Remodeling an Eichler in Silicon Valley: City Rules, Radiant Heat, Roofs and the Energy Code

Eichlers reward a good remodel and punish a careless one. The glass walls, flat roofs and heated slabs that make them special also set the rules for what you can change, and a few Silicon Valley cities add rules of their own. Here’s what to know before you buy an Eichler you plan to update, from city rules to radiant heat, roofs, windows and the energy code.

City rules

• Palo Alto. The city adopted Eichler design guidelines on April 2, 2018, and says they’re voluntary. Since February 14, 2025, though, mandatory Two-Story Objective Design Standards apply in the mapped Eichler tracts to new two-story homes and second-story additions of 150 square feet or more, unless the owner chooses the city’s Individual Review instead. In those tracts the standards cap roof pitch at 3:12 with at least 2-foot overhangs, limit height to 22 feet, favor vertical or flush siding (stucco and block are capped at 30% of the wall), and rule out a projecting entry porch. Many Palo Alto Eichler tracts also have single-story overlays; see which ones.
• Sunnyvale. The City Council adopted Eichler design guidelines in July 2009, applied through design review for larger additions and remodels that change a house’s character. Many Eichler blocks are in single-story districts with a 17-foot height limit; see Sunnyvale’s districts.
• Cupertino. In Fairgrove, R1-e zoning sets mandatory rules for new homes, additions and remodels, including a roof slope of 3:12 or less, vertical-groove siding facing the street, a first floor no more than 12 inches above grade, 9-foot side walls and privacy treatment for second-floor windows. The code says it isn’t meant to rule out “a harmonious two-story home.”
• Mountain View. We found no Eichler-specific rules, and the city has no discretionary design review for single-family homes. Some areas, such as Grandmeadow, have one-story height overlays.
• San Mateo Highlands. The Highlands are unincorporated, and we found no Eichler-specific county rules.

Two Palo Alto tracts, Greenmeadow and Green Gables, were listed on the National Register on July 28, 2005. The city says tracts listed only on the National Register aren’t subject to its historic ordinance, though its planning policies can bring a closer look at major exterior changes. More in Which Eichlers Are Historic?

Radiant heat in the slab

Eichlers were built with radiant heat: hot-water pipes cast into the concrete slab. According to an Eichler publication, the earliest homes used copper; Eichler switched to steel from about late 1951 because of a Korean War copper shortage, then returned to copper in the late 1950s. The same publication says copper leaks are usually repairable, while in a steel system a first leak can signal it’s near the end of its life. One quick check: a magnet that sticks to the manifold points to steel. Ask the seller what system the house has and whether it has been repaired, replaced or abandoned.

Flat roofs and insulation

Nearly all Eichlers have flat or low-slope roofs and no attic, and the original insulation was thin, about half an inch, according to an Eichler publication. That makes a reroof the best moment to add rigid insulation on top of the roof deck.

California’s energy code applies when more than half the roof is replaced. Under the 2022 code, a low-slope roof in Climate Zone 4, which covers Palo Alto, Sunnyvale and San Jose, needs a reflective “cool roof” surface (aged solar reflectance of at least 0.63 and thermal emittance of at least 0.75, or an SRI of at least 75) and R-14 continuous insulation, with some exceptions. Neither applies in Climate Zone 3, which includes San Mateo and Burlingame. The 2025 code took effect for permits filed on or after January 1, 2026, so confirm the current requirements with the building department.

Glass walls and windows

Under the 2022 energy code, replacement windows generally need a U-factor of 0.30 or lower, with an exception for up to 75 square feet of replacements at 0.40. The 2025 code may tighten window values in some climate zones; check before you order. Palo Alto’s guidelines suggest repairing original windows first, and using window film or double-pane safety glass.

Asbestos and lead

• Asbestos. The Bay Area Air District requires notice before removing 100 square feet or more of regulated asbestos-containing material, and before demolishing any load-bearing part of a house, even a carport, regardless of asbestos. Have suspect materials tested before you open ceilings, walls, ducts or flooring.
• Lead. For homes built before 1978, EPA’s renovation rule requires a certified firm when work disturbs more than 6 square feet of painted surface inside or 20 square feet outside, and window replacement counts. Buyers of pre-1978 homes get a 10-day window to test for lead, unless both sides agree otherwise in writing.

Before you write an offer

• Find out what heats the house: original radiant (copper or steel), repaired radiant or a replacement system.
• Ask the roof’s age and whether rigid insulation was added.
• Pull the permit history, especially for additions and window changes.
• Check the city rules and any single-story overlay for the exact lot.
• If you plan to open walls or ceilings, budget time for asbestos testing.

Our Inspection Decoder explains common inspection findings, the Silicon Valley Eichler tract index lists the tracts city by city, and the Eichler market report tracks live Eichler sales by city.

Planning an Eichler purchase or remodel? Call the Boyenga Team at (408) 373-1660 or (650) 383-8606. Commissions are negotiable, and we offer bundled services, so ask us what’s included.