Radiant vs Other - ROI for a shop

NYplumber

Hey there wallies,

New project I am contemplating. 625sq ft in an existing slab on grade shop. ~15000btu heat loss. Shop temp, 55-65*f. All labor is on the house, so lets just keep this to the cost of goods and 3-4year ROI.
Heat source will be the boiler from the house. The goal is to be most cost efficient in fuel usage.

Pellet stove
Pros: simple install. little investment.
Cons: temperature control, filling up the hopper.

Radiant over pour on r10 insulation.
Pros: Fun project. Heat the mass rather then air.
Cons: most costly.

Other source of hydronics (ie. fan coil).
Pros: Cheaper and less complicated then radiant. Instant gratification heat.
Cons: Open door out goes the heat fast.

The question boils down to, how much will the radiant save over time to make its money back? Is the concrete, insulation board, hx, injection loop from the home to the shop all worth it?

Discuss.

Gordy

Depends

Pellets are not cheap. What's your fuel source?

Seems you have the pros, and cons figured out.

What type of heat is the boiler in the home feeding?

How far away is it from the shop?

How do you plan to maintain shop environment? Steady temps? Setbacks?

If you want the shop cool because of infrequent use then fan coil type hydronic heat for quick temp boost.

Are you planning on redoing the floor, or was this rip the floor out to install radiant? Or is the floor non existent?

If your doing the floor one way, or another I would opt for the radiant. But again it's about the usage of the building, and what your willing to hold temps at. A radiant floor done right can recover, but not like other types of heat. Need to plan ahead for usage.

SWEI

I'll just add that if you have gas available (LP or NG) that an overhead radiant heater might be worth considering.

For intermittently used shops/garages in cold climates, my preferred recipe is to use in-slab radiant to maintain the building at a low base temp (something like 50-55°F) and bring the space up to comfort level using overhead radiant when occupied. Don't forget passive solar -- it can easily halve the baseload in most of the US.

hot_rod

Nothing compares to a warm slab if you plan on spending much time on your feet out there.

Along Kurts line of thought, with the right exposure you could add solar air collectors. A little sunshine and some small ECM fans, maybe even a PV module to drive the fans.

Mark Eatherton

Moe, If it were me (and it will be soon) I think I'd go with a combination slab conditioning system, and a hydronic radiant ceiling concentrated in teh aeas that will be heavily and contunuously occupied. Cars and trucks really don't care about the delivery methods, HUMANS care

Radiant floors are so expensive becasue you are thinking in the mode of a minimium of 1 foot of tube per square foot of occupied space, based on teh "warm floors " concept.

I have run tubing in large open spaces (airport hangar) at 18" on center and had perfect results. People working in a shop don't have teh same expectations as people walking around in stocking feet have, In work areas, go with a quick recovery radiant ceiling (low mass, fast recovery) and as Kurt said, use the slab to maintain standby temperatures, and teh ceiling to quickly recover. It also lends itself quite well for adding ANY alternative energy source to the mix. Solar thermal, woody biomass, ASHP for radiant cooling, and more.

If there is a spot that you might need to use to work on the underside of a car/van/truck while on your back, throw tubing into that area at 12" O.C. and keep it set as a seperate zone by controlling that portion of the slab based on slab temperature. When you need it, heat it. When you don't, throw FREE energy at it to help maintain the balance of the garage.

If this is YOUR garage, turn it into a demonstration site that you can then take customers to in an effort to prove radiant comfort, and write the whole thing off on your business expenses.

Looking forward to seeing you in Orlando week after next and introducing you to a few of our hydronic radiant friends

ME

SWEI

If your fuel costs are high, an active solar thermal system can provide some or all of the baseload heat. Annual hours of operation ultimately determine the ROI on any capital purchase. Heating baseload runs ~50% of the year in much of the US. Save the fossil fuels for the short high demand spikes -- 'peaking loads' to put it in utility terms.

hot_rod

But keep in mind, the tighter the tube spacing the lower the SWT required. That is how you can leverage ultimate performance from a mod con, buffer tank, etc. It also allows solar or GSHP heat sources integration at low, efficient operating temperatures.

Pretty much any heat generator runs more efficient at lower temperatures.

