Pex/Radient heat questions...

[53driver]

Hey everyone, I am so glad to have found this site. Been reading and searching alot. Anyway, I am planning on building my shop this late spring and had a few questions on "Radiantec"s heat quote. My shop is going to be 40x80 with 25x40 living and then 55x40 being play room. I am planning on a 2 zone system with a High Eff. water heater. (thinkin, electrin vs propane)They are telling me to use 7/8" pex in a floor that will be mostly 4" thick varing to 6" under where a lift will be. I thought that sounded a little big? The two pumps are cast iron pumps, I think I remember something about some one saying to step-up to the stainless pump? Does anyone have any experence with these guys,or anyone else? Thanks.

 

[tdkkart]

Reference a thread from me awhile back:
http://www.garagejournal.com/forum/showthread.php?t=16501

Part of the issue you have here is the size of the floor. The large zone being 2200sq/ft is sizeable. With a "standard" max of 250-300sq/ft per loop when using 1/2" tubing it makes for alot of loops, plus the total head pressure will require larger pumps.
Using larger tubing allows for wider spacing, and shorter loops.

Radiantec pushes the Polaris heaters hard, and they are VERY, bordering on obscenely, expensive. I'm sorry, but there's only so much efficiency you can squeeze out of a water heater. Beyond a certain point you are seriously wasting money trying to get that last percentage point of efficiency.

Do some more research before accepting one design..

 

[HoosierBuddy]

Hey everyone, I am so glad to have found this site. Been reading and searching alot. Anyway, I am planning on building my shop this late spring and had a few questions on "Radiantec"s heat quote. My shop is going to be 40x80 with 25x40 living and then 55x40 being play room. I am planning on a 2 zone system with a High Eff. water heater. (thinkin, electrin vs propane)They are telling me to use 7/8" pex in a floor that will be mostly 4" thick varing to 6" under where a lift will be. I thought that sounded a little big? The two pumps are cast iron pumps, I think I remember something about some one saying to step-up to the stainless pump? Does anyone have any experence with these guys,or anyone else? Thanks.

To me...using any sort of electric resistance heat to heat a building 24X7 through a Missouri winter would be a bad idea. If you want to go with electric heat...you'll need to use a heatpump to make it a reasonable proposition. I'm not a big fan of heatpumps...but it will save you 2/3 vs resistance electric in that climate.

Hydronic heating in a garage is the berries...but I can't imagine doing it on a full time basis without gas. If you try to heat the building you describe (3200 square feet) in a Midwest winter month with any sort of electric resistance heat (and that includes a hydronic system with an electric water heater)...I predict $1500 to $2000 per month power bills in your future.

You'd cut that by 2/3 with either a good heat pump system. I'm assuming natural gas is not available for you in making this recommendation. I like my hydronic heat...but it's expensive even with natural gas....and my 3-car garage is only a fraction of what you are planning.

Phil

 

[53driver]

Natural gas is not available however propane is. Would gas be more efficent for a shop of this size? Thanks for info guys.

 

[HoosierBuddy]

It's not really a question of efficiency. It's a question of cost.

You need to compare the price of power you will pay to the price you would pay for propane. Both are going to be high and may be going higher.

So step 1 is insulating everything you build to the MAX. Step 2 is coming up with a reasonable way to heat it and cool it. If natural gas is not available...the cheapest way to heat it and cool it will likely be a hybrid heat pump system using propane as a backup for the heatpump when temperatures drop down below 35 degrees. That is not hydronic heat.

A modern heat pump has a COP of 3.0 or better. That means it can move 3 btu's of heat energy into the structure for every 1 btu of energy you buy to run it. If you use resistance electric heat (an electric furnace, base board electric, an electric water heater, etc.) you get a COP of 1. That means you need 3 times as much power as the heat pump uses.

Now think about this. If power is 1.5 times as expensive as propane on a KWH/gallon comparisson (and that's likely close) it's cheaper to run a heat pump on power than a furnace right up until the electric heat strips kick in....but it will always be cheaper to heat water with propane at that price point, because the electric water heater is just another form of resistant heat.

Does that make any sense?

