You use "haya" when you're just talking about your goal (having enough room in your suitcase). That supposes a simple action in the present or the future (just make sure there's enough room while you prepare the luggage). "HabrĂ¡" suggests there are actions or circumstances that may compromise that goal, so indicative somehow shows you prompt to take steps or further actions to make sure "que haya espacio".
__________________
[gone]
|