What is PEXin construction?

On material, almost always, and the gap widens as copper commodity prices rise. On labor, PEX usually wins too: coils pull through framing in long runs with far fewer joints. The full answer depends on the fitting system, the tooling the crew already owns, and what the spec allows; some commercial specs still require copper for domestic water, and a bid that swaps in PEX without an approved substitution is a rejected submittal waiting to happen.

The letters refer to the manufacturing process (peroxide, silane, and electron beam cross-linking), not a quality grade. PEX-A is the most flexible and pairs with ASTM F1960 cold expansion fittings; PEX-B is common with F1807 crimp and clamp systems. Pressure and temperature ratings are broadly similar. For estimating, the practical difference is the fitting system and tool: expansion hardware and crimp hardware do not interchange, so the takeoff must count fittings by system.

Yes, and it is increasingly common in hotels, multifamily, and tenant work, subject to the local code and the project spec. Watch the restrictions: PEX cannot be installed exposed to sunlight, listings matter when tubing crosses return air plenums, and manufacturers commonly require a short metal connector section at water heater connections. The spec section for domestic water piping is the controlling document, so confirm acceptance before pricing the swap.