A common issue we encounter when doing layouts is how to accurately measure the reflectance in a building. The reflectivity of any surface is calculated by a numerical value 0.0 behind jet black(no reflectance) and 1.0 being as white(full reflectivity). It does not go beyond these values. Typical default values are 0.8(ceiling) 0.5(walls) 0.2(floor) which is like a dark grey concrete floor. The ceiling plays a very smaller role in boosting the overall lighting while the floor and walls are the most crucial. It makes a big deal to change this value when it is appropriate. One of the easiest ways to figure out the reflectance is to take a picture of the inside of a building and convert to it a black and white photo or better known as gray scale. This value is a perfect representation of your reflectance and is perfectly exceptable in all cases. Many programs will allow you to color pic and insert these values into the programs used to design lighting projects. Simply find that value(RGB, or HEX) and place it over. Try and include the floor and walls if possible, take several pictures if you can't get it all in. A nice shiny floor in a retail shop can up the default value to .6 in some stores, that is going to amplify your lighting tremendously.
A warehouse is typically concrete and very dirty. We often find these layouts require nothing more then a design using your default reflectance. However, in some concrete flooring could be painted white to help with lighting, in this case adjust your floor reflectance accordingly.
If you want to be able to easily pic colors. Try this cool program that allows you to hover over anything on your computer and at the click of a key it will grab the color under your mouse. A handy tool for selecting colors.