New Boiler and Indirect water heater question...

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abernat

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Windows... let's see. I'm going to categorize since they vary.

"Classic" double-hung (uninsulated sash pocket, no weatherstripping): 12.
"Upgraded" double-hung (1" foam in the sash pocket, nylon pile weatherstripping): 5
1 vinyl slider, 1 vinyl awning, 5 modern casements, 6 modern double-hungs.

It's a very window-ful house. I love the light, but it does make it hard to find room for bookshelves :)

All of the classic/upgraded have metal-framed storms in good shape. The rest don't, but are double-glazed at least. We've primarily been replacing the casements which _were_ wind tunnels; I expect to put in modern double-hungs only where the wood frames are really rotted out.

Oh, and heavy curtains, but hey.

WRT the foundation, there is actually no exposed uninsulated foundation. There's 5' of buried concrete wall (well, 6" or so showing) and then stud wall on top of that; the stud wall is insulated.

So. I just talked with the heating guy and he's happy going to a 60K boiler; but it's clear that he has no interest in running a manual-J and I'd like the insurance. Anyone want to run one for me? I assume this is something where I can do the measurements and so on?
 

Dana

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Your 100 year design frost depth in Madison is probably something between 54-60", and you are still losing a large amount of heat out the foundation.

The band joist + foundation sill is probably about 150 square feet of ~R2/U0.5, for a heat loss of about 4500BTU/hr @ 60F delta-T (assumes a cool basement.) The 6" of bare concrete is ~75' of R1/U1 for another ~4500BTU/hr. So it may be closer to 9K than 18K, it's still a pretty big number, a number that is fixable on a cost-effective basis without tearing your house apart.

From the "better than just a WAG" heat loss estimator adjustment point of view, the windows in excess of the 20 I used in my quick example adds another ~ 3K, but the reduction in above grade exposed foundation area probably knocks off ~6-9K, so the net is still at 6K lower than 52.5K I came up with previously, for something on the order of 46.5K, and it might well be under 40K.

That makes going with the solo-60 even more of a slam-dunk.

If the slab is 5' below grade, fine, it may not be worth insulating the floor unless you're finishing it as a room, but the foundation walls are DEFINITELY worth insulating and air sealing. Losses to the cold earth with is more of a seasonal steady-drain than a peak-air temp drain. Crudely modeling the below grade 5' as 55F dirt, and the foundation as R1 for a 10F delta-T, that's still 750 square feet of sub-grade R1 at 10F, for 7500 BTU/hr. Soil types vary- it could be more, could be somewhat less but it's not much less half that- maybe 12K rather than 9K would be the better guesstimate to use on your basement load (ignoring the slab for the time being.) It's still well-worth air-sealing and insulating the foundation a number reasons beyond the (still cost-effective) fuel savings aspects, comfort and indoor air quality among them. Foundation sills & band joists are often the single largest air leak in the house, and being at the bottom of the stackup, contributes a gia-normous fraction of the stack-effect driven infiltration.

BTW: Storm windows tighten up the air leakage of old un-weatherstripped double-hungs by a LOT. But if you can still detect air leaking at the sash pulleys it's worth buying a sack o' these. The installed view looks something like this:

125495427823045400.jpg
 

Dana

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If you want to do your own heat loss calc, you might try running Harold Kestenholtz's I=B=R tool:

http://www.livepast60.com/heatpro/heatfla/flashpro.html (<online, 1-room version)

Or download a standalone to play with: http://www.livepast60.com/heatpro/estimation_programs.htm

Watch out for excessive air-change numbers- the defaults of this (and many tools) is much higher than reality. A pretty-tight house can have 0.1 air exchanges per hour or less when not actively ventilating, but play around with it.

(Kestenholtz wrote one of the very first heat loss tools for computers some 30 years ago. It's not much different from Manual-J methods.)
 

abernat

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I'll definitely look into sealing the basement. The band joist is plastered over (did I mention plaster, plaster everywhere??) so getting in there hasn't been a priority. Should be one, though.

And the problem with the double-hungs is air coming through the access ports as well as the pulleys. It's okay - I'm fairly handy, and putting in weatherstripping is easy. The only part that takes a long time is stripping off the old paint and reglazing.

Okay, one estimate coming up, and a 60K.

Thanks everyone for all their suggestions!
 

Dana

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If you tighten the place sealing every obvious air leak, it's often worth hiring a pro to run a blower door test with or without infra-red imaging to nail down the rest of it. Around here (central & eastern MA), that service runs north of $500, but in combination with expert air-sealing the comfort level go up while the heating loads come down.

If your place is tight enough that it stays north of 35% RH @ 68F indoor temps throughout the winter you may need to actively ventilate, but that would generally be a GOOD problem to have.

With the band joist plastered over, if the plaster is in good shape it may be doing a decent job of air sealing (better than 95% of homes that age out there) but if it has cracks, maybe not. Either way, installing rigid foam and foam-sealing the edges (or giving it a 1-2" shot of closed cell spray foam) would guarantee it. Insulating at least the upper half of the foundation to R10 or better has pretty good payback in your climate zone. R5 XPS (1" blue or pink board) and an unfaced-batt insulated studwall trapping it in place is about an R15 wall, after the thermal bridging is factored in, and still reasonably cost effective.
 

BadgerBoilerMN

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This is a good point. After I insulate an attic, the next target is the rim joist where enormous infiltration is a given in vintage homes. Only after these are addressed, the frost line is the enemy of comfort and economy.
 
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