Skylight Replacement: Who Does It, Flashing and Cost

A skylight is a window in the roof, so replacing one is part window job and part roof job. The old unit comes out, a new one goes into the same opening, and new flashing is fitted to tie it into the roofing around it. VELUX describes the work as removing the old skylight, installing the new one and replacing the flashing, sometimes with interior touch-up at the top of the light well ⁶. A single skylight replacement typically takes a couple of hours, according to the VELUX FAQ ⁵.

Who does it depends on the roof. Fixr says a roofer or a window installer with skylight experience ⁷; This Old House says many roofing and window companies install skylights, and some companies specialize in them ⁸. If the roof itself is near the end of its life, the skylight is usually replaced as part of the roofing job instead, which is covered below.

Why the flashing matters more than the glass

A wall window sheds water that runs down past it. A skylight sits in the path of everything that runs down the roof, so the seal between the unit and the roofing does most of the work. That seal is the flashing: pieces that tie the unit into the roof covering so water is carried around it. This Old House describes flashing as thin metal sheets fitted around the edges to keep water from seeping in ⁸.

Skylight makers sell flashing designed for their own units, and the choice can affect the warranty: VELUX says its flashing must be used to qualify for its installation warranty ⁵. The roofer may care too. VELUX notes that some roofers prefer to install, or at least flash in and reshingle around, a skylight so they can keep honoring their roof warranty, and suggests checking your roofing contract first ⁵. When you get a quote, ask:

• Is new flashing included, made for this skylight and this roof covering?
• Will any old flashing be reused, and if so, why?
• Is the skylight curb-mounted or deck-mounted? This Old House says curb-mounted units sit on a raised frame, while deck-mounted units sit flush with the roofline and need more precise installation ⁸, and VELUX lists the mounting type among the things that change a replacement price ⁵.
• Who repairs the shingles around the opening, and who is responsible if it leaks later?

A step-by-step look at how wall windows are flashed is in how are replacement windows installed.

ENERGY STAR numbers for skylights

ENERGY STAR sets separate criteria for skylights, with U-factor limits less strict than those for wall windows. Its current skylight table (the October 2023 file) is ¹:

The table rows come from ¹. Both skylights and windows carry an air leakage limit of 0.3 cfm per square foot ^{1 3}. For comparison, a wall window in the Northern zone needs a U-factor of 0.22 or less on the standard (prescriptive) path, or 0.23 to 0.26 when paired with a higher SHGC under the table's equivalent-performance options ³. ENERGY STAR says skylight criteria are based on NFRC ratings and vary by climate zone, and that it does not mandate particular technologies ².

What the numbers mean: U-factor measures how well the unit insulates, and the lower the better; SHGC measures how much of the sun's heat comes through, from 0 to 1, and a lower number lets in less ⁴. ENERGY STAR caps skylight SHGC at 0.25 in every zone except Northern ¹. If a room under a skylight overheats, a lower SHGC is the number to ask about. Solar heat gain coefficient explained and energy-efficient windows explained go further.

When to replace, and when it is a roofing job

For old dome or bubble skylights, the VELUX FAQ lists discoloration from sunlight, mildew stains from moisture buildup, leaks, and condensation around the panes as signs it is time to replace ⁵. This Old House says fogging between the panes means a failed seal, which usually calls for replacing the whole unit ⁸; the same thing happens in wall windows, explained in foggy window between panes.

Lifespan estimates differ: VELUX says its skylights can last 20 to 30 years ⁵, while This Old House gives 8 to 20 years for skylights generally ⁸.

When it is a roofing job. If the roof is due for replacement, both VELUX and This Old House point to doing the skylight at the same time. VELUX says reroofing is the time to replace old skylights and that it lets you line up the skylight and roof warranties, though a skylight can be replaced without a new roof ^{5 6}. This Old House says replacement during a roof job lowers labor costs ⁸. In that case the skylight may fit better in the roofing contract than in a window contract, so the same crew answers for the roof and the flashing around it.

