Radiant Floor Heat Unit Sizing

[kyhuntclub]

Hello community. First off I have to say there is a ton of good information on this forum and I am enjoying the newly found knowledge. I have been lurking and reading alot in preparation for building my first garage/furshed. I have found answers to several construction concerns, many tips and created too many wants for my pocket book. One of those wants that I cant get out of my head is the radiant floor heat. After reading as many posts as I could find with the search function I have come down to having to make my first post and ask some questions.

Second, I guess I have to give you a visual of my plans. 32' x 56' x 12' pole barn. posts are 8 OC, trusses 4 OC, singled roof, (2) 10' x 10' overhead doors side by side on one end. Metal ceiling with a couple inches of blown insulation ontop(more in the future). Framing in the walls with 2" x 6" on 24 OC and fiberglass insulation and osb walls. If I go with radiant floor heat I will do it right before the pour with 2"insulation. I have down loaded the loopCAD program and got a plan. Here is where my questions start. I have been researching the options of outside wood burner and electric. I think I like the electric option the best.

How big of a unit do I need? 2 ton, 3 ton, btu, etc? This is greek to me. I know nothing on this subject. I am just tring to price the materials and equipment to make my mind up on the idea before I start building next month. If I decide to go with it I will put the pex in and then get a HVAC contractor to do the rest

My main goal with heat is to keep it around 68 degrees threw out winter/trapping season. KY winters are fairly mild.

 

[anthony666]

google 'heat loss calculator' .. there a lots of them available free .. plug in all your building details and it will spit out a number which basically is the amount of btu's you need to produce to counteract the amount of heat your building loses .. round that number up & match your heat source size accordingly

 

[kyhuntclub]

Thats for the advice but I am not looking for a calculator. I am looking for experience.

 

[stingry]

Thats for the advice but I am not looking for a calculator. I am looking for experience.

I hate to burst your bubble but anyone with "experience" is going to tell you that you need to start with some type of heat load calculation to get some idea of how much heat input that you will need to heat your building.

Cheers
Steve

 

[Highbeam]

If going with electric then you will find that many are sold by the watt and the rest by the btu output. If you use a calculator, try a few and you will find that the results vary widely. The results vary so much as to be nearly useless.

You need to be able to tell us the R-value of the insulation in the ceiling and walls before we can even guess. Also, the temperature outside when it is coldest. With this info there are sure to be a few members that can match your building with theirs to try and relate the experience.

You really can't oversize an electric boiler as the thing will always be 100% efficient.

 

[anthony666]

Thats for the advice but I am not looking for a calculator. I am looking for experience.

 

[kyhuntclub]

The insulation in the walls is going to be R19. I am not sure what the insulation will be in the ceiling. I have $1500 dollors in my budget for the ceiling. How ever much that will blow on top.

Temperatures here vary a lot. I would say the temps average low's at 20 and high 40

 

[BadgerBoilerMN]

google 'heat loss calculator' .. there a lots of them available free .. plug in all your building details and it will spit out a number which basically is the amount of btu's you need to produce to counteract the amount of heat your building loses .. round that number up & match your heat source size accordingly

Gosh, I wish I would have know that before I spent 25 years and thousand of hours learning how to design radiant floor heating systems. Silly me

We start with a proper heat load, performed by and experienced radiant floor designer using dedicated software purpose built for radiant floor LoopCAD certainly qualifies (not our favorite) but it usually takes some formal training to pick up the skill-set necessary to draw up a plan.

The fuel source is the second item on our list of radiant floor design questions since the source of fuel can change the tube spacing, length, depth and design water temperature of the system. Not to mention control strategies.

When deciding on a fuel source the cost of fuel per therm is determined. The lowest cost may not always dictate the fuel source but one should know. It is unusual for electricity to be the lowest cost fuel but in my own case this was the fact. Even though the bulk of our business is in gas-burning condensing boilers they do cost more to install than any electric boiler since labor may triple the installed cost.

However, if the electricity costs three times as much and natural gas--just a mile up the hill from us--the boiler would have been a condensing gas-fired and direct-vent.

Insulation is dictated by climate. The colder it gets the more you need.

One of the great things about using software to perform heat loads is the built-in energy codes and the ability to model different insulation options and instantly see the difference and calculate the pay back.

Most of the systems we consult on, after-the-fact, suffer from over-sizing, poor distribution and lack of proper slab insulation i.e. foil, blankets etc, etc.

 

[BadgerBoilerMN]

You really can't oversize an electric boiler as the thing will always be 100% efficient.

In theory. However, if a boiler serves a zone or a building that presents a load so small that the boiler cycles on and off in cycle below a couple of minutes relays and even comfort may suffer.

And then there is the extra cost of bigger boilers. We like to use a two stage or infinite output model with weather sensitive controls, which will save fuel by lowering the average water temperature along with the heat load.

 

[anthony666]

Gosh, I wish I would have know that before I spent 25 years and thousand of hours learning how to design radiant floor heating systems. Silly me

lol, you shoulda just asked me brother

 

[kyhuntclub]

Thx, I am starting to realize pretty quickly that this is something I cant do and I am too thirfty to hire someone to do it. Thx again for the input.

 

[BadgerBoilerMN]

Not trying to discourage, just get it done right. There are several reliable on-line vendors that can help with simple designs and add hide in the cost of materials so you feel no pain.

Try NRT or Blueridge.

 

[OldNeons]

Don't give up so fast, nothing good is ever easy. If you stick it out and do a radiant floor, you will NEVER regret it. At a minimum insulate floor and install pex according to a designed plan. Go back and finish system when you can afford to do it right.