Staple-Up Radiant Tube Expansion Noise

Answer 1

Expansion noise is typically a rubbing or squeeking noise, or a 'tick, tick, tick" noise that almost sounds like water dripping.   It is caused by the expansion and contraction of the tubing as it his heated.  The solution to your question depends on several factors, which type of PEX did you use?  What is the design temperature of your system?  Hotter the water the more expansion you will have.  PEX can expand quite a bit when heated so a good way to prevent noise is to leave room for the tubing to expand and contract, leave the ends of the turns open and unfastened so they can grow and shrink easily here.  Use plastic inserts where your tubing passes through wood, so the tubing is less likely to rub against it. 

Outdoor reset is part of a computerized control strategy where the computer adjusts the water temperature running through the floors depending on how cold it is outside.  For instance, super cold day outside, super hot water in the tubing.  Mild day outside, mild water temperature in the tubing.  It increases energy efficency.    Your control strategy is important and the setup will affect the tubing squeeking.  For example, if your system runs full speed for ten minutes then shuts down, then ten minutes later turns on again, runs for ten minutes, then shuts down...etc, your tubing will expand and contract (read: squeek) all day and night.  If you had constant flow with just the right temperature water this problem wouldnt happen.  I would encourage you to do a lot of research before you pursue this as it is very common for homeowner built systems to end up being dissapointing.  Or hire a professional, these things can be tricky.