This is my first post here, though I have done plenty of reading over the last few weeks. I am just beginning to build in western Montana. ICF to the roof, polished concrete floors throughout. 1100 sqft daylight basement, 1300 sqft main floor, 580 sqft garage, with 240 sqft bonus room above. Manual J shows 54k btuh at 1 degf. Gas rates ~.35/therm, and electric rate of .065/KWH. I am seeking advice on the best heat source for my situation. Including heating and hot water, and recommendations on open vs. closed systems. Some background- I installed a Takagi tankless in my prior home, and I loved it. Aside from an annual vinegar flush, it was bulletproof over 8 years. And, I have a recommendation to consider a NextGen electric boiler from the engineer that did my Manual J. I have a long held bias against electric as not economical, so I would look for information to overcome that as part of my research. Finally, I am the DIY contractor, with pretty fair experience and high mechanical ability. So, I am comfortable that I can install any recommended solution. Thanks for any advice! Scott

Either you're building the crappiest sub-code house in Montana or your heat load at +1F is a heluva lot less than 54,000 BTU/hr. Real heat loads on houses that size & configurate at code minimums would be about half that at 0F. (Seriously!) My 2400' (above grade) sub-code 2x4 house plus 1500' of conditioned basement from the 1920s comes in at about 40K @ 0F if I keep it all at 70F (including the basement.) Maybe you have more than code-max window/floor ratio or something? Something is seriously wrong with that heat load calc.

This cheap modulating condensing boiler would be right sized for 19 out of 20 houses in the US (even those with loads that are ACTUALLY 54,000 BTU/hr):

https://www.libertywholesalesupply.com/westinghouse-wbrung080w-natural-gas-highly-efficient-universal-fire-tube-boiler.html

It's the same boiler as HTP UFT 080W:

http://www.htproducts.com/literature/UFT-brochure.pdf

https://www.libertywholesalesupply.com/product-doc/westinghouse/WBRU_Brochure.pdf


With a 10:1 turn down ratio it can run at condensing temps even on 35' of crummy fin tube baseboard without cycling, is designed to run pumped direct (though in some instances the design might still be better served set up as primary/secondary), and has a separate port already set up to support an indirect tank. While it's better to be installed by a qualified tech, this is probably the most straightforward mod-con out there to install.

At 6.5 cents/kwh and 3412 BTU/kwh that's $19/MMBTU to heat with an electric boiler.

At 35 cents/therm and 95% efficiency the mod-con delivers 95,000 BTU/therm, or 10.53 therms/MMBTU, which costs $3.68, plus the control & pumping power, call it $4/MMBTU.

Feel like spending $19 when you could be spending $4? :-)

If you heated with ductless mini splits you could get that $19 down to about $6/MMBTU. If you're installing mini-splits for cooling it's worth the up-charge for making it a heat pump type, just in case the boiler craps out or the gas rates change dramatically. When rooftop solar hits a buck a watt it might be worth heating with mini-splits too, but that decision can be deferred.

Dana1, Thanks for your suggestions. If I read between the lines, you did a quick calc that the gas is cheaper on my current rates. That 54k btu includes 12k for the garage, and 10k for the vaulted ceiling over the living room, which we are working on changing the design to double upper walls. I might have asked the question a bit prematurely, but I needed the Manual J to reveal the weakness in the living room upper walls. . I appreciate your opinion that the house needs improvement, which I know.
I know minisplits are reasonably efficient, but that's for another time. With polished concrete floors, I want them to be warm.

Scott

I'm not criticizing the house design- I simply don't believe the Manual-J is correct.

Are you actively heating the garage to 68F or something? Even so, if the wall has ICF walls and an insulated garage door (that's actually closed... :-) ), it isn't going to add 27,000 BTU/hr to the heat load. If you include the garage you're talking 3220' of conditioned space, a sizable fraction of which is below grade. A code-min house that size would typically come in at around 30-35,000 BTU/hr @ 0F, and the ICF house is somewhat better than code-min. 54,000/3220' is 16.8 BTU/hr per square foot of conditioned space. That's a higher load/space ratio than many or most tightened-up 2x4/R13 houses with U0.5 windows & doors. You should be under 10BTU/ft @ 0F with some random design that's otherwise code-min, under 8 if the design has been optimized at all.

Where are the big heat losses? Big (or crummy) windows? High ventilation/air-leakage rates? How were they modeling (or what U-factors were assigned for) the ICF walls in the calculation?

