Sunpipe recommendations

[jayc89]

We're in the process of agreeing the final designs for our extension (design thread). We currently have a reasonably large, westerly facing, window over the stairs (approx 1200 x 1400), which lets in plenty of light across the staircase, hallway and landing. This is going to be lost as part of the extension as we're building out that way.

 

Our architect is recommending a series of Sunpipe; one on each half landing and 2 on the new landing to mitigate this loss of light. We can probably get away with using rigid sun pipes, which I understand emit the most light, but I'm struggling to find any solid data to be able to compare the light the original window emits vs the light these 4x sun pipes would provide.

 

Given the direction of a sun pipe's fitting (vertical vs horizontal) I assume the furthest end of the downstairs hallway would suffer the most from losing the window?

Any hints/tips/recommendations/comments/links to pages detailing the light emitted by windows vs sun pipes would be greatly appreciated.