ROOF ORIENTATION & OVERHANGS
The roof is the building's power plant and its rain hat. Point it right and size its edges, and it does both for forty years.
The ridge line gets drawn early, often before anyone has thought about it. That one line decides three things. It sets which way the roof planes face, and so how much electricity a roof array can make. It sets how far the eaves reach, and so how much rain the walls take. And it sets how snow sits and sheds, which is how ice dams start. Passive Design covers the sun angles. This page covers what the roof does with them.
East or west roof plane
ABOUT 83%
An east- or west-facing array at a normal pitch keeps roughly 83% of what the same array makes facing true south. Facing east or west costs some output, but it doesn't rule solar out.
Walls with no overhang
NEARLY 90%
In a Canadian survey of failed building envelopes, nearly nine in ten walls with no roof overhang had moisture problems. Walls under deeper eaves did much better.
Ice dams
A HEAT PROBLEM
Ice dams form when heat leaking from the house melts snow on a warm roof deck. The meltwater then refreezes at the cold eave. The fix is in the ceiling, not on the roof.
Why the roof gets drawn first
Rotating a roof is free while it's a line on the site plan. After framing, the planes face where they face.
THE RIDGE IS A SITE-PLAN DECISION
Which way the ridge runs is usually set by the lot and the street, long before solar comes up. Turning it 90° on paper costs nothing. Turning it after the trusses are ordered isn't possible.
AN EAVE IS THE CHEAPEST WALL PROTECTION THERE IS
Every foot of overhang keeps rain off the siding, the window heads and the joints where most leaks start. No membrane or sealant does that for so little money, and an eave never needs re-caulking.
SIMPLE ROOFS DO EVERYTHING BETTER
Every valley, dormer and vent pipe breaks up a plane. That gives the array less room, the snow more places to drift and water more places to get in. Big, plain planes are cheaper to build, easier to keep dry and better for solar.
Frequently Asked Questions
Our lot runs east–west. Is solar off the table?
No. An east- or west-facing roof keeps most of what a south roof would make. Splitting an array across both faces spreads output over the morning and evening, when the house is using the most power. We run the numbers for your address before anyone draws panels.
Site-specific production modeled on every project
Won't deep overhangs make the house dark?
Not if they're sized to the sun. At Plymouth's latitude, a 30-inch eave blocks the high June sun but lets the low December sun walk straight under it. Daylight comes mostly from the sky, not from direct sun. We set window head heights and eave depth together, on the same drawing.
See Passive Design and Window Design & Arrangement
How do we stop ice dams?
Keep the roof deck cold. That means a sealed, well-insulated ceiling plus either a ventilated attic or insulation above the roof deck. Heat cables melt a channel through the ice, but they treat the symptom and run all winter. The waterproof membrane at the eave is the backup, not the fix.
Air-seal and insulate first; membrane at the eaves as backup
What the package covers
Sun control is the half you can draw. Cooling a Minnesota summer night is the half that depends on how the openings are arranged.
WE SET
-
Ridge direction and plane orientation on the site plan
-
Pitch for snow shed, array tilt and headroom together
-
Eave and rake depth per elevation, not one number for the house
-
At least one plane kept clear of vents, skylights and chimneys for an array
WE CHECK
-
Shading from trees and neighbors through the year
-
Snow drifting where a lower roof meets a taller wall
-
The attic ventilation or unvented-roof detail, and the eave membrane
-
Gutter and downspout routing into rain gardens or collection
WE WON'T
-
Run plumbing vents through the best solar plane
-
Cut the overhangs off for a look
-
Quote solar production without a site-specific model
-
Call heat cable an ice-dam solution