I've stayed in nearly a dozen basement Airbnbs in DC alone and this is the best I've experienced. If you're considering elsewhere, don't, book Jane and Zac's place.
It's incredibly quiet (which is super rare for a basement), has a great full kitchen (very well stocked with pots and pans and utensils), and excellent ac/heating setup, and all the amenities (washer, dishwasher, desk, and great internet). It's a fantastic value.
I've been going back and forth to DC for work for seven years and am sad to have just discovered this place as I finally moved back permanently. But it will be my top recommendation to visitors. I couldn't recommend it more highly.