Hypothetically, you could install knob and tube wiring in a modern building – it just wouldn’t be cost-effective, as better ways of wiring buildings have been developed.
Knob and tube wiring isn’t dangerous in theory, but if you have knob and tube in your home, there’s definitely a risk. Knob and tube wiring is dangerous because it’s old – that means a number of safety precautions that exist in modern systems won’t be present. Old knob and tube wiring wasn’t grounded and didn’t use multiway switching, which can lead to serious potential fire and shock hazards.
Also, our modern electrical loads far exceed what old-school knob and tube wiring was designed to handle – homes with knob and tube wiring are highly susceptible to regular circuit breaks.
The tubes and knobs in knob and tube wiring can also degrade over time. This can lead to contact between your electrical system and your walls or floors. What’s more, movement around the open wiring system can lead to wire degradation, as well as contact between walls and wiring.