Sean's answer is more comprehensive, I'll be more brief. If you're planning on selling the home any time in the next several years and expect to get that money back it would be a bad investment. It's very hard anywhere in Columbus to invest that % of the value of the home and get it back. It would likely take many years to get the full 100% return, if ever.
But if getting your investment back is not your only concern then.....
It's a great question that many homeowners ask themselves. A few questions back to you are these:
* Would the addition be made strictly for resale value or would you and your family be enjoying the benefits of it over a period of time?
Sort of like the old saying that "when you buy a new car, as soon as you drive it off the lot, it diminishes in value," that would most likely apply here. There is really no upgrade or enhancement that will hold 100% of it's cost so erase that thought from your head immediately. (see web link below for a cost vs. value discussion)
* What do the neighboring homes offer? If they all have an addition offering the same amenities (bath, rec room, quality of upgrades, etc.) then any future buyer would be expecting those features and would not be willing to pay much more than that of similar homes.
* Finally, whether it is next week, next year or ten years from now, you'll need to answer this question - "If you knew you were going to sell, would you still have made those addition?" That one usually gets to the answer that will help you.
Remember, the next potential owner of your home might not like your additions or changes so they'll move on to the next available home or offer you less than your asking price or they might love your home the way it is today and look to make their own additions after they take ownership.
My advice for you would be to make the decisions that best suit you and your families needs and budgets today. Worry about tomorrow when it comes.
Good luck with what ever you decide.