Eichler homes -- those mid-century marvels with huge windows, open floor plans and clean lines -- are prevalent in Palo Alto, especially in the Greenmeadow, Palo Verde and Fairmeadow neighborhoods, and surrounding communities. Eichler fans can be very passionate about their houses and West Coast aesthetic but do the homes, known for their plentiful natural light, have a dark side as they age?

Lisa Knox, a Realtor with Midtown Realty, is an Eichler expert.

"I speak Eichler," she said. She and her family have lived in their Palo Alto Eichler for five years and are currently undergoing a major remodel. The majority of homes Knox sells are Eichlers, too, so she's familiar with the benefits and potential pitfalls.

Eichler homes were cutting-edge when they were designed in the 1950s and '60s but half a century later they can suffer wear and tear like any older buildings, she said.

One of the most noteworthy features of an Eichler design is its radiant heating -- a system of pipes that circulate hot water from within the concrete slab floors, warming the house from the ground up. It's a "luxurious" and efficient way to heat, Knox said, but it can be a hassle if the system goes awry. While houses built years before and after the Korean War had heating systems made with copper pipes, those built during the war period were done with galvanized-steel pipes instead. Steel, Knox said, corrodes, causing the system to fail.

Completely replacing the radiant heating can be quite pricey, she said, estimating costs of more than $30,000 for the heating system alone, not including the expense of jackhammering through, then replacing, the home's floors. Some Eichler purists find the replacement worth it. Other, less invasive options do exist, however.

Knox's own home, built in 1954, was done with steel pipes, which did corrode and fail. The previous owners chose to install a valance heating system, with pipes running overhead, instead. Another choice is to install heating pipes in the baseboards. Installing a furnace (for central heating) or an air-conditioning unit to an Eichler, she said, is awkward, as there's no designated space for them.

The Eichlers built with copper pipes have heating systems more likely to stand the test of time. Copper pipes don't corrode so they could "almost go indefinitely," she said, though homeowners may have to be willing to have a contractor go through part of the floor to check the system for leaks or perform maintenance periodically. Companies specializing in radiant heating are available to perform such maintenance and repair on copper-pipe systems.

Coldwell Banker, Los Altos, Realtor Elena Talis has remodeled her own Eichler three times (twice to expand to fit her growing family and once because of flood damage), and assists clients in readying Eichlers for sale. She's a radiant-heat fan, calling it much healthier than forced-air heating because of the reduction in dust and allergens, and the original system in her home is still going strong. However, she said original blueprints exist for Greenmeadow homes, which allow William Lipp of Lipp Hydronics to fix leaks with relative ease and limited intrusion.

"When it works right it's great but it's always more expensive to repair than a forced-air system," said Dan Salzberg of Salzberg's Radiant Heating Service. He estimated repairs at between $500 and $1,500. To replace a system, "you probably would spend a minimum $20,000 to $40,000 or more," he said, while a valance or baseboard system could cost a bit less.

Eichlers also come with slab foundations (rather than crawl spaces or basements), which make it more difficult to access underground gas pipes. In 2010, an Eichler home on Maureen Avenue in Palo Alto literally exploded due to a gas leak under the slab, prompting the city to put out a "Gas Safety Information for Homes with Slab Foundations" memo.

"Gas pipes running under homes with slab foundations ... can be exposed to surrounding soil which may increase their potential for corrosion, leading to a gas leak," Palo Alto Utilities representative Debra Katz wrote in an email. But she emphasized that corrosion is only one potential cause of gas leaks and that such situations are rare. "There is no reason for the owner of a slab foundation home to feel anxious or panic," she said, but homeowners may wish to get their pipes periodically tested.

Sergiy Smelyansky, general contractor and owner of Eichler Solutions said another common issue with aging Eichlers is replacement of their floor-to-ceiling, single-paned windows. He's been specializing in Eichlers for the past decade, after he "fell in love" with their style. Their "streamlined and elegant beauty," though, requires some upkeep.

"Fifty and 60 years ago they didn't have the same safety and energy rules as they do today," he said, so many Eichler residents opt to replace the original windows with more up-to-date glass for better insulation, energy-efficiency, cleaning ease and safety. Multiple options exist, from complete replacement to the lower-cost option of adding a film that decreases the likelihood of the glass shattering in case of an earthquake or someone crashing into it.

Depending on how elaborate a project, the price for a standard four-bedroom/two-bathroom home remodeling project may vary from $4,000 to $40,000, he said.

Greenmeadow resident Breht Napoli, who's owned an Eichler for 23 years, said that while the homes were not designed with efficiency in mind, he and his house's previous owners have greatly improved energy efficiency by installing dual-paned windows and doors, insulation and a solar water heater, among other additions.

Marty Arbunich, publisher of eichlernetwork.com/CA Modern Magazine, said Eichlers shouldn't be more expensive to maintain than any other older homes, but that it's crucial that contractors working on the house have extensive knowledge and experience with the unique Eichler setup.

Aside from radiant heating, "the No. 1 consideration is the roof," he said, as Eichler roofs tend to be flatter than standard, which can lead to leaking when water pools. "But I think any home that gets to be 50 to 60 years old is going to need special care," he said.

For the most part, though, Knox said, "Eichlers are really not that different from other homes." They continue to sell briskly, she said, adding that for buyers looking to purchase stylish homes in an affordable (for Palo Alto-area standards) price range, Eichlers are often the best choice.

For devotees, occasional upgrades are a small price to pay for "the pleasure of living in an Eichler," Arbunich said. "Most people who live in Eichler homes love them."