Advice new boilers for two apartment home.

Discussion in 'HVAC Heating & Cooling' started by JoeSolbach, Jan 19, 2016.

  1. JoeSolbach

    JoeSolbach New Member

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    Illinois
    Hello everyone, new to this forum and am looking for some advice.

    Live in a two unit home in Chicago built in 1900. Both units are about 900 sq. ft each, I live on 2nd flr., Both apartments are heated with cast iron radiators. Two boilers, one for each unit. Each one is 100K btu's in, my unit is a 15 year old Peerless and the other a 40 year old Utica. All of the piping feeding the radiators is newer copper, looks like 1" mains and 3/4" and 1/2" supplies to the radiators. EDR for the radiators comes out to about 250 for each unit.

    The problem is that the chimney, in the center of the house is in poor condition. There is no terra cotta or any kind of liner, just one course of bricks in which the two boilers and two water heaters all vent into. Water heaters are both 12 years old. The mortar is crumbling and if I look inside the cleanout it looks like about half of it is gone between the bricks. There are also several cracks in it visible in the attic and the mortar is all soft and crumbly, with some loose bricks.

    Trying to decide what to do, considering the age of the equipment. One heating guy I had came out just wanted to drop a liner down the deteriorated chimney and recommended a new 225K btu boiler for the whole building and one 75 gal water heater. Obviously, I never called him back.

    I'd like to eliminate the old chimney anyway, i want to do a bedroom, bathroom and laundry room in the attic duplexed to my 2nd floor apartment, and the chimney cuts right through where I'd like the bath to go.

    Trying to figure what my best options are, go with two new boilers, one for each unit, or one boiler for the whole place serving both units, same for the water heaters, do one or two? What kind?

    The house is balloon frame, open stud bays in the basement, no insulation in the walls except in my kitchen which I redid. Attic is semi finished, there is insulation in the rafters. Exterior is asbestos cement shingles. I've been air sealing and insulating the the open stud bays above the sill plates in the basement, but there is a lot of air leakage in the attic with plumbing chases. Even the partition walls lack top plates and are open to the attic! I've been stuffing insulation in these.
     
  2. BadgerBoilerMN

    BadgerBoilerMN Hydronic Heating Designer

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    1st, two inches of high density spray foam to seal the attic, then blow or roll firberglass or cellulose over all. Once you have this number an ACCA Manual 'J' heat load is best way to determine the proper size boiler for your job.

    A condensing boiler with an indirect-fired water is normally vented out the sill plate and fresh air, for combustion, comes to the boiler the same way.

    4 two inch holes and your all done.

    Properly sized condensing boiler are the perfect match for 100 year old cast iron radiation since the standard feature outdoor reset works with the high mass cast iron to increase comfort and lower your fuel bills at once.

    http://www.badgerradiantdesigns.com/modcons.html
     
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  4. JoeSolbach

    JoeSolbach New Member

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    In this situation would it make more sense to go with two boilers, one for each unit or just one for the entire building? The rental unit downstairs is just four rooms with one bedroom. I kind of figured on just using one indirect hot water heater for both units. I like the idea of the condensing boilers but am concerned about the reliability. I had two plumbers tell me these boilers need a lot of maintenance. Another suggested using two small direct vent cast iron boilers and a power vent water heater.
     
  5. BadgerBoilerMN

    BadgerBoilerMN Hydronic Heating Designer

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    Plumbers who don't like condensing boilers usually don't install them either. Just as well since most can't seem to read.

    If you are not concerned about metering, it certainly makes sense to install a single condensing boiler and indirect.

    Finding the right designer and a local contractor with a healthy modulating/condensing (ModCon) boiler attitude will make all the difference.

    I maintain the 12 ModCon brands I have installed on an annual to bi-annual basis with little trouble. The 25-50% fuel savings and increased comfort pay for the upgrade in short order.

    Nixing the old full-time-draft chimney should net a 5% fuel saving right off the bat!

    http://www.badgerradiantdesigns.com/contractor.html
     
  6. Dana

    Dana In the trades

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    In US climate zone 5 the vapor-retardency of the ceiling below an attic isn't important at ALL. Air sealing it with 2" of open cell foam would air seal as well as closed cell, and it would be 1/3 the cost, 1/4 the total amount of polymer, and less than 10% of the environmental damage, since its blown with water instead of HFC245fa (a powerful greenhouse gas, a 100 year potential about 1000x that of CO2.)

