Shop heat 'sources'

[David Miller]

Hi all,

Looked around for posts on this but only found different ways to heat, not the heat sources (at least for hot water).

I'm in the planning process for my new shop. It will be a 22'x30' detached building with plenty of insulation (6" walls and >9" overhead) and hydronic heat in the floor. My question is what to use to heat the water? Of course I will have electric in the shop so I was considering an electric water heater. But in my last shop I used a tankless electric water heater and the electric bill definitely reflected the usage. Anyone have experience with an electric tank water heater for hydronic heat?

Now, I am planning on having a new high-efficiency boiler installed in my house in the next month or two, but the new shop will be 20-30 feet from the house, so that source is out (I think).

I also have natural gas at my house but am unsure if the cost of installation (gas line run to the shop, installation of gas water heater) will justify it over the electric water heater.

Ideas?

Thanks,
Dave

[Ken Fitzgerald]

David......I wanted very much to have radiant floor heating in my new shop. I ran into some very stringent code issues that ended up causing me to throw my hands up in the air and say no!

Will you have water in your new shop? This was the primary cause of my dilema. Without a source of water in your shop, the heating system hot water heater or boiler has to be designed to shut off the system incase a leak develops. The project got too complex and costly. I considered putting the tubing in and then finishing the project when I had readily available cash in a few years. The local city wouldn't leave a heating permit open for an extended period. I ended up having natural gas piped into the building and for Christmas this past year the LOML bought and had installed a Lennox 75,000 btu overhead gas furnace.

In my case, the local utility cable made up a plastic gas pipe with fittings at each end. It was about 50' long and cost me IIRC about $150. The plumbers installing the furnace installed the line. It cost me $250 to have the ditch dug. They T-d into the output of the gas meter for my house and installed the line. I had them plumb in the pipe in the shop for the hanging furnace before I finished the interior.

There are a lot of internet sites with a ton of good information concerning radiant floor heating and DIY.

Good luck with you new shop!

[David Miller]

Thanks Ken. My previous shop had a closed radiant heat system. So even though I had water in the shop it wasn't tied into the heating system. I pressurized the system with a garden hose at the beginning of the season and didn't need to touch it till next year.

Perhaps having natural gas piped to the shop wouldn't be too expensive. The gas meter is on the back of my house maybe 30 feet from where my shop will be located. But I wonder if the operating costs will be any better than electric.

Thanks,
Dave

[Lee Schierer]

Is there anyone in your area that installs geothermal heat pumps. We heat our house with one, since there is no natural gas on our road. It is quiet and efficient. You can have either forced air or hot water heat. You would still need a water source for the radiant heat. No water required for the forced air systems. The ground loop needs a sizeable area of land.

[Gary Curtis]

An electric water will run about $300 at Home Depot. An electric boiler is around $2000, and its single advantage would be a waste for 400 ft/sq. That advantage is speed.

If there is a way you can tap into one of the lines from your floor heating circuit, then just plumb in a radiant panel on the wall.

In two different homes, I had hydronic systems I installed. I had a plumber put in the nat. gas boilers. An electric water heater is a bit slow to supply water to a heating system, but since you say the place is well insulated, that would not hinder you. To to this site and order their catalogue - 2hsc.com.

They can walk you through the design and the install procedures over the phone, though the catalogue has some great explanations. The key factor in cost is to keep the heater/boiler cost to a minimum and your local electric rates.

Gary Curtis
Trinity County Calif.

[Bruce Wrenn]

Why not run hot water from boiler in house to slab for heat? All you need are a couple of 3/4" pex pipes. Buy foam insulation for pipe and insert into schedule 20 sewer and drain pipe, making sure that both ends terminate above grade so as to prevent the entry of water. For insulation, look a "Dollar Store" for swim noodles for a buck Some of these can be slid over 3/4 PEX. Be sure and bury pipes below frost line. This is how water from "Outside Boilers" is run.

[Frank Hagan]

Bruce is right ... 30 feet is not an insurmountable distance to run another zone off your house boiler, assuming the boiler is sized to heat both shop and house. That would be the least expensive alternative.

It used to be that natural gas was always less expensive than electric, even with the nearly 100% efficiencies of electric heaters (inexpensive gas boilers are about 80 - 82% efficient on average). But I understand that in some areas of the country, like NW Florida, natural gas can be more expensive.