Anyway...if I couldn't get natural...I'd opt for a hybrid system. Then, I'd have a ventless gas fireplace in the living area and maybe a small ventless gas heater in the garage to use for a little extra heat when needed and as emergency heat when the power goes out. Also...your heat pump handles your a/c needs too...so you've got that covered. I'd have a propane water heater (likely a tankless one) for my domestic hot water needs, for the reasons listed above.

If you're dead set on hydronic...then again...insulate it to the gills and go with a high efficiency propane fired boiler for your heat source.

Phil

 

[tdkkart]

A modern heat pump has a COP of 3.0 or better. That means it can move 3 btu's of heat energy into the structure for every 1 btu of energy you buy to run it. If you use resistance electric heat (an electric furnace, base board electric, an electric water heater, etc.) you get a COP of 1. That means you need 3 times as much power as the heat pump uses.

I assume when you say "heat pump" you're talking about a ground source system?? A assume so, because they are the only system that I have heard of that can be more than 100% efficient.

IMO, you cannot mention "heat pump"(ground source) without also mentioning "cost of installation" in the same sentence.
For most people, the cost of installation makes ground source heat pumps a non-option for their homes, let alone their hobby shops/garages.
It's pretty much the same as mentioning windmills as electric sources without mentioning the cost of installation.

Heat pumps may be a viable option below in the lower 1/2 of the USA, but that "above 35* qualifier bites us in the **** up north where we went nearly 6weeks this winter when the thermometer never went above 32*, and was well below 0* for many nights. Electric or even propane backup gets really expensive in these conditions.

 

[kvom]

I used 7/8" pex in my slab, because that's what Radiantec provided. I found it pretty hard to handle with a tendency to kink. If you get a kink that run is ruined as the tube will leak at the kink. You definitely need two people to lay it, very carefully. 1/2" would be a lot easier to run, but as said above you would need more loops.

 

[HoosierBuddy]

I assume when you say "heat pump" you're talking about a ground source system?? A assume so, because they are the only system that I have heard of that can be more than 100% efficient.

IMO, you cannot mention "heat pump"(ground source) without also mentioning "cost of installation" in the same sentence.
For most people, the cost of installation makes ground source heat pumps a non-option for their homes, let alone their hobby shops/garages.
It's pretty much the same as mentioning windmills as electric sources without mentioning the cost of installation.

Heat pumps may be a viable option below in the lower 1/2 of the USA, but that "above 35* qualifier bites us in the **** up north where we went nearly 6weeks this winter when the thermometer never went above 32*, and was well below 0* for many nights. Electric or even propane backup gets really expensive in these conditions.

There is NOTHING more efficient than 100%. That's the 2nd law of thermodynamics.

No. I'm talking about air source heat pumps. Their C.O.P. (Coefficient of Perfomance) is above 3. That means when operated in the right weather conditions, they will "behave" as if they were a 300% efficient heater. They aren't 300% efficient. They just behave that way. They do that by moving latent heat energy from the outside into the inside of a structure...essentially running a refrigeration cycle in reverse. The downside is, as it gets colder outside the amount of latent heat available is reduced at the same time that the temperature differential between the inside and the outside of the house increases. This means that just when the unit needs to provide more heat, it can't because less is available. So, heat pumps normally come packaged with backup resistance elements that kick in at this point. That increases the electric demand by 300% to 400%, spinning the power meter rapidly and running up those bills. That's where a hybrid system has an advantage. A fuel fired furnace is used instead of resistance heat to keep the resistance heaters from ever needing to come in.

I would agree that ground source heat pumps are going to be way too expensive for almost all applications. The good news is that air source heat pumps have gotten much better over the last few years. When you say electric or propane backup heat gets really expensive, I agree. But, what would you suggest as an inexpensive heat source for weather below freezing or even below zero?

If that cheap, clean, easy, heat source is out there...I'm not aware of what it is.

Phil

 

[soarhead25]

I've just always assumed that you could hook up a waste oil boiler and connect that to the pex tubing manifolds eliminating the costly heat bills per month. If your bills have the capability to be in the hundreds or thousands per month-payback would be very quick.
I pictured in my head building my dream house which would be centered around the waste oil boiler with pex tubing in the house, garage, and driveway so I wouldn't have to shovel snow. All paid for with oil changes......

 

[chevelle64]

I used Radiantec and am very pleased. I've got a 26' x 32'. They supplied 3 300' loops of 1/2" tube. My pump is cast iron, works great, can't even hear it run. They didn't push the polaris boiler at all, actually the salesman suggested a small water heater. That's what I did and I love it. And...insulate, insulate, insulate.