    It's usually possible to blow cellulose into balloon framed buildings without a lot of drilling from either the exterior or exterior, and it's pretty cheap. More than just the fuel cost savings, having warmer walls and less infiltration (= not as bone-dry in winter) is a significant comfort upgrade.

    With high mass cast iron radiation you would be able to get very good efficiency out of a mod-con, but you may end up with sticker shock on the price of a pair of them, or even a single. If you want to split it up with mid-efficiency cast iron, at 250 sq.ft EDR per zone it would balance perfectly with a boiler output of 42,500 BTU/hr, and a ~50-55K output cast iron boiler with high-mass radiation it would be nearly impossible to short cycle it anyway. If you go that route it's probably cheaper to go with direct-vent side vented units rather than trying to resurrect the chimney with a new liner. The Burnham ESC-3 is 60K in 52K out and direct vented.

    It's likely that just one ESC-3 would be able to heat the whole building assuming separate metering for the units isn't required. Since that boiler is tolerant of return water temps as low as 110F, it's not a problem at all to hang 500' EDR on that boiler. (At 500' EDR with 52,000 BTU-in it would settle in at an average water temp of 145-150F.) If you have a fuel use history on the place it's possible to put a stake in the ground marking the maximum likely heat load on the "before upgrades" picture, and that would make it pretty easy to establish a maximum size for the boiler. The exact zip code (to be able to look up weather history) and the fuel use on some wintertime gas bills with the EXACT meter reading dates would be enough to go on.

    At 500' EDR even if you cranked the boiler temp to it's maximum the combined radiation for both units can't deliver more than about 100,000 BTU/hr. Having a pair of 80-100K boilers , or a single 200-225K boiler is extreme overkill. The biggest boiler you should ever install with that radiation would be ~100K, but that's still more than 2x your current heat load, and probably more than 3x the heat load if you tighten up the place a bit. After you air seal and insulate the place the load for the entire house is probably going to be around (or under) 30,000 BTU/hr, and right now it's probably only 40-45,000 BTU/hr. But we'd be able to establish the limits of the current heat load fairly readily with a fuel-use calc.
     
  7. JoeSolbach

    JoeSolbach New Member

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  8. JoeSolbach

    JoeSolbach New Member

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    Thanks for the advice, the few plumbers I talked with for advice all insisted on 100K btu's for each unit, which seemed excessive to me. One did offer a mod-con option but yes I was rather shocked at the estimate. That's why I figured two smaller direct vent cast boilers might be a better option, but they said they won't provide enough heat. Separate metering isn't a huge issue, my thoughts were that going again with two direct vent boilers would allow each unit their own control of the heat, it be more to buy and maintain, but I'm guessing with one properly sized boiler and the place sealed up better my bills would come down and it would just make more sense then to include it in the cost of the monthly rent. I like the idea of an indirect water heater since that's one less flue I'd have to run, last longer than a direct heated tank, and also avoid the noise and expense of a power vented water heater.

    Also, I don't intend to finish the basement off, but was thinking of adding a couple radiators down there just for some warmth, the piping feeding the upstairs now is all copper, which is insulated, and it doesn't throw off the excess heat like the big iron gravity pipes do. Bottom half of the basement is large field stones and the upper half is brick.

    I was considering blowing cellulose into the walls, but keep thinking the I'm going to get condensation and rot in the walls. The exterior is cement asbestos shingles probably installed in the 50's and inside is mostly original lath and plaster. I know in the attic I can feel the heat coming up the plumbing chases and open stud bays.

    I'd much like to eliminate the chimney. I plan on doing a single bedroom and bathroom in the attic, maybe 200-250 sq. ft. The chimney cuts right through where I need the bathroom to go. Also I just seems to waste heat, I like the idea of taking combustion air from the outside and not from the basement, which seems to make it colder. That's why I preferred the direct vent boilers.

    One thing I did notice, the other day it was -5 deg. here, and the boiler for my unit was running almost nonstop, and that gauge read 180 deg. None of the radiators except the living room one is huge, and the place generally feels warm enough except on windy days. but I'm thinking that maybe the heatloss through the attic and the open stud walls in the attic stairway, which is on an exterior wall, are contributing to that.
     
