The mid-century modern design principles behind a California post-and-beam house come down to a few moves: open the back of the house with glass, shade that glass with deep overhangs, keep the street side closed and set each house on its lot for sun and privacy. The National Register nominations for Eichler tracts describe overhangs that shade the glass in summer and let the sun in during winter, and designers who placed each house on its lot using paper cutouts of the models.
Those ideas still work, and they explain both what people love about these houses and why some feel hot in summer. This guide pairs the original design records with current guidance from the U.S. Department of Energy and the National Park Service, so you can read a house's climate design before you buy it.
Deep overhangs: shade in summer, sun in winter
Overhangs are the first climate tool on an Eichler. The Green Gables nomination says the extensive overhangs at the rear of the house provided shade in summer but let in sunlight in winter. The Greenmeadow nomination says the same about its houses and describes an overhang of about three feet above the full-width rear glass. San Jose's draft National Register documentation describes deep overhangs that keep out the summer sun while allowing warmth in winter, and the Fairglen Additions nomination notes projecting beams running front to back to create deep shaded overhangs.
The physics is simple. The Department of Energy's Consumer Guide to Passive Solar Home Design says passive solar design harnesses the sun's low rays in winter and deflects its high rays in summer, and lists roof overhangs and trees among the controls that shade windows in summer. The National Park Service's Preservation Brief 3 notes that wide overhangs minimize heat gain from the sun in warmer climates.
That's one reason Palo Alto's Eichler guidelines treat overhanging eaves as character-defining and recommend keeping them. Trimming an overhang changes how the glass beneath it performs.
Orientation: placing the glass, not just the house
Eichler's architects sited houses one lot at a time. The Greenmeadow nomination says the designers used paper cutouts of the models to place homes where they fit each lot, oriented them to the sun as well as each lot allowed and protected neighbors' privacy. At Green Gables, one plan type was arranged in four variations to suit different lot orientations.
The Department of Energy's guide gives the general rules:
For passive solar heating, windows should face within 30 degrees of true south and stay unshaded from 9 a.m. to 3 p.m. in winter.
Windows in living areas should face south, and bedroom windows north.
In warmer climates, use north-facing windows along with generously shaded south-facing windows.
Tract lots didn't always cooperate, and the glass walls face the back yard wherever it happens to be. Caltrans' statewide tract housing study cites Edward Eichler, Joseph's son, who noted that the extensive glass made the houses difficult to keep cool in summer, particularly when the glazed rear walls faced south or west. On a tour, find out which way the rear wall faces before you fall for the view.
A closed front and an open back
The privacy plan is also a climate plan. The Greenmeadow nomination says the houses present relatively blank façades to the street, with almost no street-facing windows, and floor-to-ceiling glass across the rear. Palo Alto's guidelines add that houses were arranged so windows don't directly face neighbors. Light reaches the front rooms through clerestory windows set above eye level, which Palo Alto's guidelines define as windows that admit light, fresh air or both.
The Park Service's Preservation Brief 3 lists clerestories, operable windows, interior courtyards and skylights among features that provide natural light and ventilation and can reduce the need for mechanical systems. In Eichlers, the atrium plays a similar role: Caltrans says the atrium design was meant to provide private outdoor space on small lots and bring more daylight into the house. See our atrium living and indoor-outdoor living pages.
The slab, the sun and the heat
Eichler houses typically sit on concrete slabs with radiant heating pipes embedded in them, an idea that Caltrans says Eichler and his architects borrowed from Frank Lloyd Wright's Usonian houses. The Department of Energy's guide describes concrete, stone, brick and tile floors and walls as common thermal mass, materials that store the sun's heat. An Eichler slab is that kind of material, though the nominations we read don't say the architects designed it for solar storage.
Cooling was the weak spot. Caltrans notes that Edward Eichler said the company's radiant floor heating could not be adapted to include air conditioning, and that the growing expectation of air conditioning diminished the houses' appeal. The Greenmeadow nomination notes that Eichler roofs have no attics, so there is no attic to hide ducts in; our post and beam construction page explains the structure.
Landscape as climate control
Eichler's tracts came with designed landscapes, too. Palo Alto's guidelines name landscape architects Thomas Church, Kathryn Stedman and Robert Royston as designers of rear terraces, planter boxes and patios in the city's Eichler tracts, and describe how the atria and rear glass relate to the surrounding yards and tree canopy.
Trees do real work. Preservation Brief 3 explains that historic buildings often had deciduous trees planted to the south for summer shade and winter sun, and evergreens to the north for wind protection. Palo Alto's guidelines list plantings that provide shade among the ways to reduce the need for air conditioning in an Eichler. Removing a large tree from the south or west side of a glass wall can change how much sun reaches the room behind it.
Updating a house without losing its design
Preservation Brief 3 starts with a principle that fits these houses well: before any energy measure, assess the building's existing energy-efficient features. Then work from the least invasive options:
Shade the glass. Palo Alto's guidelines suggest window coverings and note that exterior or interior roller shades were original Eichler window treatments. The Park Service recommends interior shades, blinds or shutters where awnings aren't historically appropriate.
Consider film. The Department of Energy's guide says clear glass transmits nearly 90 percent of the sun's heat. Palo Alto's guidelines say applied window film can lower heat gain without replacing windows, and that a reflective look is discouraged.
Plant for shade. The Park Service describes deciduous trees to the south as a traditional way to get summer shade and winter sun.
Add cooling quietly. Palo Alto's guidelines suggest ductless mini-split systems or low-profile ducts and recommend keeping equipment off visible roof locations.
Our mid-century modern design guidelines and Eichler renovation guide pages go further. For equipment, glass or structural changes, work with a licensed contractor or energy professional and check your city's permit requirements.
Frequently asked questions
What are the main mid-century modern design principles?
For California post-and-beam houses, the records point to a closed street side, walls of glass toward a private yard or atrium, deep overhangs to shade that glass and careful siting on each lot. Open plans, exposed structure and radiant slab floors round out the list.
Why do Eichlers have such deep overhangs?
To shade the glass. The Green Gables and Greenmeadow nominations both say the overhangs provide shade in summer but let in sunlight in winter, when the sun is lower.
Which direction should a glass wall face?
The Department of Energy's general guidance for passive solar design is within 30 degrees of true south, with generous shading in warmer climates. Edward Eichler noted that glazed rear walls facing south or west made the houses especially hard to keep cool.
Can I add air conditioning to an Eichler?
Yes, with planning. The original radiant systems couldn't be adapted for cooling, so Palo Alto's guidelines point owners toward ductless mini-splits or low-profile ducts kept out of view from the street. A licensed HVAC contractor can tell you what fits your house.
Related reading
Butterfly Roof Houses and Other Mid-Century Rooflines Explained
Mid-Century Clerestory Windows and Window Walls: How They Work
Want help judging how a house will handle sun and heat before you buy? Call or text the Boyenga Team at Compass at (408) 373-1660 or (650) 383-8606, or contact the Boyenga Team and we'll look at its orientation with you.