 

[HoosierBuddy]

I've just always assumed that you could hook up a waste oil boiler and connect that to the pex tubing manifolds eliminating the costly heat bills per month. If your bills have the capability to be in the hundreds or thousands per month-payback would be very quick.
I pictured in my head building my dream house which would be centered around the waste oil boiler with pex tubing in the house, garage, and driveway so I wouldn't have to shovel snow. All paid for with oil changes......

If you can get 150,000 BTU's of useful energy out of a gallon of motor oil, then it would take roughly 200 gallons of used motor oil per month to heat my house and garage during the winter. So, I can heat it for free as long as I have access to the oil from 160 oil changes per month.

It's a great idea. Step one is buy a Jiffy Lube franchise.

Now that I think about it? I bet those guys (oil change places) get paid for their used oil already. I bet it wouldn't be free. Seems like that oil would have value to someone already, most likely as feed stock to refine into .... I don't know.... new motor oil maybe.

Phil

 

[hyvolt]

Dont by the polaris, got one sittin next to the shop right know, lots of problems. Switched to a tankless,bills droped and never had a problem in 2 years.

 

[jeff5295]

Dont by the polaris, got one sittin next to the shop right know, lots of problems. Switched to a tankless,bills droped and never had a problem in 2 years.

Can I ask which tankless model do you have? I've heard mixed reviews about using a tankless for radiant heat so I'd like to find out more about one that someone has actually been using for this application.

I used a standard 50 gallon N/G water heater in my last shop and it worked great. I haven't yet purchased a water heater for the new shop, so I'm open to other suggestions.

 

[hyvolt]

I used a TAKAGI-JR for my 26x80 shop. Just finished a 40x60 for a friend, and used a TAKAGI T-k3. Take a look at radiantcompany.com

 

[5wndwcpe]

I have a Rinnai r85i. Nice unit.

 

[Vicegrip]

If you can get 150,000 BTU's of useful energy out of a gallon of motor oil, then it would take roughly 200 gallons of used motor oil per month to heat my house and garage during the winter. So, I can heat it for free as long as I have access to the oil from 160 oil changes per month.

It's a great idea. Step one is buy a Jiffy Lube franchise.

Now that I think about it? I bet those guys (oil change places) get paid for their used oil already. I bet it wouldn't be free. Seems like that oil would have value to someone already, most likely as feed stock to refine into .... I don't know.... new motor oil maybe.

Phil

i sell about 3000 gal of clean (no brake fluid, cleaners or coolant contamination) used motor oil each month from the large multi brand dealerships I maintain. Yes we get good money for it.

Slab heat is not efficient. insulating a slab of cement from the ground is hard. Solids move heat better than gasses. The heat in the slab still has to heat the air and contents in the space or only your feet would feel warm. Skip the slab and put the heat in the air if efficiency is a concern. If comfort without air movement is paramount then slab heat might be the ticket.

 

[jeff5295]

Slab heat is not efficient.

Great statement, but do you have any facts to back it up? My facts show the exact opposite. Mine is so efficient, it runs all day, every day, all winter long and we experience below zero F temps on occasion. Our heating season is roughly Oct to April/May. It costs about $60-$70/month to heat my 1900 sq ft shop. I don't consider that inefficient.

insulating a slab of cement from the ground is hard.

Laying down 4x8 sheets of foam board on the ground and along the side of the slab is difficult? Personally, I would insulate a slab regardless of heat type I was using.

Solids move heat better than gasses.

So you're saying the solid concrete radiates the heat effectively? I can agree with that one.

The heat in the slab still has to heat the air and contents in the space or only your feet would feel warm.

Uh, yah. Heating the objects is exactly how radiant works and why it works so well. Heating the air is just a byproduct and a benefit. The point of radiant isn't to just keep your feet warm. If that were the case I'd just wear thicker socks. My shop is the same temp floor to ceiling, within a couple of degrees.

Skip the slab and put the heat in the air if efficiency is a concern

Since hot air rises, that means most of your heat ends up on the ceiling. How efficient is that? I spend a lot more time on my floor than my ceiling.

