Fiberglass insulation

GW

would be better, are you saying the returns are up high, as in dry returns? If YES, then yes to both

<A HREF="http://www.heatinghelp.com/getListed.cfm?id=368&Step=30">To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"</A>

Pin

I'm looking to insulate the pipes in the basement and I know I need at least 1" thick fiberglass for steam pipes.

My question is, do I need to insulate the return or only the main line?

Thanks!

Brad White_191

Gary is right

Dry returns should be treated the same as steam.
The one inch thickness is a "practical minimum", meaning that less is not worth the labor to install it.

However, most energy codes prescribe 1.5" thick insulation for any steam pipe up to 1.5" diameter. Then go to 2" thick for piping 2" size and up.

The conundrum is that the colder the ambient where the piping is, the more insulation you should have. Thus, insulating the piping will drop the ambient temperature...

I sense an insulation conspiracy!

Pin

Thank you guys for the response!

I have 2" main and 1" return. I guess i'll consider the 2" thickness.

Brad White_191

When you cost it out

you may pause a bit, for it does seem more expensive than it may seem worth at the time.

But cost it out, you are going to install it once and at least the near-boiler piping, where you have space, can look so nice. And you know it is done correctly.

mark ransley

Lets think, 1" fiberglass is R 3.75" or a bit more as pipe insulation, My attic code is R 35 and thats old code, optimal is R 60 in Zone 5, im R 100. My frige and water heater are about R 8-10. Steam is near 220f. I put 6" or R 23 on everything, all pipes and and old Kiwanee. If you want heat where the pipes are 1" is good but for me its a waste of energy. 1" is not optimal on all pipes. All pipes need it, and more than 1" Its DIY, Its Howiedoit.

Brad White_191

True, Mark

I agree in general, more is better.

We have found that the minimum, 1", is at least attainable and will drop the "bare pipe" heat losses to about 16 percent of what they were. The subtext was to steer folks away from the very minimal 1/2" thickness stuff found in box stores and start going up the ladder a bit in thickness/quality.

Many folks naturally seek that balance between cost and effectiveness, something the code writers sought to do (ASHRAE 90.1 being the genesis of many). You will never get it down to zero but they sought a balance of getting the surface temperature down to within so many degrees of ambient.

For example, 2" horizontal bare pipe with 215F steam in a 60F ambient:

0.5" insulation will knock a 219.8F surface temperature down to 90.8F and heat loss of 53.35 BTUH/SF


1.0" insulation will knock a 219.8F surface temperature down to 77.5F and heat loss of 27.07 BTUH/SF

(This is what demonstrates the largest single jump in percentage from minimal half-inch to full inch thickness, naturally doubling the effectiveness for least cost increment. Not saying "stop there", but to illustrate the situation.)


1.5" insulation will knock a 219.8F surface temperature down to 71.6F and heat loss of 16.94 BTUH/SF


2.0" insulation will knock a 219.8F surface temperature down to 68.6F and heat loss of 11.98 BTUH/SF. (This is our energy code for 2" pipe by the way, about ten degrees surface temperature above ambient.)


2.5" insulation will knock a 219.8F surface temperature down to 66.9F and heat loss of 9.23 BTUH/SF.

The law of diminishing returns comes into play of course- double the insulation and halve the previously much lower heat loss from the last layer.

A full 10.0 inches will get your surface temperature down to 61.4 and 1.61 BTUH/SF heat loss. Of course, with that insulation in your basement, there goes the recreation room

The moulded fiberglass used has an R value of about 4.0. If you are wrapping batt insulation around the piping, I suspect you are not getting the full effectiveness you seek (the label effectiveness) but I also can see it being higher than lesser amounts of tightly fitted moulded fiberglass.

Just some observations..

p.s. I get my data using "3E Plus 4.0", a free-ware program put out by NAIMA (North American Insulation Manufacturers Association) and is available at pipeinsulation.org.

Very useful and full of "what if" combinations. I have some questions about some outputs and units, but overall a very nice program used in context.

mark ransley

I just went over old asbestos, which is good stuff R wise. You are right I dont get full R value but slapping up batts and using bailing wire is cheap and easy. It helps a bit I am sure. Next is Foilfaced Foamboard behind exterior wall radiators, it has to help on unsinulated old brick construction, Then foam on my leaking flat roof.

David Nadle

Diminishing returns

We've been down this road before, but I thought it might be instructive to see just how steep the marginal utility of additional insulation thickness is when you consider the cost. I attached a plot. Remember that thermal conductivity of insulation is linear with thickness but cost goes like thickness squared.

My take is that ASHRAE was right to spec 1.5" but if budgets are tight 1" is adequate.

Unknown

R value comparison

How does the R value of asbestos air cell compare with fiberglass pipe insulation at the same thickness? If you had 1" air cell and replaced it with 1" fiberglass, are you better or worse heat loss wise?

Brad White_203

Really good question, Mike.

I do not know. Sure is enough of that stuff around and it seems like it would be pretty effective. May be some old charts around, maybe in an older edition of one of my ASHRAE books... The air cell and the wet pack or moulded cement types with that canvas jacket too.

For the insulating effect, I like the idea of insulating over the old stuff, provided encapsulation is addressed. On the other hand, I would want to see the pipes labeled as "ACM's below fiberglass"... one can imagine someone tearing into it during repair or demolition some years from now.

Kool Rod

Edit- Sorry for the double post. It originally defaulted to Frank's name and address and I went to fix it, it doubled!

Kool Rod

David- Nice diagram! A visual perspective is much better than looking at a column of figures.

Unknown

Fornd something on the old asbestos air cell insulation in the 1950's B&G engineering handbook. Here is a chart which compares heat emission from pipes with and without 4 ply air cell insulation at 140F. Looks like it reduces losses to around 25% to 30% of bare pipe alone.

hvacfreak

an old timer

...told me that asbestos pipe covering is the equivilant of 1 1/2 ( inch and a half ) inch fiberglass. This chart seems to support this ( comparing to Brad's info in my head ).