System's Architect

Rod Stucker

Looking for help with integration of a solar thermal system with a 100% variable ground source heat pump, desuperheater, ERV, and ground to air heat exchanger for a hydronic-radiant floor heating and cooling system with 2nd stage fan coils for regulating humidity and staying above dew point temperature. This system will include a super-insulated 4,000 gal concrete cistern for thermal storage, and a similar sized cold water concrete cistern that will be kept at ground temperature.



Just read Dan's "Pumping Away" publication and would like to incorporate those concepts into a multi-source HVAC system for a zero net energy home including passive solar radiation. Please refer to the first few pages of the executive summary contained in the attached file. If possible, I would prefer to minimize use of heat exchangers for an all water system using a drainback tank (possibly integrated with the thermal storage concrete cistern). The heat loss for the thermal energy storage system will be minimized via super-insulation of the concrete cistern.



Programmable automated controls will be utilized for this integrated HVAC system.

Rich_49

Good ideas

Please visit this group , https://www.linkedin.com/groups?home=&gid=4967184&trk=my_groups-tile-grp . If you have an aversion to LinkedIn contact James Schenck from Thermal Battery Systems Inc , Energy Dynamics in Bozeman Montana .

Here is a short list of others that could certainly help , Robert Bean , Mark Eatherton , Rod Hyatt , Unless of course you are Rod . This is a well thought out paper you have provided and some will ask who you are , let me be the first . Your ideas are sound , I just wish there was even less dependency on mechanical equipment , it is possible you know ?

SWEI

I'm curious about the project

most particularly the overall ROI.  Is this actually going to get built with someone's hard-earned money?  I've worked on several sub-20k heat loss designs recently and we couldn't even come close to justifying the cost and complexity of a heat pump in our high mountain southwest climate (similar to some parts of southwest Idaho.)  With good passive solar orientation, R30 walls, R50 roof, and commodity double pane windows (well below Passivehaus standards) an electric resistance boiler costs about $1,000 to buy and about $50 per year to operate.  Even the cost of putting the tubing in the slab was marginal, but we and the owners both felt the future options of alternative heat sources and cooling made it worth doing.  We didn't even bother with active solar space heat in the first phase, just DHW preheating (with a single flat plate collector and pressurized drainback, simplest system we know of.)



I'd love to design and implement the controls on a project like this, but it would take a special client for sure.  Tekmar makes nice stuff, but for anything complex we find that fully programmable DDC usually costs about half what a fully-loaded multi-module Tekmar system will.



I'd suggest you take a serious look at your plan to embed emitters in the building thermal mass.  We try very hard to avoid that whenever possible, and strongly prefer a high mass building paired with low mass emitters.  If you do embed in concrete, stay away from 7/8" PEX (long story behind that particular nonstandard product, BTW.)  I usually suggest 3/8" PEX with 100' loops, giving more precise control over slab temps and making an easy job of tube installation.



Best of luck with the project -- it is quite interesting.

hot_rod

lot of work putting that together

nice work.



A few comments, I wonder about the 85% savings with ECM circs, seems a bit high?



Check on your description of braze plate HX, sounds like you are describing a tube and shell?



I question the actual performance of the hybrid collectors. Unless you have a large demand for that thermal energy, or a huge storage that can keep the fluid temperature to those PV modules, I wonder how much that adds? Along the lines of co-gen units. Unless the thermal load is high not sure the $$ payback is there?



The control-ability of those high mass storage is the trick. That one looks like they insulate the mass from the slab? The slab right on top of the sand can be a little too much during cooling seasons.



Keeping the heat in the concrete tank will also be a challange, seems 8-10" of insulation is required?

Rich_49

HR

he stated capacities between 4 and 5,000 gallons with an R value around the tanks of R150 .  What I believe will be missed in this set up as opposed to other Thermal Battery systems is a latent capability and the initial investment .  This really does exploit how much better Solar PV panels should perform though . Seems that lately much stuff is rearing its head showing how our industry can enhance and outperform what everybody else has been peddling in this game that seems to be run by Duie ,Cheatem and Howe . 

SWEI

PV-Therm

If this is similar to the SolarZentrum design, it combines an unglazed thermal collector with PV.  This creates a very efficient thermal collector at low ∆T conditions at the cost of severely limited output at low ambient conditions (winter.)  The upside is that the unglazed collector allows night sky cooling during the cooling season, which (with proper controls and buffering) could well eliminate the need for refrigerated cooling in the Boise climate.

