Reductions are used on areas to reduce the Net value for the area. One area can have several reductions, and each will in turn reduce the total net value of the parent area it’s been created on. You can use reduction to remove, for example, windows and doors, and thus get the actual facade surface.
The sum of all reduction’s values can be accessed from the parent area under the variables of RA, RL, RVO, and RV.
For rectangular objects that you can use diagonal placement for reductions when placing them on your blueprint. Start by clicking in the top left of your room and then right-click or double click in the bottom right. You will see a rectangular box with a dashed line diagonally when this mode is active.
You can lock the shape in a perfect square by holding shift while placing the area in this mode.
Rooms or shapes that have several corners or breakpoints can be measured by clicking at each corner and continuing around the lines. When you see the object taking the shape you want you can right-click or double click on the last point to create the reduction. If you overshoot a small targeting square will appear on the starting point and clicking within that point will also complete the placement.
You can press and hold shift while placing lines to lock them in 45-degree angles from the previous point.