Should I replace my 53-year old Burnham gas boiler?

Discussion in 'Boiler Forum' started by LMerriam, Mar 27, 2021.

  1. LMerriam

    LMerriam New Member

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    Hazleton, PA
    Recently moved into a house built in 1967 that has its original Burnham gas boiler. Although it has been regularly maintained when I read that boilers are good for 15-30 years MAXIMUM I thought it would be wise to replace it before next Winter (it gets cold her in Eastern PA and can't imagine what would happen if the boiler failed midway through winter with 10-20 degree weather for days in a row). Got quotes ranging from $6,700 to $9,000. Gas company guy came by this week to check a suspected slow gas leak that we could smell in our laundry room (gas dryer). Turns out there was no leak and was probably just a smell from the washer overflow drain. Long story short, he checked the basement including the boiler and said it looked to be in really good shape. When I told him we planned to replace it this year he told me "You're out of your mind. This boiler will last forever and you're wasting your money to replace it." "All it needs is professional maintenance every two years and a brushing/vacuuming around the gas-tube-burner things inside once a year and showed me how to do it." So now I'm wondering ... is he right? Should I take my chances that the boiler could abruptly fail due to its age? Or should I replace it before the worst happens? Any advice is much appreciated!
     
  2. Dana

    Dana In the trades

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    You can keep patching old cast iron boilers pretty much forever (basically until they start to leak), but that's not necessarily the "right" thing to do. But you have time to think about it and consider what to replace it with, when the time comes, whether that's next year or 10 years from now.

    Even if it's original steady state efficiency was 80% (divide the DOE-out BTU by the input BTUs), erosion on both the fire & water sides of the heat exchanger plates will usually have knocked out the true steady state efficiency into the mid-70s, if not lower. Worse, most Vietnam-era boilers are at least 3x oversized for the design heating load of the home as-is, and with the very low duty cycle are wasting a large amount of the total BTUs in standby losses to the boiler room (often the warmest room in the house in mid-winter, and rarely an INSULATED room), delivering an even lower as-used AFUE efficiency.

    To figure out your oversize factor you can use the boiler itself to measure the heat load at the 99% outside design temp (about +9F to +10F in your neighborhood- yes I know it gets colder than that, but for only ~87 hours in a typical year.) For non-modulating equipment ASHRAE recommends a ~1.4x oversize factor for the 99% design load. That is sufficient to cover the load during extreme cold snap temps from Polar Vortex disturbance events, but still yields a decently high (1/1.4= ) ~70% duty cycle under design conditions. That means when it's normal winter cold outside temps the heating system is running half the time more, and at the design condition it's over 2/3 of the time. That turns out to be considerably more comfortable than 3x oversizing where the system fires up, give you a short hot flash (sometimes overshooting the thermostat's setpoint) followed by an extended off period, since the radiation never fully cools off between calls for heat.

    AFUE testing presumes a 1.7x oversize factor, which is about as big as it can be before standby losses start eating into the average efficiency.

    Before picking a type & size of boiler, it's also important to measure up the radiation, zone by zone. With insufficient zone radiation newer mid-mass boilers need smart controls to suppress short cycling (many come fitted with such controls, some don't). With excessive radiation right-sized cast iron boilers may need to be protected from return water temps that are too cool, creating condensation problems inside the boiler or in the flue. That is an easily soluble problem, but you need to design for it. With enough radiation you may be able to take full advantage to condensing equipment (which is sometimes cheaper than right-sized cast-iron to install), which can yield even greater comfort due to nearly continuous low-fire burns during the heating season, and much higher efficiency.

    Most homes built in 1967 were using fin-tube baseboard convectors good for about 500 BTU/hr per running foot at an entering water temp of 180F. The same radiation delivers about 200 BTU/hr per foot at an entering water temp of 120-125F. With a fuel-use load number, divide the whole-house load BTU by the total length of baseboard, from which you can infer the water temps required at the average winter condition, and at design temp. The lower the water temp, the more comfortable the house will be, as long as it's still keeping up.

