The 30-second version
- Sun tunnels win when: the room has no exterior wall for a window, the attic space is small/complex, and the primary goal is daylighting.
- Traditional skylights win when: you want ventilation, sky view, larger light delivery, and can accept the higher install cost.
- Cost differential: sun tunnels $1,200-$2,500 installed, traditional skylights $1,800-$5,000 installed.
- Light output: a 14" sun tunnel delivers roughly the equivalent of a 60W incandescent bulb at midday; a 4x4 ft skylight delivers 3-4× that.
What each product actually is
A traditional skylight is a glazed opening in the roof plane — light passes directly through the glass into the room below via an open shaft. A sun tunnel (also called a tubular daylighting device, TDD) is a highly-reflective aluminum or coated rigid tube that channels light from a small roof dome down through the attic space to a ceiling diffuser in the room below.
When sun tunnels win
- The room has no exterior wall — interior bathrooms, hallways, walk-in closets, laundry rooms. A traditional skylight requires a straight vertical shaft; if the shaft would have to bend through 6+ feet of attic, sun tunnels are the practical answer.
- You want a small footprint — sun tunnels come in 10" and 14" diameter (roughly the light output of one 60W bulb). Great for supplementary daylighting; not a substitute for room-scale illumination.
- Cost matters more than sky view — installed cost is roughly half a traditional skylight for equivalent scope.
- Retrofit into existing house — sun tunnels can be installed through existing framing without cutting rafters. Traditional skylights typically require rafter cutting and structural reinforcement.
When traditional skylights win
- You want ventilation — venting skylights (Velux VSE electric, VSS solar) open to release heat and add fresh air. Sun tunnels are fixed by definition.
- You want a view of the sky — traditional skylights preserve the sensation of open space. Sun tunnels deliver light but not view.
- The room is large — a great room, kitchen, or open-plan living space needs the light output of a traditional skylight (or multiple). A single sun tunnel isn't enough.
- You want dimmable or blind-controlled light — Velux Solar Blinds are available for traditional skylights but not sun tunnels.
- Chapter 7A / VHFHSZ property — Velux's Chapter 7A-compliant skylights (Class B glazing or better) close the fire-code requirement. Sun tunnels have simpler roof profiles that are generally easier to detail Chapter 7A-compliant, but light delivery is limited.
Light output comparison
- 10" sun tunnel: ~150 lumens at ceiling diffuser (midday clear sky). Roughly one 40W incandescent equivalent.
- 14" sun tunnel: ~300 lumens. Roughly one 60W incandescent equivalent.
- Standard 2x4 ft fixed skylight: ~1,200 lumens direct sunlight entry. Roughly three to four 60W bulbs equivalent.
- 4x4 ft skylight: ~2,400 lumens.
These are ceiling-level delivery numbers. Actual room brightness depends on room size, wall color, and time of day.
Typical LA installed costs
- 10" Velux sun tunnel: $1,200-$1,800 installed (rigid tube runs) or $900-$1,400 (flexible tube runs)
- 14" Velux sun tunnel: $1,500-$2,500 installed
- Standard Velux fixed skylight (FS or FCM): $1,800-$3,500 installed
- Velux venting solar skylight (VSS): $2,800-$5,200 installed (before 30% federal tax credit)
How to actually choose
The decision tree for most LA homes:
- Does the room need ventilation from the skylight? → Traditional venting skylight (VSE or VSS).
- Does the room have an exterior wall you could open (window instead)? → Consider a window first; skylight second if the roof daylight would be materially better.
- Does the room lack any exterior wall (interior bath, hallway, closet)? → Sun tunnel is the practical answer.
- Do you want sky view? → Traditional skylight.
- Is budget the primary constraint? → Sun tunnel where light quantity is sufficient.
Halo Build Co is an authorized Velux dealer for both skylights and sun tunnels. See our Velux sun tunnels guide for product details, or our Velux fresh-air skylights guide for venting-skylight comparison. Request an on-site consultation to determine the right product for your specific room.
Frequently asked questions
How much light does a sun tunnel actually deliver compared to a skylight?
A 14" sun tunnel delivers roughly 300 lumens at the ceiling diffuser at midday — equivalent to about one 60W incandescent bulb. A standard 2x4 ft skylight delivers ~1,200 lumens (about 3-4× the light). Sun tunnels are excellent for supplementary daylighting in interior rooms without exterior walls, but they're not a substitute for room-scale illumination in a great room or open kitchen.
Can you retrofit a sun tunnel into an existing home without cutting rafters?
Yes — sun tunnels are specifically designed for retrofit installation without cutting rafters, using flexible or angled rigid tubes that navigate around existing framing. Traditional skylights typically require rafter cutting and structural reinforcement, making them a more invasive install. This is one of the primary reasons sun tunnels are chosen for interior rooms in older homes.
When should I choose a skylight instead of a sun tunnel?
Choose a traditional skylight when: (1) you want ventilation, (2) you want sky view, (3) the room is large and needs high light output, (4) you want dimmable or blind-controlled light. Choose a sun tunnel when: (1) the room has no exterior wall or the shaft path would bend heavily through the attic, (2) small footprint is fine, (3) cost is a primary consideration, (4) the room needs only supplementary daylight.