efficiently reach the HVAC naturally. If you have ducting run through the attic then simply run the exhaust duct to a duct box and the best idea is to use a vent that matches other HVAC vents and no one will think about the purpose of it.
Options for Venting Back into the Home/Office
Have to determine what type of exhaust vent is desired and this is mostly about aesthetics.1) Match existing HVAC grills in the house and that will probably require a trip to Home Depot/Lowe's to get a standard duct box and grill that matches. Also get a collar that connects to the duct box and ducting.2) You can use our 4x8 duct box and the 4x8 grill and for this will need a 4x3 reducer. Here's the parts list: Insulated Duct Box OR Non Insulated These are 4x8 duct boxes, Grill 4x10, Reducer 4x33) Can use this elbow and grill. Duct Elbow, Grill that fits into Duct Elbow4) Will add this option as well, it is a smaller box and grill. Duct Box, Grill 4x5, Reducer 4x3
Products For Remote Venting. This discussion is relevant to the Inline Duct Fans, Ceiling Vent System and for commercial applications the Ceiling Grid Vent System but they normally vent into the plenum space in a drop ceiling.