I dont know about basements but we put a sunsquare flat rooflight over our dingy kitchen. It has transformed the room. Everyone comments on it. Natural light is unbeatable and even if it is still considered to be a basement with a skylight that is still a lot better than a straight basement! If you already use it a good amount i reckon daylight will extend that use and be attractive to others when you sell. Watch it tho - if it the glass is set at low level you may need to have it designed as a floor. Also do not skimp - get an opening one. Pref electric. We regret this bitterly! Good luck. Ps ours was 1000 ex fitting for 1.2x1.2m sq.
Since half your basement is above ground level it should not be difficult to add an opening window that would help with ventilation, the window would be best located on a south facing wall to allow light all day if possible and if it could be installed would add value to your home as when a window is installed into the basement it can then be classified as a room thus making your property more sellable
We have a large basement, which we use as a second sitting room and for storage, however, it is a true basement with no windows, so no natural light or ventilation. Half the basement is under the ground floor, but half is under the garden so I was wondering about having a skylight or light tube put in, coming out in the decked area of the garden.
If you've had a job like this done, roughly how much did it cost? Do you feel it was a good investment? I think we would get more use out of the room (as a playroom perhaps) if we could get light/ventilation in there... however, we are only planning to stay here for the next ~5 years, so if it would be very expensive, it would need to add some value to the property.