I am in the design process for building a new home in Kansas City. I want to heat the house with  a radiant floor system, and wish to utilize solar energy to provide as much of the heat as is practical. I assume I will need a backup heat source (high-efficiency boiler or other?). In addition, I would like the system to be able to provide, or at least pre-heat domestic hot water, and to heat my swimming pool during the warmer months. What kind(s) of expert should I be searching for to design a functional and efficient system? Is there any such expert in the KC area who can assist?

Also, we will need an air conditioning system. I have read that mini-split systems might work well for a non-ducted house with radiant floor heating. I need the same system design help for this, or are the other (perhaps better) alternatives?

In a new house, I'd calculate the cost/benefit of going with a super-insulated design (Larsen-Truss or insulated concrete forms/SIPs of R40 or better), compared to the cost of the relative mechanical systems required for a less-insulated home, especially if you hope to get a useful fraction of the thermal inputs out of solar. You may find that the need for AC actually goes away, or night-ventilation in combination with a heat-recovery ventilation (HRV) during the day, or with a tiny quarter-to-half-ton system.

In KC I'd think the pool heating could be done with standard cheapo unglazed solar pool heaters more cost-effectively than trying to kludge it into your heating & DHW systems. I'm assuming this is a May-October use pool, never year-round?

You basically need to find a solar contractor who is comfortable working with various radiant heating/cooling systems. (Don't know if that's a rare species in KC, it might be- often is.)

But seriously, superinsulating & sealing the building envelope will DRAMATICALLY reduce the size, cost, and necessary-efficiency of whatever you're trying to heat/cool with. With much reduced loads you may be able to run both heating & cooling off a very small air-source heat pump (with solar boost.) The PassiveHouse in Urbana IL has ~R55-R60 walls, R60-R70 roof, and uses a 1000W electric heating element in the heat-recovery ventilator as "backup heat", yet uses only using 350kwh in January for ALL electrical use. (The average not-electrically-heat US home uses about 1000kwh/month.) R60 might not be cost effective in your case, but R40 probably is, if done Larsen Truss style (google it, if you're not sure what that is.) Building new stuff, achieving high R value just isn't all that expensive (compared to retrofits, which are another matter.) Perhaps the expert you're really looking for isn't the heating f& solar designers, but the super-insulating folks.

The first-rule of solar is "Reduce your loads to the minimum practical achievable". Once you do that the rest is relatively easy (and a helluva lot cheaper too!)

Dana is right as usual. The best you will get from solar in a conventional building is perhaps half of your domestic hot water load (most of this in the summer months). Solar heating is for the super-insulated homes and those who live in the southwest.

Radiant floors can be too much for an R50 home in milder climates like yours. I like Dana's ideas for HRV and back up, but humidity control in SIP and ICFs is critical, takes careful experienced design.

I really appreciate your input. Will run these thought and recommendations thru my architect and see what we can come up with- thanks!

We are currently working on a couple designs along these lines. The overall concept is to capture as much of the potential 30% tax credit for the solar side as possible (labor and materials on panel install and primary tank). On the current project (3,600 sq ft + pool 500 sq ft surface) we will have a flat panel drain back system, all solar collectors are directed at domestic H20 production, thus qualifying for 30% tax credit on solar domestic h20. Surplus heat from solar collectors will be directed at a storage tank, coils in tank will provide heat transfer to both the pool and the house RHT floor panel system. The condensing boiler will function as back up for the domestic H20, residential heat and pool as needed.
This project is located in Seattle.
Dan

I have a design for a 5-panel, solar/radiant/DHW/spa heating system that I am going to install in a new house in Carmel, CA. The add-on for the "solar part" of the project is about $30K or so, before the 30% credit, and I expect to save about $1200 / year, according to my own model. It's not a great ROI - 15 years - but it's good enough for me to install it.

Carmel is a coastal town, and we have heating loads for most of the year, and the spa and DHW help. Hence, even during the summer, I am able to use more than 70% of the heat produced from my 5 panels and 240 gallons of water storage e before I have to turn the drainback system off. I ran my model with more tanks and more panels - and fewer tanks and fewer panels - and found that 5/2 was my own sweet spot. I expect to cover about 60% of my heating load, including my space heating, my spa, and my DHW. More panels and more storage provided only increasingly limited benefits.

One interesting thing that I found was that given my own situation, and the design of my radiant system (where I can use 90 degee water without reheating it, if the boiler's reset curve calls for 90 degree water) was that the heating of my house consumed about 80% of the panels' ouput, and that if I simply "deleted" the link the the DHW and the spa, that 80% would go to 90%, and I'd only forfeit about 10% of my produced heat. In other words, I could probably save about $3K or so, and only forfeit about $120/year. I've not decided to do that, but I am close.

What I found in my case was that the ability to model - and then to USE - the lower temperature, solar heating storage water in the radiant heating system was very important. I can use 110 degree water for 80% of my days in Carmel, and that provides me with the ability to "reuse" the capacity of my system every single day. That is something that a DHW tank - always pre-heated to 120 degrees - does not provide. I had to pay very, very careful attention to the design of the radiant system to accomodate this low temperature water, a task that seems to be beyond most designers, and it increased the cost of the radiant heating system by a few thousand $$$ as well, but it is going to be a nice, mechanically well designed system.

Jeff

Were it that the rest of the country had Carmels' weather. Here in Minnesota ROI on Solar heating exceeds the lifespan of most who can afford it.

I like your approach and integrated design.

One of the things that I found, before I simply gave up and designed my own system at some great cost of education and trial and error, was that there seems to be a grave lack of knowledge in the "solar" industry as to how to design good and efficient systems. One day, I will write a book about it, but in the past 4 or 5 months, I have seen so many bad solar designs that it makes my head spin.

