I don’t know what current construction standards are but my house was built in 1995–not so new, but at a time when everybody started to worry about energy efficiency. Why wasn’t consideration given to insulating the water pipes? What is the standard practice today?
Hot water pipes will radiate heat in the winter, so the heat isn’t wasted but I would rather have the water hot at the tap than heating dead space in my house. In summer, radiant heat from water pipes is at war with my air conditioning.
The opposite is happening with cold water pipes but the temperature differential is not as dramatic. But I don’t need my cold water to suck heat of the air in the winter.
I would be happy to add insulation but I’m not going to tear out all the walls and floors to do it.
Someone with construction experience might want to weigh in, but my supposition is that ordinary piping just doesn’t have enough surface area to make insulation worthwhile – the amount of heat transfer/loss to the outside air is pretty minimal. You might note that in houses heated by hot water, the radiators are designed to maximize surface area, either by having the water pass through many large steel loops or having radiator fins like on an A/C compressor. Also, many materials like foam that make good insulators are also a potential fire hazard. And many modern plumbing systems nowadays are made with PEX rather than copper, which is much less thermally conductive.
That said, it’s not unusual to have at least the first several feet of accessible pipe emerging from a hot water tank in the basement wrapped in foam insulation. It costs practically nothing and since all the hot water coming into the house comes out of that one pipe, it slightly prevents heat loss to a cool basement. But doing the whole house is generally just not worth it.
Much depends upon the age of the structure and where you live subject to local codes.
In cold-weather states (like Minnesota, Illinois, or Maine), code requirements usually kick in based on the location of the pipe within the structure:
Unconditioned Spaces: This is the big one. If pipes run through an unheated attic, a crawlspace, or an unheated garage, code almost always mandates insulation (usually a minimum of R-3 or R-4).
Exterior Walls: Most modern codes actually discourage or prohibit putting supply lines in exterior walls in “Freezing Design Standard” areas. If they must be there, they must be on the “warm side” of the wall insulation and often require additional pipe-specific sleeving.
I live on the east coast of Virginia and after a freeze many years ago resulting in frozen and burst pipes, local codes were updated in an effort to address this but that applies to new construction only. Builders of older homes were understandably cost focused and may have been tempted to accept the lowest plumber’s bid that adhered to local codes in effect at the time.
99% of this is price, pure and simple. Buyers do not actually care enough about energy efficiency to pay more for the house. They’d much rather have upgraded bathroom fixtures for the same extra money. Same reason a hell of a lot of houses even now are built with inadequate wall and attic insulation. Customers would rather (unwittingly) pay an extra $1000 every year to heat & cool the house than pay $1000 once to have it adequately insulated from the git go. Apartment owners would much rather each tenant pay an extra $1,000 a year to heat/cool than they spend an extra $1000 per apartment to insulate during construction.
Building codes are always a compromise between what the builders’ lobby wants (cheap & no interference), what the insurers want (whatever will reduce claims regardless of cost), what landlords want (cheap and no interference), and what homeowners want (pretty much nothing one way or the other). “Logic” is not a large input here.
I’ve always assumed that pipes running through an interior wall are already effectively insulated, by the couple inches of dead air space surrounding them in the wall. Since that air is trapped by the walls and joists, there would be very little convection. I would think that adding additional insulation would provide minimal return on the cost.
In most cases, by the time you go to use the hot water, it has shed most of its heat. So the hot water has to travel from the tank to the tap before you get hot water. Given pipes are long and thin, they have a lot of surface area for their volume, and will lose heat quickly. You can buy pipe insulation, a foam jacket slit along its length to put on. But I suspect in most use cases, the hot water in the pipe will still be tepid next time you go to use it.
Are you losing heat? If heat stays in the house, so what? If the pipe is run along an outside wall - that is a bad idea, it’s inviting freezing (possibly bursting) the pipe. And in a normal house, the outside wall is fully insulated already. The only reason to insulate the hot pipe is maybe, if you live in a place where air conditioning is heavily used. But really, how much ehat are we talking about?
The ideal setup for instant hot water is either on-demand heater under the sink, or a circulating pump to keep the water in the pipes freshly hot and feed the recirculated still warm water back into the tank. (In that case, insulating the pipes makes sense). I discussed this idea with someone who, like me, has a tank a decent distance from their bathroom. I suggest the pump be tied to something like the bathroom light or fan so you are not circulating hot water unnecesarily.
I have some of that pipe insulation - on my cold water feed pipe. The plumber cleverly ran the main feed for the house above the electrical panel; in humid summer, it would sweat onto the panel. Insulation at least stops the sweating there. A dry electrical panel is a happy electrical panel.
I don’t understand - why is there hot water in the pipes? Doesn’t the boiler have a check valve of some sort to prevent heat from escaping when faucets are closed?
You turn on the hot tap. The tank is, say, 30 feet away so you get a stream of room-temperature water that eventually gets warm as the hot water reaches you, but has lost heat warming the pipe; until evetually you get water the temperature of the tank, but the pipe is also that hot. You turn off the water when done, and that hot water sits in the hot pipe slowly cooling so within 10 or 15 minutes, the water is cooled. That heat simply dissipates to the house. My point is insulation may delay that to a half hour or so to cool, but your experience every morning or evening will likely be the same, unless you are second in line for the bathroom.
