Insulation thickness recommendation needed

Dave in QCA

I need to replace some missing insulation on the steam pipes in my basement.  I have been looking at the fiberglass insulation with white jacket and I see it comes in 1/2", 1", 1 1/2", and 2" wall thicknesses with corresponding r values of 2.2, 4.4, 6.5, & 8.7.  What is the general recommendation for insulation thickness?  

The steam system is 2 pipe, actually a vapor system.  Very rarely builds any pressure at all, cut-off is set at 1 LB, but even with one cycle per hour, the system may only build a few ounces of pressure if the temp is below 0 outside.

Thanks,

Dave

jpf321

1inch

1inch is the thickness generally recommended and suggested on this site. there are various threads about this previously with the reasoning behind 1inch .. but that's the short answer. 

Unknown

Insulation

Hi- With insulation "more = better". However from a cost/benefit standpoint, as Jpf321 mentioned, 1 inch of insulation gives "the most bang for the buck". Insulating your steam pipes pipes makes a lot of difference. Here's a link to a good article on insulation

 http://www.heatinghelp.com/article/11/Hot-Tech-Tips/300/Why-you-should-insulate-steam-pipes    Shop around as prices can vary greatly. You might use the Wall search function and look for past posts on insulation suppliers.

- Rod

gerry gill

we use 1''

so that it looks the same as the asbestos did, especially if its mating up to the old asbestos..

The Steam Whisperer (Formerly Boilerpro)

International Energy Code recommendations..

For low pressure steam and typical higher temp hot water

Runouts up to 2inch  -1inch thick

for piping 1 inch to 2 inch -1 1/2 inch thick

for over 2 inch - 2 inch thick

This makes me think typical American practice of 1 inch thick is not up to snuff.

Steamhead

Possibly

but if the outside of the insulation is cool when the steam is up, wouldn't that mean it's thick enough? 

Unknown

Cost/Benefit

Attached is a chart done by David Nadle that I saved from an earlier Wall insulation discussion. Looking at the chart, economically 1 inch insulation appears to give you the most benefit for the least expenditure. From the quotes I got, increasing the insulation thickness to 1 1/2 inch ups your cost to around 50% more while not gaining all that much addition insulation benefit.  I guess it just depends on how tight your budget is. 

- Rod

The Steam Whisperer (Formerly Boilerpro)

I remember that...

but notice that the curve goes flat at 1 1/2 to 2 inch not 1 inch.   Also just think for a moment,  We want R-38 in our attics (typical 40 delta tee mid winter) , but only R-5 on our pipes (typically100Delta tee mid winter), something doesn't compute.  Attic/ wall insulation provides year round benefits, but even then I think we can so better.

Unknown

Insulation Thickness

Boilerpro- I definitely understand and agree with what you are saying. It's just that if you look at the difference in cost between 1 inch of insulation and 2 inches of insulation for a 2 inch pipe, the cost difference is over 2 1/2 the times more for the thicker insulation *. Even though you cut your heat loss a bit more, I'm just wondering if it is really worth the extra cost?  I can see where it could be beneficial to use the 2 inch insulation if your piping was running through an uninsulated crawl space, however, since most pipes are in the insulated envelope of the house, any slight "leakage" still benefits the heating of the house. (This is not suggesting to anyone that you don't need insulation on your steam pipes. From my own experiences, insulting your steam pipes, including the near boiler ones, makes a HUGE difference!!)



 What are you thoughts about insulating the returns and lower boiler piping to cut down heat lost in the condensate?  It would seem to me if one could use less btus to bring the boiler water back to a boil when a new cycle starts, there would be a saving.  If this is so, having a limited budget, then would it be better to spend the money on 1 inch insulation on all piping ( boiler piping, mains. laterals, returns) or spend it just 2 inch insulation on the pipes that hold steam?

As always I appreciate your comments and opinions.

- Rod



( *I looked up actual dollar figures to check the graph. The numbers used are from the McMaster Catalog - not necessarily the best insulation prices but the ratio of pricing between thickness seem to stay approximately  the same no matter what price level you are getting)

Unknown

I`m curious Rod,,,,

If you insulate the returns(to keep condensate hotter), what if this should flash to steam? How will you know what trap perhaps failed, or orifice, is letting-in too much to the return piping?