Just because someone doesn't understand how something works, doesn't mean it can't work. All I'm saying is do a little research and actually experience a radiant system before saying it's bad. I just can't understand why so many people are bashing radiant heat, when they have no actual experience with it. If you don't want it, don't think you'd like it, don't think it could possibly be as good as I say it is, that's fine. But I don't see the point in piping in to say it doesn't work, when you've obviously never had one. I've had both and will never go back to air heat. Believe it or not, radiant is very efficient and very effective.

 

[hyvolt]

Good post jeff5295, some people just dont understand how it all works. Radiant floor systems are the most efficient source of heat.

 

[6806goats]

Thanks jeffs295 and hyvolt. I'm a newb to the site and radiant but my future home has it (ok if the deal closes) and I 'm sure I mentioned elsewhere in here about wanting to do the shop. But the slab has been poured and unless it's cracked up then no need to replace. Ya, I'm stupid in many ways, I haven't seen the place in person, only on the internet. ****, why am I doing it now that I say it like that. I hope the Misses knows whats she doing. Uhhh right.

Anyway, I asked a hydronics instructor (a P.E. who writes instructional material, designs these systems and much more) about how to build a shop floor strong enough to handle a 8000 lb truck. He said they use rebar, a 6" pour and 2" high density foam to support their 10k truck. I think I'll stay with that mindset. I still think that solar hot water heating would be the way to go. Flat panels are cheaper then evacuated tubes but the tubes are more efficient at producing heat. Build a system designed to produce heat in the winter and if it get too hot in the summer I guess block the panel. I'm just learning all that **** but there has to be a happy blend somewhere. And no, the blend I'm talking about doesn't go in a pipe. LOL

Cheers

 

[walrus]

. Build a system designed to produce heat in the winter and if it get too hot in the summer I guess block the panel. I'm just learning all that **** but there has to be a happy blend somewhere. And no, the blend I'm talking about doesn't go in a pipe. LOL

Cheers

Where you don't want to produce heat in the summer, place the panels vertical, the low sun angle in the winter hits them directly, high sun angle in summer doesn't hit them directly. I plan on building them into my south wall, a slight overhang from the eave will shade them in summer, in winter a direct hit. May still cover them in summer with a tarp or something

 

[ScaldedDog]

He said they use rebar, a 6" pour and 2" high density foam to support their 10k truck. I think I'll stay with that mindset.

That's exactly what I did to support my 8000lb Excursion.

Mark

 

[KELLHAMMER]

We did a 1652 sf garage w/ 5/8" tubing @12" o.c. 2" rigid foam under the whole floor and 1" at the edges. No loop was longer than 300 feet. Theres a finished 2nd floor over a portion thats about 1000 sf. We use a 14k output Modulating electric boiler. Kept heat at 65 in the dead of winter and it kept the whole building warm. Electric cost about 300 bucks total for December to march. I like Radiantec, but they wanted me to use the Polaris water heater which would have been more than 50k too much output and cost a whole lot more to purchase and operate. They also said the second floor would not get much heat. But, it turned out that we didn't need to heat the 2nd floor at all. It Stays warm from the residual heat of the garage space below Total cost to install was about 2800 in material and a 1000 labor.

 

[unimog1300]

I use a Rinnai(?) tank less also. Morton Building, 30 X 60 with 16' ceiling, fully insulated, and steel interior. Three garage doors 12 X 14, 10 X 8, and 8 X 8, walk door and two windows. Six zones in the floor, 2" foam insulated footings and 1" 4 X 8 foam on the perimeter only under the slab. I keep the building 50-52 starting Oct/Nov until............still turned on. Also I live in central Illinois. My propane bill is included with my wife's shop that is 22 X 28 and it is stick built, 2 x 6 walls and 2 x 12 ceilings, two story, one two car garage door. Our propane bills have been in the $1200 range for the entire heating season.....total for the two. She runs hers 60 plus for her comfort. The tank less in my building does an excellent job. I would definitely do it again the same way.

I also agree on the ground source (geo-thermal) being too expensive for most people on their building. I had it installed on my house going on 3 years ago and it cost $15,100. Heat bills , electric only, have dropped over $70/month. Next house if we do one will incorporate building, her shop, and house in one structure with geo-thermall heating it all in the floor.

I forgot to mention the propane for my building also runs a standby generator that runs once a week for 15 minutes, unless of course it has to run.