Posted By toddm on 11 Feb 2013 01:50 PM
These people made a fireplace unit that qualified for energy tax credits back when (efficiency >75 percent.) http://www.icc-rsf.com/c/iccrsf/file_db/pdfs.pdf_en/Focus_Handout_EN.PDF.pdf It is expensive, particularly after pricing the required custom chimney pipe. It has hvac ducting to tie it to central forced air as well. It's possible to adapt an air/water heat exchanger to make it hydronic output. OWB folks know how to do the math.

On that subject, you can avoid OWB pollution issues by installing a heat storage system. (I.e., the boiler runs flat out heating several thousand gallons of water. Goes out. The radiant system draws on the storage tank. The process starts over in a day or two after the heat storage tank cools.) hearth.com has any number of DIY approaches, most of which seem to involve reusing propane tanks. Or Garn sells systems with major storage. With a boiler that accepts logs, the workload drops more. If you own a woodlot, your cost drops to the point where fireplace efficiency and log construction no longer matter.

My solution was to buy one of the small indoor wood boiler stoves that are common in Europe. My 60k btu/hr Statford Eco-boiler is 70 percent efficient and puts out 70 percent of its heat as hydronic. I couldn't find an online dealer who would export, but I found a retailer on ebay.uk.co who was delighted to help me. Indoor boilers are exempt from EPA certification, but as dana says, some states are stepping in. A vented (nonpressurized) boiler shouldn't require UL certification but it's something you want to check first with your inspector. The stoves have CE or European ratings instead. Europe is light years ahead of the US in biomass technology.

Todd, do you have a link to the dealer for the Stafford ecoboiler. It is one of the ones I was looking at.

WI HANK are you saying your logs are 18-22" in diameter? that would certainly help the analysis.

NRT Rob, yes my logs are 18 - 22" in diameter, hand scribed w/ saddle notched corners. The hand scribe log-home is far from eco-green friendly as far as controlling air infiltration (IMO), from a settling stand point.

ok, then I could believe it being close to stick. most log walls I've seen are half that thickness. very different.

Gents
Thanks for all the input. I am starting to move in the direction everyone is suggesting..
I have another subject that needs a decision, as well....
Where to put the pex on the main floor? Under the floor and between the joists, with aluminum heat dispersers holding it up, and even insulation under that to capture the heat? or
on top of the subfloor, covered in gycrete - which on the surface would seem to be more efficient. But then you have floor covering issues, yes?

Bugzee,
Such a wealth of info from these pros that I am embarrassed to even comment amongst these pros but here goes... I have had great success with a sandwich design with insulation between the joists, bubble insulation on top of that and then used OSB subfloor, laid the tubing between sleepers with aluminum heat transfer plates and then another floor on top. In my case I actually used the top OSB as the finished floor which I cut into 4x4's, and a 1/2"strip of maple between, sanded the $^$%^ out of it and then stained and sealed it. By doing this, I am maximizing the heat transfer by only having the sanded 3/4" OSB on top of the tubing. Sorry that I can't talk numbers WRT efficiencies but logic tells me that it must be about as efficient as as it could get! I have done away with the idea of a wood burning stove as I really don't need it although the experts I consulted (not these fine folks unfortunately) claimed that I would need supplemental heat. I would post pictures to show you more detail but I don't see where it is possible to post pics. If someone could tell me how to post a pic here, great, otherwise give me your email address and I can send you some pics of my insulation, layout and finish. Good luck!

I believe each system has its up and down. and each has its place. I use mod cons all the time, Im just getting into geo, but in the end a heat source is a heat source and will function to spec so long as its installed correctly. I've seen some backwards installs and in fact a lot of my money is made fixing these upside down systems where people use standard water heaters to heat homes. or when they try to use tank less water heaters as boilers. the one main reason I like geo over boilers is that in new construction you can completely get rid of gas in the home, lowering insurance rates and even overall cost of the home.

I've been posting on here about how I'm integrating 3 sources of heat (solar, geo and electric backup) into 3 loads, Fan coils, radiant floor and DHW... for me its a little bit easier to make econ sense as I get many of the plumbing components at cost as well as much of my labor is free. However the right system in the right location can make a good deal of sense! the other things is geo is the only heat source that you can produce 100% of the energy needed. I can make power, I can't make gas, or wood

just my $0.02

thanks again for the input - all good. the reason I was questioning geo is because of all the comments I've been seeing about maintenance and warranty issues. I agree that any designed system SHOULD work right, but there has been many stories about problems with heat pumps, coils, condensers, etc, etc that made me start to re-think the whole idea. Especially given the high start up costs. The geo concept is great for all the right reasons, but the problems listed above gave me cold feet :) I believe you suggested looking at Warmboard, which I have done. I am very interested and have contacted the company to look at my floor plan. I am curious if you used this product ON a slab, or as subflooring only? They do talk about going on top of a slab but do not go into it in detail. The Polaris water heating system seems a perfect fit with Warmboard, but I'm not breaking ground for a couple of months so there is time to do more research.