Rod Stucker

Professional Colleagues

I am familiar with James Schenck and Rod Hyatt, have spoken with both of them. My approach is unique regarding the size and location of the thermal energy storage system and the programmable automated controller (PAC) that integrates the solar thermal system with the water to water GSHP, Desuperheater, and ERV/HRV.

Rod Stucker

Adding Value via Innovative Construction Management

I have always been concerned with costs, and remain so today. One of the key components is reduction of mechanical requirements through passive house design. In addition, due to relatively low peak heating and cooling loads, I am considering using the footing trench for placement of a hydrated sand bath with slinky coils (refer to attachment), mostly for use with cooling but it could also be used in heat mode when necessary with a reversible GSHP. This can substantially reduce installation costs. I have located a 100% variable water to water GSHP with COP over 7.0 for a 2 ton unit that is being developed by Enertech in conjunction with their Sweedish partner, and should be ready for use in about 12 months. Any way I look at it, the costs of a solar thermal system integrated with a water to water GSHP, Desuperheater, and ERV/HRV is spendy. Hence, I am looking at ways to reduce construction costs using ICF big block technology, experienced crews, and some homeowner sweat equity programs to make it feasible.



Cost of ECM and profitability is based on actual cost of pumps and MIRR. Your estimate of EPS insulation is accurate, though polyiso can provide the same R-value with half the inches of insulation. The actual size of a 4,000 gal. concrete cistern is actually smaller than one would think. We will be using water, not sand as our thermal energy storage medium, and then insulating it from our concrete slab so that we will have better control of heating and cooling, etc.

Rod Stucker

3/8" PEX vs. 7/8" PEX

I would like to learn more about your preference for using 3/8" PEX? I have considered using 7/8" PEX since I can go with longer circuits and deliver more BTU's which reduces my Delta T and should make the radiant floor heating and cooling system more efficient. There are a lot of differing opinions on this subject, but I have yet to hear a logical response in regards to the laws of physics as to why 3/8" is preferred over 7/8" PEX??? However, I am open to any suggestions that you or others may have.

Rod Stucker

Initial Investment

Using ICF technology, we can quickly build and insulate a concrete cistern, so labor and material costs are minimal. Hoping to develop an integrated system with minimal heat exchangers using 100% water. That should further reduce costs and improve thermal efficiency. Minimizing heat loss and Delta T are the keys for a relatively low temperature radiant heating system, at least according to my calculations. Integration of the solar thermal system with a 100% variable water to water GSHP with COP of 7.0, Desuperheater, and ground to air heat exchanger with 97% efficient ERV/HRV, should allow us to achieve zero net energy, hopefully in sustainable fashion as described in earlier wall response.

Rod Stucker

Sunvelope Solar Technology

I have recently been looking at Auguste LeMaire's Sunvelope Solar Technology. It is a very innovative technology approach which looks like it could help simplify design of the solar thermal system and integration with other components:



http://www.sunvelope.com/

SWEI

Sunvelope collector

Design looks interesting,  No spec sheets on their site that I could find, but they just got OG-100 certified so we have the performance data.  Looks like they perform pretty well at low ∆Ts, but performance falls off pretty severely as the ∆T increases.  Not so good for cold climates.



The system diagrams look fairly conventional.



What are you actually trying to accomplish with this system?  Is it a research project?

hot_rod

good catch on performance

of that collector, it does drop quickly at category "D".



You can plot the performance of the collector across all operating conditions using that SRCC data, the method is explained in this idronics



issue.http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_3.pdf



That collector design looks a lot like the old Olin RollBond built in the 1970's. An Italian company produces a similar design.



I like the machines he has designed to fab them, odd dimension 21 square feet? 7X3 perhaps?

SWEI

PEX sizes

First off, 7/8" is not a standard tubing size -- most of it seems to be sold by a certain online supplier with a penchant for questionable designs and a propensity for lawyering.



In North America, PEX is sold in Copper Tube Sizes - the nominal size refers to the outside diameter of the pipe, and the inside determined by the SDR 9 standard.



