Why you should insulate steam pipes

HeatingHelp

Why you should insulate steam pipes

Read the full story here

speedbird

I'm afraid I'll have the opposite problem and have an oversized boiler.

ckbawden

Hi Dan: I have a two pipe steam system and I've insulated most of the larger pipes overhead in the basement. I seem to recall being told not to insulate the return pipes.... something about a needed drop in temperature for the returning steam but i'm not sure. Is that true?

gfrbrookline

I have an oversized boiler with the main vents just short of the dry returns dropping and turning into wet returns. Should the returns be insulated? I have also been told the condensate is slow to return to the boiler which is why the LWCO is adding water during a heating cycle. If I remove the insulation will that speed the condensate returning to the boiler and offset some of the oversized boiler?

Jamie Hall

For @ckbawden -- say what? There is no need for the condensate to cool on the way back to the boiler. On the other hand, the amount of energy saved by insulating the returns is minimal. Now if the "returns" are carrying live steam -- some do -- they should indeed be insulated. If they are real two pipe system dry returns -- carrying only air and condensate -- there is no need; indeed, if they are very hot, it means that there is a bad trap somewhere.

For @gfrbrookline -- ditto. There is no need to insulate wet returns. That makes no difference to condensate being slow to return -- which is a symptom with several possible causes. Among others -- the wet returns are gunked up and should be flushed. The boiler pressure is too high, keeping condensate out of the boiler (anything over 1.5 psi is suspect -- and in many systems anything over about 10 ounces per square inch is suspect). Just to name two... And there is no helping an oversize boiler; it is what it is, and it will short cycle to match its capacity to the load.

gfrbrookline

Sorry, I was referring to insulating my dry returns, 50 feet roughly. I have the vaporstat set to 16oz. cut out, 4 oz. cut in and system runs for 15 min then cuts out on pressure and runs in increments of 2-1 minutes depending on how cold it is outside on pressure. I have 1 big mouth and 1 gorton #2 on each main so I should have enough venting. I am wondering is removing the insulation from the dry returns would add to the edr and minimize some of the boiler over sizing keeping in mind my main vents are at the end of my dry returns.

Jamie Hall

Assuming that those steam mains and dry returns are a normal size -- more or less -- they have about 0.7 sq. ft. of EDR per foot of pipe. Not enough to make much difference to an oversize boiler in terms of the cycling -- and at the risk of being obvious, unless you are actively heating that space anyway, the fuel which would be used in a slightly longer on phase of the cycle isn't doing anything helpful. Just money up the stack.

gfrbrookline

Thanks, I was just looking for a way to minimize the cycling. The mains are 2.5", 50' each and the dry returns are 1" also 50', they are both insulated, mains with 2" returns with 1" insulation.

DanHolohan

ckbawden said:

Hi Dan: I have a two pipe steam system and I've insulated most of the larger pipes overhead in the basement. I seem to recall being told not to insulate the return pipes.... something about a needed drop in temperature for the returning steam but i'm not sure. Is that true?

Just the opposite. If you insulate the returns the water will stay hotter, which saves fuel. It also makes it less likely that the condensate will absorb carbon dioxide and become acidic. Thanks for asking!

HenrikW

Hi Dan - how hot does the return pipe on a steam heat system typically get from the returning condensate? The one in my house runs behind the wall and is uninsulated. I'm worried about contact with other materials that were used in construction.

- H

DanHolohan

It varies, but it’s not hot enough to case a fire if that’s your concern.

Dot_W

This is very clearly written and was very helpful. Thank you!

AnthraciteEnergetics

Henrik,
Condensate return will be the same temperature as steam (212 or so), unless it traveled so far as to cool down in the pipe. Unless the condensate is traveling through inhabited space, or you need to cool it (e.g. Open system like district steam with condensate dumped to drain), it's a heat loss made up for by extra fuel consumption.

Jamie Hall

AnthraciteEnergetics said:

Henrik,

Condensate return will be the same temperature as steam (212 or so), unless it traveled so far as to cool down in the pipe. Unless the condensate is traveling through inhabited space, or you need to cool it (e.g. Open system like district steam with condensate dumped to drain), it's a heat loss made up for by extra fuel consumption.

Um... well, yes but. If we are talking a residential system -- and not a huge commercial setup -- there is astonishingly little heat in the condensate from a radiator, assuming that the trap is working or, if it isn't trapped, that the feed is correct (two pipe). Two reasons. First, the volume (mass) of condensate is, or should be, quite small. Second, you are looking at the heat capacity of water, not the heat of vapourization of steam. So... in a typical residential dry return (vertical or horizontal) if the temperature a few inches below the trap is mich over about 180, there is something wrong. A few feet away, the pipe will be warm, but you should be able to hold your hand on it at least briefly.

