5. Deck off the master bedroom
Now here's a project that seems really luxurious, promising views and fresh air along with your morning coffee. Of course, the coffee maker is downstairs or on the other side of the house, so for most people this winds up being one of the most underutilized living spaces, says Stewart Davis, design director of CG&S Design-Build in Austin, Texas.

"90% of the folks we talk to never go out there," Davis says.

Yet it's not an inexpensive project, costing at least $10,000 and requiring regular waterproofing and other maintenance.

6. Elaborate home theaters
Just as McMansions are falling out of favor, so are rooms that serve just one purpose.

With so many nice home-theater packages containing surround-sound speakers, amplifiers, bass modules, media centers and other controls and costing $3,500 or less, you can turn your flat screen in any family room into a home theater, instead of shelling out $20,000 or more for the whole shebang, including cinema seating, tacky red carpeting, projector, Blu-ray player and big screen.

And there's no guarantee that the next buyer will want the "Metropolitan Opera meets bordello" look of many theater rooms.

 

Another plus to updating your family room's acoustics instead: If you work with what you have, you're not bringing in a lot of new synthetic material, Vila says, and therefore don't have to deal with all of the outgassing, or release of fumes, from these materials.

7. Hot tub
This bubbly oasis seems relaxing and luxurious and is certainly much cheaper to install than a swimming pool, but many homeowners find that its upkeep, heavy energy use and repairs become a burden when compared with the time they actually spend using it.

Moreover, it gobbles up backyard space that could be used for seating, an outdoor kitchen or garden, designers say. And like the movie "Hot Tub Time Machine," it almost transports your backyard décor back to the 1970s or '80s.

Some homeowners weighing in on these fiberglass tubs on gardening websites actually wound up using them as raised beds for gardening, rather than forking over the bucks to rip them out or get them working properly.

If you simply must have it, the better option might be to buy a portable unit. That way, you can take it with you or stash it out of sight when marketing your house.

8. Overly complicated home automation
It's hard to tell people to stay away from something that sounds smart and could save them on their home-energy costs. But it's easy to go too far with home automation, the centralized control of audio, video, lighting, heat and household appliances, experts say.

"You shouldn't aspire to that without knowing that maintenance for that kind of system might be costly," Vila says. "Obsolescence is a matter of fact." 

Indeed, "montalvo," a homeowner on a home-remodeling forum who spent $100,000 on a system that controlled everything from audio and video to lighting, security and temperature in his 7,100-square-foot California home, said the convenience continued to cost him even after he built his home.

"It entails significant monitoring, maintaining, repair and replacement costs," he said in a recent post. "For the first two years, the system's installer was at our house several times a month, doing reprogramming, system upgrades, etc."

While some simple radio-frequency lighting systems can be installed for about $2,000 to $3,000, says Brian Scott, president of San Diego Automation, the wiring and equipment involved with more comprehensive systems can cost tens of thousands of dollars. And even software-based solutions are not without costs on the back end, as people feel the need to upgrade.

Scott's firm is now installing wireless systems for audio, video and lighting that are controlled via an Apple iPad. But just as many iPod users have traded up to an iPad, so, too, may many homeowners feel the need to upgrade to the next generation of controllers.

"It will evolve," Scott says. "But it's more about having all the features -- the latest and greatest."

The best advice for people without a big budget or the patience to learn the intricacies of a big system is that old acronym KISS: "Keep it simple, stupid."