For residential scale radiant, 1/2" tubing is by far the most common size used.  Conventional wisdom recommends 300' loop lengths, but even those have higher head losses than we prefer to work with.  Like high R-values, low friction is a gift that keeps on giving, saving you a little bit of money every hour of every day your pumps are running.  I try to keep my loop head under 4 ft, which allows me 0.5 GPM on 100' 3/8" loops or roughly 0.8 GPM on 150' 1/2" loops.  Either is short enough to put small rooms on their own loop, which allows us to balance the system much more easily than longer loops will.  3/4" PEX is ideal for larger spaces like warehouses and commercial garages, but in general the smaller the room, the smaller the tube size we need.  3/8" PEX is easier to install than 1/2", and we find 100' loops to work best on many of our projects.  If you're doing a dry floor system, 3/8" also allows a slightly lower floor profile.



Why will longer loops allow a lower ∆T?  In my book, they generally result in difficult to balance systems that require far too much pump head.

Rod Stucker

3/8" vs. 3/4" PEX

I am not so much concerned about longer runs as I am increasing delivery of BTUs. I am leaning towards 8-9" spacing with clockwise in and counterclockwise out layout. My understanding is that for both radiant heating and cooling, you want the ability to OPTIMIZE delivery and BTU transfer rate which is provided by the larger volume and surface area provided by 3/4" PEX. I am also leaning to putting bedrooms and less used rooms on a different zone, while the south facing family room that gets solar radiation will be on a different zone.



I haven't calculated the head loss for the PEX radiant tube system yet, but I have calculated the head loss for the geothermal field loops. By going with relatively short runs (400' if I remember right) using 1.25" HDPE tubing, our head loss drops to 0.89/100 ft. I couldn't agree more that design is the most strategic means of reducing head loss and power consumption.

Rod Stucker

Simplicity of Design & Freezeproof Characteristic

I am intrigued with the ability to reduce the need for heat exchangers and use 100% water for a relatively simple design and installation. It appears that the only heat transfer loop we will need will be for the DHW. Since we are planning on using a desuperheater, we may never need an alternative heat source for DHW. However, when the sun is shining, we won't be running the reversible heat pump, so an electric on demand water heater may be required?? unless we can do that with the GSHP?? I am planning on plumbing the majority of the solar thermal system with PEX and have it circulate through the DHW tank first, then on to the solar thermal energy storage tank. Not sure yet of the best design approach?? Obviously I would like to incorporate all of the advice listed in "Pumping Away" by Dan.

Rod Stucker

Zero Net Energy - Passive House Model Home (ZNE-PHMH) Design

Our objective is not so much to conduct a research project as it is to demonstrate state-of-the-art technology via our ZNE-PHMH. The first one will be built in Boise, ID. Interestingly, the Sunvelope solar thermal collectors were invented and are being installed in the Intermountain West and have also been installed in Michigan, both of which are relatively cold climates. I will look into your comments and ask Auguste to respond.



Since most general contractors are not early adopters of innovative and/or emerging technologies, we will be showcasing leading technology directly to homeowners and then contracting to build new homes. We will then train contractors to build these smart homes and distribute materials and equipment manufactured by our industry partners.

hot_rod

be careful

with large diameter tube, especially on small, bedroom zones. With short loop lengths your flowrate may drop below 2fps. This makes air elimination tough, and heat transfer can be a problem if the flow rate drops too much.



The RPA suggests 500 foot loops for 3/4 and 1.2 gpm flow rate.



Also 3/4 is tough to make tight loops.



If you are going to zone bedrooms and small micro zones, 3/4 may not be a good choice.



Tighter tube spacing allows lower fluid temperatures which is huge with solar or heat pumps. Here is a graph to show that relationship. My next radiant slab would be all 6" OC!



The volume of fluid in the tube has little to do with the heat transfered.

hot_rod

I wonder

what the over-heat protect mechanism is for that direct solar?



If you size the array large enough to cover some of the heating load, beyond the DHW load, what happens in the summer months and during low DHW loads?



Most flat plat collectors stagnate well above 300°F.



Certainly you would not want pex anywhere near those temperatures.



I see that he offers glycol and drainback methods. You may be better served with DB if you have lopsided loads as mentioned?



I applaude you concept and project, but no need to re-learn some of the solar "lessons learned"



In fact grab Tom Lanes book "Lessons Learned" to help avoid some costly mistakes with the solar design.



Here is my experience with pex and solar. It sounded like a gun shot when it let go.