This does not apply to one pipe steam, as the only pipe is carrying live steam, and should be nice and hot -- and, if possible, should be insulated.

Not that insulating returns is a bad idea. It's a good idea, from the overall efficiency standpoint. The problem is the usual -- the return on investment will be very low, if not negative.

kbetzing

I have lived in my historic house with a steam boiler for 22 years. We got a new boiler 6 years ago and everything was the same in the house as far as heat patterns, We had the asbestos insulation removed last year, which did not cover every inch of the pipes. There was several feet uninsulated throughout the basement and our basement was always warm, but no too warm. We had it insulated by a company and they covered every inch of the pipes and now our basement is so cold that the first floor is freezing, we can not even walk without slippers and the worst part is our boiler is running non stop so we are going to have high gas bills. I am wondering what we should do about this. Someone suggested adding a few radiators in the basement but I think it would be far easier to remove some of the insulation. Anyone with knowledge about this have any ideas?

Shalom

I insulated my dry returns, but only because I was tired of smacking my forehead on them every time I went downstairs. At least now they're cushioned.

Jamie Hall

Something else may have gone amiss. But my first reaction on the basement is that in most truly historic houses, the basement is cold. It shouldn't be freezing cold (literally, that is) but it wouldn't be at all odd for it to be in the 40s. That said, however, may I ask if you have checked very carefully for infiltration into the basement? A broken window, perhaps? Something of that sort?

On the cold first floor -- the best approach, assuming that you don't have infiltration in the basement, is to insulate the floor.

On the boiler now running non-stop when it didn't before -- that is where my reaction is that there is something else amiss, possibly quite seriously amiss. Insulating a previously uninsulated pipe -- or pipes -- will not cause the boiler to run more.

Look around.

BobC

Broken windows

When I bought this house it came with a 1948 Delco steam boiler and a cracked window pane in the back cellar window and a neighborhood stray cat. A few years later we were having a a real cold snap with bitter wind to make it even more enjoyable.

It seemed cooler than normal in the house one night so i went down the cellar to check the boiler and after checking the gauge glass my eyes traveled up to the top of that boller (almost 4 ft tall) and I found the neighborhood stray cat stretched out on top of the boiler. This guy was a huge old Tom that was king of the block (the Malmute across the street had a tussle with him and lost badly) but in reality a gentle giant.

I also found he had forced his way through the cracked window so I put a flap over the window so he could come and go as he pleased

Bob

DanHolohan

Bob, that is a priceless portrait. Thanks for painting it for us.

Jamie Hall

Trust a cat...

MrSteam

Thank you Dan for the excellent article. I'm doing renovations and improvements on my parents' house which is a 4-level gas-fired water boiler-heated brick home with concrete basement built in the late 60's. Incredibly after a new gas-fired water boiler was installed recently, I discovered that no one bothered to insulate the copper hot water pipes in the basement which carry hot water from the boiler to the radiators on each floor. The copper hot water pipes hang from the basement ceiling drywall and first floor joists. You can really feel the warmth from the warm copper pipes in the basement area, which is a waste. While I don't want to tear open upper floor walls to insulate pipes in the wall, I can cover the whole length of the copper pipes in the concrete basement.

A few quick questions:
1) Can standard foam pipe sleeves be used over the copper hot water boiler pipes, with heat tape to seal them? Will the foam be able to withstand the heat of the hot water copper pipes?

2) What thickness of foam pipe sleeves would you use?

3) Right now the copper hot water pipes are supported by metal U clips hanging from the first floor joists and ceiling drywall (the basement ceiling is partially covered with drywall, and partially open to the floor joists - something I'm also remedying by covering any open areas of the ceiling with two layers of Reflectix to bring it to R21 - one layer stapled halfway up the joists and one layer to the bottom of the joists). I have room for foam pipe sleeves, but then the pipes won't fit into the metal U clips they hang from unless I leave the 1 in. space of the U clips open in the foam for the clips, or get much larger clips that can go around the pipe insulation. Is it better to get new larger U clips to hold the wider foam sleeves, or to keep the current metal clips that fit right over the copper pipe, and try to cover the 1 in. wide clips as best as possible with some type of insulation?

4) How close to the boiler should the foam insulation sleeves be mounted on the copper hot water pipes coming out of the boiler?