    If running a fuel-use load calculation use WINTERTIME ONLY fuel bills (late November through late February) and use the nameplate efficiency- don't discount for age. If it's a 2x4 framed house with some fluff in the wall cavities use 65F (or 5F cooler than your thermostat settings) as your base temperature base. If it's an uninsulated masonry house use 68F (higher if you usually keep it north of 70F indoors). Do not discount for hot water use either- the error from hot water use is offsetting the error from window solar gains.

    If the boiler is 3x + oversized and you're keeping it for another 5 years or more, installing a heat purging retrofit boiler control can recover most of the efficiency losses due to oversizing. Installing an outdoor-reset controlled mixer to the radiation loops can deliver the same comfort of a modulating condensing boiler, albeit at lower overall efficiency.

    Or you can save all of that equipment money and apply it to a cold-climate ducted heat pump system once state & federal subsidies kick in hard under some future "green new deal" type policy push. The US will never get to net-zero carbon emissions with gas fired heating equipment, but it's getting easier every year to get there with heat pumps and lower-carb grid resources. With the fuel-use load calculations you'll be ahead of the game on sizing it correctly.

    Alternatively, if installing or replacing central air conditioning it's reasonable to upgrade to a cold-climate heat pump solution at that point rather than AC-only, with or without subsidy money driving it. Right-sized modulating heat pumps are very quiet (sometimes quieter than your refrigerator), and in some local electricity & gas markets (like mine) are comparable to or cheaper to run during the heating season than 80% efficiency gas. YMMV
     
    Last edited: Mar 27, 2021
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  4. fitter30

    fitter30 Well-Known Member

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    Check with your gas provider for any rebates also with your electric company for insulation upgrades. More insulation smaller boiler.
     
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  5. LMerriam

    LMerriam New Member

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    Thank you very much for the detailed reply. Now I've got some homework to do!
     
  6. LMerriam

    LMerriam New Member

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    Great advice, thank you!
     
  7. Dana

    Dana In the trades

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    For the record, how big is the house?

    Full basement, slab on grade, crawlspace or... ?

    Replacement windows? (If yes, low-E or no-E?) Storm windows over single panes?

    Any existing central AC? If yes, are the ducts in the attic, above the insulation, or are they all inside the insulation boundary of the house?

    The cost of gas is... (take the whole bill in $, divide by the usage numbers) ?

    And electricity (whole bill $ divided by kwh)?

    The nameplate BTU-in and BTU-out (the raw DOE BTU number, not "net water" or "I=B=R".)
     
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  8. LMerriam

    LMerriam New Member

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    For the record, how big is the house?
    // 2,400 sq ft, two-story, brick & vinyl siding

    Full basement, slab on grade, crawlspace or... ?
    // full basement EDIT: there are three zones on this boiler

    Replacement windows? (If yes, low-E or no-E?) Storm windows over single panes?
    // all windows are newer sliders, high-quality, low-E, no storm windows

    Any existing central AC? If yes, are the ducts in the attic, above the insulation, or are they all inside the insulation boundary of the house?
    // no a/c, just three minisplits (two up, one down)

    The cost of gas is... (take the whole bill in $, divide by the usage numbers) ?
    // $0.90/ccf

    And electricity (whole bill $ divided by kwh)?
    // $0.13/kwh

    The nameplate BTU-in and BTU-out (the raw DOE BTU number, not "net water" or "I=B=R".)
    // House inspector said he couldn't find a nameplate but heating contractor guy said there was one (I just looked and don't see one on the cabinet exterior (is it hiding inside someplace?) THANKS AGAIN!
     
    Last edited: Mar 28, 2021
  9. fitter30

    fitter30 Well-Known Member

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  10. Dana

    Dana In the trades

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    A 2x4 framed insulated 2400' house over reasonably tight full basement would typically have a heat load under 35000 BTU/hr @ +10F, and could easily be in the 25-30K range if the basement walls are insulated & air tight. Run the fuel use heat load calc, see where it comes in with all the standby & distribution losses included.

