Daylight at Home
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An independent guide

Daylight from above, explained plainly

How skylights, roof windows and sun tunnels work, what they do to heat and comfort, and what to settle before anyone opens up a roof. Sourced from public bodies, with nothing for sale.

Start with the basicsBrowse all guides
A roof section with a skylightA schematic cross-section of a pitched roof. The sun is at upper left, light passes through a skylight set in the sunward slope and lands as a patch on the floor of the room below. Glazing Sun Patch of daylight
Daylight entering a room through a roof window. Schematic, not to scale.

01

Pillar guide

What a skylight is, and what it is made of

A skylight is a window in a sloping roof, and the word covers more than one product. This guide sorts out the types, the glazing and the frame, and explains why the parts matter before you read a single rating.

Read: Skylights explained →
Layers of a double-glazed skylight unitA schematic cross-section of a skylight: an outer pane, a coating on one surface facing a sealed gap, an inner pane and a frame, with daylight passing through to the room below. Outer pane Low-e coating Sealed gap Inner pane Frame Room below
Layers of a typical double-glazed unit. Schematic, not to scale.

02

Pillar guide

What a roof opening does to heat and comfort

Light is free, but the opening is not neutral: it can gain heat in summer and lose it in winter. The guide walks through what the ratings measure and how room, roof and climate change the outcome.

Read: Energy and comfort →
Sun angles through the seasonsA schematic gable house in cross-section. A high summer sun ray and a lower winter sun ray both reach a skylight on the sunward roof slope. Skylight Summer: sun high Winter: sun low Room
High summer sun and low winter sun reach a roof window differently. Schematic, not to scale.

03

Pillar guide

Installation, leaks and how long they last

Most skylight trouble starts where the unit meets the roof. This guide covers what installation involves at a high level, why leaks happen and how to think about repair versus replacement.

Read: Installation, leaks and lifespan →
Roof build-up around a curb-mounted skylightA schematic section through a roof: rafters, deck, underlayment and shingles, with a raised curb carrying the skylight and flashing that overlaps the shingles on both sides. Arrows show rainwater running toward the flashing. Glazing in frame Curb Flashing Shingles Roof deck Water
How a curb and flashing sit in the roof build-up. Slope shown flat for clarity. Schematic.

Shorter guides

Ten questions, answered one at a time

Each guide takes a single question from the pillar guides and goes deeper: a label, a material, a detail on the roof, a rule.

Three kinds of skylightThree small schematic skylights side by side. A fixed unit that does not open, a vented unit with a sash tilted open, and an electric unit with a motor box and a supply wire. FixedVentedElectric Does not openOpens to let air outMotor-driven opening

How we write

Public sources, no products, no prices

Every figure on these pages traces to a page that was opened and read, usually from a government agency, a national laboratory, a standards body or a building science organisation. The guide names no manufacturers and no installers, and gives no quotes or estimates.

  • Energy agencies
  • National laboratories
  • Rating bodies
  • Building science
  • Model codes
Read the editorial standards →
The sun's arc over a roofA schematic of the sun's path as an arc over a small house roof on the horizon.
An independent, educational publication. About this guide.