Build rate
From Supreme Commander Wiki
Build rate is important in this game as it affects how fast something is built. The larger the number the faster the building/unit is made. A build rate of 30 is better than a build rate of 5. However the higher the build rate the faster resources drain. This may not seem a problem when building a wall section, but if you were building an Experimental unit then this would have a bigger impact on your economy.
Build rate also plays on the speed of reclaiming, capturing and repairing.
Here is a little table to show which units build at which speeds:
