Priority when insulating hot water heating system pipes

Rav

I have a natural-gas hot water (not steam) boiler heating system.  (Domestic hot water provided separately by a water heater.)  The black pipes from the boiler run near the ceiling of my unfinished, air-sealed basement.  Two walls are completely underground, two are partially so.  It's warmer in there than it needs to be.  I'm in the middle of insulating the pipes, using 1"-thick-wall fiberglass.  I've just finished insulating the main (trunk) supply lines.  The question is, what should the priority be of what to do next?  Should I do the main return lines next?  Or continue with the supply lines, i.e. branches, and even twigs, before moving on to the return lines?  I had been thinking I'd get the biggest bang for the buck doing all main lines first (supply and return), before doing the many smaller diameter pipes, but wanted to get peoples opinions.  Also, I was thinking that by leaving the branch and twig lines uninsulated, that would ensure that the basement doesn't get too cold; I was thinking that after finishing the main lines if it's still warm enough down there to safely insulate more, I could always do the branches/twigs then.  Thanks.

STEVEusaPA

Ideally.....

you want them all insulated.  I would keep insulating all the supplies first.  You want to get the heat to where it has to go without losing any on the way.  Then the returns, the warmer the water returns, the less energy will be needed to heat it back up.  Seems like the bulk of your basement is underground.  If you need heat down there, because youre going to finish it, then I would insulate the walls, and add a properly sized zone down there.

Btw, I've heard of 'branches', but never 'twigs'

Harvey Ramer

Check out this site

http://www.engineeringtoolbox.com/copper-pipe-heat-loss-d_19.html It should help you get a better handle with what's going on with heatloss from your pipes.

Rav

Priority when insulating hot water heating system pipes

Harvey:  I checked out the web site you suggested (www.engineeringtoolbox.com).  The table and graph there are for copper pipe, and I have black pipe (which I assume is cast iron).  Perhaps the info for copper is similar for black pipe.  It seems clear that there is more heat loss with larger diameter pipe than smaller, which makes sense and is what I assumed.  But I'm not sure how that helps me answer my question, namely which to do first, the rest of the (smaller diameter) supply pipes, or the (main) return pipes.  Larger pipe may lose more heat for a given length, but I want to know if it's more important to finish supply pipe first before moving on to return (STEVEusaPA seems to think so).  It would be easier for me to move on to the main supply pipes since there are fewer of them and straighter runs, but I want to do this job right.



I'd appreciate hearing what others think, too.  I'm hoping to get a consensus.  Thanks.

Rav

Priority when insulating hot water heating system pipes

Oops, I meant it would be easier for me to move on to the main RETURN pipes since

there are fewer of them and straighter runs, but I want to do this job right.

Harvey Ramer

I agree with Steve

Insulating the supply lines would be my first priority. I would do the mains first and then try to get all the branches done at the same time. This should help eliminate the possibility of certain areas of the house to heat up faster due to insulated lines in just that section.

Jean-David Beyer

Priority of insulating pipes.

I think in the last analysis, you want to insulate all of them. If you want to get the maximum payback if you are not going to do it all at once, I would insulate the hottest pipes first because these are the ones that will be losing the most heat because the greater the temperature difference (between the surface of the pipe and the surrounding air), the greater the heat flow. So as long as this is a hot water system, you could feel the pipes with the system running and see which are the hottest and insulate those first. I do not think I would want to touch a functionning steam pipe, but you could measure it with an IR thermometer or something.



There are exceptions. If you want to heat where the pipes are, you might leave some uninsulated. But it would probably be better to do that with baseboard or something more under your control. Also if it is zoned, you might give priority to the zone that is on the longest time or something. If you have an indirect fired domestic hot water heater, the loop from the boiler to the indirect would probably have the hottest water in the supply pipe, so do that one first.

Gordy

Depends

All we know is that you have hot water heat. What kind of emitters?



Was there a problem with heat being delivered to the emitters.



Remember the cooler you make the basement by taking away heat that was generated from the uninsulated pipes. May reflect in the 1st floor being cooler then before also.



I would go with what Steve said.



Gordy

Rav

Priority when insulating hot water heating system pipes

Assuming I understand what you mean by emitters, we have radiators.  There wasn't a problem, per se, but the black pipe in the basement is giving off a lot of heat, which is making our unfinished basement much warmer than necessary, and we'd rather preserve that heat for the living space upstairs.  We have no intention of ever finishing the basement.  I understand that making the basement cooler may remove some heat rising up to and heating the first floor, but a lot of the heat being given off by those pipes is being wasted heating the basement walls, floor, contents, etc.



I am going to go with what Steve (and others) recommended, namely finishing all the supply lines first.  Thanks for your help, everyone.