    A heat pump with a modest HSPF of 10 (there are many in the HSPF 12+ range now) would deliver 10,000 BTU/hr per kwh so per million BTU (MMBTU) it takes (1,000,000/10,000=) 100 kwh,which at 13 cents costs $13/MMBTU. That's an all-in operating cost, since electricity is the only energy input.

    At 80% combustion efficiency (the absolute best your existing cast iron beast could possibly deliver) is ~80,000 BTU/ccf, so it would take (1,000,000/80,000=) 12.5 ccf, at a cost of (x $.9=) $11.25/MMBTU, plus something for the control & pumping electricity- call it ~$12/MMBTU, best case. If the as-used efficiency is much under 80% (it's probably running quite a bit less than 80% AFUE, due to oversizing & age) a middle-of-the-road heat pump solution would be cheaper to run.

    If your mini-splits are heat pumps they will likely be MUCH cheaper to heat with than gas during above-freezing temps, since the efficiency & capacity doesn't start to roll off very fast until the 20sF. With a cold-climate mini-splits the efficiency & capacity doesn't fall dramatically until the low- teens outdoors. What model numbers?

    Most Burnhams have the nameplate numbers mounted on the boiler sheet metal somewhere inside the removable front panel, (which is usually a 2 finger lift). The 2 black circles near the top of the panel are plastic grommets to protect your fingers while sliding the panel up to remove it. Some older models only have one finger hole. :

    [​IMG]
    Somewhere just inside the front panel area you'll find a nameplate sticker/label that looks something like this:

    [​IMG]
     
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  11. LMerriam

    LMerriam New Member

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    Thanks very much for the replies. Having started my homework I came across this cautionary note and wondering if it's true in my case?
    https://www.usboiler.net/what-is-outdoor-reset-control.html
    "Understand that not all boilers are outdoor reset compatible. Older boilers usually do not have the capability to function with an outdoor reset control."
    Assuming this is doable -- or, if not, that something like the Intellicon 3250HW+ (which is apparently discontinued but may have an available equivalent would work) -- is there anything else I can do to upgrade our boiler efficiency? Have decided, based upon the feedback here, that I'll keep this one for awhile and do what I can to improve it in the meantime (and hopefully to have any upgrades compatible with my replacement boiler in a few more years)? Based upon quotes I've received a condensing boiler would be too expensive to seriously consider (roughly 40% higher cost). Haven't looked into the "heat pump" suggestion but plan to. Thanks again! P.S. Wanted to take a photo of the nameplate but the boiler was running and I'm not that brave/stupid to mess with it. Three zones, btw, as you can see in the photo.
     

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  12. Dana

    Dana In the trades

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    That looks like an absolute beast - an 8 or even 10 plate boiler based on it's width. How wide is yours?

    [​IMG]

    It looks like your front panel (the panel with the Burnham name plate on it) lifts out with hooks or now-missing knobs on the upper corners on either side of the vent louvers. The bent vane in the middle looks like somebody may have used a large flat screwdriver or flat wrecking bar to lift it up from the center, which may work just fine. The ratings plate is behind that panel.

    That's probably on the order of 250,000 BTU/hr (in) or more. The current Burnham Series 2 P208 is 28" wide across the front of the jacket (dimension "B" on p.2) , drawing 232,000 BTU/hr, with a DOE output of 191,000 BTU/hr. If your fuel-use load calc comes in at the anticipated <35,000 BTU/hr you're looking at an oversize factor of 5 or more, which means it's average duty cycle is in the dirt, well over the cliff of the knee in the as-used efficiency curve.

    A retrofit outdoor reset control probably WOULD work with your beastie-Burnham, but outdoor reset probably wouldn't increase efficiency much (it would increase comfort though). With some re-plumbing an outdoor reset controlled mixer could be used while still operating the boiler at a higher temp.

