Next free inspection Tue 11:30
06 · Ventilation & skylights
A cooler attic, a drier skylight
A hot, damp attic shortens the life of any roof. We balance intake and exhaust vents, and install or reflash skylights so they stop being the first place a roof leaks.
(Who it is for)
Signs the attic is working against the roof
Most ventilation problems show up somewhere else first: in the shingles, in the ceilings, or as ice at the eaves.
Ice dams at the eaves
Warm attic air melts snow, which refreezes at the cold overhang and backs up under the shingles.
Frost or rust on nail tips
Moist house air condensing on the cold underside of the deck in winter.
Shingles ageing fast
Blistering and curling years early, especially over a hot attic.
Musty smell or dark sheathing
Mould on the underside of the deck, usually near bathroom fans that vent into the attic.
Skylight stains
Brown rings around the shaft, or drips in heavy rain only.
Upstairs rooms too hot
Heat radiating down from an unvented attic in summer.
(How it works)
Air in low, out high, in equal amounts
Cool air comes in at the soffits, sweeps the underside of the deck and leaves at the ridge, carrying heat in summer and moisture in winter.
How much you need: the 1-in-300 rule
1 square foot (144 sq in) of net free vent area for every 300 square feet of attic floor, split half and half. Footages assume typical products: about 18 sq in per foot of ridge vent and 9 sq in per foot of continuous soffit vent. We check the maker's rating on every job.
| Attic | Net free area | Roughly |
|---|---|---|
| 1,000 sq ft attic floor | 480 sq in total · 240 in, 240 out | 14 ft ridge · 27 ft soffit |
| 1,500 sq ft attic floor | 720 sq in total · 360 in, 360 out | 20 ft ridge · 40 ft soffit |
| 2,000 sq ft attic floor | 960 sq in total · 480 in, 480 out | 27 ft ridge · 54 ft soffit |
| 2,500 sq ft attic floor | 1,200 sq in total · 600 in, 600 out | 34 ft ridge · 67 ft soffit |
(What is included)
What we do
Every job starts with the attic: temperature, moisture and a count of the vents you have.
Attic and skylightsWhat we do
- 01Measure the attic
Floor area, existing vent area, temperature and moisture readings. We work out what you have against what you need.
- 02Intake at the soffits
Continuous or individual soffit vents, with baffles so insulation does not block the airflow.
- 03Exhaust at the ridge
Shingle-over ridge vent cut in along the ridge. We remove mixed exhaust (box vents plus ridge vent) that short-circuits the airflow.
- 04Bathroom and kitchen fans
Ducted in insulated pipe out through a proper roof cap, not into the attic or the soffit.
- 05Skylight reflashing
New manufacturer flashing kit and ice shield collar, with the shingles around it relaid.
- 06Skylight replacement or removal
New deck-mounted unit with its own kit, or removed and decked over if you would rather not have it.
(Skylights)
Reflash, replace or remove?
A skylight is a hole in the roof with a window in it. When it leaks, the flashing is usually the cause, not the glass.
- Unit under 15 years old, glass sound, leak at the edgesReflash
New flashing kit and ice shield collar. From $690.
- Glass fogged or cracked, or unit over 15–20 years oldReplace
New deck-mounted unit with its own kit. From $1,850.
- Roof being replaced anywayReplace
The kit is designed to go in with the roof, not cut in later.
- Room is bright enough without itRemove
Removed, decked over and shingled to match. From $980.
(How it runs)
How a ventilation job runs
Usually half a day, a full day with a skylight replacement.
- Visit
Attic survey
Area measured, readings taken, photos of every vent and fan outlet.
- Quote
Balanced plan
What to add, what to close off, and the net free area before and after, in writing within 48 hours.
- Install
Intake first, exhaust second
Soffit vents and baffles, then the ridge cut and vent. Fans ducted out through the roof.
- Follow-up
Readings again
A second temperature and moisture check in the next season, sent to you with the photos.
(Price guide)
Guide prices
Including materials, labour and making good the shingles around the work.
| Job | What it covers | Guide price |
|---|---|---|
| Ridge vent conversion | Cut in shingle-over vent, up to 40 ft, close off old box vents | $690–$1,100 |
| Continuous soffit intake | Per foot, with baffles in each rafter bay | $12–$18 / ft |
| Bathroom fan ducted through the roof | Insulated duct, new roof cap and flashing | $420–$650 |
| Skylight reflash | Existing unit, new flashing kit and ice shield collar | $690–$1,050 |
| Skylight replacement | Deck-mounted, fixed 2 × 4 ft unit with kit | $1,850–$2,900 |
| Remove skylight and deck over | Shingled to match, ceiling left ready for plaster | $980–$1,500 |
(Projects)
Ventilation fixed as part of a new roof
(Questions)
Straight answers before you call
Still unsure what your roof needs?
Book a free inspectionHow much ventilation does my attic need?
The usual rule is 1 square foot of net free vent area for every 300 square feet of attic floor, split evenly between intake low down and exhaust at the ridge. The table above works it through for common attic sizes.
Can I have too much ventilation?
It is rare, but mixing exhaust types (box vents plus a ridge vent, or a powered fan plus a ridge vent) can pull air from the wrong place. More exhaust than intake can also pull conditioned air from the house.
Should I replace my skylight when I replace the roof?
If the skylight is more than 15 years old, usually yes. Its flashing kit is designed to be installed with the roof, and replacing it later means cutting into new shingles.
My skylight only leaks in heavy rain. Is it the glass?
Rarely. It is usually the flashing, or condensation running off the inside of the glass. We check both before recommending anything.
(Roof notes)
Read before you decide
(Free inspection)
Ask about your attic.
We measure what you have against what you need and send a balanced plan in writing within 48 hours.