Light meter phone apps

Although I have found some light meter apps to be remarkably accurate and useful for informal measurements, I don't recommend it for this application. Somewhere in the fine print I believe a "calibrated" light meter is required. Not 100% sure but it seems likely. We send them in every couple of years to be re-calibrated.

Sara, there is no fine print in the v2009Reference Guide or the addenda, that I can find that suggests or requires the use of a calibrated light meter. There is nothing that the you must provide or the reviewer can ask for that confirms the use of a calibrated meter. The measurement option really is one the most lenient and flexible credits. As long as you have 4 measurement points per space you should be fine.

On the professional side, I would only consider an app valid if I did a side by side comparison with a meter and would personally just use a meter. But there is nothing that would stop you from using an app, I would just validate it with a meter first.

Joyce, would you be willing to share which apps you have found to be accurate? I've tested six different apps and have found them to be nowhere near accurate as compared to my calibrated professional meter.

As to the question, I'm disappointed if there is nothing that mentions a calibration requirement, but not that surprised. I think this goes in the pile of questions with the answer "use your professional judgement and reputation" on determining the appropriateness of your light meter.

Alas, just compared the app on my current windows phone to a calibrated meter reading and it failed miserably. Last test was 2 yrs ago with an iPhone app and results were within 5fc for daylight harvesting calibration. No good for emergency egress lighting. I'm with you. Let's stick with professional calibrated meters whether or not LEED requires it.