  9. BadgerBoilerMN

    BadgerBoilerMN Hydronic Heating Designer

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    OK Dana,

    Now let me get this straight.

    You don't want 2# foam for the attic because it will hurt the environment, but a conventional cast iron boiler (the ESC being the best of the worst) at 85% AFUE spewing: nitrogen oxides (NOx), carbon monoxide (CO), and carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), volatile organic compounds (VOCs), trace amounts of sulfur dioxide (SO2), and particulate matter (PM) is OK?

    A 95% ModCon in contrast will lower the NOx and SOx while cutting consumption 25-50% on average. Not to mention eliminate required, uncontrolled combustion air for the boiler and water heater.

    If the OP has twice the EDR he needs before insulating, the design supply water temperature will also be much lower and return temperature well within the sweet spot for a properly sized ModCon.

    Direct vent, without sealed combustion requiring outside supply air, is wasting energy, be a boiler or water heater.

    When you combine both with one vent and one sealed intake you get uncompromising efficiency in the physical footprint and the operating efficiency.

    A ModCon should last two decades with reasonable care and a SS indirect 3 without worry.

    Insulate, blower door, ACCA Manual 'J' heat load and proper specification of equipment before you entertain HVAC installation bids.

    While foaming, don't forget the second most important area, following the attic; the rim joist.
     
  10. Dana

    Dana In the trades

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    Morgan: A mod con won't cut the consumption by 50%, not even 25% from what a right-sized 85% AFUE cast iron beastie with heat purge control would deliver. The percentage difference will be in double digits, but low double digits. I'm not particularly recommending it for anything other than a plan-B (call it the best of the worst- that's fair enough ;) ) if the sticker-shock of a right-sized mod-con proves to be too much.

    Unlike some retrofit applications, here you'd actually GET the 95% efficiency out of a mod-con, and while that would surely save 25-50% on fuel use from the existing ridiculously oversized PAIR of boilers, each 2x oversized for the radiation they're hooked up to. But a single right-sized cast iron boiler with heat purging controls would also save at least 25% from the current setup.

    It has no particular relevance to the 2lb foam issue though. The 2lb foam solution is both more expensive and more damaging, with no adavantage over the cheaper-greener solution in this application. Save the 2lb foam for where it actually does some good. In applications where there is no advantage to the 2lb foam it's better not to go there. The lifecycle damage of just the HFC245fa (not including 4x the polymer) is probably more than the lifecycle difference in emissions between a mod-con and a right-sized heat cast iron boiler with heat purge control.

    JoeSolbach: "Also, I don't intend to finish the basement off, but was thinking of adding a couple radiators down there just for some warmth, the piping feeding the upstairs now is all copper, which is insulated, and it doesn't throw off the excess heat like the big iron gravity pipes do. Bottom half of the basement is large field stones and the upper half is brick."

    The BASEMENT is where you should be applying the 2lb foam. Even if you aren't going to finish the space, it's a significant fraction of the heat loss, between the air infiltration of the field-stone and brick foundation and the direct conducted losses through the above grade brick. The brick is at BEST an R2 wall (unless it's 5 wythes thick?) or about U0.5 or higher. At a typical Chigagoland outside design temp of 0F, even if it's only 50F in the basement every square foot of above-grade foundation is losing 25 BTU/hr. If that's 3' of exposed foundation and a 120' perimeter (a square 30' footpring) that's 360 square feet, x 25 BTU/hr= 9000 BTU/hr. If you raise the basement temp to 60F with some radiators for comfort that'll be about 11,000 BTU/hr, and that's just the above-grade section- there is still a significant loss from the below grade brick & fieldstone portion too.

    A 2" shot of closed cell foam there would both air-seal and insulate that foundation, and you won't even need the radiators to keep it in the 60s down there. It would cut the ~10K or higher conducted losses of the above grade foundation walls down to less than 1K. The deep subsoil temps are in the low 50s, the ceiling would run maybe 65-68F, and the idling & distribution losses of the boiler will then keep the average temp above 60F. Depending on your local codes you may be able to use intumescent paint sprayed onto the foam for fire safety, but you may be required to install a fire-rated assembly between the foam and the basement. A cheap 2 x 4 24" o.c. studwall with unpainted wallboard would meet that requirement.