For house heating, yes, the boiler is supposed to produce steam that goes through the house, and check valves prevent condensed water from running back into the boiler. I have fond memories of old large buildings like our school going “clang, clang!” as the steam gets into the next part of the radiator system, then condenses and the valve clangs shut; then more steam, a bit more goes in and condenses, more clang, until the system is fully up to pressure and hot and steam is flowing. But if the goal of the piping is to heat the building, there is no logical reason to insulate. For certain areas of the building, where a lot of pipes go by, those pipes may be insulated (Wrapped in asbestos insulation, those were the days!) so that particular corridor or basement area or the furnace room would not get excessively hot. I recall seeing this in old 1900’s large houses, where the basement was not heated, so the pipes were wrapped there to ensure the heat was for the upstairs.
My house is 15 years old. 2 stories. I installed a convection(?) recirculating hot water system. The hot water pipe goes from the water heater in the basement to a point near the upstairs bathrooms, tees off and returns to the bottom drain area of the water heater. The water slowly cycles through so I only need to wait a few seconds for hot water to reach the bathrooms. The water will get slightly hotter a minute or so later but saves time and water by not having to turn the faucet on for several minutes to get hot water.
The original plan had a hot water recirculating pump but the cost of the pump and it having to have its own dedicated circuit was one of the “like to have but don’t really need” items that got cut due to budget concerns.
If anyone wants near-instant hot water at a distant bathroom or kitchen, this is the low-to-nil cost rig you want:
It uses a thermostatic valve installed under the remote sink to use your existing cold water supply as the was-hot-now-tepid water return line. The pump costs almost nothing to run per day and can be set on a timer to not run while everyone is in bed.
If you have various remote sinks scattered about the house, just add a valve to a sink on each branch circuit where you want the quick hot water.
I’m not endorsing that particular brand; there are dozens and this was simply the popular choice at Amazon today. I’m endorsing, from experience, the idea of these low cost under-sink valves and the single low-cost pump installed at your HWH.
Builder here–it’s a combination of all of the above–a cost/benefit situation. The delta between house temp (70F-ish) and hot water (110-ish) is not that great. Steam and AC pipes should definitely be insulated–the delta is much much higher. To insulate every pipe in a house would be thousands of dollars if done correctly (fitted, taped) and the savings/convenience don’t really justify it. The delta for radiant or radiator supply lines is higher but as noted the heat stays in the envelope, so who cares?
Hot water 110°? Maybe if you have young children and set it low to avoid accidental scalding; but everywhere I’ve lived or visited, hot is about 130-135°, hot enough to be painful and could be a problem for more than a second or two. But all the taps are “mixers”, one spout.
I measured it once, my kitchen requires me to run a gallon of water before it’s hot. Same for th master bath, but the other bathrooms - maybe 10 feet from the hot water heater - are pretty close to immediate.
This became apparent in our condo in Anchorage. It had hydronic baseboard heating and some genius ran the piping across (and under) the front steps without insulating that 2’ run. I had to call out someone to thaw the piping on a weekend. I later found the culprit when I tore out some sheetrock below the pipe in the basement. The fix was simple: a two foot piece of pipe insulation.
Hot water is, legally speaking, fully potable. People can develop all sorts of concerns about things that are are not real. Or that are theoretically an issue, but practically are not.
At least for me the idea there’s anything undesirable about HWH output water for cooking or drinking is unfounded. But that’s me & YMMV.
OTOH …
There might be a kernel of legit concern back in the days of lead-soldered pipes, or before that, actual lead pipes. Hot water would be marginally more capable of leaching lead into the flow. How much? Beats me.
I haven’t lived in a place with lead soldered pipes past maybe age 8. And maybe not even before then.
Heh, i just got a letter from the water company saying they have no records of what the pipe that runs into my house is, and it might be lead, and so i should do a bunch of stuff including not drinking the hot water. Also, my interior pipes are old enough that there might be lead in the solder.
But hot water heaters get really gross inside. Even if the water isn’t toxic, it tastes nasty.
Running the system all the time so that there is always instant hot water is very expensive. You are constantly keeping the entire hot water line at temperature. Our gas bill doubled when I ran the system like that.
Feeding back hot water into the cold water line means that when you turn on the cold water it will be hot (or at best lukewarm) and you need to run it for a while to get cold water. This is a PITA. You can design a house with a dedicated return line for the hot water, but this is nearly impossible to retrofit.
We originally put thermostatic valves at both the kitchen and MBR sink. The need to run the cold for a bit was a real pain in the kitchen, so we put a small electric heater in the hot water line right under the sink.
We kept the valve in the MBR but have the pump on a timer to run only in the normal morning shower times. It does save a lot of water every morning.
It is also possible to rig up a push button to activate the pump, you hit it a few minutes before you need the hot water. I haven’t tried this yet.
Agreed, the amount of insulation you can actually achieve around a pipe isn’t great, and typical residential usage is infrequent enough that the water would still cool down in the hours between use.
Also agree. The typical spec in the plumbing code is that no fixture requiring hot water shall have more than 50’ of pipe between it and a hot water source, and a recirculating loop counts as a source. So you can mitigate the amount of heat wasted by not running the loop all the way out to every fixture, but being more strategic about it. For instance in a multi-story house, you only run the loop along the basement ceiling to the vertical risers that feed fixtures above. Any first floor fixtures would have to wait only a few seconds for hot water, but second floor fixtures would still see wait times cut from say 40 seconds to 10 or 20. The shorter loop means less standby losses.
A benefit to insulating the hot pipes, especially in a recirculating situation, is to prevent them from warming up the cold water pipes next to them. It’s frustrating when you’re blanching vegetables and need to stop them from cooking and the coldest water you can get out of the tap is tepid. We could get really deep into the weeds for large buildings where you may need both a hot and cold water circulation loop. In situations like that though, the cost of running the pumps becomes a significant factor since they’re pushing so much volume through so much piping with high friction/resistance. That’s not the case in a single-family residence though.