    The Intellicon 3250HW+ (or Hydrolevel Hydrostat 3250, which has an optional outdoor reset function, and comes as standard equipment on some cast iron boilers right now) would recover a large fraction of the efficiency hit due to oversizing. The size of the efficiency hit (and of the potential savings) depends on the actual oversize factor. I expect in this case you'd be saving at least 15%, maybe more. Heat purging economizers exercise the thermal mass in the system & boiler, and with an oversized high mass boiler many calls for heat from zones would be satisfied without firing the burners, sipping heat out of the boiler without firing until the boiler hits it's low-limit temp. That makes for longer, more efficient burns while lowering the average idling temperature (lowering standby losses.) If you're reasonably satisfied with the comfort as-is, a heat purge economizer would be the way to go if you're keeping it.

    To get a better handle on how oversizing an old gas fire cast iron boiler takes a hit on efficiency, see system #8 in Tables 2 & 3, and the regression curve in Appendix 8 of this research document from the Brookhaven National Labs. Even at a combustion efficiency of ~78% it's steady state efficiency is only ~73% due to high jacket losses, and at an oversize factor of 3 (the column in Table 3) it only musters 62% as-used AFUE. Looking at the "Output (% of maximum)" curve on p3 of Appendix 8, with a 5x oversize factor you'd be at the 20% mark , burning only a 20% duty cycle at your 99% outside design temp, and below the 10% mark for the seasonal average, probably in the mid to high 50s for as-used AFUE. ( But it's good to know you have enough burner to theoretically keep the place warm even when it's colder than -200F outside, eh? :) )

    With a heat purging economizer it moves the knee in the curve way the left. See the similar curve for System 3 in Appendix 3, which is an oil fired boiler with a heat purge control. Even at the 10% bar it's only lost a few percent, and doesn't fall off the efficiency cliff until it's a bit below the 5% mark (= 20x oversize factor).
     
  13. Dana

    Dana In the trades

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    BTW: It doesn't look like your foundation walls are insulated or finished. The current IRC code minimum for basement walls is R15 continuous insulation (2.5-3" of rigid polyiso, or 4" of EPS). If there is very much above-grade exposure on the foundation or if you have damp or clay soils, 15-25% of the total fuel bill could be losses through the foundation walls. It's probably nice and toasty in the boiler room in the dead of winter, making it even lossier still. It's a substantial DIY project, but air sealing the basement walls & band joists is usually "worth it" from both comfort and long-term financial points of view, even with cheap fracked gas. There have been multiple threads on the topic of how to do that without breaking the bank or creating a mold farm in various forums on this site over the past decade.
     
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  14. LMerriam

    LMerriam New Member

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    Going to keep this boiler in operation for a few years more. Based on the recommendations here I'm thinking to upgrade it with this https://www.grainger.com/product/INTELLICON-Energy-Efficiency-And-Economizing-4HVJ5 rather than an traditional outdoor reset control which is not necessarily compatible with my boiler. I saw the same LCH unit on ebay for $900+ while Grainger has it for just $202.40. The former is more than I would be willing to spend, but $~200 (plus installation cost) is something I could handle. Any further suggestions would be appreciated. TIA!
     

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  15. Dana

    Dana In the trades

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    The Hydrostat 3200 heat purging economizer is very similar in it's economizer function, under $150 at internet retail pricing.

    Download the installation instructions from any economizer you are considering. Most are a reasonable DIY for those with modest to middling (or better) electrician skills.
     
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  16. LMerriam

    LMerriam New Member

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    Thanks, Dana!
     
  17. Splashoil

    Splashoil Retired!

