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Old 02-19-15, 06:41 PM   #491
Drake
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I do not expect answers to any of my questions. And it because of the complexity that I ask them. If I can get a response to my inquiry I am delighted and give the response great consideration. If I appear to repeat myself it is in the wish to make sure that I'm being understood and that I understand in return. I have been, I hope, on the innovative edge of retro fit remodeling much of my life so I am always interested in discussing the new. As yet hydronic radiant is a much used heating method in my area, especially high mass/ low temp slabs, so I don't have my normal contacts with contractors so that I can really pick their brain.

I have checked out Radiant Works and don't really think it customizes enough to be on the current edge of knowledge or application practices to be the "bible" on hydronics or how to build towards it. IMO. The layout it gave of the three common patterns that inquired earlier about(that to me did not address to me more heat to exterior/ less interior). Which in the separate thread a couple of generous responders helped me resolve to my satisfaction. As DIY'ers we all have to find our own level of confidence that we can undertake our projects or we could hardly accomplish them. For myself, I often complicate my readiness by liking to have more knowledge(if I can) than needed to just follow someone else's plan and be able to repurpose used or nontypical materials if I can rather than buy just the "right" everything.

I am very thankful for any information I get.

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Old 02-19-15, 06:54 PM   #492
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Drake, the reason 1/2" tubing is used is because it is the closest size to the 16mm tubing used Europe. Full stop. When I started radiant, all that was available was metric tubing (16mm OD) and when Wirsbo first started making it here they needed it to fit some standard fittings and meet an ASTM standard so the 1/2" was used.

The 1/2" tube gives the best heat transfer with usability (remember that you have to pick up and move many rolls of tubing) and cost. It is a good balance. Where 1/2" tubing may cost $.5/ft (for example), a 3/4" tube will be close to $1/ft. There is no way the 3/4" offers twice the value and usability for the average residential build. I have used it on an aircraft hanger and for supply lines to manifolds.

The reason for the spacing is simple....the closer you can make it, the lower the water temp to get the same floor surface temp and transfer and therfore the more efficient the heating system will be. Simple.

It is no issue to make a 8" dia U bend, and there is no reason to try to get better than that even if you are having a 6" spacing. Don't sweat it, it is not that important. What is important is linear ft of tubing/ sq ft of space.
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Old 02-19-15, 09:04 PM   #493
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...I have checked out Radiant Works and don't really think it customizes enough to be on the current edge of knowledge or application practices to be the "bible" on hydronics or how to build towards it. IMO...
I'd have to say that my experience with RadiantWorks was quite unlike your experience.

If a curious mind is looking for something to draw your PEX layout for them, then RadiantWorks would be lacking.

Regarding the heat-load calculation section, if A curious mind is interested is understanding the interplay between the heat load effects of wall insulation, windows, ceiling insulation, floor insulation, then working with RadiantWorks can quickly provide the user with not just numbers, but with a 'feel' of how the variables interact.

In the hydronics design section, there are choices of various slab thicknesses, various PEX diameters, various spacings, various fluid flow rates, etc, etc. Again it can quickly provide the user with not just numbers, but with a 'feel' of how the variables interact.

The only thing I found lacking was the ability to model PEX spacings closer than 4".

Also it had nothing for high-performance low-mass top of floor installations, which you are not interested in.

So, Drake, if you found it to be lacking in the "current edge of knowledge", what exactly did you find lacking?

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Old 02-20-15, 10:25 AM   #494
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In the last years as the reality of my plan to heat my new project with hydronic radiant floor heat I began seriously researching what was current radiant application and what the design variations were so that,because I am building from scratch, best design my structure to make use of radiant. I was very happy to find that high mass/low temp radiant design is one of the highest efficiency/renewable compatible heat source design directions one can go. It also compliments my wish to maximize passive solar gain design into my structure as a two for one. So my first goal in understanding HyRdt was to best design my structure for it. I am confident that I have done that to the level I am willing to pay for at the best level of working knowledge that I was able to incorporate till the time I had to start(because go/no go has to be sometime and what can't be changed accepted). During that time aside from personal information seeking I contacted four major radiant DIY companies for their input into my project. From this I got four different design(pex size, spacing layout patterns) recommendations for the same, very simple, 16x32 4" slab floor. Each company had very convincing explanations for their designs and components. Pex size ranged from 7/8" to 1/2". Any of the companies design may have been the best, each may have done the same thing a different way, I do not claim to be an expert on HR design. I can see that there is not one common practice being used and that I'd better be very sure that I am getting a design that will do what I need. Granted my floor install is modest in size and the structure being maximized against heat loss may not be adversely be affected by not the "VERY BEST" design application. So maybe I'm over thinking minor things. But if I can identify a better way to go I will go it. Such as I plan to build a second floor radiant loop into my open lofted sleeping area even if I don't connect it. Right now the existing cabin structure(built on a similar floor plan but only half the insulation of the new addtn) has never needed the baseboard heat that is in it. I will be putting a thin slab floor upstairs for solar gain so I might as well run pex in it at the same time.