Hands-down the cheap 80K mod-con with the 10:1 turn down ratio is going to be the better choice for you than an electric boiler, even if they were offering 3 cent off-peak rates. Mini-splits would just be a "plan-B" backup. If gas prices quadrupled and you could get the design load down to something more reasonable there may be hydronic air source chiller heat pump options, but not at 54,000BTU/hr (if that's even real, which I serioiusly doubt that it is.)

I'm ignoring for the moment the Manual J, as it's being reviewed by my engineer anyway. But, if you use the Mod-Con boiler, do you prefer an open or closed system to work the hot water and radiant heat and DHW?

The heating system needs to be closed loop to avoid the introduction of oxygen into the system, which will shorten the lifespan of system components. This isn't a preference- it's mandatory. The boiler wasn't designed to take 100% fresh water, even if it's stainless heat exchanger probably can take it.

Open systems aren't a great idea anyway, even when the heat source is a tankless hot water heater and all the valves & pumps are selected to be fresh-water tolerant. In a low-load house with slab radiant heating the heating system water wouldn't rise out of the legionella growth sweet spot temperature range, and eventual contamination is more likely than not. Open systems aren't even legal in some states (or only legal under a prescribed set of conditions, as is the case in my state).

With a closed heating system the slab radiant tubing should all be oxygen-barrier PEX, not the potable-water stuff, but you won't have to use bronze-impeller pumps etc. the way you would with an open system driven by a tankless.

All mod-cons can be set up to run an indirect fired hot water tank (with an internal heat exchanger separating the potable from the heating system water), which usually involves more plumbing and some design work for the installer. But the WBRUNG-080W ( UFT-080W) simplifies that by having internal controls and pre-plumbed ports out the bottom for an indirect hot water heater, which greatly simplifies the system design & installation for a heat + hot water situation.

http://www.htproducts.com/imgProd/UFT-big1a.jpg

HR heating systems should always be closed loop and O2 barrier PEX should always be used. Unfortunately, selecting the best heat source is not always quite as simple as just selecting the heat source option having the lowest monthly operational cost. In addition to the monthly operational cost, you should also consider the acquisition cost, installation cost and maintenance cost when doing the heat source Return on Investment (ROI) analysis...which you should always do before making the final heat source selection. You may also need to consider “time to repair” if the building is in a remote location. It can often take a significant amount of time to get service or obtain the required parts to repair some of the more complex heat source options. So if you select one of the more complex heat source options and the building is located in a remote area where below freezing temps occur frequently, you may want to consider having a back-up heat source option. If you do, this additional expense should perhaps also be factored into the ROI too. Sometimes it makes more sense to pay a little more as you go, especially if you will not be a long term building resident to benefit fully from the ROI.

When the marginal $/MMBTU of one source it ~5x that of another alternative, the cheaper alternative is almost always the right choice.

A $1700 mod-con designed for ease-of-installation is pretty compelling against any electric boiler solution. In this case, the difference in operating cost could pay for a an entire spare boiler in less than 2 years. There's some amount of design and cash required for the rest-of-system components, but it doesn't take the hard-math or huge money to get there.

The western MT locations that are on the gas-grid isn't exactly rural Uzbekistan- you can get overnight delivery from just about anywhere in the US, and in less dense areas people are accustomed to dealing with remote suppliers/support.

Right, the math is far from hard, but you do have to actually do it before you can call the ROI analysis compete. Yes, since the NextGen already provides many of the required HR components that don’t come with the other heat source options, that savings should be factored into the ROI analysis too. A 5x difference in energy cost is indeed very compelling. However, one should also consider if this will remain the case for the period used in the ROI analysis. Speaking of fossil fuels like natural gas, I hear that coal is also going to be getting very affordable very soon...

Oregon Renewable Energy Bill

My idealist vision is a future where electric is the ONLY fuel and is 100% generated via carbon neutral and renewable resources. I suppose until then natural gas will have to be tolerated and the adverse environmental effect of fracking ignored, but a true environmentalist concerned about man-made global warming probably shouldn't overly endorse it, lol!

Thanks for your feedback guys!
Given the relative fuel costs, I will likely end up with a gas boiler. Dana, Thanks for the explanation of why closed systems are the right answer. It is unfortunate that dealers and designers will show both open and closed systems and leave it up to novices to decide what they want. It's great to be able to get those things sorted out here. I'm sure I will have other questions as we finish design and make decisions about systems.