    Right now you have air leaks in the basement, and probably dozens of flues called "balloon framed stud bays" extending unobstructed from the basement to the attic for maximum stack-effect drive. That depressurizes the basement relative to the outdoors, pulling a lot of air into the basement from the exterior which makes the basement even cooler. If you seal the basement and plug the stack effect flues with air-retardent insulation the amount of cold air coming into the basement will drop by more than 95%.

    The concern about condensation & moisture accumulation risk with retrofit cellulose isn't well founded. Shingled siding is at least somewhat back-ventilated, and most circa 1900 homes would have enough layers of paint to limit moisture diffusion to tolerable levels. Unlike rock wool and fiberglass, cellulose can buffer and redistribute quite a bit of moisture, and is protective of the structural wood. As long as there is plank sheathing on the studs and some sort of tar-paper type material between the sheathing and the asbestos shingles the risks with cellulose are quite low. A detail that has to be considered and possibly rectified before insulating is the window flashing, particularly on the lower level, unless the house has 2-foot overhangs everywhere. Direct rain wetting of windows with improper or no flashing or is improperly flashed carries some risk even before insulating but after insulating that risk would be higher.
     
  11. Dana

    Dana In the trades

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    FWIW: About 3 years ago I was involved in a deep energy retrofit on a 3-story + basement 1892 vintage balloon framed house in a comparable climate (Worcester, Massachusetts, outside design temp = +5F, 6500-7000 annual heating degree days) . The walls were sheathed with ~12" wide-plank boards with some sort of antique paper air barrier on the exterior of that. The original ~4-5" clapboards had several layers of peeling paint, and had been covered over with asbestos shingles at some point in the 1940s or 1950s.

    In the early to mid 1980s the walls had been insulated with cellulose, and when the interior was gutted that cellulose was as perfect and dry as if it had been installed the prior week. There was no hint of rot even on the clapboards with the failing paint (that got torn down and dispose of as a lead hazard, along with the asbestos shingles.) The walls got treated to a layer of crinkle-type housewrap, and 3" of reclaimed roofing polyiso, followed by another inch of foil-faced polyiso under new fiber-cement siding. The cavities got insulated with foam for extra air-tightness, but it would have been fine if they had kept with the original 1980s cellulose (though it had to come out anyway to fully inspect the structure before building it back up.)

    Like your house, the foundation was fieldstone & rubble from the dirt floor up to about a foot below grade where it transitioned to brick. The solution there was to dig down the basement floor 6-8" to install a perimeter drain, a passive radon system, and 3-4" of washed gravel, with 1.5" of rigid polystyrene foam under a new 3" slab. The walls were treated with 2" of 2lb foam and intumescent paint, no finish walls. The house is now heated with mini-split heat pumps on each floor, but the basement hangs in the high 50s all winter despite having no heat sources other than a washer & dryer and (wall-hung tankless) water heating equipment.

    A full-on deep energy retrofit on your place may not be cost effective, but insulating the basement and walls would be.
     
  12. BadgerBoilerMN

    BadgerBoilerMN Hydronic Heating Designer

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    Still with you, but you need a relined chimney for that new antique boiler, add $1000 you will not get back. You will also need a 50 gallon atmospheric water heater. The combination may cut the fuel bill by 25% but the capital investment and one time labor cost is better spent on eliminating the chimney, for-ever.

    Though a cast iron boiler may last 30 years, the conventional water heater will be replaced every 10 with 80% equivalent efficiency, max.

    No bargains here.

    By the time you line the chimney and run gas and vent that water heater and boiler will cost the same as a low-end ModCon with the extra 25% annual savings paying for the best alternative.

    Size the ModCon for the new insulated design conditions and use the appropriate foam as you can afford it.

    Foaming rubble walls in basements is standard procedure here in Minneapolis.
     
  13. JoeSolbach

    JoeSolbach New Member

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    Thanks again for the advice. Most of the advice I'm getting from plumbers/hvac guys I've asked seems negative and biased. One guy actually said he won't install anything under 100K btus! Another said your better off converting to forced air, which I'd never do, even though a lot of people around here seem to do that. I hate forced air. Another suggested eliminating the linen closets on each floor and installing two metal B-vent chimneys instead, one for boilers another for water heaters, I said no thanks. And when one plumber saw I had a radiator sizing chart and mentioned EDR, was suprised and annoyed and told me do the work myself! This probably all sounds crazy but that's the answers I've been getting!

