Radiant heat radiator question

bmoon

Figuring out what BTUs I need is turning out to be tough. We have an ICF house with a 8" core and triple pane windows. Our slab is insulated and we are doing in-concrete radiant floors in the slab and on floors. We have 11,000 sq feet in the building (home and work spaces) but of course some is large garages that we can keep at 50-60 degrees. We have warehouse spaces and storage rooms that we can keep those loops at lower temps also. And rooms that are used often we would keep more comfortable. Our temps drop in the 30s-40s in the winter, so the average exterior to interior difference most winter days is 30-40 degrees. Our summers are mild so we will just have a few mini splits to use on hot days in main rooms. We dont need whole house hvac.

Trying to figure out the best option for boiler. Should we have one for the radiant heat, and a separate hot water heater (or instant hots) for the household water usage? We only have 3-4 full time occupants so household usage isn't actually that high. I'm seeing a lot of people complaining about the cost of propane and even one boiler company who sells both - suggested we go electric. But our friends who are electricians say to not go electric on the boiler since they see problems with the all the time. SO I feel like we are spinning in circles and I just want to know what to buy that will cost us the least monthly on a regular basis. What would you do and why??
FYI: We don't live in an area for geothermal use or solar unfortunately. Electricity is $.12kwh. Propane is $2.44 currently.

hot_rod

If everything in the home can be heated with water temperature below 120f, a heat pump will be the most efficient way to heat and cool.

You do need an accurate heat load to size correctly.
Some of the heat pumps now have a DHW mode.

or maybe a small Lp boiler to help the HP if needed, with an indirect for dhw

Any other LP load, cooking, clothes drying fireplace?

www.coalpail has a handy spreadsheet for comparing various fuels.

bmoon

Just cooking and a small gas fireplace that likely wont be used often.
We don't have the ducting or want forced air from heat pumps, we literally only want to turn on the few we have in the rooms that need AC when it calls for it a few times a year.
we want the radiant heat and will be using it for heat. Just looking for the best way to use it.

Ironman

Has anyone done a Manual J load calculation? That’s the foundation for all design work. That will also determine what maximum supply water temperature is needed to heat the house on the coldest night of the year (aka design temp).

As hot rod said, an air to water heat pump may be viable is nothing requires SWTs above 120*

On a project like yours, you really need a good radiant designer since that’s the key to getting a system that functions properly and economically.

Try contacting @Rich_49 (Rich McGraph) here on the wall.

Rich_49

How much of the rather large building will you be heating and cooling ? Where are you located ? Heating and cooling a THERMOS is not very difficult nor does it usually require much energy . ICF with triple pane windows should be a very good envelope . Where you are is important though to know for sure the right way to go taming EVERYTHING into consideration

hot_rod

.12 kWh with all the fees included? Very reasonable,
Even so, lp at 2.44, 87% efficiency, still comes out about 500 less$$
Heat pump, is less than 1/2 of lp.

With a super efficient building you may not get warm floors, the load calc is critical to making a good decision.

bmoon

Thanks everyone for your comments.

Rich we are in the pacific northwest, a bit northeast of Seattle. Our winter average low temp is 25-40. High 40-55. They have tested for geothermal in our area and it does NOT work. We simply don't have enough ground heat unfortunatly - which I think is what you are talking about? I looked and researched and it would have been wonderful, but UW did a 300k test near here and it just is not feasible. I researched solar, and that also doesn't produce enough. And I even looked into a system that produces electricity as a byproduct of producing heat, but we simply wont produce enough heat to make that worth it either.

hot_rod, thanks for the cost comparison chart. So without being able to use the geothermal, it does help to see that lp came out less than electric.

We used loopcad to design the in floor radiant system. I did like how it calculates everything out. So we have all the pex ready and each line calculated and will number each roll and follow the maps the loopcad produced and each will be zoned according to their manifolds etc.

Here is our energy calc according to coolcalc. It quite possibly be overkill because I don't believe it was set for triple pane windows. Probably about 5000 sq feet will be to a warm 70 degrees or so on a regular basis, and the rest of the spaces will be set around 60.



