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.