Generally speaking, there are two ways to go about making home improvements. Either you splurge for something purely for the sybaritic pleasure of having it — the Italian marble bathroom you’ve dreamed about; that skylight that your spouse has been hinting at for the last six years — or you take a pragmatic approach, buying an energy-efficient furnace or repairing a leaky roof because you want to increase your home’s market value.

Don’t expect to score on both counts. “Just because you pour $20,000 into your home doesn’t mean that your house is worth $20,000 more,” says Frank Dell’Accio, a real-estate broker in Lindenhurst, N.Y. “I had a guy who invested $100,000 in a $130,000 home after he lived there for four years. He put it on the market at $225,000. He was offered $170,000.” His mistake: spending money on amenities that were only peripheral to the value of the house. “He wanted phones in the bathroom,” says Dell’Accio, “but [who else is] going to pay for them?”