Our hot water heater is in the basement and I plan to insulate the pipes with inch-thick fiberglass. The pipes are clamped to the 2×10s in the unfinished ceiling, with no space between pipe and wood. How do I accommodate the insulation?
I could use larger brackets and let the insulation force the pipes to hang an inch lower, but I don’t know if the runs will flex that much, or if it will be necessary to resolder everything.
I could cut an inch-deep notch across the beams.
Or leave those sections of the pipe uninsulated.
What is the best approach?
Janet
Replies
My opinion: notch the insulation to fit over the bracket and then around the framing. Wood isn't the best insulator, but it's far from the worst, either. Most would butt up to the framing and leave the bracket bare ... a mistake, I think. Don't forget all the joints and unions and other weird stuff ... it all can add up to much more than the framing intersections you speak of ... and they tend to be more difficult to do.
Yeah, notch the insulation however you have to. The notches won't cause that much loss.
Buenos notches.
Why not use foam insulation? All the home centers carry foam made to fit the pipes. It's fast, cheap and probably has a higher R value than fiberglass. You can fit it over as far as it will go in the places where the pipe is tight to the wood.
Foam has lower R-value
This is from FHB's article "Cheaper Hot Water":
Choose the best you can afford; fiberglass or elastomeric foam will save you more than cheaper foam tubing.
We spent a lot on hot water this winter.
Janet
How much fiberglass are you planning to use? The foam insulation is used to insulate refrigeration lines on every job I've ever seen with the exception of 4" chillers lines which do use dense fiberglass. 1/2" fiberglass insulation is has a 2.2 R value while foam has 3.2. If you bump up to 1" foam gets about 7.3 while glass is 4.4.
elastomeric foam will save you more than cheaper foam
Read that again. The "cheaper foam" is the gray styrofoam type stuff, while the "elastomeric foam" is the black rubbery stuff. And with any of it the quality of the installation is likely to be more significant than the material used. It's important to seal the slit in the insulation as well as possible, and the black rubbery stuff is probably the easiest to seal -- either with peel-and-stick strips or with a sort of rubber cement. Plus the rubbery stuff conforms well to elbows, valves, etc.
Using both
Cheap grey foam was the only kind I could get from HD, so I'll look somewhere else for elastomeric foam.
I plan to use thick fiberglass in the basement because the longer runs will not require much shaping. In the rest of the house I can only get at short runs with bends and valves, so elastomeric foam makes sense there.
Any idea where I can find Armaflex 520 BLV adhesive?
Janet
Forgot to mention: I want to use fiberglass because it has a higher R-value than foam.
Janet
But it doesn't, that's the whole point. Inch for inch elastomeric foam has almost twice the R value of fiberglass.
That's not what the article said--but then, I had my doubts about the usefulness of the comparison chart. Firstly, they compared fiberglass with foam--but didn't specify which type of foam was used in the comparison. Secondly, 1-inch fiberglass was compared to 3/4-inch foam. Apples and oranges, it seemed, but as they were clearly rooting for fiberglass, I just assumed that I was missing some obvious logic. Janet
Try a little bit of the fiberglass and a little bit of the foam, and see which goes on easier, with better coverage. The theoretical difference in R value is a nit.
You are right, apples and oranges and not identifying the insulation types. The fiberglass is different than regular fiberglass you put in your walls. A LOT denser (and better R per inch).
Comparison charts like that leave out too much information for me to consider them very usefull or informative. As some posters pointed out the grey and the black are different. If you used a urethane cousin, that may be even more different (although not sure if they make pipe insulation w/ urethanes and the like).
The insulation only is useful to limit heat loss when you are actually running water and if you use the hot water frequently (e.g. often in one hour). Once the pipe fills with hot water ... there will be heat loss ... no matter what ... then the next time you use it ... you'll have to heat the mass of the piping up again and waste water while waiting for it to get hot. This is moot if you have a recirculation line on your hot water system ... then you'd do well to have some kind of control to minimize the circulation time ... which is the biggest energy loser for those types of systems.
Make sure you have heat traps in your water heater .... much more useful for saving energy than insulation of piping (in GENERAL, but I'm not advocating skipping the insulation.
Which is worse for the planet, the energy loss of a recirc system, or the water loss from waiting for the shower to heat up?
I searched FHB but couldn't find a definition of heat trap. What is it?
Janet
Unless you live in an area where water is scarce, it's going to be better to run the water waiting for hot than to have a constantly-running recirculating system. Where it gets iffy is with the various intermittent schemes. The simple Taco-pump-under-the-vanity setup where you press a switch and wait is definitely "greener", but other schemes that use a pump and thermostat at the tank are probably a net loss in most situations.
A "heat trap" is a pipe nipple with a special valve built into it to prevent hot water from circulating out of the water heater due to convection. They come in pairs, one for the cold intake and one for the hot outlet. Have been code-required (though not necessarily installed) in most jurisdictions for 10-15 years now.
BTW, when it comes to insulating the water pipes, you can do the most good insulating the 2-5 feet closest to the water heater on both the hot and cold lines.
How do I delete an accidental posting?
Pipe insulation
Because the insulation is so cheap you should consider insulating the old pipes as well.
1) It will reduce the likelihood of condensation forming on them if you have a humidity problem.
2) It will reduce noise.
3) It will stop them from “stealing” heat from any hot pipes they run next to, or in the same cavity as. In a way you can think of cold water flowing through a pipe as very localized draught of cold air (and you are putting a lot of effort in to preventing that problem).
insulation blowers
May reduce condensation, may make it worse.