Final answer:
Repairs or modifications to existing townhouses without sprinkler systems generally do not require the installation of an automatic fire sprinkler system, whereas renovations and additions might.
Step-by-step explanation:
An automatic fire sprinkler system is not required when repairs or modifications are made to existing townhouses that do not have a sprinkler system. While renovations and additions may trigger the need for compliance with current building codes that could mandate the installation of such systems, ordinary repairs and modifications typically do not. This is because building codes, designed to ensure a minimum level of security and safety, generally recognize that not all work on a building warrants a full upgrade to meet new code standards. Importantly, insurance companies look favorably upon properties that have taken measures to increase safety, such as installation of fire sprinkler systems, by sometimes offering reduced rates on property insurance.