Debugdiag shows “Microsoft VC Runtime Heap” using over 1gb

Question

Hello I have a leak in my WPF application and I'm trying to use the memory dump file to track down where the problem is.

Using WinDbg and SOS I couldn't find anything suspicious. Then I tried DebugDiag and I got that Microsoft VC Runtime Heap (private) has 1,42 GBytes of commited memory.

Do you know why does this happen?

Heap 1 - 0x003b0000

Heap Name   Microsoft VC Runtime Heap (private)
Heap Description   This is a private CRT heap used by mscoreei 
Reserved memory   1,43 GBytes 
Committed memory   1,42 GBytes(99,21% of reserved) 
Uncommitted memory   11,48 MBytes(0,79% of reserved) 
Number of heap segments   242 segments 
Number of uncommitted ranges   242 range(s) 
Size of largest uncommitted range   124 KBytes 
Calculated heap fragmentation Unavailable 

Thanks,