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    My vote would be to replace that old non condensing boiler. There are so many issues involved that also led me
    To tear out my 1974 National Boiler. I was reluctant to take it out because I had installed it. Pride led me to revamp the piping to deal with the sizzling condensate on the cast iron. After making a lot of changes, I eventually concluded it
    Was a waste of time and fuel to keep it.
    I bought a copy of John Siegenthaler’s classic Modern Hydronic Heating and lurked around here and other sites until
    I had a plan. Then shopped for the parts: condensing mod-con boiler, smart ecm pumps, air and dirt separator, old cast iron baseboards and radiators. Put it together and made a much more comfortable house with lower gas and power bills.
    The old National went for scrap. I did not want to fool someone into trying to make a free boiler work.
    I don’t advocate this project until you have researched it and have the skills or can hire the talent.
     
  18. Dana

    Dana In the trades

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    While it's possible to properly DIY a mod-con installation it's well beyond the design & implementation skills of most.

    A proper DIY installation of an economizer control is orders of magnitude easier.

    The boiler's nameplate indicates it's "only" the 6- plate P206, not the P208 or bigger, with an input of 164K, and DOE output of 136K (=83% combustion efficiency):

    [​IMG]
    [​IMG]

    That means it's "only" ~4x oversized for the design load (as if they were expecting it to sometimes drop to -170F during a cold snap :) .)

    That's an oversize factor low enough for a heat purging economizer to pull the as-used AFUE efficiency fairly close to whatever it's current steady-state efficiency is, which could easily be still north of 80%. At that oversize factor the seasonal duty cycle has been very low- it's burner on-time over the past 53 years has been only ~25-30% of what a right-sized boiler would have run, so it's the burner-time equivalent of a ~15 year old right sized boiler. There are no guarantees, but with total lifecycle burner on-time being so minimal, with reasonable maintenance it'll probably keep going for a least another decade, or until the owner is just plain sick of it, or burning of natural gas in homes is regulated out of existence for climate change reasons.

    If a primary goal of addressing is short financial payback the economizer should work, and the real money can be spent on where the real comfort, control, and efficiency problems (usually) are in houses of that vintage, namely the air infiltration & insulation deficiencies of the house.

    Assuming a professionally installed mod-con boiler would run ~$10K, and save about 15% on gas use from what the P206+ Hydrostat 3200 or similar would use, is that the best use of the $10K right now, assuming the P206 probably will be just fine for at least 10 years? (I've seen many 70-80 year old cast iron boilers with dumb controls still chugging along just fine.) The anticipated lifecycle of air sealing and insulation improvement efforts would be several times the 15-25 year reasonable lifecycle to expect out of a new mod-con boiler. That much money would buy quite a bit of retrofit air sealing & insulation upgrading, in most case saving MORE than 15% on the gas bill on a 1960s vintage house if done in the right order (putting "new high performance windows" on the very BOTTOM of the list, or skip it entirely). Typically uninsulated, unsealed basement foundation walls are probably 15%, the air leakage out of the attic is probably another 5-10%. If the framed walls in the finished floors are uninsulated or only built with half-depth "econobatts" (surprisingly common even in 1967) or deteriorating R11s, dense packing those walls with cellulose could be another double-digit percentage, and make a large difference in comfort (and noise penetration from the outdoors).

    If the house doesn't currently have air conditioning, applying the $10K to a heat pump solution capable of covering both the heating & cooling loads would be another option, though that has the same lifecycle issue as a new boiler- it's really better to just start with the house. If PA begins to follow other states on zero greenhouse gas emissions policies there may come a time in the next decade where installing a heat pump solution becomes a financial no-brainer (still TBD.) This isn't some crazy theory- technologically heat pumps have come a very long way since the 1980s. Most 1960s vintage 2x4 framed ~2400' houses in PA could be reasonably heated with a 4 ton cold climate heat pump, and most houses that have undergone more than a cursory round of air sealing & insulation upgrading can be handled by a 3 tonner, or even a 2.5 tonner, at outdoor design temps that bump into low negative digits F. The local design temp here is ~ +10F, dead-easy to design for with any heat pump utilizing enhanced vapor injection scroll compressors & ECM drive motors for the compressor & blowers, and is within the capacity range of many heat pumps using simpler-dumber compressors.