love warmboard and as a retrofit it might make sense as an overlay. new construction 99% of the time the right answer is to put the tubing in the slab, if the slab is being installed anyway.

ok, this is good. slab has not been poured yet. assuming 2" of bluboard, what is your recommendation on slab (with pex installed) thickness. also, do you recommend an area in the middle as a heat sink?

slab thickness is a structural question. if you are more than six inches thick though, I''d definitely reconsider.

absolutely not to the heat sink question. and fire anyone who suggests it to you.

Posted By bugzee on 18 Feb 2013 02:45 PM
ok, this is good. slab has not been poured yet. assuming 2" of bluboard, what is your recommendation on slab (with pex installed) thickness. also, do you recommend an area in the middle as a heat sink?

For a heated slab in a US climate zone 6/7 location, unless you expect your heating fuel to be getting cheaper over time (not a bet I'd take), there's a pretty good rationale for more than R10  (2" of the blue stuff) under a heated slab.

Folks who like to staple the PEX to the foam prefer XPS (blue, pink, green, whatever), but it's usually cheaper to use EPS (1.5lb density "Type-II" is plenty for most residential applications, but won't support the full weight of a masonry chimney, but then again neither will 1.5-2.5lb XPS)  For non load-bearing residential slabs, even cheap roofing EPS (1lbs density "Type-I") has sufficient compressive strength to support even your F350 with a full load of firewood on a 4" slab.  Local codes may require Type-IX EPS, which has comparable structural aspect to most grades of XPS, but may not be a cost savings.

At even-money costs between EPS & XPS it's greener to go with EPS though (especially at higher R values), due to the comparatively higher environmental costs of the HFC134a use for blowing XPS (~1400x C02 greenhouse potential, just for starters- HFC production has other environmental costs too), relative the pentane (~7x CO2 greenhouse potential) used for blowing EPS.  It's the same polymer, and will be in equal amounts when the densities are equal, but the difference in hit of the blowing agents is huge- two orders of magnitude.  In a sub-slab application anything past the first 1.5" XPS may have a larger lifecyle greenhouse footprint than the energy use additional thickness would offset, but at 0.5% the greenhouse impact you can go a LOT thicker with EPS before it becomes a net-negative from just the climate impact aspect, ignoring the other damages.  Pentane is just much nicer stuff overall.

If you prefer to staple PEX to foam, using multiple layers of foam with the top inch being XPS sheathing works.  In your location, for a heated slab insulated with Type-II EPS there's a pretty good long term economic rationale for R20 under the slab if you're heating with propane, electric boiler, or heating oil, and even with cheap natural gas or wood boilers there's an economic rationale for at least R15.  That's about 4-5" of foam, not 2".  (3" of EPS at any density runs ~R12 in this application, 4" would be R16. Add R5 for the inch layer of XPS for the better staple retention.)

Even for UNheated slabs there can be an economic rationale for R10-R15, but it's over a much longer term.  (I personally wouldn't build anything with less than R10 under the slab in your neighborhood, even if heating with wood stoves and mini-splits.)  If you can find local outlets for reclaimed roofing foam, the very low cost of reclaimed goods makes the argument for ~R25 something of a no-brainer. (It's typically 1/4-1/3 the cost of virgin-stock). Be careful what you're buying though- polyisocynaurate is to be avoided under slabs due to long term moisture retention issues, but either EPS or XPS is fine, even low-density EPS works for less-structural slabs. (Use high density goods under footings, or between the foundation stemwall and the bottom course logs as a thermal & capillary break.)

I tried posting yesterday but my phone and this website do no agree. There have been a few posts between now and then so I know this maybe out of place but I wanted to post it anyways

I hope you will not rule out GEO thermal or heat pump tech in general. Don't judge a technology on its failures. but rather on its success. Learn from the failures and find out what questions to ask the installers and the seller to keep them from happening. dont be scared away by installer trying to things but make sure they have a fix or solution should it fail. and stay a way from people trying to put a bunch of untested ideas in your lap. If I'm trying something new with a client I'm open about it and I tell them that if it doesn't work that I will do X and it return it to a "normal" setup. If they say no thank you the first time I bring it up I don't push the topic and give them a standard working system. So of my ideas and theories have panned out, some have not, But ALL my clients are happy. When the idea didn't work I was right there installing the fix at my cost, Innovators drive progress!

In my mind HP (Geo/Air) is the only true "green" or "renewable" heating and cooling technology. its the only source that doesn't require you to be connected to an external fuel source, be it propane, wood, oil.... You can produce all your own power making you truly independent. Wood take years to grow and LNG or propane require drilling. People are always going to have problems with their hardware, and 75% of the time is because they tried to save a dollar and end up having to spend $5 to get it fixed. My other suggestion is once you find an installer for any product, let them do their job. I have a phrase I use when a client tells me they want to save money by allowing them to help. "$50/hr if I do it, $75/hr if you watch and $100/hr if you help".

I've done a lot of work trying to find the point of diminishing returns on insulation and energy saving things. The fact is its very dependent on what your own goals are. For my commercial clients they don't want a product if it doesn't pay off (with out incentives) in under 10 years, residential is 15-20 years. So do some math work, learn a little bit of the science and figure out what you are trying to do and they will 9 times out of 10 dictate how you do things.

"In my mind HP (Geo/Air) is the only true "green" or "renewable" heating and cooling technology. its the only source that doesn't require you to be connected to an external fuel source"

If you don't count refined, expensive electricity as a fuel source.

Maybe you were thinking "geo" thermal, like "Old Faithful"?

I let my customers help all the time. There are many jobs that require modest skills and I don't need the exercise.

GSHP payoff in 15 years, residential? Maybe if your fuel is double the national average.

GSHP payoff in 15 years, residential? Maybe if your fuel is double the national average.

Or you don't have access to natural gas in a very cold climate.

Heat pumps are the ONLY source of heating AND cooling that you can power totally off grid. No i'm not thinking of Old faithful.... come on really? You can generate AND storing heat with solar thermal but doing so in any large amount is far more expensive than any PV system capable of powering a battery bank capable of running a HP. Even if you are connected to the grid you can install solar to really provide as much power as you use. I also do systems where solar thermal works all day to charge a tank with heat and that tank last though the night to heat the house and the HP will come on the next morning once the sun is up. providing a true Netzero system. But you can never make you own natural gas, propane and even wood takes 100 years to grow...

I refuse to let my clients do work with out signing a document declaring that they are voiding the warranty. They are not trained and me spending hours looking over their should to make sure they make a connection right or don't poke a tube doesn't save them or me any time or money.. And if things go wrong the blame game starts. its better to let pros do their job.

Every thing I install has an organic ROI of <20 because I don't mark up 30%. I sell Cost +10% & labor. Im more worried with my clients and making a difference then selling stuff at crazy prices...

Batteries & PV are more cost effective than low-temp thermal for heating energy collection & storage in typical off-grid installations?

Really?!

Show your math!

My gut-math sez mid winter in a cool climate when it's really cold your mini-spit might be averaging a COP of 1.5-2, and the solar-uptake is at it's annual lowest, but getting maybe 10% net efficiency from PV->battery->inverter-out if you do a truly great job engineering the system. If you're optimistically saying the COP=2, that's a net 20% efficiency on that meagre solar uptake. A typical flat-panel system storing 100F water suitable for slab-radiant heating in a cheap DIY oversized buffer tank can beat that by 2x on efficiency, without a huge system cost.

If you've built the off-grid thermal storage + PV heat pump systems, you can perhaps document the components that went into it, and the approximate location on earth where it was installed, for climate comparisons?

Also, wood grows on trees, and it doesn't take huge acreages or the cited century of growth to be sustainable for the modest thermal loads of a 1500' IRC2012 code-min house. (Details on how many acres depends on local climate though.)

In agricultural areas people can and do make their own methane, but it's not cost effective for single-family sized homes. Dairy farms can typically make enough methane to power on-site generators that make it a significant profit center for the farming operation in areas where electricity is expensive.

Posted By Dana1 on 21 Feb 2013 11:52 AM
Batteries & PV are more cost effective than low-temp thermal for heating energy collection & storage in typical off-grid installations?

Really?!

Show your math!

My gut-math sez mid winter in a cool climate when it's really cold your mini-spit might be averaging a COP of 1.5-2, and the solar-uptake is at it's annual lowest, but getting maybe 10% net efficiency from PV->battery->inverter-out if you do a truly great job engineering the system. If you're optimistically saying the COP=2, that's a net 20% efficiency on that meagre solar uptake. A typical flat-panel system storing 100F water suitable for slab-radiant heating in a cheap DIY oversized buffer tank can beat that by 2x on efficiency, without a huge system cost.

If you've built the off-grid thermal storage + PV heat pump systems, you can perhaps document the components that went into it, and the approximate location on earth where it was installed, for climate comparisons?

Also, wood grows on trees, and it doesn't take huge acreages or the cited century of growth to be sustainable for the modest thermal loads of a 1500' IRC2012 code-min house. (Details on how many acres depends on local climate though.)

