Signs you need a new furnace, possibly requiring emergency replacement, include increased heating bills, frequent repairs, and uneven heating in your home. Listen for unusual noises like banging or rattling from your furnace, indicating internal issues. Watch for a rise in dust and allergens, suggesting declining efficiency. A heating system over 15 years old often needs replacement. If these signs are present, promptly contact a local furnace replacement specialist to ensure safety and optimal heating performance.