Hello everybody, I'm currently building a new 2800 sq ft home in upstate NY, I've decided to go with a geothermal heat pump installation and had hopes of radiant floor heating for a long time. I'm in that that horrible position of having to give up something I've really wanted because I just don't think I'd be able to do it the right way and still stay in my budget but as a last resort I'd like to hear what formula you use to calculate the amount of heat transfer plates you would need in a home. I'll have standard 16" O.C joists. As far as pricing the plates I've found that I can get a 4' Extruded Aluminum plate with omega groove for roughly $5.80 locally, of course on the internet I've seen them a little lower but can't verify the quality. Using my info I've figured that the plates will cost anywhere from $10k-13k(being safe), can anyone tell me if this is a reasonably safe estimate to go by? Thanks again guys for all the info, I've learned enough from reading through these forums that trying to nickel and dime your way through a quality & efficient radiant floor heating system is just a recipe for disaster, and while using either a cheaper transfer plate or none at all would probably make the radiant option affordable again, it seems a bit foolish to proceed using the bare minimum of materials and cheapest quality components and expect a high quality efficient heating system.

With a new house, you have the advantages of being able to use in-floor vs underfloor plates. And good insulation and air sealing so that load is low. I doubt that anyone will say much about total price without your load data.

Under-floor plate systems have the highest acquisition cost (because of plates and increased labor) and the highest operational cost (because of significant inefficiency). If the heated floor is above conditioned living space, much of this inefficiency may be mitigated (i.e. the heat loss from the heated floor provides supplemental heating to lower conditioned living space). Under-floor plate-less systems may sometimes be accomplished with limited success in situations where 15 Btu/hour-sf or less of upward heat output is sufficient to satisfy the design heat load requirements (e.g., very well insulated, highly energy efficient buildings).

Use of an above-floor system like Warmboard would have a lower acquisition cost (although still much higher cost than a slab system) and also provide lower operational cost (although less efficiency than a slab system). You will first need to determine your heat load requirements before selecting your hydronic radiant floor heating strategy and designing your system.

If this will be a 100% DIY project, you can likely easily save 2/3 of the total project cost if you are capable of doing this as a DIY project. We have free DIY heat loss analysis and hydronic radiant floor heating design software on our website.

There are a lot of ways to install your heat.
Topping pour of 1 1/2 concrete (some call it light weight) will add about $1.50 for the concrete place plus additional joist structure.Gype creet will cost more. Pipe and manifolds run about $1.00 or less square foot. Topping pour has the added value of the heat sink.
We market RHT floor panel system. This is a surface mount that runs about $3.00 square foot for materials plus labor. It is an easy install on top to carpenters can average about 500 square feet a day (yes I ment carpenters), good fuel efficency this type of system as you are not pushing heat through the envelope, delivered water temps cna be considerably lower(90-100 degrees is typical).
The staple up method is ok, lots of work on the install, and fuel efficency is less. Delivered water temps cna be considerably higher(130-145 degrees is typical).
Any of these will work with the geo,
Dan

We install a lot of sub-floor radiant heating system using heavy extruded alumimum heat transfer plates in new construction and renovation. The potential output and "efficiency" of such systems in dependent on many factors, most particularly heat loads and floor coverings. The upside to sub-floor systems is the ability to leave floor coverings and heights unchanged. The down side is the potential for low outputs or slow response time. Having designed many space heating systems using radiant floors, walls and ceilings I often have to fend off misconceptions held by the public and even the professional. As I sit in my living room typing this my own heavy extruded aluminum plates are keeping my feet warm with a current supply water temperature of 98°F. This is over 3/4" T&G and 3/4" Red Oak. When is below zero the design water temperature will be 124°F. No lag, no over-run, no high fuel bill. Were I using a condensing boiler I would always be in the sweet spot but, since this is electric with ODR, no worries.

Labor is a factor and there are systems that are faster to install, for the typical renovation with 100-year-old flooring, give me a heavy aluminum plate. We just finished such a system for a 1955 brick bungalow here in Minneapolis. No wall insulation and heat loads in the 20,s. Plates will cover it nicely and always in the sub-130°F return range for their new IBC boiler. Our success with extruded plates has been unlimited, often installing them where misinformed contractors have hung bare PEX below the sub-floor without the benefit of aluminum plates or even insulation!

If this is a DIY radiant floor heating system you will want an experienced professional to design it for you.

Keep in mind that with geo, lower supply temperatures provide for higher efficiency. And the less insulation you have between the pipe and the room, the lower the supply temperature. Insulation in the walls goes the other way - more provides for lower supply temperatures.

If you elect to do less than 100% DIY, make sure that the professional designer/installer that you do hire is licensed to operate in your state so you have legal recourse for remedy when you have problems. Way too many horror stories about online, out-of-state, less-than competent, professional designers blaming professional installers or DIYers when things go wrong. Always best to have the designer/installer be one and the same or at least both be licensed in the same state as the job.

