I just saw your post. I’ve never done what you’re trying to do, but here are a few items you can try.
1) Project schedules have a priority associated with them. By default, they all get the same priority of 500. If you access the Project Information window, you will see a field where you can change the project level priority. If, for example, you want all the work to schedule around the non-productive hours, try setting the non-productive task schedule to a higher priority.
2) Tasks also have priorities. You can set the non-productive tasks to a higher task level priority by changing the task priority field to a value higher than 500. If you wish to try this, you’ll also need to change your leveling order (in the Leveling Options) to be Priority,Standard.
3) The third option is a bit more complicated since it involves changing task assignment units at the resource/task assignment level. In the non-productive tasks, set the assignment units to 37% (3/8). Then on the other tasks, change those assignment units to be less than 63%. Essentially, what this is doing is telling Project that 37% of the resources 8 hour day (about 3 hours) can be allocated to the non-productive tasks and all the other tasks can then be allocated at a maximum of 5 hours/day (63%). The key to this option is making sure that tasks that should be running in parallel are not combining to a total resource allocation exceeding 100%.
I work in an enterprise server environment and we have a similar environment where we have operational work schedules (non-project work) with fixed allocations and then project schedules as well. We don’t try to level all schedules together since this adds exponentially higher complications to the leveling. In our environment, we basically follow option 3, making sure that individual resource task/assignment units in the project schedules do not exceed availability of the resource to perform project work. Meaning, if the resource manager tells us the resource is available to the project at 20 hours per week, we set up the schedule to ensure that the resource usage doesn’t exceed 20 hours per week by adjusting the task assignment units.
Hope this gives you a few ideas.