Whether you're doing it DIY or hiring it out to someone with hydronic heating experience, I strongly recommend hiring out the system design & specification of every pump valve, and manifold & PEX loop on the system, once you have a credible room-by-room Manual-J, even if it costs you a grand or more. The "once size fits all" tankless based radiant heating designs and kits found on the internet are mostly pretty junky solutions. Spending on competent design saves on equipment cost, operating cost, and maintenance cost down the line. There are competent designers who do this as a service via email.

Coal as a space heating fuel in a modern coal stove is pretty cheap, and 3-4x as thermally efficient than the typical coal fired powerplant (and 2x as efficient of even modern super-critical coal power plants), but there's a dearth of equipment available for making it work with hydronic floors.

I'm skeptical that 35 cent natural gas will be around forever, but I'm even more convinced that 6.5 cent electricity will drop to under 1.5 cents, which is where it needs to be to compete with 35 cent gas. Even if natural gas quadruples in price it'll still be cheaper than 6.5 cent electricity in an electric boiler. But if the price difference ever tips strongly in favor of an electric boiler solution, it's a fairly cheap swap-out.

Dana has it right, as usual.

I see a locally supported ModCon boiler and indirect-fired SS water heater in your future. NG pricing is likely to be stable and as more electricity is generated with NG they will be more closely tied to one another.

I have been designing "closed" hydronic systems since 1987 using condensing boilers and SS indirect water heaters. The only excuse for an "open" heating system is the short-term acquisition cost. Every other argument for open systems is specious as reflected in Dana's comments.

If people would reject all the offers from all the people who promote open hydronic systems they would miles ahead of the crowd.

Dana has it right, as usual.

I see a locally supported ModCon boiler and indirect-fired SS water heater in your future. NG pricing is likely to be stable and as more electricity is generated with NG they will be more closely tied to one another.

I have been designing "closed" hydronic systems since 1987 using condensing boilers and SS indirect water heaters. The only excuse for an "open" heating system is the short-term acquisition cost. Every other argument for open systems is specious as reflected in Dana's comments.

If people would reject all the offers from all the people who promote open hydronic systems they would miles ahead of the crowd.

Beyond price, another thing to look at in the all-electric dream scenario is the net carbon footprint of the different solutions.

Burning natural gas produces 117lbs of CO2 per MMTU:

https://www.eia.gov/tools/faqs/faq.cfm?id=73&t=11

So burned at 95% efficiency in a mod-con the heating system has a net carbon footprint of 117/0.95= ~123 lbs/MMBTU .

At the current energy mix on the MT grid, electricity is delivering more than 2300lbs /MWh. See the year 2020 business as usual projections from the EPA:

http://www3.epa.gov/airquality/cpptoolbox/montana.pdf

Normalizing to MMBTU, at 3.412 BTU/watt hour, that's 3.412 MMBTU/MWh, so the carbon emissions for electricity at a COP of 1 in an electric boiler becomes 2300lbs/3.412 MMBTU= 674 lbs/MMBTU.

That's more than 5x the carbon footprint, at current grid emissions.

If MT meets their EPA defined Clean Climate Plan targets the emissions will drop to ~1300 lbs/MWh by 2030, making the carbon footprint of an electric boiler something like 380 lbs/MMBTU, but that's still nearly 3x the emissions of a mod-con boiler.

But leveraged by a hydronic chiller or a mini-split at a COP of 3 it starts to pretty much break-even on carbon, and maybe even operating cost, depending on how things shake out by then.

Unless your local utility is offering green-up plans for all renewable power, or you happen to be on a heavy-hydro utility, at the MT average levels you'll have far lower carbon footprint running the mod-con boiler over a 15-25 year anticipated lifecycle. By the time it craps out there might be heat pump options that make heating with electricity more carbon favorable (and cash affordable) too.

Science is a beautiful thing, especially when you are vindicated by its immutable truth, wielded by a master of the craft.

More proof that being GREEN is more than a feeling...

P.S.

If you want to have warm floors you have to design a system that reflects the required response time and surface temperatures desired. As Dana suggests; a room-by-room Manual 'J' is the best way to model the as-built operation of any radiant heating system. Over-insulating, over-sizing boilers, poor thermostat placement, zone delegation and outdoor reset programming can make all the difference. Even mechanical engineers should use radiant specific software before specifying anything.

Posted By BadgerBoilerMN on 04 Mar 2016 04:24 PM
Dana has it right, as usual.