    I'm not planning on reusing the existing chimney. It's in poor condition, just one wythe of brick with no liner. Looking inside from the cleanout door, much of the mortar between the bricks is gone. The chimney is very tall, and angles in the attic and exits the peak of the roof. In the attic, there are numerous cracks and loose bricks. The mortar is crumbly and the roof leaks considerably around the chimney. Above all, the chimney cuts right through a space in the attic where I plan to put a bathroom eventually, and I'd much rather have the space. I planned on going direct vent with a cast iron boiler if I went the cast iron route, and an indirect water heater which is quiet and doesn't need a separate flue. I never liked the idea of taking combustion air from inside the basement anyway, which just seems to make an already cold space colder.

    I didn't think I could have the rubble and brick foundation walls directly foamed. The basement is mostly dry, I know there are two areas that get wet and seep when it rains. That and a lot of the bricks are covered with that white powdery efforescence. I know about the rim joists leaking air but never really gave much thought to how much the foundation itself contributes to heat loss of the whole building. Actually there is no rim joists, the 1x8 sheathing comes right down to the sill plate, as do the studs. The floor is poured concrete and breaking it all up to put insulating foam and new concrete would probably be a lot of money. At the very most we may use the space as an informal rec room but not every day. Just want to be sure the floors on the first floor stay warm over the cooler basement.
     
  14. BadgerBoilerMN

    BadgerBoilerMN Hydronic Heating Designer

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    Your experience with the local mechanics is all too common and embarrassing for those of us who are licensed and literate. Stick to your guns bucky!

    As for sealed combustion, direct vent cast iron clunkers. By the time you dress up the pig to make it look like a princess you will have more money in it than a ModCon. More than this, those who take the time to understand and properly apply a ModCon with indirect are almost always a cut above the lazy fellas that do what Great grandpa did. If your new man can produce a computer generated heat load analysis you've found a winner.

    Wet basement walls are almost always the result of poor surface water management. Foam after you check the downspouts, rain screen and landscaping details such as they are.
     
  15. Tom Sawyer

    Tom Sawyer In the Trades

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    If you have natural gas, I'd do a couple of Baxi Luna's
     
  16. BadgerBoilerMN

    BadgerBoilerMN Hydronic Heating Designer

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    Baxi Luna? Well if you find a committed installer with lots of experience. Stock-on-truck and good local support.
    Don't forget the boiler chemistry if you get that froggy.
     
  17. Dana

    Dana In the trades

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    BadgerboilerMN: The ESC-3 is a direct vent/sealed combustion side-vented version of a "new antique boiler" and doesn't need or want to use a re-lined chimney, which is one of several reasons I posited it as a "Plan-B". It may well very well be in the "lipstick adorned swine princess"category, but will cost substantially less than a mod-con.

    JoeSolbach: So, the local hacks refuse to install less than 100K of boiler PER UNIT, despite the fact that the radiation in any one unit can only deliver about half that? That's PATHETIC! You can clearly do the math better than they can. So, let's do the fuel-use against heating degree-day arithmetic, just for giggles to drive it even more emphatically home.

    The efflorescence means ground moisture is moving in- the only thing keeping the basement dry is the huge air leak. An inch of closed cell foam would air-seal & dry it out, but it's worth putting at least 2" on the above-grade section from an energy use point of view. It about a buck a square foot per inch of thickness. Yes it's expensive, but it may be subsidized, and even without subsidy it would have payback of less than 10 years even at this year's cheap natural gas pricing (and the savings are in after-tax dollars.)

    Even the smallest Baxi Luna can only throttle back to about 19,000 BTU/hr at minimum fire, which is probably not much less than (and could be more than ) the 0F heat load of just one of the apartments. It's just a bit silly to have a modulating boiler that never (or rarely) actually modulates. It's not really any better than the cast iron swine-princess solution.