In agricultural areas people can and do make their own methane, but it's not cost effective for single-family sized homes. Dairy farms can typically make enough methane to power on-site generators that make it a significant profit center for the farming operation in areas where electricity is expensive.

I think you missunderstood me. Im not say geo thermal replaces solar thermal. IN no way is that true. what Im saying is while you can do solar thermal, in reality you can only store enough heat in a tank for at most a day maybe a day and a half if in the middle of a storm here in colorado. However you can store power in batteries for a lot longer if needed. The idea is that you use your solar thermal system as much as possible. then the system could start to draw on the batteries for power for a heat pump. in a grid cut out or natural disaster where gas is shut off and the grid goes down. solar (both thermal & PV) is going to be one of the only ways to keep you home warm indef. Trees still take many years to grow and require a climate that can support them. it also require a whole other set of processing to make it ready for heating. I would love to see dairy farms in the high mountains or in the very cold parts of the world. you just dont. I'm talking more in the sense of a system that could provide self reliance and there for a more renewable system. Wood heating and even methane requires some type of burning. where heat pumps and solar thermal require none. Once you have the system installed you don't have to pay for a fuel from any one, it also doesn't require you to tend to it every day like a methane system would or even a wood burning system would. Where I live trees are very sparse but open sky isn't its to dry here to keep pines growing on the planes and would require way to much water todo.

Also using other types of batteries (LiFePO4's) you can get much more life. for much less money. the cost per batteries is higher but you don't need to replace it, refill it and you can get 50% more power out of a LiFeP04 then you can out of even a Deep cycle in a charge/discharge cycle

i should also mention that i get a lot of stuff at cost, PV, themral, batteries, electronics, tanks. heat pumps, pluming.... Im not against sharing these benefits for the right reasons. I do it all the time. I place an order, ship it to someones door and they do the rest them self and pay far less than you would if you bought it on line. I dont see the need for me to charge 30% to spend and hour on the computer placing and order I will never have to touch.

One fuel source I use and am working to make my home totally self sufficient is biodiesel from algae . I have complete my small scale test and am working on gather parts for full scale production. the system even reuses the CO2 produced by the generate in the growing process of the algae. to meet all my power and fuel needs for my trucks and cars (all diesels) I need a little over 1/2 acre to produce enough fuel each year. this also provides a source of compost for my garden and the only things I need to buy are lye and menthol. However, after the initial perchance 75% of the menthol in the system is recoverable. The start up cost are high but I look at it this way. once I get going and can produce my own fuel, most of my food, heat and power I have very little need to work once the house is paid for. in the long term will save me far more money then working my ass off for a the rest of my life! :)

Clearly no one model fits every climate and location. Frozen algae ponds don't have any better output in high algae arid mountains than non-existent dairy farms those locations either, eh? The solar energy collection efficiency of algae pretty pathetic next to PV in ANY climate, and burning the output product of the algae in a ~20% efficient Rankine cycle piece o' crap makes the sun-to-wheels efficiency truly pathetic next to PV + electric vehicles.

But everything has a place where it's a good/better/best and most economic fit. While I too am a fan of heat pump technology, it's not always the best fit, most economic, or the greenest. The lifecyle environmental hit of the refrigerants should not be ignored, any more than the sooty particulate local pollution issues with biomass and biodiesel fuels should be. But an 80%+ efficient wood burner is a pretty cheap & green heat source where the wood can be harvested sustainably compared to the lifecycle hits from batteries, PV, & heat pumps.



Since bugzee isn't a Nepali yak herder in the high Himalaya, I suspect the woodlands of his northern WI location will sustainably support the annual heating loads of quite a number log houses of this size (when used in reasonably efficient woodburning appliances), and it would have a miniscule net lifecycle carbon footprint compared to just the R410A charge in a mini-split or GSHP, let alone the rest of it for an off-grid solution. But yes an R410A heat pump has a much lower hit than heating oil/propane/gas use, provided the power source is similarly low-carb, like the heavily hydro & wind supported grid in his neighborhood.

Move the same house to the coal-fired grid in WY/UT the math would work differently, putting a much higher net COP constraint on the heat pump to break-even on net carbon emissions with condensing natural gas. When CO2-refrigerant heat pumps become widely available the lifecycle gap between biomass & heat pump will narrow dramatically, but will probably never close completely.

I think that moisture retention in a heated slab is irrelevant with vapor barrier in place a heated slab in cold climates can't retain moisture sans high ground water with a whole other set of issues. You will have to do the math for me again, as R10 in the field of the slab seems more than appropriate for low temperature radiant floors. I certainly could go for 20 or 30 at the perimeter in cold climates like mine.

EPS is dandy if you can keep it together until covered. We find EPS a bit like standing on a coffee cup. Not so bad if you use Rob's CreteHeat with increase tensile strength.