Eichler skylights can bring daylight deep into a house that already opens to the yard through walls of glass. They're also openings cut into a flat or low-slope roof whose underside is the finished ceiling, so a skylight that leaks, overheats a room or sits in the wrong place shows up quickly. Getting one right takes roofing, glazing and energy code details all working together.
This guide looks at how mid-century houses were originally daylit, what goes wrong with skylights on low-slope roofs, the rules for replacing or adding them under California's codes, and how to place them so they suit the architecture.
How mid-century houses were daylit
The original answer was mostly vertical glass. The National Register nomination for Palo Alto's Greenmeadow tract describes floor-to-ceiling glass along the back of each house, clerestory windows on the front and clerestories set in the gaps between roof levels, which bring diffused light into the kitchen and dining area. The nomination's descriptions of the original Greenmeadow models don't mention skylights at all.
That's worth knowing because skylights in a mid-century house may be later additions of varying quality. Before you plan work, find out when yours went in. Permit records, past inspection reports and the seller's disclosures can help. Other tracts and models were built differently, so check your own house rather than assuming.
Why skylights leak on low-slope roofs
The Greenmeadow nomination describes rooflines that are flat or close to a 2:12 pitch, and California's Energy Code defines a low-sloped roof as one with less than a 2:12 rise to run. On roofs like these, water moves slowly and the joint between the skylight and the roof does a lot of work.
The California Residential Code addresses that joint directly. Unit skylights installed in a roof with a pitch of less than 3:12 must be mounted on a curb that extends at least 4 inches above the plane of the roof, unless the manufacturer's installation instructions say otherwise. If your skylight sits nearly flush with the roof surface, ask a roofer to look at it first.
When water shows up near a skylight, check these places before deciding on a fix:
The curb and flashing. Look at how the roofing laps up the curb and whether the flashing is intact.
The roof surface around the curb. Water that ponds near a skylight keeps the joint wet.
The glazing itself. Cracked or crazed plastic, failed seals between panes and loose glazing gaskets can all let water in or fog the view.
The ceiling around the opening. Stains on the wood decking or beams show where water has traveled.
Condensation. Water isn't always a leak. Cold glazing can collect condensation, and NFRC window labels can include a condensation resistance rating.
Repair or replace an existing skylight
A small flashing repair can solve a leak, but a skylight that's cracked, fogged or poorly curbed is often a candidate for replacement, especially when the roof is being redone anyway. Coordinating the two lets the roofer flash a new curb into new roofing in one sequence.
California's 2025 Energy Code, which applies to permit applications filed on or after January 1, 2026, sets a standard for replaced skylights: a U-factor no greater than 0.40 and a solar heat gain coefficient (SHGC) no greater than 0.30. The code defines a skylight as glazing installed on a roof less than 60 degrees from horizontal, so it covers the flat units on a mid-century roof.
The roof rules matter too. When more than 50 percent of a roof is replaced, the Energy Code's reroofing requirements apply, and in Climate Zone 4 that can mean continuous insulation above the deck. A thicker roof changes curb heights and flashing, and the code's exceptions recognize that added insulation can conflict with required flashing heights. Ask your roofer how new insulation and existing skylight curbs will meet.
Adding new skylights: code and energy rules
Adding a skylight means cutting a new opening in the roof structure, so involve your building department early. The rules that come into play:
Glazing materials. The California Residential Code limits skylight glazing to laminated glass with a minimum interlayer, fully tempered glass, heat-strengthened glass, wired glass or approved rigid plastics. Fully tempered or heat-strengthened glass generally needs a broken-glass retention screen below it, with limited exceptions.
Labels. Unit skylights and tubular daylighting devices must be tested by an approved independent laboratory and labeled for compliance with the AAMA/WDMA/CSA 101/I.S.2/A440 standard.
Energy limits. In Climate Zones 2, 4 and 6 through 15, an exception in the code's prescriptive window rules lets up to 16 square feet of skylight per home use a U-factor up to 0.40 and an SHGC up to 0.30, instead of the stricter values in the code's main table.
Area caps. Skylights count toward total window area, which is capped at 20 percent of conditioned floor area. Skylights with a pitch under 1:12 count as west-facing no matter which way they tilt, and Climate Zone 4 caps west-facing area at 5 percent. Additions of up to 16 square feet of new window or skylight area are exempt from both caps.
Tubular skylights. Up to 3 square feet of tubular skylight area with dual-pane diffusers is exempt from the code's U-factor and SHGC requirements.
See the California Energy Commission's 2025 Energy Code page for the standards. This is a planning summary, not legal advice; your building department and licensed contractors make the call on your project.
Placing skylights so they suit the house
In a post-and-beam house, the roof decking is the ceiling and the beams are on display. A skylight changes both. The Greenmeadow nomination's evaluation criteria count noticeable changes to the original roofline, atrium covers that significantly alter the roofline, and beams cut so they are no longer rectangular against a house's integrity. Its contributing roofs have exposed beams that are squared-off and unornamented.
Work between the beams. Size and place openings so no beam is cut. If structure has to change, a structural engineer should design it.
Keep the profile low. A curb-mounted unit that meets code but stays low is less visible from the street.
Finish the opening cleanly. The sides of the light well show from below, so plan how they meet the wood ceiling.
Think about heat. Compare SHGC values before you buy, and plan for shading if the room already runs warm.
Consider the atrium. If the house has an open atrium, daylight may already reach the rooms you want to brighten. Our page on atrium living explains how that space works.
For how skylights fit into a larger project, see our Eichler renovation guide and our overview of mid-century modern design guidelines.
Questions to ask before you hire
Is this a flashing repair, or does the skylight itself need replacing?
What are the replacement unit's U-factor and SHGC, and does it carry the required label?
How tall will the curb be, and how will it be flashed into the roofing?
If the roof is being replaced, how will added insulation affect the curb?
Will any beam or roof decking be cut, and has an engineer reviewed it?
What glazing material will be used, and does it need a screen?
Who pulls the permit?
Frequently asked questions
Did Eichlers come with skylights?
The Greenmeadow nomination's descriptions of that tract's original models rely on glass walls and clerestory windows for daylight and don't mention skylights. Other tracts and models varied. Permit records can help you find out when a skylight on your house was added.
What energy rating does a replacement skylight need?
Under California's 2025 Energy Code, replaced skylights must have a U-factor no greater than 0.40 and an SHGC no greater than 0.30. Check the label on the unit and confirm with your building department.
Does a skylight on a flat roof need a curb?
Usually. The California Residential Code requires unit skylights on roofs pitched under 3:12 to sit on a curb at least 4 inches above the roof plane, unless the manufacturer's instructions specify otherwise.
Is a tubular skylight easier to add?
It needs a smaller roof opening, and the Energy Code exempts up to 3 square feet of tubular skylight area with dual-pane diffusers from its U-factor and SHGC limits. It still has to be tested and labeled, and the roof penetration still has to be flashed properly.
Related reading
Eichler Roof Replacement: Foam, Membranes and Above-Deck Insulation
Mid-Century Modern Window Replacement: Retrofit, Film and Title 24
Flat Roof Drainage on Mid-Century Homes: Fascia, Gutters and Grading
More guides on this topic: Owning & Renovating a Mid-Century Modern Home
Weighing skylight work on a mid-century home, or wondering about the skylights in a house you're considering? Call or text the Boyenga Team at (408) 373-1660 or (650) 383-8606, or contact the Boyenga Team and we'll help you sort out next steps.