As you know,, condensate return piping was not sized for that.

Unknown

Insulating Returns

Hi Dave- I can see where flash steam could present a problem if your residential steam system was outside the normal operating envelope, that is, above 2 PSI or above 5 inches of vacuum. I imagine that on a true vacuum system you'd definitely have to keep the possibility of flash steam in mind. I've seen what were called "cooling legs" put between the radiator and the trap on vacuum system which I believe were to allow for this possibility.

 Obviously you would want condensate to stay condensate. My thinking was that if you could save some of the heat loss in the return, you would be saving fuel needed to bring your boiler water to the boil. Whether insulating your return is practical, economically (or otherwise) was the direction of my question.  With the cost of fuel (especially with this oil spill) going up, even a small amount of fuel saved adds up over the winter.

- Rod

The Steam Whisperer (Formerly Boilerpro)

Returns, et el.

I'll have to do some calcs on the savings of 2 inch versus 1 inch and I agree that the "waste" heat is going into the building to a certain extent, but usually into an unheated basement.   I figure, so long as the basement stays warm enough so the pipes don't freeze, the colder the better (keeps the mice down around here it seems).  My own basement gets down into the 40's in severe weather (used to be low 40's until I sealed the joint between the foundation and sill beam).  As to insulating the returns, you may save some fuel on one pipe where the return is right near steam temp.  However, on two pipe it depends on how oversized your radiation is.  If your radiation is oversized greatly, or simply at light load, your condensate will already be near room temperature.    Another potential advantage of keep your condensate hot is to reduce acidic buildup in your returns since hot water does not absorb air easily. 



However, all this may get turned on its head as more condensing steam boilers come on the market that may take advantage of cold condensate returns to improve efficiency.  It looks like the folks over at Rayes boiler will be using combustion air preheat as thier condensing heat exchanger, but the Superboiler uses cold condensate (or fresh make up water) and combustion air preheat.   In this case, you would prefer colder condensate.

The Steam Whisperer (Formerly Boilerpro)

Operating cost calculations

Here are the assumptions:

2inch pipe using Brads data

27 btu/hr/ft for 1 inch

10 btu/hr/ft for 1 1/2

5 btu/hr /ft for 2

Total yearly operating hours: 2231 ( for approx. 6200DD at Wilkes-Barre, PN from PK Short cycling paper)



For each foot of 2 inch pipe,         

1inch thick loses 60,000 btu/yr                                                            

1 1/2 inch thick loses 22,000 btu/yr

2 inch thick loses 11,000 btu/yr



At $1.00 per therm, 80% eff,

1 inch waste costs  $0.75/yr

1 1/2 inch waste costs $0.275/yr

2 inch waste costs $0.139/yr



Plug in you per foot costs and you can see what the savings are.  Oh, course, I am not sure what the conditions where for Brad's data (room temp and steam temp).  Also this assumes a system perfectly matched to the heat load.  If it is not, the piping  will spend less time at full temp per year.  Probably a safe number is to assume that the yearly on time is about 60% of the full load on time, however the piping still gives off heat between cycles.  This at least can give you  an idea.

Unknown

1 inch versus 1 1/2 inch

Boilerpro- Very interesting! Thanks for working the figures out. It really validates the International Energy Code recommendations. The benefit between 1 inch and 1 1/2 inch is probably worth pursuing especially as fuel prices go up and payback is much quicker.

- Rod

The Steam Whisperer (Formerly Boilerpro)

Knauf's data.....

shows the 1 1/2 and 1 as closer.  All you need to do is multiply the loses in the chart by the operating hours and that should give you a matching set of numbers. I've been using 1 inch myself, so I think I may begin recommending heavier after completing this exercise. Most of the time I insulate just the piping and not fittings, and am able to keep the basement temps below. 60 on typical winter days.   I would definitely keep the insulation heavy in boiler rooms where the heat loss is almost completely wasted since most of it goes up the stack. 

Dave in QCA

Thanks for the great information on pipe insulation!

