(MONEY Magazine) – A seven-year study of 29,000 home sales in the Philadelphia area shows how much certain features add to--or subtract from--the value of a home. The numbers below may vary from region to region, but "the general trends would still be in place," says National Association of Realtors research chief Paul Bishop. --CYBELE WEISSER

Extra bedroom 4.1% Extra bathroom (full) 24.1 Extra bathroom (partial) 15.0 Central air conditioning 12.4 Sitting area in bedroom 8.0 Professional office -5.0 Basement 9.1 Basement laundry -2.0 No laundry -15.0 Wood frame 8.5 Stucco siding 9.7 Vinyl siding -3.5 Whirlpool 7.3 Security system 5.6 Fireplace 12.0 Two fireplaces 28.9 Skylight 3.0 Garbage compactor 4.5 Built-in dishwasher 2.4 Built-in refrigerator 8.4 Kitchen island 5.3 Double oven 8.8 Patio 2.1 Porch -2.0 Outdoor sprinkler system 8.7 Deck 1.9 One- or two-car garage 12.9 Oversize garage 13.8 In-ground pool 7.9 Style: contemporary 4.4 Style: ranch 1.7 Style: Victorian -5.8

NOTES: The study was funded by the National Association of Realtors and conducted by Florida State University professors G. Stacy Sirmans and David Macpherson, who examined 29,000 Philadelphia-area home sales between January 1996 and March 2003. The average home sold for $213,335 and had 3.5 bedrooms and 1.8 full bathrooms.