The Dutch term lichtkap carries more than one meaning. In roofing it is a short rooflight: a raised daylight opening in a roof or wall. In lighting it is the shade that gathers, directs or screens the light from a lamp. And in older building literature “lichtkap” is sometimes used as a synonym for the clerestory.
Because the meanings diverge so widely, it is wise to use the more specific word in a specification or on a drawing: continuous rooflight, dome rooflight, luminaire shade or clerestory.
| Roofing | A short rooflight: a raised daylight opening in a roof or wall |
|---|---|
| Lighting | The shade that gathers, directs or screens the light from a lamp |
| Older building literature | Sometimes used as a synonym for the clerestory |
1. The light hood as a daylight element
In this sense a light hood is a short, raised daylight opening — shorter than a full continuous rooflight, larger or more elongated than a single dome. Think of a hood over a stairwell, above a bathroom with no external wall, or over the middle of a house where no window is possible.
The build-up is broadly that of a continuous rooflight:
- an upstand (kerb or insulated upstand construction) rising out of the roof plane;
- a glazed or plastic-filled top section, flat or slightly pitched;
- a sealed junction between the roof covering and the upstand.
The key design questions are always the same: how much daylight is needed, how much summer heat gain is acceptable, does the hood need to open for ventilation, and how will it be cleaned and maintained?
2. The light hood in lighting
In lighting a light hood is the screening around a light source: a shade that gathers, diffuses or blocks light. The term appears in luminaires, in illuminated curtain pelmets (a light trough above a window) and in display case and aquarium lighting. Functionally it is always the same job: avoid glare and steer the light where you want it.
3. The light hood as a clerestory
Occasionally “lichtkap” is used for the clerestory: the window zone high in the nave of a basilica, above the aisle roofs. This use is mainly found in older texts; the standard word is clerestory.
Points to watch on a daylight hood
- Insulate the upstand. An uninsulated kerb is a thermal bridge on which condensation forms in winter; that drips inside and is often mistaken for a leak.
- Consider fall-through risk. A plastic daylight opening in a trafficked roof is not walkable. Provide a fall protection grille or a physical barrier where maintenance traffic crosses the roof.
- Shading belongs on south-facing units. A horizontal or shallow-pitched daylight opening catches more summer sun than a facade window of the same area.
- Plan the cleaning. A hood you cannot reach gets dirty and, over time, transmits noticeably less light.
Related terms
- Continuous rooflight
- Dome rooflight
- Rooflight kerb
- Clerestory
- Roof window
- Light transmission
Want to know more about building terms? Take a look at our knowledge base on fredsdiyplans.com.