5) Will insulating the full length of copper hot water pipe in the basement with foam sleeves be helpful even though I can't insulate the copper hot water pipe as it runs up the walls to upper floors? I think so, because those are small spaces between joists on heated floors.

MrSteam

And an additional question, which I separated out as it's different enough from the ones I just posted below. You wisely mention sealing cold air leaks in the basement. Here's my question regarding that:

I've discovered a cold air leak coming from a 6 in. x 6 in. and 1 ft deep drain in the garage concrete right above the front of the basement that is supposed to direct rain water to the sewer and a sump in the basement, with a pump in the sump that pumps the water into the sewage system. Instead of the drain only directing water into a 4 in. wide pipe that sits perpendicular to the bottom of the drain down into the sewer/sump, I discovered there are 2 holes in that concrete drain - one above the 4 in. drain pipe, and one to the side of the pipe opening - which allow cold air to leak into the space where the top of the basement concrete wall meets the floor joist seam. Those holes also allow some rain water to leak in down the basement wall near the sump. I can seal those holes with concrete or other waterproof sealant, or stop the air leak for now with moisture-resistant insulation foam. While that will stop the ingress of cold air, that is the only fresh air that gets into the basement (though the basement can be ventilated through a door to a den just half a flight up from the basement, though that den is only heated when occupied.

The gas-fired water boiler has a chimney which vents up through the basement ceiling, up the entire house and out the roof. However, I'm assuming the combustion air comes from the basement itself. Is it a problem to to cut off the only fresh air flow to the basement because the boiler may draw its combustion air from the basement? There would still be a bit of air flow under the door to the den and under the basement door to the stairs going up to upper floors.

KC_Jones

IF you have a steam system in that house you can not use foam insulation. Fiberglass is the only thing that will handle the heat.

With fiberglass it is generally accepted that 1" is the minimum, but more gets to the point of diminishing returns.

For pipe hangers you can insulate around them, or get bigger ones with metal shields that then go on the outside of the insulation.

You insulate all the way to the boiler.

If someone use copper they did it wrong. The steam system is supposed to be piped in black steel pipe and iron fittings. I can't imagine someone re-piped the entire steam system in copper, are you sure you have a steam system and not a hot water system, especially given the vintage of that house.

Post some pictures.

MrSteam

KC_Jones, Thank you very much - I stand corrected and have edited my original post below - it's a Gold CGa Gas-Fired Water Boiler, so those copper pipes must be carrying hot water to the radiators. The Gas-Fired Water Boiler is a Weil-McLain Gold CGa and I called Weil-McLain and verified that they recommend that the water temp be set at minimum 180F and in the colder months to as high as 210F for faster and more even heating.

So that means the copper heating water pipes are carrying 180-210F, though this probably drops quickly as the water exits the boiler and travels along the copper piping. Especially since I can feel those copper heating water pipes are hot to the touch (but not so hot that I can't touch them). A customer service rep at Weil-McLain said they don't particularly advise insulating the copper hot water piping and that most customers don't because there's a bit of a benefit of the heat radiating from the copper piping warming and drying your basement, but then said that it's possible insulation around the pipes could slightly improve heating and lower costs (I know, not a scientific answer). I can post some photos if you like - sorry for the newb question which probably has a very obvious answer, but how do I post photos here?

dave22

I have a new steam boiler installed and the flue pipe goes between the two risers (it is a New Yorker where the flue pipe is in the front of the boiler - but chimney is behind boiler). I want to insulate the pipes, but if I use 1" insulation it will only leave a 1" gap between the insulation and the flue pipe. I can't use fiberglass insulation with facing because I believe it will be to close to the flue pipe.

Will using rock mineral pipe insulation with no facing (temperature rating up to 1200F) work? Or what is generally recommended?

MrSteam

For hot water boiler systems piped in 1 in. copper piping, do you also recommend insulating the exposed copper piping attached to the joists of the basement ceiling?

Fiberglass insulation would certainly insulate the copper hot water pipes, but it's not inexpensive so I'd like to make sure before purchasing. When I called the boiler company, I was surprised when the rep said they thought most of their customers didn't bother to insulate the piping, and that the exposed pipes helped provide some heat and drying to unheated basements.