Rod Stucker

Drainback System

Yes, Auguste also recommends a drainback system. I am thinking it may be best to use the concrete cistern, our thermal energy storage, as the drainback tank. He has a system setup using PEX with some copper where it is needed to avoid problems with over-heating due to stagnation. I hope to be able to develop a redundant circulation system and fail-safe mechanisms via our programmable automated controls, where once it reaches a temp. threshold the solar thermal system shuts down and the water drains into the drainback tank/thermal energy storage tank.

Rod Stucker

Circuits & Zones

I am not sure I understand your comment about volume of water/BTUs having little to do with heating and cooling?? The more thermal energy you can move, the more efficient will be your heating and cooling system.



We certainly agree on the importance of spacing. With 3/4" tubing, I am thinking that 8" spacing should be sufficient. The only area I am concerned about making tight turns is in the center of a space as we wind back out. Since the entire structure including interior walls and vaulted ceiling will be concrete and function like an energy storage medium, I am thinking of running the radiant tubes right next to the walls.



In regards to circuits and zones, we will optimize our circuit lengths as you suggest, e.g., 500' for 3/4". That means that we may put a few rooms and hallways, etc., on different circuits, but on the same zone. I hope to have at most, two zones per floor, primarily to deal with solar radiation on the south side of the structure. I personally prefer to keep bedrooms at a considerably cooler temperature as I sleep better that way!

Rod Stucker

The Simpler the Better

Aside from eliminating heat exchangers/coils except for the DHW system, I am not sure what else we can do to simplify our design? I am open to specific suggestions. However, I am not a plumber or a mechanical engineer. As you have no doubt surmised, my focus is on systems architecture.



We will be dependent upon temperature sensors and programmable automated controls for both safety precautions and fail-safe mechanisms.



The ground to air heat exchanger for the ERV/HRV is merely an earth tube in which air flow should avoid any concerns for mold or mildew. This technology has been successfully implemented and we will provide access for cleaning the earth tube if that becomes necessary.



I tend to prefer using valves for zones instead of multiple pumps for our hydronic-radiant delivery system.

Rich_49

400 '

ground loops with a low head loss like you state can be a scary thing , have seen many shorted ground loops end up with disastrous results . Longer loops with higher flow have a higher Reynolds number and provide better heat transfer . Don't doom your hard work on the thermal storage aspect by cheaping out on tubing and drilling . If in fact you will use the thermal storage tanks why even bother with the ground loops to begin with ? You could simply charge the tank/s with the solar possibly up to 160* and mix down to a real nice number for the HP and when the sun is not out you still have a monster mass of fluid quite possibly still at a higher temp than the loop field would have given you .  Is it a must to locate the tanks below ground ?  These tanks are sweet ,  http://cocoontanks.com/ , support the drainback approach also . 

 The investment and PITA of 3/4 tubing over 1/2 bypasses the point of diminishing returns by a good amount . Keep the loops shorter and tighter and the SWTs low . 

hot_rod

volume vs flow and temperature

true you can store more energy in more volume.



Heat transfer is accomplished by flow rate and temperature difference ∆T.



It you are talking stored energy, volume buys more stored energy.



Transfering energy, flow and temperature change are the main drivers.



Rate of Heat Transfer= 500X flow rate (∆T)



assume a 300 foot circuit of 1/2 pex about 3 gallons of fluid

1.5 gpm flow rate, 120F supply 100F return



500 x 1.5 X 20= 15,000BTU/hr.



Changing nothing but the tube size, and the volume of fluid, will not change the heat transfer rate that much, perhaps a small amount due to increased surface area.



Pump a loop so the flow rate is between 2-4 fps is a common industry standard. Larger tubes can move more energy because they allow higher flow rates.



It will have more energy available to transfer in the additional volume.



Of course with 3/4 tube you could at least double the flow rate and transfer more energy.



3/4 pex for example needs a flow rate of 2.3 gpm to provide 2 fps velocity

At 4.6 gpm you will be moving 4 fps.



Flow a 500 foot loop of 3/4 pex at 2 gpm and at 9" on center you could expect a floor output over 50 btu/sq. ft./ hr. I can't imagine any residential loads even close to that?



Spread to 15" on center and expect 30 btu/sq. ft./hr. But wide spacing allows for uncomfortable striping. RadPad calculations.



That is why the 3/8 or 1/2 diameters 6- 9" on center are adequate and much easier to install.