It may also be a roofing question when the leak is not the skylight itself. Water stains near a skylight can come from the roofing around it, or from condensation rather than rain, so have someone who works on roofs look at the shingles and flashing around the opening before a new unit is ordered. For leaks in wall windows, see window leaks when it rains.

When it fits a window project. When the roof is sound and the skylight is simply old, fogged or inefficient, a window company that does skylights can replace it along with the other windows. A same-size replacement avoids reframing; Fixr notes that a skylight wider than the usual 24-inch spacing of roof rafters or trusses means reframing that part of the roof, which takes more time and skill ⁷.

What it costs

Most survey figures are for new installations. VELUX's FAQ is the one source here that prices replacing an existing skylight, including interior and exterior finish labor.

The VELUX figures are a manufacturer's own ranges for its products, and VELUX says the price depends on roof height and pitch, the mounting type, the complexity of the job and the contractor ⁵. Fixr describes its national range as a mid-range project of two skylights ⁷. This Old House says its figures come from Fixr and Angi estimates unless stated otherwise ⁸. Fixr adds $119 to $216 in labor for a skylight in a spot that never had one, and $435 to $793 for an electrician if the unit is powered ⁷. This Old House puts permits at $500 or more and says contractors usually handle them ⁸. Whether your job needs a permit depends on your local building department; see do you need a permit to replace windows. This Old House lists roof pitch and access among the factors that raise labor ⁸. For window prices across a whole house, see the window replacement cost guide.

Before you get quotes

Note each skylight's size, whether it opens, and its model plate if one is visible. Find out how old the roof is. Then ask each company who does the roof work, whether a matched flashing kit is included, the skylight's NFRC U-factor and SHGC, and what workmanship warranty covers leaks. Is the installer licensed in your state for roofing work? How to choose a window installer covers the rest. When you are ready, you can compare quotes from window installers.

We are not affiliated with the manufacturers named.

About these figures

• ¹ Official record: ENERGY STAR skylight criteria table (October 2023): U-factor 0.45 or less in the Northern zone and 0.50 or less elsewhere, SHGC 0.25 or less outside the Northern zone, air leakage 0.3 cfm per square foot, checked October 27, 2026.
• ² Official record: ENERGY STAR key product criteria page, on skylight criteria being based on NFRC ratings and varying by climate zone, checked October 27, 2026.
• ³ Official record: ENERGY STAR certification criteria table for residential windows, Northern zone U-factor of 0.22 or less (prescriptive) or 0.23 to 0.26 with a higher SHGC (equivalent performance), and air leakage of 0.3 cfm per square foot, checked October 27, 2026.
• ⁴ Official record: DOE consumer guide on what U-factor and SHGC measure and the SHGC range of 0 to 1, checked October 27, 2026.
• ⁵ Reported: VELUX FAQ on replacement time, replacement price ranges ($900 to $2,400 fixed, $1,200 to $2,700 manual venting, $2,000 to $3,600 solar-powered, each with finish labor), what moves the price, roofers and roof warranties, reroofing, the 20 to 30 year lifespan of its skylights, signs an old dome skylight needs replacing and its flashing warranty condition, checked October 27, 2026.
• ⁶ Reported: VELUX article on who replaces skylights, what the job includes and replacing during a roofing job, checked October 27, 2026.
• ⁷ Reported: Fixr skylight installation range of $1,080 to $1,966 (average $1,523, described as a two-skylight mid-range project), the 24-inch rafter spacing note, replacement labor of $176 to $320, new-location labor of $119 to $216 and electrician cost of $435 to $793, updated January 31, 2025, checked October 27, 2026.
• ⁸ Reported: This Old House skylight installation range of $1,000 to $3,000 (average $1,800), labor of $300 to $2,500, permits at $500 or more, curb- and deck-mounted units, who installs skylights, 8 to 20 year lifespan and timing with a roof job, updated March 30, 2026, checked October 27, 2026.