So I guess it comes down to, whats the favorite boiler? And should I do a closed system for the radiant heat and do the house water heat on something else? Whats your favorite system?

Rich_49

How many baths and occupants ? What is the expected usage for domestic hot water ?

Rich_49

You said : "Rich we are in the pacific northwest, a bit northeast of Seattle. Our winter average low temp is 25-40. High 40-55. They have tested for geothermal in our area and it does NOT work. We simply don't have enough ground heat unfortunatly - which I think is what you are talking about? I looked and researched and it would have been wonderful, but UW did a 300k test near here and it just is not feasible. I researched solar, and that also doesn't produce enough. And I even looked into a system that produces electricity as a byproduct of producing heat, but we simply wont produce enough heat to make that worth it either."

They tested for Geo thermal , who is they , more guys like the guys who did it poorly so many times in the past because they were smarter than everyone and cut the absolute wrong corners in their feeble attempt to harvest BTUs that really never existed ?
Those BTUs actually did exist , like I said though , they screwed the pooch by being smarter than the rest of us . HEAT is where you find it , the heat is there in the ground , it's in all the ground , how you pay attention to what type ground you have and what method you use for your loop field , VBH is all the difference . They studied improprieties , unless you can point me to results and the methods used I'll stand by that .

Solar was also tested as you state . What type of solar , solar thermal or solar PV ? Again , like in previous tests and studies , they missed the mark most likely . See the first and third discussion , these guys really are shills for an industry that could care less about them . I and several others participated in these discussions and they do get heated . https://www.greenbuildingadvisor.com/?s=solar+thermal+is+dead+ . I just looked at these links , read the 1 titled solar thermal is not dead also , it explains quite a bit

Solar thermal is a great way to harvest heat , store it in a tank , mix it to a nice temp , run it through a WWHP and end up with system COPs north of 10 , that is of course , if you really want to use a heat pump and electricity because you believe all the hype .


I think you are speaking of a CHP system by stating a system that produces electricity as a byproduct ? If this is incorrect please say so .

If propane is an option it sounds like your best bet would be 2 small LP boilers cascaded and a properly sized indirect tank stored at a temp of 160* to kill Legionella and protect the occupants / users and a mixing device to increase efficiency and get to a usable temp . 2 boilers cascaded should be no bigger than 80K with a generous TDR . This configuration will sip fuel , have enough power to handle high DHW usage periods , provide ample heat at design and below and should one unit fail , give you time to replace while not being in a rush to do so . Feel free to contact me . Hope this helps .

bmoon

Holy cow guys, I think I had the heat pump conversation completely wrong. I've been researching some more and JUST learned about heat pump water heaters! Is this what you guys were talking about? I honestly only knew about heat pumps - ducted through to do forced air. I didn't even know heat pump water heaters existed! Is this what you guys were talking about?

Rich, yes I was looking at microCHP.

Here is a pic that shows probably the simplest way of seeing the geothermal problem in the state (it would be awesome if it worked, we would totally do it). This is from the WA state energy dept. I have a client who works in energy and even she said its really not a very good producing area for the cost it would be to put it in, it won't cover much of what's needed. This is my specific county "In 2010-2011, the PUD worked with two independent geothermal consultants to evaluate geothermal feasibility in or around Snohomish County. After drilling a series of test wells, and evaluating sites with consultants, the PUD determined the temperatures and permeability conditions did not warrant additional exploration. The PUD continues to monitor geothermal developments in the region in case viable projects are identified."

Rich_49

Heat pump water heaters still have their issues . Some are loud , others just don't have the longevity they should and they are not very forgiving during high demand events . I would not suggest one if you're going to be heating with another type of technology that will be using water as the medium . The only one I would suggest is a Sanden .

hot_rod

Air to water heat pumps are another option 
In some cases the can be a substitute for a boiler. If you can keep the required SWT below 120, you may see 2.5- 3 COP

with low electric rates and potential PV capacity it could be a viable option

Look at ccA2WHP. Cold climate heat pumps
These are split systems, so the noise is outside🙂

SpacePak Soltice is one brand to search

search www.dsireusa.com for heat pump and other high efficiency incentives in your area

download this Idronics issue to learn more