If you go with 3/4 pex, install it on a warm sunny day. It's a gnarly tube to uncoil and install when it is cold.

Rod Stucker

Both Heating & Cooling Loads, Low Delta T

What you are saying about heat transfer I follow and agree with according to the laws of physics. Thanks for the math calculations.



However, we are using the same radiant system for both heating and cooling. The 3/4" PEX design with 8" spacing is primarily for the cooling mode which is much less efficient than the heating mode. In the cooling mode, the 3/4" PEX will allow for increasing performance substantially compared to the 3/8" PEX since we will be "extracting heat" rather than delivering it. Then there is the objective of minimizing Delta T, which should be much easier to accomplish with larger sized (more volume) PEX that can carry more BTUs at lower temperatures than is possible with smaller sized PEX.



Ideally, I would prefer to put the cooling tubes in the ceiling. However, that would be costly. Instead, since we are using concrete floors in an all concrete structure with super-insulated exterior walls, the medium thermal conductivity of the concrete should allow for releasing some of the heat through both the top and bottom of T-beam and slab structure of the ICF panel flooring/ceiling and vaulted roof. There is no where else for the heat to go.



Subject to providing proof of concept, using the heat capacity of concrete (we are looking at some very interesting concrete, pozzolan and other green concrete mix designs that substantially increase heat capacity while providing slow release of thermal energy) the Portland Cement Association calculates that we can conserve up to 44% of our energy for heating and 32% of our energy for cooling (refer to thermal mass attachment). We are obviously looking forward to validating this information which doesn't appear to be included in the modeling and simulation software that I have been using (BEopt). I am sure some of you may have access to more sophisticated modeling and simulation software such as TRNSYS?? I would love to get my hands on that software or see it incorporated into the BEopt program for the benefit of the average Joe!



As can be seen from the increase in GPM, from 4 to 8, for going with 1" vs. 3/4" size tubing, the increase in heat transfer is substantial. Though this illustration is primarily for geothermal tubing, obviously the same would apply to hydronic-radiant tubing for use in both heating and cooling systems. Makes me think we should use 1" tubing to drive down our Delta T and increase responsiveness of the radiant floor system. However, will this lower Delta T decrease our heat transfer even if our flow rate is doubled from 4 to 8 GPM? Of course, the larger size tubing also reduces our pipe friction, thus minimizing head loss.



As Hot Rod indicates, the 1" size PEX is probably overkill, but using the same GeoPro software for calculating head loss, I have attached PDF printouts that include Reynolds numbers and increases in flow rates (6.5 GPM for 3/4" and 8.0 GPM for 1") that can be achieved. Though these are for geothermal HDPE applications, I would think that PEX tubing would perform similarly??



Regarding heat transfer rate, the 3/4" tubing at 6.5 GPM results in a velocity of 3.6 fps, Nu = 141.23, h = 649, and a headloss of 7.74 ft/100'; 1" tubing at 6.5 GPM results in a velocity of 2.29 fps, Nu = 115, h = 422, and a headloss of 7.74 ft/100'; and 1" tubing at 8.0 GPM results in a velocity of 2.82 fps, Nu = 139.01, h = 510, and a headloss of 3.83 ft/100'.

Rod Stucker

Ground Loop Calculations

I think I follow what you are saying. My ground loop calculations were performed using the online software provided by a reputable software company developed by geothermal engineers whom you may know (GeoPro - refer to attachment for two flow-rate printouts using 1.25" tubing).



http://geoproinc.com/resources/calculators.html



I follow you on the heating mode, but it is always nice to have some redundancy. Having said that, I am most interested in geothermal for the cooling mode. Since we are looking at installing our field loops in our footing trenches, it is a minimal cost. Nevertheless, if we put a cold water tank in separate from our thermal storage, as you say, we may not need the field loops?? Until we can validate that, I would rather be safe than sorry.



Though 4,000 gal. of thermal energy may seem like a lot of thermal storage, as the Delta T increases, the heat loss increases proportionately and can rapidly deplete our thermal battery. One interesting side note, if we ever have excess thermal heat, we could use our geothermal field loops as a heat dump in the Fall when it starts getting cooler. It makes for a very interesting thermal battery system that I have seen James Schenck and others use in their designs. We could then deplete the thermal energy from the soil prior to the summer and use it for cooling if that was necessary. With cool air flush and our ground to air heat exchanger, I expect our peak cooling load to be minimal for our desert environment here in Boise, ID.