    It won't usually be cheaper in most market to run heat pumps than an 80% efficiency gas boiler at current pricing, (particularly in fracked-gas country like PA) but it almost always beats #2 oil & propane hands-down. With any significant amount carbon emissions pricing tacked on to natural gas heat pumps quickly become the lowest operational cost option. In my own locally high priced electricity and high priced gas market heat pumps are already pretty much at parity with 80% efficiency gas, but are still more expensive to run than condensing gas. With my own low-temp hydronic heating system (~125F water temps) I have limited options to electrify, but not ZERO options. A 4 or 5 ton LG Multi-Vs with a hydro kit would do just fine, but by the time the state & federal policy incentives kick in I'm hoping there will be more options. There are currently MANY more hydronic heat pump options being marketed in Europe. In North America there are several hydronic output heat pumps available that are "monobloc" style, where refrigerant loops are self contained in the outdoor unit. Those require only water connections to the system, but that would require anti-freeze in my area- something I'd prefer not to have. A split system (like the Multi-Vs with only refrigerant and electricity going through the walls just works better for me. (YMMV).

    If my gas burner crapped out right now this week I'd probably still just swap in a cheap mod-con and wait for the incentives to align. But I'm also sick enough of my ridiculously oversized AC that it won't take too much shift in policy carrot (& stick) incentives to revisit that.
     
  19. Splashoil

    Splashoil Retired!

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    The elephant in the basement is that gravity vent and combustion air requirements (cold air coming in t0 heat and send up the stack.) If basement is intended to be heated space the standing pilot and burners work against that. There are many DIY creations that go in bypassing the inspections that look at this stuff. I have a Daikin monobloc in the crate that may go in the mix at my place if the TT 60 fails but it is performing very well and is isolated from the basement space with the direct vent. Swapping out the fin tube copper baseboards for vintage cast iron radiant baseboards has made the house much more comfortable with the outdoor reset running the show rather than the sizling cast iron boiler when heating demands are low. I never imagined how well all this stuff would work.
     
  20. fitter30

    fitter30 Well-Known Member

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  21. Dana

    Dana In the trades

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    The priority is still air sealing and insulating the house. Yes, the stack is 24/365 parasitic load, but as a fraction of the current overall heating bill isn't all that high- a low to mid single digits percentage.

    Later versions of the P206 with standing pilots came with stack dampers integrated into the ignition controls that "prove" the damper is open to enable the ignition. A simple retrofit stack damper is easy enough to cut in, and could be worth a couple percent of the bill, which might be considered at some point. If by some stroke of luck they manage make the place tight enough to need more makeup air for the stack to operate correctly it's cheap & easy enough to add a zone-damper type ducted proximity vent (to be proven in series with the retrofit stack damper) if it comes to that.

    So it depends on what the goals are here. From a net present value of future energy savings point of view it's hard to rationalize doing anything but tweaking the existing boiler. From a comfort improvement point of view it's almost always better to spend the first tranche of home improvement on the house itself. At some point the house might be tight enough to force another decision point (is it time to add a makeup air damper or just get rid of the thing?). In homes without air conditioning that decision point might come when it's time to install the AC, making it a heat pump instead.

    Yes, real radiation (rather than convectors) comes with real comfort benefits, even at sub-90F water temps.

    But it is not necessarily "worth it" in everyone's book to buy better radiation (or even a retrofit outdoor reset control), especially when there is still plenty of other low-hanging fruit on the building efficiency front.

    It IS worth it to most people (once they understand it) to improve the air tightness & insulation of the house, which shrinks the room to room temperature differences, and makes it easier to control heat and moisture transfer through the house, and to control indoor air quality, etc. On a house this size getting the blower door tested air leakage to even <<2500 cfm @ 50 pascals (lower is better) can do wonders, and most homes built in 1967 aren't there yet.
     
    Last edited: May 3, 2021 at 3:44 PM
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