Should I Install Hot Water Pipe Insulation?

by Erik North on November 30, 2011

Should I Install Hot Water Pipe Insulation


Funny aside: I was looking for a clear photo of hot water pipe insulation. I went through about 25 audit files and nothing.

Every time I found a photo, it was unusable. Eventually, I grabbed a camera and went to my basement and snapped a photo. So that’s my basement. Notice the XPS insulation in back.

Hot Water Pipe Insulation?

Anyway there’s a lot of dissenting opinion on whether insulating your hot water pipes is worthwhile. And here’s another one.

Insulating hot water pipes at first blush is a *shrug* project. They’re hot and radiating heat and you can insulate them … and they’re inside your house. Any heat radiating from the pipes is pumping more BTUs into your house, so what’s the big deal.

The point is that building enclosures are all about controlling energy flows. If heat is radiating willy-nilly from the hot water pipes, the odds are good (100% chance, give or take 10%) it is heading somewhere you’d prefer it not to.

Should You Install Hot Water Pipe Insulation?

Should you insulate your hot water pipes? Absolutely. That way you’ll control where the heat you’re paying for is going.

First, I’m mostly talking about forced hot water systems distributed by baseboard units. The same thinking applies to all hot water lines but the distribution loops are more fun to discuss.

Hot water pipes are usually PEX or copper (or if they’re very very old, lead) pipes that carry hot water through your house (for baths, showers and cooking) or through your heat distribution system to baseboard heaters or radiators.

Bath and shower water will wash out the drain, heat and all unless you have a hot water heat recovery system (These are cool, pun intended…I’ll get to writing about them at some point).

Hot Water Pipe Insulation – Where’s The Heat?

Your heating pipes loop through the house, sometimes running as much as 120 feet before returning to the hot water system. The water leaves your boiler/hot water tank/on demand system and circulates through the house, shedding heat as it goes. The water starts around 140 – 165 F and can finish the loop at or near room temperature.

Where has the heat gone? A big chunk diffuses through the baseboards/radiators and into the house. Another big chunk radiates through the pipes. What’s the big deal, you say. All that heat should be staying in the house, right? Hold on, senor smarty pants.

A big chunk of the heating distribution pipes run is around the basement’s perimeter. They’re strung along the basement joists, up into baseboard heating units and along the entire perimeter. Imagine it’s the dead of winter and about 10 F outside. Your 3/4 inch copper pipes run about 6 inches from the wood sills/band (R-value of 2 or so) and just atop the concrete foundation (also an R-value of 2ish).

We have 140 F water in copper piping (a great conductor … the exact opposite of insulation) next to 1 1/2 inches of wood and 1 foot of concrete. Between your hot water pipes and the chilly winter air, there is maybe R-2 worth of thermal resistance. Awesome. The heat is radiating out of the pipe and right through the foundation wall. That’s a nice chunk of change that is heating your house not at all.

Hot Water Pipe Insulation – What To Do?

Well, I suppose the good news is that unlike forced hot air duct work, we don’t have to air seal, just insulate. I’ll go into this in greater detail in another post but there are several commonly used hot water pipe insulations. Polyethylene foam, polyurethane foam, fiberglass wrap, reflective foil bubble wrap.

For standard residential PEX and copper pipes, I use pre-slit, self-adhering closed cell polyethylene foam (that’s a mouthful). These foams are more flame resistant than rubberized foams with superior R-value to fiberglass.

Should you insulate your hot water pipes? Absolutely, and make sure your heat stays where you want it.

Links to Hot Water Pipe Insulation:
Here’s a link to some pipe insulation on Amazon.

{ 1 comment… read it below or add one }

thermowell installation February 1, 2012 at 10:51 am

The priority measure when water pipes burst is to locate the shut-off valve to stop the flow of water and prevent potential flooding. Locate the pipe and check for damages such as cracks or breaks. Never use a flame torch when thawing the pipe because of potential fire hazards.


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