Rod Stucker

Cocoon Tanks

Thanks for the lead on these super-insulated tanks. I like the design, but the larger volume tanks are relatively tall which increases surface area exposed to the environment. For placing in conditioned space, these tanks could be ideal for an insulated utility room. I like the idea of underground concrete cisterns simply to conserve space. It also keeps our coldwater tank at ground temperature. The further deep in the soil we go, e.g., 8-16', the cooler is the soil temperature with less variation due to solar warming.



Got a phone call from Rod Hyatt regarding to Cocoon tanks. He told me of an experiment that they conducted with a relatively tall cylindrical tank they buried in the ground, filled it with 160 F water, then let it sit for 9 days. They lost only 10 F during that period with only R-40 of EPS foam insulation and a Delta T of 110 F. Very impressive! Makes me want to see that replicated and then reconsider going with R-150 which may be overkill. We had an interesting discussion about the lack of conventional R-value calculations to accurately model heat loss, either buried in the ground or in conditioned space. I am of the opinion that due to the heat transfer of water vs. air, the latter in a conditioned space would perform significantly better.



I am looking forward to seeing more data from Rod Hyatt and the Cocoon group. My only concern is the cost/gal. for purchasing and shipping insulated tanks vs. building them using ICF technology.

hot_rod

got it

I was involved with some radiant cooling slabs in Utah back in the 1990. Granted they were in a mountain climate with low cooling loads, but they were installed with the early rubber tube RadiantRoll product, about 1/4" ID!



The main complaint, as they were both commercial buildings with office personal , was the cold feet issue. Folks sitting at desks ended up with rubber mats under them for some insulation away from the chilled slab.



Ceiling radiant or emitters like the Zehnder products would be sweet, if the budget could allow.



My last word of caution would be to not install products that are not listed and approved for solar. Many of the system failures in the 70s, 90s and even 2008 era were caused by product failure. Plumbing and hydronic products are not up to the task for solar.



I've been installing and servicing solar since the 1970's and I am in contact with a lot of designers and installers in my current position as a trainer, too many horror stories out there, still.



We lose a lot of customer confidence when systems fail or are obsolete several years after they are installed. Both product failure and poor installation workmanship, continue to haunt us, it's worth doing right.



There are plenty of domestic solar products and components available with 30 plus year track record, just a thought.



There are a number of engineers i work with that could do some modeling for you. Or maybe NREL would take it on as a research project, they have the knowledge and staff to do that model.



Have you considered PV to thermal with resistance elements?

SWEI

I would prefer to put the cooling tubes in the ceiling

However, that would be costly.



Costly?



Your design seems to be a cost-no-object approach to extracting the last 3-5% of possible energy efficiency from a dwelling.  While this is a noble and quite interessting goal, it is not cost effective by any stretch.



Pareto Principle still seems relevant to the world most of us inhabit.  Spend another couple bucks a square foot, move your tubing out of the thermal mass, and you'll end up with a much easier to control system.

SWEI

Zoning with the sun

is how we prefer to manage things.  We also zone for wood stoves, large western exposures, and intermittent occupancies (guest rooms, workshops, etc.)



Proportional zone valves will be critical, especially if you elect to leave that tubing in the slab.

Rod Stucker

PV to Thermal via Resistance Elements

With the low costs of PV and prices expected to drop another 30% by 2016, I have looked at it briefly. I have also looked at Echo/Sun Edison's PV/T technology which from a science standpoint should be very efficient, but they have been slow in rolling out their product and have been making several modifications.I am actually intrigued with using PV to power our GSHP with COP 7.0, e.g., 700% efficiency. It would be ideal if I could compare that efficiency with electric resistance to determine which is superior?? Any ideas? I think it might be tough to compete with the efficiency of these new 100% variable GSHPs.I hear you loud and clear on going with solar approved equipment to avoid problems. Like you say, we need to learn from the mistakes of others.

Rod Stucker

Thermal Mass is an Advantage via Systems Architecture

We may be able to accomplish the same thing via thermal mass, e.g., concrete floors/ceilings in which we are inserting our radiant tubing. Some of the insulation of the ICF panels will make this more difficult, but it will be interesting to observe. We could remove the insulation on the ceiling side of the ICF panels, but not sure yet if we will need to do that???