Again, HR heating is not a much used heating method in my area yet so finding example to query owners on is minimal. I appreciate the input from those who are doing a lot of work with it. If you think that there is just one "best" way to do anything than I don't work in the same world of contractors and journeyman.

I was impressed with Radiant Works but it did NOT layout a design that accomplish to me the ability to supply more heat to the exterior walls than the interior of room as I have tried to discuss in length. As I have admitted the size of my heated floor may make the need of this an unnecessary design consideration but even when I increased it's size in Radiant Works by 4 it did not address it any better IMO. I tried to explain my discontinuity of this commonly accepted heating practice(which I also heard from radiant floor people) and the examples of radiant layouts I have found published. In my project I have no fear in not being able to supply my space with enough heat, it is far more in not over or unequal heating it and designing to heat it no more than I need to(because I'm frugal and a closet greenie).
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Old 02-20-15, 12:33 PM   #495
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Quote:
Originally Posted by Drake View Post
In the last years as the reality of my plan to heat my new project with hydronic radiant floor heat I began seriously researching what was current radiant application and what the design variations were so that,because I am building from scratch, best design my structure to make use of radiant. I was very happy to find that high mass/low temp radiant design is one of the highest efficiency/renewable compatible heat source design directions one can go. It also compliments my wish to maximize passive solar gain design into my structure as a two for one. So my first goal in understanding HyRdt was to best design my structure for it. I am confident that I have done that to the level I am willing to pay for at the best level of working knowledge that I was able to incorporate till the time I had to start(because go/no go has to be sometime and what can't be changed accepted). During that time aside from personal information seeking I contacted four major radiant DIY companies for their input into my project. From this I got four different design(pex size, spacing layout patterns) recommendations for the same, very simple, 16x32 4" slab floor. Each company had very convincing explanations for their designs and components. Pex size ranged from 7/8" to 1/2". Any of the companies design may have been the best, each may have done the same thing a different way, I do not claim to be an expert on HR design. I can see that there is not one common practice being used and that I'd better be very sure that I am getting a design that will do what I need. Granted my floor install is modest in size and the structure being maximized against heat loss may not be adversely be affected by not the "VERY BEST" design application. So maybe I'm over thinking minor things. But if I can identify a better way to go I will go it. Such as I plan to build a second floor radiant loop into my open lofted sleeping area even if I don't connect it. Right now the existing cabin structure(built on a similar floor plan but only half the insulation of the new addtn) has never needed the baseboard heat that is in it. I will be putting a thin slab floor upstairs for solar gain so I might as well run pex in it at the same time.

Again, HR heating is not a much used heating method in my area yet so finding example to query owners on is minimal. I appreciate the input from those who are doing a lot of work with it. If you think that there is just one "best" way to do anything than I don't work in the same world of contractors and journeyman.

I was impressed with Radiant Works but it did NOT layout a design that accomplish to me the ability to supply more heat to the exterior walls than the interior of room as I have tried to discuss in length. As I have admitted the size of my heated floor may make the need of this an unnecessary design consideration but even when I increased it's size in Radiant Works by 4 it did not address it any better IMO. I tried to explain my discontinuity of this commonly accepted heating practice(which I also heard from radiant floor people) and the examples of radiant layouts I have found published. In my project I have no fear in not being able to supply my space with enough heat, it is far more in not over or unequal heating it and designing to heat it no more than I need to(because I'm frugal and a closet greenie).
Drake,

Thank you for taking the time to compose a detailed answer.

There are some Acronyms that you are using that I don't understand. I even tried to Google them, with no luck. What do you mean by "HyRdt"? The best I could come up with is 'elevated radiant change-over-time'... Is that what you mean?

Also you used the term "HR heating"... do you mean hydronic radiant heating?