    If going with a condensing boiler, a single HTP UFT-80W serving both apartments as separate zones, plus an indirect fired tank would be a better solution. That unit can modulate down to 8,000 BTU/hr- which is probably close to or less than the average winter load of just one zone, yet still has more burner at high fire than the combined radiation of the whole house can actually emit. Set up correctly and with the outdoor reset control tweaked-in the burns would be nearly continuous, at VERY high efficiency and high comfort, with no real temperature cycling of the radiators, only a continuous heat that slowly rises and falls with temperature. The benefit that may be worth the upcharge is that extra comfort more than the marginal improvement in heating costs.

    The insulation is also a comfort factor issue, by limiting just how cold those wall will get, raising the average radiation temperature in the room, which is more important to human comfort than air temperature. That's how you can feel just fine standing in direct sun on a 15F windless day, despite the sub-freezing temperature.
     
    Last edited: Jan 25, 2016
  18. Tom Sawyer

    Tom Sawyer In the Trades

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    The Baxi does domestic hot water too. He had ci radiators, it will condense just fine. Did you read his post? There's no way in hell 8000 btu is going to heat that place unless you expect him to cough up 25 grand or so to insulate it. He said there's virtually no insulation in the walls.
     
  19. Dana

    Dana In the trades

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    Sure I did read his post- all of it. But apparently you didn't read (or understand) mine?

    I didn't say it wouldn't condense, only that it wouldn't modulate except during the coldest days/nights. It would primarily just cycle on/off, and the temperature of the radiators would rise & fall. That's what he's used to, but it's less comfortable than a modulating system that's running constantly, which was the point. Set up properly the Baxi could hit it's efficiency numbers, but so what? What's the point of a modulating boiler that never modulates?

    I also said that 8000 BTU/hr would be about half or even less than the average mid-winter load of just one zone, which means it would modulate, even with just a single zone calling for heat. The thing has a 10:1 turndown ratio- it can crank up to 80,000 BTU/hr when it needs to, which is the most his radiation can deliver with 180F output water, and a firing rate he doesn't actually need. But it also modulates down low enough to modulate most of the season, well into the shoulder seasons.
     
  20. JoeSolbach

    JoeSolbach New Member

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    Yes, sadly the one plumber, older guy, said he would never install a boiler smaller than 100K per unit, which is what is in here now. I asked him why and he said that you need to support the radiaton there, and these old homes lose so much heat. All of them actually suggested large boilers, two suggested single 200 and 225K btu. boiler for the whole house. Funny, I calculated a total of 38K btu's for all the radiators in each unit at 180 deg. water. That's 76K total, plus when I do a bedroom and bathroom in attic that would be additional 250 sq. ft of living space, and then the basement, which I just plan for storage and occasionally rec use. This guy also said direct vent anything is junk and also suggested that I replace the radiators with fin tube baseboard. Yeah sure! Not happening, I have all the original 10" high oak baseboards in my house!

    For hot water I figure one indirect for the both units, reguardless if I did one or two boilers. Two indirects would be expensive and unnecassary. Just me and my wife, and the rental is one bedroom whom one person is going to rent now, and prob won't be more than two ever.

    Right now, the first floor is vacant, and the it's boiler was leaking badly so I turned it off and drained it. For the time being, I have one of those vent free 20K btu heaters keeping the first floor warm. Suprisingly, this small heater does a decent job of keeping the space warm, considering it's about 800 sq ft. lath and plaster walls with no insulation, above an uninsulated basement! Once temps dip into the teens or lower then it starts to really cool off. It's just temporary but I was shocked at how much 20K btu's heated that space! The old Utica for this unit is 100K in, but only 68K out, and 60K IBR!

    The foundation does need some tuckpointing and there are a couple areas that seep a lot when it rains, so I need to repair that. I've been air sealing the rim joist areas with spray foam and foam board. I didn't know you could spray foam directly over the brick and stones. That would be great but wouldn't it cause problems with mold or cracking from not having the heat going through and drying out the stone and brick?

    I'm gonna dig out my gas bills, how many previous bills do I need to do the calculations?
     
  21. Dana

    Dana In the trades

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    There is now a lot of history on insulating fieldstone brick & rubble foundation with 2lb polyurethane. It's very effective and essentially trouble-free. Brick and stone can tolerate being saturated with water, it's when moisture is flowing THROUGH problems can occur, notably the degradation of the mortar, which shows up as efflorescence. Depending on the mortar type used it may be possible and beneficial to slather on a parge of lime-mortar before spraying the foam, but in most cases simply fixing the obvious defects is all that's necessary. With the foam applied the below-grade masonry will be close to saturated with moisture, but it's moisture that's not moving, taking dissolve salts from the mortar with it (which is what efflorescence is all about.)