The hot water boiler is a Weil-McLain Gold CGa 140,000 BTU unit in the mostly below-ground basement (only the top 1 ft below the ceiling along one half of one side of the basement is above ground). I think it has a 2 gallon water reservoir. The boiler heats 3 floors of living space above it. This hot water boiler is supposed to exit water from the boiler at 180-220F depending on how you have it set, though I'm sure the water drops temperature upon leaving the boiler. The cement basement is not heated by radiators and doesn't have windows and has some fresh air venting to outside air, though the boiler and uninsulated copper piping does heat the space a bit (which has some advantage in helping prevent the cold water pipes from freezing, which have never frozen in 50 years).

I can only insulate the copper pipes when they run exposed along the basement ceiling, not where they travel up through the walls to upper floors. Thank you for your advice and thank you for maintaining this very helpful website and community!

tctulloch

Great site and a great article. I have a home energy assessment late next month, but I have been wondering about this in the house.

From the steam boiler in the basement, the piping runs in the ceiling in the basement. Half of the piping runs through an unfinished area of the basement(utility room) and it is not insulated. The other half runs through a finished area in the basement. It isn't insulated, but it has what appears to be reflective material that sits on top of the pipe. I assume that is to reflect some of the heat down into the finished area of the basement.

We just moved in and the boiler is a Burnham SIN4LC-LE2.

We definitely have the hammer noise and I'm looking at the pitch on all the radiators in the system. They all have quick vents as their air vents.

Jamie Hall

Since this popped up again... for @tctulloch -- the steam pipes should be insulated. The reflective stuff is pretty well useless. However, before you go and start insulating pipes, be sure to check all of them for pitch and no sags, since you say you have hammering.

Also look for air vents on the mains; they are needed to help (read: make it possible) balance the system. It's likely that the quick vents on the radiators are too quick, and are trying to compensate for poor or non-existent main venting.

tctulloch

Jamie Hall said:

Since this popped up again... for @tctulloch -- the steam pipes should be insulated. The reflective stuff is pretty well useless. However, before you go and start insulating pipes, be sure to check all of them for pitch and no sags, since you say you have hammering.

Also look for air vents on the mains; they are needed to help (read: make it possible) balance the system. It's likely that the quick vents on the radiators are too quick, and are trying to compensate for poor or non-existent main venting.

Thanks. I know the reflective stuff does very little from a insulation standpoint, but it's in the finished area of the basement. So my assumption is that it was done that way since it's the only source of heat in the finished area. If that segment of pipe becomes insulated, then the finished area has no heat at all.

I checked the mains and there is air vents there. We have a tune up to schedule for the boiler itself, so I will inquire about the system as well.

Jamie Hall

Not the first place to depend on uninsulated steam pipes to heat the basement. It is not, however, best practice, as the uninsulated steam pipe sections will slow steam distribution to the rest of the building quite dramatically, and may make balancing almost impossible. As well, they may be contributing to the hammer problem: an uninsulated section of steam pipe will condense a surprising amount of steam which, unless things are very well managed indeed will get picked up and blown along once the pipe warms up, and slam into the next handy fitting.

tctulloch

tctulloch said:

Jamie Hall said:

Since this popped up again... for @tctulloch -- the steam pipes should be insulated. The reflective stuff is pretty well useless. However, before you go and start insulating pipes, be sure to check all of them for pitch and no sags, since you say you have hammering.

Also look for air vents on the mains; they are needed to help (read: make it possible) balance the system. It's likely that the quick vents on the radiators are too quick, and are trying to compensate for poor or non-existent main venting.

Thanks. I know the reflective stuff does very little from a insulation standpoint, but it's in the finished area of the basement. So my assumption is that it was done that way since it's the only source of heat in the finished area. If that segment of pipe becomes insulated, then the finished area has no heat at all.

I checked the mains and there is air vents there. We have a tune up to schedule for the boiler itself, so I will inquire about the system as well.

Update:

Boiler is fine and on the last tune up, the quick-vents on the radiators were adjusted. He did agree with insulating the pipes, but I forgot to ask how thick of insulation should I got with? The main pipe is 2" and the branches running to the radiators is 1"(or 1.5")

Jamie Hall

Use 1" insulation. It's enough to do what's needed.

duce7268

i have 4"steam pipe some have asbestos insulation and some are bear cast iron. can i leave the asbestos on and just cover the whole thing

Jamie Hall

Yes. So long as you don't disturb the asbestos, the worst that will happen is down the line if and when you want to sell you'll have to disclose it. I have had great success encapsulating it -- which you should do -- with plaster impregnated gauze tape of the sort used by surgeons to set bones -- and modellers to create scenery. Just get it wet and wrap... makes a bit of a mess, but cleanable.

Then insulate the bare cast iron with appropriate 1 inch fiberglass.