In today's building industry, "smart" houses are all the rage. They're new houses packed full of energy-saving devices and computerized gizmos that are voice-activated, motion-controlled and light-sensitive.

A lot of us, however, live in "stupid" houses where windows and doors leak like sieves, attics have little or no insulation, plumbing systems allow only one faucet to run at a time, electrical systems fade in and out every time that old window air conditioner kicks in, and furnaces use fuel as fast as a Lear jet at takeoff.When it comes to state-of-the-art gizmos, you have your clock radio.

But contractors say it is possible to raise your house's IQ. Although it may never qualify for membership in Mensa, it can end up a lot smarter.

Jim Klappa, owner and president of JDJ Builders Co. in Milwaukee, says safety should be the first concern. That means looking at the electrical system.

"The older the home, the older the wiring will probably be, and the older the service. Years ago, when some of these houses were built, they didn't have all the appliances they do today. A lot of older homes are not qualified to take this additional load - especially their bathrooms and kitchens."

Most homes require 100-amp service, whereas older homes may have as little as 40 to 60 amps, says Klappa, who specializes in updating and renovating. He also suggests adding ground fault outlets in bathrooms and kitchens to eliminate the danger of electrocution should an appliance come in contact with water.

The cost to update service and outlets in an average 1,000-square-foot home would be around $3,000, he says.

Next, homeowners should look for ways to save energy.

"Nine out of 10 older homes are energy inefficient," Klappa says. "Homes built prior to 1980 were 2,000 to 2,500 square feet. They were bigger and built with less regard for energy efficiency.

"Adding attic insulation is one of the best ways to smarten up a house. Attics in older homes are generally poorly insulated. Some very, very, old homes have none. It's incredible. You're just losing everything. Your heat bill will skyrocket."

Even the highest-efficiency furnace won't reduce your heating bills if your attic is poorly insulated because your heat will just escape through the roof.

Home inspector John Geiger agrees. "The attic is the place where it pays very well to insulate. It's cheap and it's easy to do. But it's also important not to over-insulate," he says. "Once you get to a certain level of insulation, you reach the point of diminishing returns."

Mike Mueller, coordinator for low-income weatherization at Wisconsin Gas, said homeowners generally see a payback in less than five years when insulating attics and walls, depending on use and lifestyle.

The next priority should be windows. Klappa estimates that 20 percent of the heat in a home is lost through old windows, which are usually single glazed and have poor weather stripping.

Geiger suggests first tightening up rather than replacing windows. He says the only time windows should be replaced is when it is absolutely necessary, such as when a home is undergoing renovation or remodeling.

"People can spend up to $10,000 for windows. That owner, his children and their grandchildren are never going to see a return on that investment. It's virtually impossible to get a return."

In addition to weather stripping, homeowners should add sash guides and "fill the old counter-weight spaces with insulation."

He estimates the cost at about $120 per window with new sashes, $10 to $20 per window without.

"A brand-new high-efficiency window, with installation, could run from $500 to $1,000 a window," he says.

Klappa agrees that homeowners would generally not soon recoup the cost through low heating bills, but that they would see a fast return on the investment in terms of the home's overall worth and its eventual selling price.

Mueller believes it's smart to insulate windows, but there may be times when it pays to replace them.

"Most people are sitting with a storm window and a primary window. That's approximately an R-2, so there is definitely some reason to do something with the windows. Caulking and weather stripping can help eliminate air that leaks in," Mueller says. "To get a higher R-value, you have to either add a third pane or go with a replacement window. Some are R-5 or better."

Ventilation is third on Klappa's smartening list.

"Older homes are often not vented or improperly vented. You see bathrooms and kitchens that don't have vent fans. Without proper venting, condensation and high levels of humidity form in a home," leading to condensation on windows, rotting wood, mold and mildew.

By adding attic insulation, tightening up windows and venting a home properly, a heating bill could be cut by a third, Klappa estimates.

High-efficiency water heaters and furnaces should be considered next.

"Older homes often have oversized water heaters and furnaces. A home may have a 75-gallon water heater, and it may only need a 40-gallon water heater," Klappa says. "An efficient 40-gallon water heater will do the same job as an inefficient 75-gallon water heater because there is a faster recover rate, which saves energy."

As with windows, homeowners generally do not need to replace water heaters and furnaces if they are working properly.

"It depends on their condition, and if it is needed due to a renovation or expansion," Klappa says.

Geiger says furnaces he has seen in older homes are usually about 60 percent efficient. A new high-efficiency furnace is about 95 percent efficient and could save one-third of a heating bill. But that one-third savings "is going to cost you somewhere in the neighborhood of $2,500 for a new furnace."

So what is the cost of smartening up? Klappa says that if a homeowner insulated the attic, replaced windows, added venting, replaced a water heater and a furnace, it could cost around $20,000.

That includes the cost of adding air conditioning, which often is included with a new heating system.

"It's $10,000 to $12,000 just to replace the windows. A furnace, with central air, can run from $4,000 to $5,000. Insulation, depending on if you had to do the walls, could run $1,500. A water heater would cost from $300 to $400," he says.

Electronic gizmos are generally a homeowner's last priority.

Klappa says anything that can be found in today's new, smart homes can be added to the homes of yesteryear.