I partially solved the problem using i8kutils. Here's a guide about it:

Keenformatics - How to solve Dell laptops fan issues in Ubuntu

and a discussion here on askubuntu:

Dell Inspiron 5521 i7-3317U Fan CPU too Noisy

Here are the main steps as written on Keenformatics site (my blog).

How To solve Dell laptops fan issues in Ubuntu

1. First of all, let's download and install i8kutils. Open your terminal and write:

   sudo apt-get install i8kutils

2. Now you've got to add i8k to your modules. Open the modules file:

   sudo gedit /etc/modules

   and add the string "i8k" (without quotes) to the file. Save and exit.

3. Create an i8k.conf file

   sudo vim /etc/modprobe.d/i8k.conf

   and fill it with this code:

   options i8k force=1

   Note: Some older guides will tell you to create a /modprobe.d/options file. The "options" file isn't used anymore on Ubuntu. What does matter is that you create a file with a .conf extension (the filename isn't important, but I decided to name it i8k.conf for clarity). So beware of older i8kmon configuration guides.

4. Now restart your computer, or run this code to make i8k run:

   sudo modprobe i8k force=1

5. We will now create a i8kmon.conf file which will tell the i8kmon utility how to behave.

   sudo gedit /etc/i8kmon.conf

   Paste the following code in it:

   # Run as daemon, override with --daemon option
   set config(daemon)      0
   
   # Automatic fan control, override with --auto option
   set config(auto)        1
   
   # Report status on stdout, override with --verbose option
   set config(verbose) 1
   
   # Status check timeout (seconds), override with --timeout option
   set config(timeout) 20
   
   # Temperature thresholds: {fan_speeds low_ac high_ac low_batt high_batt}
   set config(0)   {{-1 0}  -1  40  -1  40}
   set config(1)   {{-1 1}  30  60  30  60}
   set config(2)   {{-1 2}  53  128  53  128}
   
   # For computer with 2 fans, use a variant of this instead:
   # Temperature thresholds: {fan_speeds low_ac high_ac low_batt high_batt}
   # set config(0) {{-1 0}  -1  52  -1  65}
   # set config(1) {{-1 1}  41  66  55  75}
   # set config(2) {{-1 1}  55  80  65  85}
   # set config(3) {{-1 2}  70 128  75 128}
   
   # end of file
   

   This has been edited to match my Dell Inspiron 15r 5521 fan configuration (and I hope I did it well). If you want more informations take a look at the documentation on Ubuntu Manuals: http://manpages.ubuntu.com/manpages/gutsy/man1/i8kmon.1.html

6. Now you should be able to run i8kmon from your terminal and see if (and how) it's working. Simply run:

   i8kmon

Finished!

The Asus Z87-A has a Nuvoton NCT6791D SuperIO chip to read temperatures and fan speeds and control the fans. Instructions on how to read and control the fan speeds are given here fan configuration of Z97-E under OpenSUSE. They are for OpenSUSE and the Z97-E motherboard but the process will be pretty much identical for the Z97-A under Ubuntu.