Aren't light weight concrete and gypcrete both lightweights when it comes to heat transfer efficiency, too?

No, not compared to a below-floor plate system which is about as bad as is gets...unless you elect to do a below-floor plate-less system. A thin slab system is 8.1% less efficient than a slab-on-grade system. An above floor plate system is 11.3% less efficient than a slab-on-grade system. A below-floor plate system is 48.4% less efficient than a slab-on-grade system. A below-floor plate-less system is 78.2% less efficient than a slab-on-grade system. One can easily do a very nice slab-on-grade system for under $1.50/SF for typical new residential construction.

Yeah, I avoid all that plate stuff as it is pricey, and I'm not too sure how efficient or green it is. The thought of radiant retrofits other than thin slabs leaves me cold.

My comment had to do with the practice of using "lightweight" slabs and gypcrete as opposed to standard density concrete. It all sounds good and it's pretty clear that contractors like to put them in because they are easy, but the fact is that as you reduce the density of your thin slab material, you also decrease the heat transfer efficiency. If your heat transfer efficiency goes down, you have to increase the supply temp. If you are boiler driven, that may not matter much, but, as jonr points out above, supply temp goes hand in hand with efficiency in a heat pump (geo or air source) system.

All you have to do is look at the r-value of the varying mix densities to see how they affect heat resistance or transmittance. Regular concrete is down in the 0.1 range, while gypcrete is more like 0.4-0.5 and lightweight concrete can be all the way up to R 1.5 or more.

Contractors around here tend to forget that every time.

An above floor plate system is 11.3% less efficient than a slab-on-grade system.

None of these figures are accurate to even 1% (.1% is ridiculous). For example, above floor plates vary with what you put over them, spacing, % coverage of the plates, plate thickness, etc. You can make above floor plates more efficient than a full thickness and weight concrete slab. And with less over and undershoot (which reduce efficiency and comfort).

Precisely ICF, a little research and knowledge goes a long way to achieving an efficient and successful outcome. You always want to strive for the lowest supply temp, the highest heat transfer coefficient, and the lowest floor covering R-value if your care about maximizing floor heating system efficiency. The aforementioned floor heating system efficiency numbers are for an equal comparison 12 inch tube spacing with a 0.5 R-value floor covering. I agree ICF, we also consider floor heating retrofits to be a very foolish investment and we don’t recommend or do them. Frankly, one would be better off selling their old house and properly building a new house to get cost effective and efficient floor heating. However, many contractors love doing below-floor plate system retrofits precisely because of the high labor and the associated opportunity to extract a high profit margin, and they will go to great length to market their floor heating retrofit products/services. There is apparently no shortage of clueless people who are willing to pay big dollars just to get floor heating in their old houses, so this is apparently a very good business opportunity too.

Sailer has gone off the deep end. I can't compete with such fiction...

Out-of-state horror stories.

Licensed contractors.

Pleeeeease.

Agreed
Staple ups been around a long time, may not be the best but no doubt it would be a viable option to buldoze the house to place above platform heat in a new building.
The world is full of a lot of good well intended builders doing the best they can with what they have to work with. Better to save the broad brush for painting the barn.
Dan

This somehow reminds me of a colorful story once told by an exterminator after receiving an ethics award at an annual contractor state license board conference. This exterminator would intentionally keep a set of worn out brake pads on one wheel of his truck. Apparently there are always a few cockroaches that survive even the best extermination attempts and these cockroach survivors eventually became very sensitized to the sound produced by a squeaky wheel. In short, these cockroach survivors quickly learned to associate the squeaky wheel sound with an imminent survival threat and would react strongly whenever hearing it. Research has shown that a complex balance exists between cooperation and competition with regard to cockroach behavior…truly fascinating stuff:

Cockroaches

Whenever this exterminator would drive his truck through a neighborhood, the sensitized cockroaches would cause many of the other clueless cockroaches to crawl out from where they were hiding. So in addition to making many homeowners cognizant of a cockroach problem that they may not have been previously aware, his squeaky wheel also generated more business for this exterminator and eventually earned him a reputation and an award for being an outstanding and ethical contractor.

The sad part of this blog is the pure arrogance.
The blog is not a discusion but a ego chalange.
Sadly
I enjoy creative soultions, Have years as a contractor, homes we built are loved, and have worth.
To saddle the contractor with a cockroch view is miopic
I am thankfull I am no so smart.
Time to go back to my hole and live in the dark ages.
Adios,
Dan

I'm still waiting for the punch line on the cockroach story. I'm expecting it to be something about "a squeaky wheel".......

I used the 4" x 48" panels, two per joist bay.

On the 843 sq.ft. second floor (which I have the layout drawing handy) I used 235 panels.

There are a lot of things "in the way" such as beams etc. Also, you have to leave enough room on the ends (rim joist, beam etc) to loop back so the panels end 16-18" from the "end". Then there is the allowable end gap between panels.

Anyway its hard to estimate the number of panels. For what its worth it appears I was getting a net 3.6 sq.ft. per panel.

John