I see a locally supported ModCon boiler and indirect-fired SS water heater in your future. NG pricing is likely to be stable and as more electricity is generated with NG they will be more closely tied to one another.

I have been designing "closed" hydronic systems since 1987 using condensing boilers and SS indirect water heaters. The only excuse for an "open" heating system is the short-term acquisition cost. Every other argument for open systems is specious as reflected in Dana's comments.

If people would reject all the offers from all the people who promote open hydronic systems they would miles ahead of the crowd.

Morgan- have you personally installed a UFT-080W /WBRUNG-080 yet? (NRTRob seems to think they're pretty kewl units.) Until I saw Liberty Wholesale's pricing on the Westinghouse-labeled flavor I had no idea just how inexpensive they are, which makes me think the new generation of stainless steel fire tube mod-cons is becoming a disruptive player in the boiler market.

It's cheaper (and more appropriate for space heating applications) than many condensing tankless HW heaters- even cheaper than some better-class 2 & 3-plate cast iron dinosaurs.

You know that I have the same affection for Rob as I do for you; and he is right.

I know the local HTP rep. (an ME) and he convinced me to install one in my new design studio/shop. It arrives on Monday via the local distributor as the backup boiler mandated for the dual-fuel Ex-Gen electric boiler.
I have been using HTP products from the beginning, (that 1987 SS indirect was one of the earliest SuperStors) and a new Pro-series 30 gallon indirect will be driven for by the UFT.

Like I needed to put another ModCon in, but when you run out of manufacturers you have to try every model therefrom. I'm excited. From the specs. it appears to be on the cutting edge of ModCons from the plastic collection pan and built-in LWCO, to the 10-1 turn-down.

I'll let you know when it's done, around June.

It bears repeating in a concise statement - in most cases, one should be producing heat with either nat gas or a heat pump. Long term, I expect a shift to the latter.

Posted By jonr on 04 Mar 2016 05:09 PM
It bears repeating in a concise statement - in most cases, one should be producing heat with either nat gas or a heat pump. Long term, I expect a shift to the latter.

The "long term" is definitely going to differ by location and goals. If carbon emissions is one of those goals, running the napkin math on the state-by-state CPP targets from the EPA is an easy place to start. Most states are going to hit those targets with or without the CPP actually being, just on the ever-improving economics of wind and solar. By the time the subsidies for those fade away in the early 2020s they should have no trouble at all competing against the (also subsidized in different ways)fossil fuel or nuclear sources of electric power. They're already competitive in many unsubsidized energy markets elsewhere in the world

For the first time ever there is slated to be more PV solar capacity installed in the US in 2016 than all new fossil burners combined, and even more than wind-capacity. Adjusted for actualized capacity-factors (the average annualized output relative to the nameplate output) there was still more new gas generation installed than wind or solar, but not more than wind and solar combined. Year on year installations of both wind & solar are on the rise, and accelerating as the prices keep dropping dramatically. In the case of wind, capacity factors have also been increasing dramatically, making formerly marginal wind resource areas financially rational to exploit. On a raw levelized cost basis fossil fueled generation is really looking like toast 5 years out. The subsidies are rolling it out more quickly than it would happen otherwise (just as it has with gas generation over the past decades), but those cost & capacity factor trends would still be in play without subsidy. The CPP is really a stripe on the floor, not a real hurdle.

https://www.eia.gov/todayinenergy/detail.cfm?id=25172

Totally agree Dana. I am just impatient that the electricity grid is still not 0 lbs/MWh. That’s what ultimately needs to happen and coal, gas and oil need to be totally banned before I will be happy. The environmental cost of gas fracking is way more than the 117 lbs/MMTU would suggest. However, I am very proud what Oregon accomplished this week:

1. Took Oregon out of the market for coal-fired power, making Oregon the first state to transition away from coal via legislative action.

2. Doubled the amount of energy Oregonians will receive, so that by 2040, 50% of our power will come from renewable resources such as wind and solar.

3. Committed to dramatically increasing the number of electric vehicle charging stations around the state so that Oregon's transportation sector, a major source of greenhouse gas pollution, can transition to clean, electric energy.

4. Created community solar programs so that the benefits of rooftop solar can expand to even more people, including 10% of new participation being provided to low-income Oregonians struggling to pay their utility bills.

5. Finally, and most importantly, showed our elected officials that there is a broad-based, business community from industries across the state dedicated to reducing pollution and creating a clean energy economy that benefits us all.

And have no worries, we will take excellent care of MTicf too.