Leveraging thermal mass, which functions as a thermal energy storage device, is a key strategy to conserving as much as 40% of our energy. I hear you in regards to cost, but if we are already building a concrete structure, we can install the radiant tubing for minimal cost, particularly through sweat equity programs. Reducing our solar and mechanical requirements is the key to reducing our costs. As already stated, if we can reduce material and labor costs through state-of-the-art construction management, our systems architecture approach should help us reduce costs. It may seem like we are not sparing any cost, but that is not the case if we can reduce our peak heating and cooling loads, and subsequently reduce our mechanical requirements. I just wish we had better modeling and simulation tools for these types of integrated HVAC systems focused on hydronics.



I am mostly concerned about the costs of the programmable automated controls (PAC) and home energy management system. Still, if we can reduce labor costs by up to 50%, that and sweat equity programs will offset much of our costs. If we can get a production builder on board, we could potentially purchase materials and equipment directly from the manufacturer which would further reduce costs. Again, this an advantage of our systems approach.

SWEI

Thermal mass is a good thing

and I'm not suggesting you reduce or remove any of it.  I am saying that when you embed your emitters in the thermal mass, the system becomes much harder to control. 



The most common problem we see is overshoot from winter sunshine.  If you pour heat into that slab at 4:00 AM to keep it (and the room air temp) at setpoint, the morning sun will come in and raise the space temp.  When you turn off (or throttle down) the heat source, the effect will be delayed by several hours due to the thermal mass, resulting in baked occupants.  We have developed mitigation strategies for this (moving OAT sensors to the north end of the east wall to anticipate the solar gain, embedding slab sensors where AM sunshine hits them first, etc.) but the best answer is to separate the emitters from the mass.  This gives you far greater control authority, increasing both occupant comfort and energy savings.

hot_rod

ICF

I have done a number of jobs with various brands. I have several projects at my own place here in SW Missouri. I'm having problems with the in-ground ICF being eaten away by bugs? I am not sure if the warm temperature from the radiant slab contact, moisture, noise, ?? Something attracts some burrowing insects to ICF as well as the blue or pink boards.



I spoke with one local ICF supplier that had lived in Australlia. He indictate they wrap all the in-ground ICS jobs with a stainless screen type of material, down under. Some versions have waterproof membrane included.



Wonder if you have any experience in the dry western areas with this? The builders I worked with in Utah tried ICFs 20 years ago and have all moved away from them.



I did a small in-ground pool with ICFs and it is heated with a radiant floor. I should check on that job someday , it's been in service about 9 years now. I threw in some aluminum transfer plates also.



I've heard a Borate treatment helps, but needs to be retreated from time to time.

Rod Stucker

Solar Radiation, Avoiding Overshooting & Automated Shades

I am aware of this issue, all the more reason to enhance responsiveness to solar radiation via temperature sensors and programmable automated controls. If the temperature of the concrete can be controlled including turning radiant heating off in anticipation of solar radiation, then we should be able to avoid overshooting. In addition, if it gets too warm, we can merely use automated exterior blinds. I am intrigued with using the latter in conjunction with home automation and retaining heat when the sun goes down by closing the window shades. I have been informed by glazing engineers that in their configurations, the automated shades and low-e coating on the exterior glass resulted in a lowering of the U-value by 0.03. For HP windows this is very impressive! Not sure yet how spendy the automated shades will be?? It is possible they could be powered by very efficient ECMs. This would probably be a luxury option today, but probably not in the future.

Rod Stucker

Durability & Waterproofing of ICF Materials

I have never had a problem with bug damage to ICF foam blocks. But chickens caused considerable damage. Maybe the chickens were after the bugs Thanks for the photos.



Most ICF builders are coating the foam exterior with a waterproofing or waterdamping membrane these days. My first ICF home was built in 1990 in Draper, UT. They used an asphalt coating back then, but only for the underground section of the foam. Rod Hyatt says they are now using a better waterproofing coating (similar to PVC) and I have also seen some builders use a 15 mil vapor barrier.