You can do the calculations yourself by knowing the conversion factors. You'll have to know how your local utilities charge. Electric is usually billed by the KWH (kilowatt hour), the amount of energy used per hour, and the output in heat is about 3,414 BTU per KWH. That's without any losses, but they are so small in the case of electric heat that it almost doesn't matter.

Natural gas is usually sold by the cubic foot or therm, with total BTU/hr of somewhere around 1,000 BTU per cubic foot (it varies by region). Then you have to take your efficiency losses off, so its sometimes easier to consider the natural gas at 820 BTU/h per cubic foot (for an 82% efficient appliance).

A therm is 100,000 BTU/hr, so the math is pretty easy if you convert everything to BTUs.

[J. Scott Chambers]

Why not run hot water from boiler in house to slab for heat? All you need are a couple of 3/4" pex pipes. Buy foam insulation for pipe and insert into schedule 20 sewer and drain pipe, making sure that both ends terminate above grade so as to prevent the entry of water. For insulation, look a "Dollar Store" for swim noodles for a buck Some of these can be slid over 3/4 PEX. Be sure and bury pipes below frost line. This is how water from "Outside Boilers" is run.

This sounds like your best solution. It won't cost anymore to run the PEX piping than it will to run the additional gas piping and buy additional equipment. Add to that, using the boiler gains the advantage of a better recovery speed.

A newer residential boiler shouldn't take up anymore space than a water heater, not much anyway.

[John Bush]

Hi David,
I heat my 1600 sq ft shop with a gas hot water tank, a four zone manifold, pump, relay and thermostat, and the system works perfectly. Another poster had mentioned recovery time and I don't think that will be an issue when the floor mass is up to temp. I'm not in the construction biz, but I did most all the work myself and as simple as all the systems were to install I would recommend you tap into your domestic boiler as a heat source. I would joint trench with your electric, heat lines and water line, add an empty conduit or two for future communications lines(cable for ESPN and the big plasma screen above the lathe) and also put in a gas line for future use if you decide to change systems later. I know there are some limitations on joint trenching and mixing utilities, but the joy of doing your own work is the ability to "improvise" as needed. Seems as if you have several good options. Good luck, JCB.

[David Miller]

Thanks all! To pass on a little more info, I am currently waiting for the quote to install a Buderus high-efficiency boiler in my house. When the contractor stopped by to look things over I asked him to add in a zone for my shop. At that time (last week) I was planning on connecting the shop directly to the house. But now I will have a separate building.

I'll ask him about running the zone to the shop. I am worried about heat loss and how much the boiler would have to run just to get the hot water to the shop.

I'm also waiting for a quote from radiant heat company on the energy needed to heat the shop. When I have the BTU's needed I can calculate what will be the most efficient source of heat.

I plan to run the other utilities (electric, phone, internet, water) in conduit. Maybe I will run a gas line too, just in case.

-Dave

[Gary Curtis]

The heat loss from a boiler to an adjacent building is almost nil. You simply wrap the copper piping in 1" foam insulation and bury it.

Heating requirements for a room are about 25 btu per square foot. An unusually high ceiling would change that, as would lots of windows. But 25 is the rule of thumb.

My old home had a 6-car garage and a 2-car garage. We converted the double car unit to an apartment for my mother-in-law. The structure is very well insulated. I plumbed an extra zone onto the existing boiler (28,000 btu).
This is in Southern California, so temps are moderate. The thermal mass of the structure took 3 days of continuous heating to warm up initially.

That was in December. After that, the zone rarely calls for heat more than 10 minutes at a time. My memory isn't exact, but I recall that 3 radiant panels and 1 pump cost a bit over $600 in 2003.

Gary Curtis

[Robert Mickley]

The heat loss from a boiler to an adjacent building is almost nil. You simply wrap the copper piping in 1" foam insulation and bury it.
Gary Curtis

I wouldn’t waste the money on insulated lines. I have a 60-foot run from the boiler to my house. When I put it in I was broke and couldn’t afford the insulation for the lines. I buried them 3 feet deep and I have a 1-degree temperature drop from the boiler to the house with a water temp of 150 degrees.

When I first hooked it up I was waiting on the trencher and needed heat the lines laid out on the ground for two weeks even then I only had a 6-degree temperature loss. The insulation is just a scam to get more of your money. You have to remember at 3 feet down the ground is not going to freeze, its going to stay about 55 to 60 degrees.