Regarding the very different advice you've gotten from different contractors, part of the reason could be that what you are trying to do, by radiantly heating your new building by primarily using solar (low temp) energy is very new. It is called "low temperature heating", or "low exergy heating" to be more precise. It is being practiced in Europe more than in North America, so the pool of practical knowledge on this side of the pond is just not so large. Even John Siegenthaler, the most up-to-date North American expert on radiant heating is still a bit behind the curve on low temperature heating.

You've gotten some great advice here, from seasoned installers, who have nothing to gain from advising you. That's a very good thing.

So, I was looking into this very same heating approach and one thing I learned (by using RadiantWorks) that hasn't been mentioned so far in this thread is that to squeeze every last BTU out of your low-temp water, you will need to increase the flow rate (gal/min) of the water through the slab.

If you increase the flow rate through a given PEX diameter, you will increase the velocity (ft/sec) of the water through the PEX. When you increase the velocity, the fluid resistance to that flow will increase by the square of velocity increase. What this means to you is that you will need to increase your pumping power by the square of velocity increase. That means more $'s of operating cost.

The solution to this is to increase the diameter of the PEX so that it becomes possible to increase flow rate without increasing fluid velocity.

So for instance, you might need to double your pumping power, but not quadruple it.

There's another consideration regarding flow rate and velocity...

When fluid flows through pipes, it may flow gently and evenly (laminar flow) or it may flow in a haphazard, tumbling manner (turbulent flow). Turbulent flow is much better for transferring heat than laminar flow.

There is an engineering term to determine the proper flow velocity, called "Reynolds Number".

There are charts and formulas for determining this.

What I'm suggesting is that designs you have seen that use larger PEX diameters than is conventionally used, may not be so crazy after all, if their reasoning is sound. If their reasoning is not sound, then of course, they are Coo Coo.

So, I'm suggesting going with the closer-spacings as has been advised, AND increasing the tubing diameter, so that you can get elevated fluid flow without unduly increasing pumping power requirements.

* * *

But above all this, my primary advice would be to
  • make sure that your house is properly oriented and fenestrated to the sun's energy
  • drastically decrease your infiltration to absolute minimum levels
  • use an extremely high efficiency (=>85%) HRV
  • insulate your house far beyond what you think is $ufficient and prudent
  • forget about a deluxe radiant heating system, because you won't need it.

If you have done all of this properly, you will be able to turn off the lights and power, buy a plane ticket for you and your wife, fly to some sunny southern climate for a week or two, and never worry about any pipes freezing, because the house will take care of itself, by design. That's what a Passive House is all about.

Best Regards,

-AC
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Old 02-20-15, 02:32 PM   #496
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Yes, the acronyms are poorly for hydronic heating. AC, what you are stating is exactly what I have found info on and is why I am still asking questions to try to get agreeing opinions on what may be being done on the direction of hydronic heating that will fit my build. Your info on flow rate and pex size is something I have not found and I thank you for sharing it. It is a good example though of some of the conflicting choices to be made though. The innovating direction seems to be smaller pex, closer spaced. But this does not match well with flow/rate/effec as you detail, and as you state the largest pex one can physically layout to a closer spacing should be better. Hence my choice to use 5/8 pex at 1/2 spacing(besides being all but free for me) it should be even better. How does this info on increased flow rate affected pump choice now? Will a set speed pump be better for a constant on/off increased flow rate than a variable spd pump which might not be able to do it?

I can't thank anyone who has given me input anymore than I have without sending them cards or shaking hands.

AC, to your bullet points 1)my new structure is first and for most maximized for solar gain(which I have been enjoying the benefits of in the existing half of our cabin for many years). 2)The detail with which I am preventing air infil is fanatical(which I will document as my aboveground construction season begins this spring), every rough framing joint will be glued or caulked and my vapor barrier will be broken only by doors and windows. Even basement will be isolated from heated living space. With zero ventilation for combustion.
3)Research is still ongoing for me on HRV's, even beyond DIY ones. I will first incorporate all means I can find to minimize the amount of fresh air needed than provide what I can with passive and low tech means(already posted photos of tubing install for below ground air tempering). 4)The super insulation level I will be building to will be to what I consider cost effective and what can be accomplished without having a space that is more exterior wall than living space. 5) I live in MN,lol. You can have all the heat you need 364 days a years and the wrong one you don't you're dead. It may be wishful thinking but I don't plan to need much heat most of the time but when I need it I'll need it.