Rod Stucker

Calculating & Modeling Heat Loss

Rod Hyatt and I both question the accuracy of conventional wisdom when it comes to accurately modeling and simulating heat loss for underground and conditioned space installations of hot and cold water tanks including relatively large thermal energy storage aka thermal battery systems. TRNSYS software appears to be capable of accurately evaluating the heat loss for various applications but is apparently very expensive to conduct?? The key to success appears to be keeping the foam insulation dry, both from the water in the holding tank and from the ground water. From the results that Rod Hyatt has obtained for his ~1900 gal. tank in which he lost only one degree F./day, if that can be replicated I am convinced that the following formula may not be entirely accurate when it comes to evaluating heat transfer vs. R-value??



BTUs/hr = (Area/R-value) (ΔT) x 24 hr. = BTU/day



There has been some interesting research conducted in Germany which was discontinued?? Refer to attached research papers, the final one of which I believe is in German.

hot_rod

not easy to model

I asked Siggy once about modeling tank loss, on an inside storage tank for my wood boiler, with his FEA program. The tricky part is the stratification, which could have a different heat loss every inch or so of the tank height.



A tall tank could be 140F at the bottom, 180F at the top so that loss number gets fairly complicated to nail down. And that would have been in a fairly consistent ambient air temperature space.



Obviously if the tank were in service that water temperature gradient would be ever changing.



In ground brings a lot more variables. The ground temperature changes across a time period. In the fall the ground may be 55F at a 6' foot depth.



I have thawed water mains that were 6 feet deep in Utah during low snow, cold winters. So you could potentially have a 100°∆T or more, fluid to ground temperature, in portions of that tank in winter.



I suppose a data logger with sensors ever so many inches could help pin down a number.



But would the heat loss of a tank of still water be that useful, knowing that an active system would never produce those conditions?



Mechanical-hub.com has an interesting article on underground insulated piping on a job in Finland, MN McKinstry Mechanical did some heat loss calcs on the old fiberglass pipe compared to a new Ecoflex system. You might contact Bernie to see how he ran the calcs.



As you eluded to, any water around that insulation would make those numbers, if you did crunch them, all but useless.



I have seen some outdoor wood furnaces lose 60 degrees from the heat source to the building when ground water surrounded the insulated pex. Waterproofing and drainage, possible a sump pump might be wise.





Keeping a jug of water hot in the ground may not be as easy as it sounds.



Thermal storage is the holy grail of solar energy, all sorts of methods have been tried. One of the more interesting thermal storages was Nevada 2 solar farm where they could store a days worth of thermal at super-heated temperatures, in molten salt.



Plenty of salt across a State border, not far from your project

Zman

Tanks

It is curious that these guys are putting the insulation on the inside of the concrete tank. They are loosing out on the additional BTU storage potential of the concrete itself.

Have you considered a precast concrete tank with a closed cell spray foam polyurethane applied to the outside? You can get almost R7 per inch at around 80 cents per board foot.

As far as the insects go , as much as they will vary by location, A dense closed cell foam will help. I have heard of additives that can be put in the foam to resist insects although I have not used them.

Very interesting dialog. I have learned much.



Carl

Rod Stucker

ICF Concrete Cisterns

Carl, I agree with you about putting the insulation on the exterior of the concrete thermal energy storage tanks, as long as we have a waterproof/vapor proof lining/barrier on both sides of the concrete. As indicated in previous posts, due to varying results from different experiments and lack of accurate data logging for stratification, etc., for actively performing tanks vs. static tanks, etc., and the varying methodologies for calculating/predicting heat loss via R-values and simple calculations vs. more sophisticated modeling software such as TRNSYS, there still seems to be much that is not known about heat transfer, particularly for underground tanks such as concrete cisterns that are actively being used. It would be ideal if we could get NREL's BEopt team to help us out with incorporating TRNSYS modeling and simulation into their BEopt software which is available to the public. I am going to submit a request!

Rod Stucker

Floor Coverings & Cold Feet

As is illustrated on the Idronic graph that Hot Rod has provided, tube spacing and floor coverings dramatically effect efficiency of a radiant floor system. I am planning on installing concrete decorative floors that look like marble, possibly some wood floors in the kitchen that have minimal effect on heat transfer such as clear vertical grain fir, etc. We can also use some throw rugs where desired, hopefully without significantly affecting performance.Though cold feet has been expressed as a concern for many people, I merely wear socks and/or slippers around the house. I actually prefer that over going barefoot. For those who prefer going barefoot, throw rugs will help. However wearing socks or slippers is a small inconvenience in return for optimizing efficiency of the radiant floor heating and cooling system.