near boiler pipe insulation

steamer45

What size wall thickness is recommended for fiberglass near boiler pipe insulation? I am awaiting a quote from a supplier to see what they spec. I would think a minimum of 1" though 1.5 would be considerably improved. The existing insulation on the mains look to be 1"

ChrisJ

Hatterasguy said:

1" is the preferred choice when cost/performance is calculated.

1.5" is the preferred choice if cost is no object and the maximum performance is desired.

Wouldn't 2" or thicker fall into that category?
You can do multiple layers of 2"....

All of my stuff is 1" but to be honest, I wish I had done 1.5 and even 2" in the coldest areas, it wouldn't have been that much.

vaporvac

When buying from my local place, I didn't really find the 11/2" much more expensive and I am using 2" in a unheated garage. Somewhere someone posted a chart showing the best thickness for various size pipes etc, so that is what I went by. The main cost differential sees to be led by the pipe's diameter. 1" insulation was much more expensive for a 3" pipe than 2", but the 1 1/ 2"only marginally more and the 2" insulation was nowhere near 2x as much. For the nb piping, I'd think it would be worth it. For an entire mains, I'd have to think about it.
Does anyone know of chart converting the old asbestos thickness Rvalue to fiberglass thickness?

ChrisJ

@vaporvac

I viewed mine differently. My boiler is directly below our livingroom area stays fairly room so the insulation near the boiler is least important vs a lot of piping i have in very cold crawl spaces.

vaporvac

Yeah I know what you mean. MY mains all have the original asbestos except that in the garage. I just think there's a scientific way to judge floating around here.

Fred

My piping has about 80% original asbestos (about 1.5" thick with covering) and 20% 1" fiberglass. All of it in the basement. I have to say just from feeling the exterior of those insulations that the 1" fiberglass does a better job of insulating than the 1.5" of asbestos. I agree that 1" fiberglass is probably plenty where the piping is in a basement but that maybe 1.5" to 2" max would be better in crawl spaces and unheated garages. I doubt that anything more than that adds much value.

rlaggren

Here's an insulation guide covering most types available. The one standout is the phenolic type with less than half the conductivity of most others which seem to cluster around .25-.3 conductivity - which is about R3/in if i did my math right. So the phenolic is about R6/in.

https://www.wbdg.org/design/midg_materials.php