Using a basement as additional living space in single family home

[Patrick Micozzi]

This is a valuation question regarding finished basements and the effect of them on the properties value.  Certainly, there are many things that enhance the quality and livability of the additional space created.  A few being, 1)open stairways to main living spaces and the out side  2) window wells that allow natural light 3) amenities such as a bathroom 

Please share your thoughts on the effects on resale value and your valuation method for calculating these effects.

Thank you

Patrick