In our environment, after the upgrade from Teradata 12 to Teradata 14, on the same server, the Spool space utilization has been increased. Its not a drastic increase, the maximum variance noticed so far is 14% with other cases of small variances as well.
Can we point out a few things which can be causing this? One guess is the bigger block size of Teradata 14 might consume more spool as compared to Teradata 12.
Would be worthwhile to check if you do have any missing/stale stats which might cause a different query plan for the same query .