monoflo issues in one zone

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Ctreefer

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thanks again!

Ahhh, Poly Iso is Polyisocyanurate. I didn't reason that one out.

Just out of curiosity. I follow the rock wool notes but I'm wondering.... The current boiler runs year round (indirect hot water). I wonder if I just left an 18" space (no insulation or framing) around the flue if that would be OK. Since it's year round operation the block in that area is always "warmed" by the flue so there shouldn't be any issues with condensation and heat loss would be minimal if its just 18" square.

I say this because I'd like to upgrade to a gas boiler (high efficiency likely) so my not need the flue in the near future anyways. This way once it's gone I can just seal it up the way the rest of the walls are.
 

Dana

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That 18" + flue-radius CIRCLE are the lossiest square footage in your house, since it's the highest-temperature interior wall with the least amount of insulation!

Since it's going into (moisture tolerant) masonry or concrete it wouldn't matter if there were a wintertime moisture drive or not, but assuming an average wall temp within the circel of about 100F (it might be higher- you'd have to measure it with a IR thermometer), with ~R2 of concrete &/or brick that section is losing 35BTU/square foot per hour at an average outdoor temp of 30F (about your three month winter average temp).

For 100 days of winter that's 2400 hours x 35BTU/hr= 84,000 BTU/ per square foot of loss, add in your shoulder season losses and its about a gallon or more of fuel use per square foot of near-flue wall.

Insulate with R13 batts in steel studs you cut loss that by about 75%

Assuming an 8" flue with an 18" clearance that's a 22" radius circle, which is about 10 square feet, or on the order of 10 gallons/year. That could be cut to 2.5 gallons/year with less than $50 worth of material. At $4/gallon you'd be paid for the material in under 2 seasons, maybe only one. That's a better payback rate than the rest of it.
 

Ctreefer

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Well, it was a long weekend but my monoflo system is no more. Lot's of planning for rerouting lines to balance the system. Ended up going with the same 3/4" copper instead of Pex. My skinny fore arms are sore from all the cleaning of fittings and pipe. In between fingers I've got a nice little rash from the flux. (not to mention I can't seem to get all the black out of my hands.) I was using gloves for the most part....

Glad to say the heat now works on both sides of the house. It's awesome to get "real" heat coming out of those last baseboards at the end of the one 60' loop that never got hot before.

Only bummer was Sunday morning realizing that my pressure/temp gauge on my boiler wasn't working (no change in pressure readings). I seem to recall now the last time it was serviced the guy telling me that. Would have been good to have one on hand to replace while the system was down.

Thanks for all the input. Now on to trying to get more insulation in the house....
 
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