For the cost of pex or PERT I certainly entertain 6- 8" on center for any slab. Especially the size slab you are talking about.

While 18" OC may cover the load or warm the slab you will experience some very wide temperature gradient between those tubes.

Ceilings are nice and quick responders but they don't warm under benches or vehicles, if that is the use for the space. Radiant energy is a sign of site transfer.

Gordy

i think if I were to go through the whole process of doing a proper radiant slab. The extra tubing becomes a mute point for its cost. When talking an area of 625 SF. Now a hanger yes it adds up with associated hardware.

Also agree with @hot rod on the tubing density no matter the radiant plane. Dropping SWT creates alternative fuel source options. Thinking the solar end. Of course there is diminishing returns of pex cost to density ratio.

Gordy

Also the shadowing experience with either radiant surface. Again depends on usage of the space. I think insulating a slab alone will be a significant improvement to comfort with only a radiant ceiling. Breaking the ground to slab conduction allows the ceiling radiant to heat that slab. Wide open with no blockage for shadowing of course.

interesting how a shop can benefit from differing planes of radiant depending on usage. As usual MRT being the key component. Mass of objects in a shop are quite different than in the home.

Mark Eatherton

hot rod said:

But keep in mind, the tighter the tube spacing the lower the SWT required. That is how you can leverage ultimate performance from a mod con, buffer tank, etc. It also allows solar or GSHP heat sources integration at low, efficient operating temperatures.

Pretty much any heat generator runs more efficient at lower temperatures.

For the cost of pex or PERT I certainly entertain 6- 8" on center for any slab. Especially the size slab you are talking about.

While 18" OC may cover the load or warm the slab you will experience some very wide temperature gradient between those tubes.
True, but its' not like he's going to be walking around in bare feet working. Overall, the occupant will still be significantly more comfortable just due to the fact that we are dealing with radiant and a higher average MRT.
Ceilings are nice and quick responders but they don't warm under benches or vehicles, if that is the use for the space. Radiant energy is a sign of site transfer.

Regarding the under sides of tables and benches being cool, I find that to be somewhat true when accelerating my ceiling heating system from 40 dergees F., but have looked at it with my IR camera after giving everything a chance to thermally stabilize, and there's really not a huge difference. Maybe 2 degrees F. Once the space is full charged, one can sit at the chair with his legs sheltered from teh source and be comfy overall. Primary transfer is line of sight, but after that, it's boune and reflect time when ma nature kicks in her homogenization process.

Thermal energy flows omni directionally in her effort to make all things equal, mass core temperature and surface emitting wise. At least that's my experience with my system. Depending upon other factors (AUST, ACH, insulation placement etc,) your milage may vary, of course.

ME

Mark Eatherton

SWEI said:

If your fuel costs are high, an active solar thermal system can provide some or all of the baseload heat. Annual hours of operation ultimately determine the ROI on any capital purchase. Heating baseload runs ~50% of the year in much of the US. Save the fossil fuels for the short high demand spikes -- 'peaking loads' to put it in utility terms.

I had a student who built a garage, around 24 x 24 IMSMC, and insulated the slab with 2" XPS. He then tapered the slab such that it was like 2' thick in the middle, and 6" on the edges, with tubing at 12" OC. He had a lean to array of Solaron panels, 10' by 4' times like 6 panels. These panels were directly connected to the radiant system with a 6 gallon electric water heater as a drain back reservoir. He had also installed tubing in the slab apron outside the garage for 10' out away from the garage, by the width of the garage. He had a thermostat connected to a 3 way valve. If the garage was above 45 degrees, then any solar radiation was sent to the snowmelt slab.

The guy raised worms, red worms for composting food scraps. He said if it got below 40 degrees F that all of his worms would die. He'd never lost any worms due to cold, and he never had to shovel the space directly in front of his garage. And it was VERY comfortable over all in his garage. (R19 walls, R30 celing, insualted garage doors)

Whole system was filled with glycol, so no exchanger, nothing but a Taco 00 pump, relays and 3 way diverting zone valve. The ultimate in stripped down system and efficiency. He said if need be, he could plug in the elements on the electric water heater, but hadn't had to in the 5 or 6 years the system had been running.

Solar can be some POWERFUL stuff...

