Orientation and Installation Methods
Tilt, azimuth, and spacing
- Face collectors true south in the northern hemisphere (true north in the southern), correcting magnetic bearings for declination.
- Year-round DHW: tilt approximately equal to latitude.
- Winter-dominant space heating: latitude + 15°.
- Summer-dominant pool heating: latitude − 15°.
- Azimuth within about 30° of true south is usually acceptable; 15° costs only a few percent.
Row spacing: find the lowest sun elevation that matters (winter solstice at solar noon) and prevent the front row from shading the one behind. elevation α = 90° − latitude − 23.45°; shadow length = collector height ÷ tan α.
Installation method
- Flash every roof penetration; sealant alone is not flashing.
- Support rails and standoffs for wind and snow loads; verify rafters before drilling.
- Slope collector and exterior pipe so drainback systems drain fully and air pockets cannot form.
- Support and slope potable piping; insulate with UV-rated, high-temperature insulation, protected against birds and thermal expansion.
- Provide isolation valves, a fill/drain point, and a vacuum breaker at the high point.
Worked example
Latitude 40° N, collector height 1.2 m. Winter-solstice noon elevation = 90 − 40 − 23.45 = 26.55°. tan 26.55° ≈ 0.50, so shadow length = 1.2 ÷ 0.50 = 2.4 m. Add clearance for the next row's frame and you need roughly a 2.5–2.7 m row pitch; a 2 m pitch shades the array in December.
Traps
Using magnetic south; calling a flat roof "0° tilt" when the collectors sit on tilted racks; ignoring inter-row shading; running pipe level so drainback traps water that then freezes.