PaulS:
(labview is also an option).
You have labview on your phone?
I have labview on pc (labview only exists computers and for windows phone)
i was thinking of making a server with labview that makes a webpage or server list or so (i dont even know if this is possible 
) but labview can connect trough usb with the main arduino.
PaulS:
The moment i pres a button (hardware or software) i want near real time response of the attinys if possible.
I'm not sure how you would connect an ethernet shield to an attiny. Even if you could, instantaneous reaction is an unrealistic expectation. It takes time to convert the data to a usable message on the PC/phone side, to transmit that message to the ethernet shield, to get that message to the Arduino/ATTiny, to decipher that message, and to implement the instruction(s) contained in that message. We're not talking minutes, here, but we are not talking instantaneous, either.
PaulS:
i dont really want to use an arduino with ethernet. I prefer a computer as server. or even a raspberryPi
You want the PC to act like a raspberry pi?
With the PC as the server (or the raspberry pi, in case it was just a word order mismatch), you still need some way to get the user-intent to the Arduinos/ATTinys. How is that to happen?
oric_dan(333):
The major problem with your idea is you have sensors all over the house, which means
running bundles of wires every which way. That will rapidly become a big hassle, and also
make an unsightly mess. Also, I2C typically uses 5V signals [sometimes 3.3V], and the I2C
buss is not made for use with wires more than a couple of feet long, at most. You will
probably need to consider another communications hardware scheme.
i first was thinking about making multiple attinys with I2C/twi and letting them talk to 1 arduino uno connected with usb to a computer OR letting the attinys talk trough i2c/TWI to a raspberryPi (the raspberry pi should be configurable as a webserver)
there are also these chips that are called I2C extenders for about 2.50 euro each. link: http://www.nxp.com/documents/data_sheet/P82B715.pdf and http://be02.rs-online.com/web/p/i-o-expanders/0821784/
About the speed: maybe i could lower the i2c to 40 Hz or even less for less interference with any magnetic field things (couldnt get the right word)
SO, one arduino in each room and connecting them with I2C extenders???
btw thanks for the reply guys 