I have no doubt that I could layout my radiant any number of ways and be able to supple the heat I need and thought more goal is not an absolute zero net structure I would want it to as low as I can get for what I think is a reasonable expense. The more DIY I can do the more I can afford to attempt.
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Old 02-20-15, 07:57 PM   #497
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http://www.uponorpro.com/~/media/Ext...spx?sc_lang=en

See Table 15-1

They say turbulent flow starts with water around 8'/sec & stay below that speed.
Nominal 5/8" pex can deliver about 50% more heat than 1/2"

Use ECM pumps like Grundfos Alpha.

I think radiant floors are more-or-less self-adjusting on moving heat into areas of room that need more heat, especially with constant or semi-constant circulation.

If an area under a window needs more heat, the slab will become cooler there, more heat will be pulled out of the pex there, and more heat will be radiated there.
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Old 02-20-15, 08:11 PM   #498
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Originally Posted by buffalobillpatrick View Post
http://www.uponorpro.com/~/media/Ext...spx?sc_lang=en

See Table 15-1

They say turbulent flow starts with water around 8'/sec & stay below that speed.
Nominal 5/8" pex can deliver about 50% more heat than 1/2"

Use ECM pumps like Grundfos Alpha.
But the question is......do you need it? A typical 1/2" tube on 8" spacing with 110F water can give 50 btu/ft2. I'll bet Drakes home won't need more than 10-15btu max. There is no need to try to get the most heat out of a tube when it will only make your feet uncomfortable.
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Old 02-20-15, 08:18 PM   #499
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Such as I plan to build a second floor radiant loop into my open lofted sleeping area even if I don't connect it. Right now the existing cabin structure(built on a similar floor plan but only half the insulation of the new addtn) has never needed the baseboard heat that is in it. I will be putting a thin slab floor upstairs for solar gain so I might as well run pex in it at the same time.

Again, HR heating is not a much used heating method in my area yet so finding example to query owners on is minimal. I appreciate the input from those who are doing a lot of work with it. If you think that there is just one "best" way to do anything than I don't work in the same world of contractors and journeyman.
20+ years ago I built a house for my mom with 2x12 plates and offset studs, filled with cellulose. It is a 2 two storey place with 2 bdrms, bath and office on the 2nd floor.......and no heat. The only heat is from a 1/2" tube floor heat system in a 6" slab, fed by an electric water heater and 4 solar panels. Point is, the difference in temp from the main floor to the second floor was 2C and the HRV moved the heat around. When you get down to the level of heat loss that you are seeking, efficiencies present themselves. We save a nice chunk of money by not putting heat on the second floor. By all means, rough in the supply tubing for a manifold up there but I suspect you won't need it.
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Old 02-20-15, 08:27 PM   #500
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Quote:
Originally Posted by AC_Hacker View Post
So, I was looking into this very same heating approach and one thing I learned (by using RadiantWorks) that hasn't been mentioned so far in this thread is that to squeeze every last BTU out of your low-temp water, you will need to increase the flow rate (gal/min) of the water through the slab.

If you increase the flow rate through a given PEX diameter, you will increase the velocity (ft/sec) of the water through the PEX. When you increase the velocity, the fluid resistance to that flow will increase by the square of velocity increase. What this means to you is that you will need to increase your pumping power by the square of velocity increase. That means more $'s of operating cost.

The solution to this is to increase the diameter of the PEX so that it becomes possible to increase flow rate without increasing fluid velocity.

So for instance, you might need to double your pumping power, but not quadruple it.

There's another consideration regarding flow rate and velocity...

When fluid flows through pipes, it may flow gently and evenly (laminar flow) or it may flow in a haphazard, tumbling manner (turbulent flow). Turbulent flow is much better for transferring heat than laminar flow.

There is an engineering term to determine the proper flow velocity, called "Reynolds Number".

There are charts and formulas for determining this.

What I'm suggesting is that designs you have seen that use larger PEX diameters than is conventionally used, may not be so crazy after all, if their reasoning is sound. If their reasoning is not sound, then of course, they are Coo Coo.

So, I'm suggesting going with the closer-spacings as has been advised, AND increasing the tubing diameter, so that you can get elevated fluid flow without unduly increasing pumping power requirements.


-AC
AC, It is all great to understand how turbulent and laminar flow affects heat transfer but there is something you forgot to mention. If you increase the diameter, your flow will become more laminar and the reynolds number will drop. The increase in heat transfer is not as great as you may think and you must think of the whole package (tubing, flow rate, concrete....and it ability to transfer the heat) including whether you need to use that heat. Not in this case. Drake is at the low end of the scale and the tubing choice is due to it being free (otherwise I would use 1/2"). He will never need to pump fast enough to get turbulence in the tubing.

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