My cold air returns ar located main floor on the floor below is insulated garage where furnace is located. New home however is it normal to feel cold air blow up through the returns whwn its windy out?

No it is not normal but when you have your heating equipment in a cold garage this can and does happen.

I would start by having someone check your duct system for any problems with its construction and attachments. Then it is back to the builder for repair.

If you just contact the builder they will probably tell you it is normal and they have always done the furnace system this way. That is the reason for the independent inspection.

Most houses have have have drafts -- doors and windows that don't seal

Plus heat rises and is draws heat out the top of house -- cold air is drawn in

At the bottom of doors... when garage door is open and furnace runs it

May draw outside air in return -- if there is are returns or registers in the

Garage maybe they need to be closed or covered in the winter...