My house is one year old and it smells like sewer gas from time to time. All traps are full of water, no noise coming from drains and there is no smell outside. The temp outside is -4

Typically there are only a couple of ways for the sewer odor to get into your house. Most of the time it's through a dry trap. Did you make sure ALL of them are full? Double check that the trap for a washing machine is full - sometimes they are not used for a while. Double check floor drains in the basement or garage - they can dry out. And once I had a client with the same problem and, after much agony and looking I noticed two copper stubs sticking out of the garage wall - but no drain pipe stub. I told him to look 'right about there.' Sure enough, he found the sheetrockers had covered an open drain outlet the plumbers left inside the wall. It was able to vent into the wall and throughout the house.
That solved the problem.
The cold temperatures can cause a reverse-flow of the vents also. That happens in Alaska some times.

Mmy house smells like turnips must be sewer gas. I noticed t first at the furnace the wind is blowing very hard. Could the sewer vent be blowing into the furnace pipe?