Can I use Siri on my iPhone without having to speak?
You can do what you want with the Type to Siri option.

On your iPhone do as follows:


Open Settings
Tap on General > Accessibility
Swipe up until you see the Siri label
Tap on Siri and enable the Type to Siri option at top of screen
Exit Settings


Now when you hold your Home button down you’ll get a keyboard pop up from the bottom allowing you to type directly to Siri (see screenshot below):