I'm afraid it's not possible to create a room that disables chat in HipChat at this moment. However, I can see that there's a similar feature request raised before at:
I would suggest you Vote and Watch the feature request so that you'll receive an update when it is accepted in the future.
...from the beginning. We have built up a lot of content in HipChat, with it being a core tool in our distributed company model. While it is true that we didn’t need to move to Slack immediately, we felt it...
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