by increasing your RAM size, integrated graphics should be able to allocate more. At 16GB system memory, 2.1GB is assigned to VRAM on HD4000.
However this is dynamic allocation, so you won't lose the free RAM space when not needed.
I recommend checking the maximum amount and type of memory supported by your system model if you would like to increase it.
You may check the options that you have in BIOS but the graphics memory is dynamically allocated. Please refer to the article below.