Pex is designed to handle higher temperatures for house heating.
 

Copper tube used in any kind of water distribution system will not melt, burn or give off toxic fumes. While a home fire can reach temperatures of 1,500 degrees of F, Copper offers an extra margin of safety with a melting point of nearly 2,000 degrees of F. For these reasons, copper tube is preferred for automatic fire sprinkler systems.

Copper plumbing has a proven track record of handling extreme conditions without constantly having pipes bursts and water damage. Copper tube can withstand more that 1,000 pounds of pressure (normal system pressure is about 50 pounds per square inch) Although no system should be allowed to freeze, copper systems can withstand repeated freeze-thaw cycles. Open flame or electrical resistance heating can be used to melt frozen water in copper tubing.

This space saving, highly efficient boiler/ tankless water heater can heat up to 600 square feet to 6,000 square feet and so there's no end to your supply of heat and hot water. With advanced computerized sensors and safety devices, this "smart" product monitors the water temperature, and modulates the gas valves according to the demand. Engineered with total efficiency in mind, the boilers/ tank-less water heaters will deliver convenience, space savings, and endless heat and hot water for all your household and commercial needs.

Baxi Luna boilers/ tankless water heaters work by fully modulating gas output. So, it knows when to be on high fire for great demand and knows where there is less demand of gas. This is direct savings to you the consumer.

Since it has neither a storage tank to keep heated all day, nor a pilot light water heaters only burn gas when you need hot water. This eliminates standby heat loss, which can be as high as 3-4% every hour for storage tank type water heaters. This higher efficiency can allow you to save up to 50% off your utility costs. You have already known that natural gas prices are rising, nationwide.