I am quite amazed and pleased and the great information that has been supplied to this thread!  It is great information to have.  Now, I why it makes sense to use 1" insulation to replace what is missing.... or why it would make sense to use 2", and perhaps have it all removed and install 2" all the way. 

By the way, I am finding prices for pipe online at  http://expressinsulation.com/fiberglass_insulation.html  as follows, 2" pipe x 3' length.   1" thick = 4.95, 1 1/2" thick = 8.84, 2" thick = 13.05.

On another subject, all of you steamers should be quick to guess the practical purpose of the arch structure between the back corner of the house and the garage, as shown in the attached 1923 picture.

The Steam Whisperer (Formerly Boilerpro)

QCA......

I'm guessing  = Quad City Area.  from the caption on the photo.  I'm only an hour away.

Dave in QCA

QCA

Yes,... Quad Cities Area!   One of the greatest things about the area is that real estate is cheap.  It is amazing what you can buy sometimes.... mansions for the price of a 500 sq ft condo in Chicago.  Conversely, one of the biggest problems is... the price is real estate is too low!  People are afraid to invest the amount that it can take to renovate a grand old home because they might not be able to get their money back out.   Ahh....such is life!   Anyway, this is a good place to live. 

Steamhead

The arch

carries the steam main to the garage/carriage house?



What type Vapor system is this?

Dave in QCA

Steam to the Auto House

Yes indeed! 

The steam line comes out of the boiler room, located inside the visible basement windows, then proceeds through  crawl space under the 2 story sun porch.  At the corne of the sunporch, it goes up inside the corner pier, then goes horizonatal and enter the garage space about a foot below the ceiling.  The main looped around and fed radiators in the chauffer's apartment above, and probably down fed radiators at the floor level, or ceiling radiators.   The condensate return is beside the steam main all the way, so I assume their were ceiling radiators.  However, the is a 16" tile that runs from the floor of the garage to the boiler room and floor level radiators could have returned via that route.  It is hard to tell for sure because the garage was convereted to an apartement in 1950 and most of the evidence is behind sheetrock walls.  About 20 years ago, the owner removed the radiators from the chauffer's apartment and installed a gas forced air unit in the attic, but the steam piping is all still in place.

Steamhead

Steam-heated garages

are very common in Baltimore. Most of the ones I see are shut off, since we now have antifreeze to keep the cars' engine coolant from freezing. But we have a couple of customers who still heat their garages, in these cases the rooms are also used as work shops, weight rooms etc.



Part of the reason the garages were connected to the boiler in the house was so there would be no flame in the garage. That was the era when people had just learned how easily gasoline ignites. I've seen some garages that actually had their own underground gasoline tanks!



When that furnasty dies, find some rads and hook them back up. Make the previous owner spin in his grave.......

Dave in QCA

Continuing as new post, Best Heating System

Due to a little interest in this system, I am continuing this discussion under a new thread, the Best Heating System. 

It may be too long, and I'm not sure what the size limits of this site are, but I'll give it a try!

David Nadle

Chart confusion

I'm afraid the chart has been misinterpreted. The y-axis is not heat loss, it's delta (change in) heat loss. The actual heat loss values for 2" pipe are:



thickness  Knauf  Brad

0  168  169.19

0.5  39  53.35

1.0  23  27.07

1.5  18  16.94

2.0  15  11.98



The Knauf conditions are 200 F operating, 80 F ambient, no wind, ASJ jacket. I don't know what Brad's conditions were. But you can see that the reduced heat loss from 1" to 1.5" insulation is a bit smaller you calculated.



1.5" insulation for 2" pipe should cost 1.75x 1" insulation because it has 1.75x the cross sectional area. Compared to no insulation, 1.5" saves 150 BTU/ft/hr and 1" saves 145 BTU/ft/hr, a 3% increase (7% using Brad's data) in performance for a 75% increase in material cost.



If you factor in labor the effect of an extra half inch on total installation cost is going to be much less than 75%. It might be worth it to go with 1.5", especially if you're paying someone to install it. But if you are doing it yourself and looking to economize, I still think 1" is a good choice.