Should Tubing Be Insulated in a Floor Joist Installation?

PEX Tubing

• Cross-linked polyethylene (PEX) tubing usually carries potable water supply or forms radiant-floor heating systems in residential structures. PEX is a flexible tubing material that withstands high temperatures and connects without solder or glue. For potable water supply systems, PEX manufacturers recommend that you insulate around PEX tubing, particularly if the tubes will experience freezing temperatures. Insulating around the entire tube prevents heat loss. For radiant-floor installations, manufacturers advise insulating below PEX tubing and around the floor's perimeter; this arrangement directs the radiant heat to the flooring surface.

Copper Tubing

• Copper tubing commonly runs through joists for residential water supply lines. To prevent freezing and bursting, copper tubing requires insulation. Even if your area doesn't experience freezing temperatures, you should insulate copper tubing in joists to prevent heat loss. Lost heat equals lost money; you can't reclaim the energy that your water heater used to warm the water. It's also common to insulate copper tubing against vibration by surrounding tubes with plastic inserts, called isolators, where the tubes penetrate joists. Installing isolators, during new construction, eliminates bothersome pipe noises and prevents pipes from banging against joists.

Drain Tubing

• Drain, waste and vent tubing typically runs through floor joists. Plastic and metal tubing, usually ABS and cast-iron, are common drain tubing materials. Because they don't hold water under normal circumstances, these pipes rarely require insulation for protection against freezing. However, you can insulate these pipes to deaden the sound of draining water. If you're working on floor joists above a living space, deadening the sound of rushing water can significantly increase the room's livability.

Insulation Materials

• Foam and fiberglass are the most common tubing insulation materials. Foam insulation is available in hollow tubes. The tubes open along a seam, slip over piping and seal with self-adhesive strips. Fiberglass tubing insulation is available in a similar tube form and also in more familiar batts and rolls. Rolls of fiberglass tubing insulation, typically called "pipe wrap," are smaller and thinner than rolls of wall and ceiling insulation.