Central Air Drafts: vents and registers

[jcreturns]

We have a 4 year old contemporary ranch-style home with 2800 sq ft of living space on the main floor and a 746 sq ft second floor room. We have a split system (hot water baseboard-heat, 3 zone central AC). We have severe (breeze-like) drafts that come through most of our AC vents and registers. Even with them closed, the air just comes through. I know I can do various things to cover the vents/registers, my main concern is the source and if I can do anything to stop the problem. Most of my ductwork utlimately resides in the unfinished space above our garage. I didn't know if there was a way to verify if the dampers that control the air to the 3 zones are fully closed or if there was someway to verify if there was a large gap/leak in any of the ductwork, particularly those that are in the finished walls. If I can provide any additional details, please let me know. I would greatly appreciate any feedback or direction.

Much Thanks!

[sminker]

so basically the air handler is in an unheated space during the winter and you run hot water baseboard for the heating.the air handler is acting like a static heat sink and chilling out being in the attic.the air even though it is not moving as in a fan running ......is actually migrating down as cold air does.if it was mounted on the garage floor just as you enter the house from the garage you would have minimal cold migration.the solution disconnect the discharge duct and the return ducts if it is flex type right at the air handler and cap the flex......or block the main supply trunk into the house with a slide in piece of styrafoam as if a filter would slide...also cut a piece to fit in the return grill also.dampers are good if air is moving on them but when its cold out and migration is happening they are just another cold sink and looking to drop the cold air down into the lowest point......your house.extreme solutions relocate the air handler to the garage floor,heat the attic with some of that baseboard ...just kiddin' don't do anything in the rooms on the registers isolated the sources

[jcreturns]

Thanks very much for the feedback and explanation. It sounds like blocking the draft sources is the practical resolution.