    The foundation will then only dry toward the above-grade exterior, and only in rare cases would that result in more efflorescence on the exterior. If and when that happens sacrificial parges of lime mortar every 40-50 years will protect the masonry. This is a common problem (and solution) in antique buildings in western Europe.

    To run the fuel use number you start with the amount of fuel used between two exact dates. Download a daily base-65F heating degree-days (HDD) spreadsheet from a nearby weather station from degreedays.net, and add up the HDD between the meter reading dates. (Include the HDD of either the first meter reading day or the last meter reading day, but not both, since you don't know exactly what hour the meter was read.)

    Then convert the therms or ccf or decatherms on the billing to BTUs (1-therm= 100,000 BTU, 1-ccf= 102,000 BTU, 1 decatherm= 1,000,000 BTU.)

    Multiply the BTU by the efficiency of the boiler (DOE BTU-out divided by BTU-in) to come up with the net BTUs delivered to the heating system.

    Then, divide the net-BTU by the HDD for a BTU/HDD figure.

    Then divide the BTU/HDD by 24 hours in a day to come up with a BTU per degree-hour number.

    Using base 65F presumes a heating/cooling balance point of 65F, which is about right for your house. A higher-R house might use base 60F. Heat load grows with the difference between the outdoor temp and 65F fairly linearly. So, if your 99% outside design temp is 0F, you have 65F-0F= 65F heating degrees. If your 99% outside design temp is +3F, you have 65F-3F=62F heating degrees.

    Multiply the BTU per degree-hour by your heating degrees to come up with the implied heat load.

    When you have ridiculous overcapacity like yours, that implied heat load is going to be truly an upper-bound, could be easily 15-20% higher than reality.

    But it's not going to be a 15% under-estimate ever, since that would imply that the it took more to heat your house than the source-fuel BTUs that actually heated the house. The old boilers simply aren't 100% efficient or higher (especially the 68% efficient Utica- are you sure you read that right? Even 50-60 year old gas burners were in the 75-80% range when new.) Steady state (burning constantly 24/7) they might be at most 82-85% efficient, but cycling on/off at your level of oversizing a brand new 83% boiler efficiency boiler would probably average less than 78% as-used efficiency, dumping a likely double-digit fraction of their heat into the heat-leaky basement while idling.

    So, with your best fuel-use calculated heat load you have a starting point. As long as the new boiler's output isn't more than 1.4x the fuel-use calculated number a new cast iron boiler would hit it's numbers, since that probably wouldn't be more than 1.7x the actual heat load. (AFUE testing presumes 1.7x oversizing.) After the arithmetic machinations I expect you'll probably come up with something between 45-50,000 BTU/hr for a calculated heat load @ 0F, and the real heat load at 0F will likely be 15% or more below that. A 3-plate Burnham ESC delivers 52,000 BTU/hr, and is probably enough boiler to get you through a Polar Vortex cold snap even without the auxilliary gas burner you installed on the first floor.

    After tightening up the place, if you insulate both the balloon framed walls and the foundation walls your whole-house load will likely be under 40,000 BTU/hr, maybe even close to 30,000 BTU/hr @ 0F. At 30K of load the smallest ESC would be 52K/30K= 1.73x oversized, still pretty close to the AFUE test presumption, but you'd still have enough boiler to have you covered down to -45F or so.

    The HTP UFT-80W would still be the better choice from an efficiency and comfort point of view, but if all the local contractors seem to be hacks the last thing you'd want is to let an unqualified hack install a mod-con. You might try to figure out who the local distributors are for small mod-cons with min-fire inputs of 13K or lower, and ask the distributors to recommend an installer. They know better than anyone which contractors are installing them in the dozens per year with no warranty returns, and which are tying up their technical support line with idiotic questions that could be answered by reading the manual. There are others- the Lochinvar WH-055 is probably a contender, Bosch Greenstar 57 - I'm sure BadgerBoilerMN could add to that list if you were interested in pursuing it, once we have a better handle on the heat load numbers.
     
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