The 30-second version
- Roof windows are not skylights — they're windows in the roof plane that open manually within reach, suitable for egress, cleaning, and full ventilation.
- GPU (Top-Hinged): top control bar for low installation. Views from standing or seated position.
- GGU (Center-Pivot): most popular. Sash rotates 180° for cleaning the outside pane from inside.
- GXU (Roof-Access): opens wide for roof access, emergency egress, and maintenance.
- GDL (Cabrio Balcony): transforms from roof window to small balcony in seconds. Floor-to-ceiling views.
- Best LA use cases: attic conversions, ADU builds, hillside lofts, and high-ceilinged rooms where reachable operation matters.
Roof window vs skylight: the important distinction
A skylight is a fixed or top-vented glass panel high in the roof plane — you look up at it. A roof window is installed lower on the roof plane, positioned so you can operate it and lean out or look through it while standing or sitting inside the room. It functions as a real window that happens to be in the roof.
Roof windows are ideal for angled ceilings — attic conversions, loft bedrooms, ADUs with roof-plane walls, hillside modernist homes with steep pitched ceilings. Anywhere the ceiling and the wall are the same surface, a roof window is the right choice.
GPU — Top-Hinged Roof Window
The GPU has a control bar across the top of the window frame and a bottom handle. You lift the control bar to unlock, and the window swings outward from the top — like awning windows in a traditional wall. Suitable for roof pitches 15°–55° (3:12 to 17:12).
Best for:
- Loft bedrooms where the window is above the bed — you want an unobstructed view outward when open
- Attic offices at desk height where you want to lean into the opening
- Rooms where you'd put the operable window low on the wall in a traditional layout
The GPU includes a unique ventilation flap with a reusable filter that provides fresh air even with the window closed — useful in LA's dusty Santa Ana wind conditions.
GGU — Center-Pivot Roof Window (most popular)
The GGU pivots around a central horizontal axis. You turn the top handle, and the window rotates — top swings out, bottom swings in. This 180° rotation lets you clean the exterior glass from inside, and it opens more fully than the GPU for maximum ventilation. Roof pitches 15°–90°.
Best for:
- General-purpose attic conversions where cleaning access matters
- Homes without ladder access to the exterior of the roof
- Any application where a large ventilation opening is a priority
- Situations where the GPU's top-hinged geometry conflicts with something outside the window (a nearby tree branch, a satellite dish, etc.)
The GGU is the most-installed roof window in the Velux residential line. Available in the widest range of sizes (11 standard sizes from CK02 to UK08).
GXU — Roof-Access Roof Window
The GXU opens wide — up to 45° — specifically to allow you to actually step out onto the roof through it. Designed for roof access for maintenance, emergency egress, and cleaning solar panels or gutters from the roof plane. Pitches 15°–85°.
Best for:
- Attic conversions where an egress window is required by code
- Roof-mounted solar panel installations where periodic access is needed
- Homes with flat solar panel arrays needing cleaning access
The GXU has an innovative locking device that keeps the window open at your chosen angle — it won't fall shut on you while you're working.
GDL — Cabrio Balcony Roof Window
The GDL is Velux's most dramatic residential product. It's a two-part roof window that opens to reveal a small balcony in seconds — the top half tilts outward, the bottom half swings out with integrated railings, creating a Juliet-style balcony from what was a flat roof plane. Roof pitches 35°–53° (8.4:12 to 15:12).
Best for:
- Signature architectural moments — the "wow" upgrade on hillside estates in Bel Air, Brentwood, or Palos Verdes
- Attic conversions where a small outdoor moment adds significant property value
- ADU projects with high-value tenants or short-term rental focus
The GDL comes in MK19 and PK19 sizes — considerably taller than standard roof windows. Two flashings and installation coordination are required (the top half and bottom half seal separately).
Standard sizes at a glance
Roof windows use a two-letter size code where the first letter is width (C=22", F=26.5", M=30.7", P=37", S=44.9", U=53.3") and the second letter + number is height. Common sizes:
- MK06: 30.7"×46.4" — the "medium standard," most-installed size
- MK08: 30.7"×55" — often satisfies egress requirements
- PK08: 37"×55" — larger option, still egress-compliant
- SK06: 44.9"×46.4" — wide format for larger rooms
- UK08: 53.3"×55.5" — the largest single-panel GGU
- MK19 / PK19: 33.1"×101" / 39.4"×101" — GDL Cabrio sizes only
Egress and California building code
California Building Code requires bedrooms to have at least one egress window meeting minimum opening dimensions (5.7 sqft net clear opening, minimum 20" wide × 24" high). Not all roof windows satisfy egress — check with your local plans examiner or your Halo Build Co project manager. The GXU is designed specifically for egress; certain larger GGU sizes (MK08, PK08, MK10, PK10) satisfy most egress requirements as noted in the Velux catalog.
LA-installed cost ranges (2026)
- GPU / GGU standard sizes (MK06): $2,200–$4,500 installed with Velux EDL flashing kit for shingle roof
- GPU / GGU larger sizes (SK06 / UK08): $3,000–$6,200 installed
- GXU roof-access model: $3,200–$5,800 installed
- GDL Cabrio balcony: $8,000–$16,000+ installed — includes both flashing kits, framing modifications, and railing components
- Add manual shade: $150–$500 per window depending on shade type (blackout / room-darkening / light-filtering / venetian)
- Structural framing modifications for the rough opening: $500–$3,000 depending on truss layout
Attic conversion + roof window combos we recommend
For a typical Los Angeles attic conversion (converting unfinished attic space into a bedroom, office, or ADU), we spec 2–3 GGU MK06 windows evenly distributed along the south-facing roof plane. This gives excellent daylight without overheating the room. On the north-facing plane, one larger GGU MK10 or PK08 for cross-ventilation. Total cost for the window package: $7,000–$14,000 depending on flashing type and framing complexity.
Get a free Velux quote for your LA home
Halo Build Co is a Velux-authorized dealer serving the Greater Los Angeles area. Every quote includes site inspection, skylight sizing recommendations, cutout and flashing details, and total installed cost — no hidden fees. Text, call, or fill out the form.