ME

njtommy

Radiant floors would be great in a garage especially working in there for long periods of time. You could still add a fan coil unit as a second stage to make up for set backs and bringing the temp back up quickly after opening the large garage doors.

NYplumber

Thanks all for the replies.

Fuel source is NG. I will be using my home boiler which is right sized for design day. Every other day it is over sized so worst case the slab is going to make longer run times when the house needs heat.

Mark, it is for me and that is a great idea to use it as a show area. I can go as far as making a doormat of glass to show the tubing if i want to go all out. Looking forward to meeting the legends of the industry.

HR, the idea of solar is good however that area has tall trees and i dont plan on adding tree trimming to my resume in the near future.

To all....What it comes down to should i spend the grand or so on concrete and foam or on the stove? Will radiant cost less to heat then a pellet stove? Cost per therm is about a buck. Cost for pellets are about $5 for a bag of quality pellets.

Gordy

The pellet stove won't last forever. There is maintenance, and parts to wear out. Pellets to NG last I had the wild idea the pellets were more than NG, and the work involved.

The radiant slab will last a life time. Of course the connecting hardware can wear out, and break. You already have the boiler, and like ME says right it off on the business.

My question is if there is a slab there already, and in exceptable shape then maybe ceiling radiant is a good option. Either will give you good results. I certainly would not tear out good concrete to install radiant.

NYplumber

@Gordy slab is in good shape, this would be an overpour. Ceiling is not an option since it is not 90degrees to the floor and, i would like to keep the ceiling available to hang items.

SWEI

The difference in comfort going from a ~40°F slab to a ~65°F slab is staggering. If you're going to show it off, I'd go ahead and do the overpour with radiant OH gas supplemental heat. It's the perfect demo for a certain kind of customer. Think semi-enclosed residential or restaurant patio space in addition to the classic mechanics bays or hangar setup.

Gordy

Why not run some good old cast iron rads, or Ci baseboard? You would be surprised at recovery, and comfort. Ask me how I know

Gordy

What exactly will the shop be used for. You have been some what silent with information allowing us to give you the oyster with out the shell

njtommy

@Gordy how do you know?

Gordy

I have it in my garages. 16' of ci baseboard, and a thin tube radiator. Keep the garage at 50.

NYplumber

@Gordy shop will be for hobbys, supplies, man cave, office work....

I will price up the concrete work as its the one thing i do not want to do. Im already in charge of the electrical, insulation, wall covering, shelving, etc.

NYplumber

The more thought tbat goes into it makes me think in the form of ceiling and wall panels
I already have wall and floor radiant in the home. Ceiling would be nice to try. I wonder how it would play with concrete floors.

Mark Eatherton

If you can put 2" thick XPS insulation on the exterior of the slab, it will go a long ways towards conservation, and comfort.
Personally, I don't think you will regret going with radiant ceilings or walls. We as an industry seem to have forgotten that walls, radiators and ceilings were out and more popular than floors were for many years. Floors are fantastic, but do come with a premium, and anyone with a radiant ceiling KNOWS that the floors are NOT cold to the touch, It's the nature of the heat flow beast.

I think you will end up with a fine demonstration laboratory that people can feel and experience. You could always do "Spot treatment" of radiant floors directly in front of the work benches, etc so you can show potential customers the differences betweent he methods employed.

ME

Gordy

I'm sure the ceilings will work alone. Walls may be tough in a garage setting with perimeter stuff blocking output.

I,can tell you the difference in floor temps with my radiant ceiling is maybe 1 degree below set point of the thermostat. That is over an unconditioned portion of the basement.

What is nice about ceilings is it turns objects in a room into micro radiators. With floors those very same objects can actually hinder the floors output.

I should note my garage is 588 SF. No wall, or ceiling insulation, and I can bring the space up to 62 quite easily with 160 supply temps. The convection gets ferocious with the cooler floor. About 16k worth of emitters. Mostly stays at 50.

hot_rod

Are you planning on driving vehicles in that shop?

If not consider an over the slab installation. It will be quicker responding and allows a wide range of floor coverings. There are some really cool floor covering options for shop and work spaces. Even a poured epoxy coating is durable enough for shop use.

NYplumber

HR, no cars or large equipment. I think i settled in ceiling panels unless AHR changes the plan.