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Rav 12-07-2011 09:02 AM

Insulating hot water heating pipes
Greetings. This is my first post. I'm not a pro, just a homeowner who enjoys improving and fixing things up myself. We have a natural gas hot water boiler, high-limit set at 150, which heats our 1931-built house. It's in the unfinished basement, two sides of which are underground and two partially so. During heating season it's always warmer in the basement than the upper floors because I think the pipes are giving off a lot of heat that would otherwise go upstairs (and, because it's partially underground, better insulated than the upper floors). The first few feet coming off the boiler are newer copper pipes, but after that it's all old black pipe supply and return lines. I've measured the outer diameters of the various-size black pipes at approx. 2.35", 1.9", and 1.3". I would like to insulate those pipes. I assume I should use fiberglass, i.e. those 3' length tubes "hinged with self-sealing lap." Assuming this is a good idea, what thickness would be effective? Should I only insulate the supply lines, or also the return lines? I also figure that I won't bother insulating right at the joints where the smaller pipes branch off, not just because that's probably hard to do correctly but also it would leave SOME pipe exposed to keep the basement from getting too cold.

So, is this a worthwhile project which will save energy and reduce costs over the long run? We plan to stay in the house many years. Thanks for any advise you may have.

housegsx 12-07-2011 09:17 AM

I've been wondering the same thing. We just closed on a 1920's house with gas fired hot water boiler. At the same time I was wondering if the radiant heat from the basement will warm up the wood floors in the living room above.

biggles 12-07-2011 09:20 AM

any insulation will mean a truer boiler temperature into the space and shorter run on the system burner,same with the return back to the boiler.any temperature below the supply/returns around them will pull/loss of temp and insulating will trap the heated pipe .if you have a flue pipe run out on the boiler that burner temp with keep the basement safe.if your gas on the fuel might consider a honeywell vent damper that shuts off on a stat being satisfied and locks the left over heat within the your boiler a cold start or does it maintain the water as a stand alone with the stat not calling in for the circulator...just wondering

Rav 12-07-2011 09:30 AM

Replying to Biggles: Thanks for your reply. It sounds like you think this would be a worthwhile project. There is a flue pipe which gets plenty hot, so I see what you mean about keeping the basement warm enough with that. Don't know what you mean by "is boiler a cold start ...." If that has anything to do with the boiler also heating water for household use, no, we have a separate gas hot water heater for that.

biggles 12-07-2011 11:02 AM

cold start boiler is when the stat shuts it off it doesn't maintain any water within the tank like the older types did.constantly cycling to make a standing set when the stat called you had instant heating but killed the bill.if you have old fashion radiators with radiator covers might consider slipping a sheet of 1/4" styrafoam foil backed between it and the when the heat runs the foil reflects the heat out into the room instead of going to the colder walls..could go with armaflex insulation or that fiberglassed with paper wrapping and aluminum straps to lock it up...using a hacksaw for the 90 degree bend cuts would seal them right up do a couple of hours ever weekend and you'll knock it right off.that flue is in excess of 200F going out the chimmney they have aluminum fins you can wrap the flue with so they get hot and transfer that into the basement...even a small fan blowing over the flue pipe 12" away will dump that heat pick up then into the basement short video on fiberglass insulation east to work...if he had cut 45s he would of covered the elbows...same with armaflex at HD/LOWES..nice project to do. after the holidays at you leisure

Rav 12-07-2011 11:17 AM

biggles: Thank you. If it helps any, what I have is a Weil-McLain series 8 CGM-5 (see if you're interested). It was installed in 1985, and was recently serviced and is working great.

I do have old radiators, and around 10 years ago I cut styrofoam to fit and stapled heavy-duty foil to it to reflect the heat back from the walls.

I just did a quick Google on armaflex; it looks like a foam-based product. Would that do just as well as fiberglass? As far as sealing, I would probably go with a self-sealing product, whether armaflex or fiberglass tubes. If I go foam, what thickness should I use? And what for fiberglass? And, where can I get those fins from?

biggles 12-07-2011 12:21 PM

i have a 1989' model as yours with that vent damper setup so it is a cold start or whatever was left over from the last heating cycle.the thickness might be 1/2" or so armaflex is rated at 200F might want to price both and i think HD/LOWES carries both i have to dig for those add on fins your already well on your way to tightening up that heat..what typee of stat do you have setbacks digital...?

Rav 12-07-2011 12:58 PM

I'll check into Armaflex, thanks. Since I have a Carrier Infinity A/C system which supports hydronic heat during the heating system, I have the Infinity Control, which is a digital thermostat.

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