I saw one design for a 7,000 square foot, LEED platinum house (no, I'm not kidding) that included glycol, 5 panels and ONE 80-gallon storage tank in a sunny area near here. The entire building enevelope was conditioned, including the enormous basement, and the contention was (apparently) that they'd be able to quickly get rid of 150,000 BTU's / hour (well, the house did have an indoor lap pool!) without some sort of heat dump. When the heating load of the house is ZERO in June, July, and August, that's hard to believe.

I saw another, uninsulated house (it was a post adobe "family heirloom", and the owners had too much money and not enough common sense) that must have had a design day heat load of 150,000 BTU/hour and had 10 panels and a 600 gallon tank, but the panels were 200 feet out in the yard (so that the owners didn't have to look at them) and the system must have cost well over $200,000. One of the heat exchangers in the tank (it had 3, I think - one for heating, one for DHW, one for the outdoor pool!) had a leak, and as a result, they installer blew 2 or 3 pumps (via cavitation) before they had to saw the tank apart to fix it.

The first heat load analysis that I had done for my home (before I simply did it myself) included 5,000 BTU's of heat loss out of the unconditioned basement - this after the heat loss into the unconditioned basement was already included. When I asked about that, I was told, well, "that's the way that we do it, and it's good to have some margin of error." I'm all for margin of error and a bit of overdesign, but you have to start with accurate numbers before you introduce that margin - you can't start with garbage that can be too high or too low, and assume that you have "margin of error" already built in.

I've seen designs for boiler based radiant heating systems that, in their zeal to use only one radiant pump, install loops with engineered head losses of more than 10 feet of water (so that the flows will be balanced) and group loops together that have "desired" water temperatures of more than a 25 degree variance. Admittedly, I use three loop pumps rather than one for my zones, but through proper engineering and some iterative tweaking, my pumps are tiny, my engineered head loss averages 0.3 pounds of water, and my requested water temperatures through each pump differ by no more than three degrees. My home will have finished concrete, wooden floors, and radiators whose total design day temperature differential is 24 degrees.

To me, the amount of poor design that passes for radiant and/or solar systems is incredible. Homeowners will surely get bad tastes in their collective mouths when their glycol breaks down every year (and the $150,000, 5 panel system that will save only $400 per year costs $1000 more per year to maintain) or when their valves break because they open and close 20 or 40 or 100 times a day, or when their boilers malfunction because they short cycle, or when their concrete floored rooms never come to temperature because the installer was too lazy to install a mixing valve to turn down the water temperature going to the concrete.

Of course, this is really no different than the rest of the building industry, but that will be the subject of the sequel.

Jeff

How true, but still no match for Jimmy Carter's debacle. I am sad to say, I have taken out many more solars systems than I have installed or even designed.

What would you say are the reasons that you are called to take out the system? What are the top 5, or top 10?

#1: system never worked

#2: system worked marginally and then quit.

#3: system worked well for several years but could not be repaired (ususally the original installer went out of business, the repairs were not financially viable or the repairmen was unable to decipher the many elaborate and unfamiliar controls used in the 70's).

We still lack the body of knowledge (due to our relatively low fuel costs) that the Europeans enjoy. But we are learning and improving on their history.

Right, but what was the "underlying cause" of the system not working? Gunked up glycol? Too much shade? Equipment breakdown of panels or tanks? Are they mostly hot water systems, or more involved? Does anyone ever ask you to try to fix them, or do they just want the damn thing off of their roof?

Jeff

Yes...

Poor design, shoddy installation and no maintenance.

The biggest problem was "free money". "Solar Contractors" came out of the woodwork and went away when fuel prices plummeted. When you are not spending your own money, scrutiny often goes out the window.

I learned alot about the solar trade while taking a course on hot water heat taught by an old pro who installed systems in CA and offered courses at Red Rocks community college in Lakewood, CO. I believe Eatherton now teachs the course but I don't know of a formal school for solar.

I have to take some issue with the "zeal" comment jbaron.

we generally follow a max head loss of 10 feet of head around here, and we're usually only hitting that on the largest of jobs. But I'm not aware of any pumps currently available in the NA market for regular purpose that could use less power than a single up15-58 (or Alpha, perhaps, even better) for instance. Unless you're using domestic recirc pumps, perhaps, which would be a lot of additional expense with no payback or ROI at all in most situations.

Further, the "desired" variance of 25 degrees is quite routine. There is an awful lot of things that modify that: desired room temperatures in actual practice vs the "design targets", the required level of precision in each space for room temperature in the first place (closet vs bedroom, mudroom vs living room), mass in your emitters vs your heat loss characteristics (likelihood of overshoot/undershoot), and last but definitely not least, the ability of your thermostatic controls to handle wider differentials from "ideal"... PID logic can do an awful lot to tame a water temperature differential. I routinely run 30+ degree differential from "ideal" in basements (since they often only need 80 to 90 degree water), for example, but with a capable thermostat you would never be able to tell... high mass emitter with a nearly unchanging heat load (on a daily cycle) means the need to be "ideal" is very, very low. With floor sensing the difference is even smaller.

Multiple mixed water temperatures is not an ideal (unless you sell mixing valves :D), and as much as I like the numbers, having them meet some arbitrary threshold is not an ideal either. An ideal is a very comfortable house, running efficiently with reliability. The rest of your points are interesting and in my experience true; I just wanted to to explore those comments a little more deeply since they, in themselves, are not necessarily indicators of poor design.

I couldn't have put it better myself! All the more true when designing for condensing boilers. How refreshing to be in the same "room" with a smarts guys.

Building your own home can have multiple choices regarding home heating source. Solar heating works much cheaper than electricity. So I need to rebuild my house now.