Considering floor heat for a new construction workshop

[Onebean]

I’m in the planning stages of a new construction workshop approximately 36’x36’ with 12-13’ side walls. Side walls would be 2x6 with the maximum R value they will hold. The ceiling will be blown in insulation in the range of R20-30. My current plan is to use tube heat in the floor to maintain a reasonable temp (50-55 degrees), and I will have an HVAC system to bump up the temp if needed while I’m working. The HVAC will also give me the opportunity to keep the space cooled in the peak heat of summer. Nebraska weather can have sustained temps below 20 degrees for January-March, and sustained temps above 90 July-mid September. I will not be in the building everyday, maybe 3-4 times per week, but would like to control the temp so I can work for an hour If the time permits. Here are my current questions related to tube heat:

Is Propane an effective fuel for the boiler? I will not have access to natural gas, and I’m concerned electric will be much more expensive to run.

What would you estimate the cost per square foot for a turn key system including under slab insulation, boiler, pipe, manifolds, and installation?

Are HVAC installers the best folks to have quote the tube floor heat, or is this more of a plumber job? I have a local builder quoting the workshop build, and I’m just trying to avoid getting taken advantage of by an installer.

I will have a bathroom and small kitchen in the work shop. Can I use the boiler as a hot water heater for the sinks too?

Is tube floor heat the least expensive way to keep the space warm 24/7?

Thank you.

 

[Dagny]

I am from a much colder place and install both. Propane is better than electric. In floor is nice but it is expensive especially if you use good quality pipe type A pex is what I use. Most will recommend the hang on the wall boilers because they are easy to install and can run at lower temps. However they dont last as long as a conventional cast iron boiler. Lots of minerals in your water will multiply the problems you have. If you are going to walk around in your stocking feet in floor is the way to go. If not a furnace will work fine or a reznor unit heater.

 

[Onebean]

Dagny, thank you for the response. Can you estimate what I can expect to spend using the good pipe and boiler you mentioned to heat 1300-1500 square feet? Is the in floor radiant heat cheaper to operate than a propane forced air furnace? I can get a competitive bid for a forced air system with duct work all day long. Guys are lined up to quote those forced air systems, in floor tube heat not so much.

The existing garage attached to my house is well insulated, and in the 18 years I have lived here, I’ve never had it freeze in there. I have a forced air furnace that I run when I’m going to work in there, and it will warm it to 60-65 degrees quickly in the beginning months of winter. By the end of December I can really feel the cold coming from the concrete. It takes quite a bit of effort to warm that slab back up, I usually have to run the heater at 70 degrees for close to a week to overcome the obvious cold feeling from the concrete. It’s still cold, just not to the point of freezing my feet in sneakers. Based on this experience I was leaning toward floor tube heat.

Do you think insulating under the concrete floor would dramatically reduce how cold the floor gets in the coldest months of winter? Do you think a forced air furnace set to 55 degrees could keep an insulated concrete floor from feeling cold all winter?

 

[walrus]

Is it worth more for comfort and will you be using the shop all the time? I'd say floor heat is much better as it stays closer to the floor where you are working. Radiant can't be turned up and down quickly, so if you want to set it back at night it isn't going to work. Floor heat will cost much more to install as compared to a hanging hot air furnace. I'm not convinced Radiant costs more to run once installed. Insulation under the floor is a must for either if you ask me. Propane works well for either type of heat. If you can afford to buy your own tank(1000 gallon) you can shop price in summer when its cheaper. I'd make the building as insulated as you can and as tight as you can. It easier to do while building then it is after its built. As a Guess I'd bet 6 grand or more for a radiant system.

I have a solar radiant system in my shop, I built a panel into south facing wall, keeps shop from freezing but wood stove gets it up to temp if I'm out there a long time. But floor is around 50 or so most of the winter so not freezing on the feet.

 

[Alcap]

May I suggest what a friend did . He had a new pole barn / garage put up and before the masons poured the concrete floor he bought all the pex tubing and all things needed to go in the slab , I believe there are special holders to keep the tubes at the correct height. That was as least four years ago . He hasn’t finished the floor heat but figured its there when he‘s ready

 

[Will S.]

If you install in-floor radiant heat, it will be the most comfortable shop you could ever imagine. Wish I could have afforded it when I built my shop, but budget was tight and I got a smokin deal on a new showroom display propane furnace. It does the job, but the floor is always cold.

 

[yeldogt]

Radiant is not for saving money -- it's more to install and there is very minor savings with the running cost if at all. You do it for comfort -- quiet comfort. In my neck of the woods it's typically a combination of the concrete guys and the plumbers ... your area may differ.

w/o natural gas I go propane as my area has very high electric. What is the KW price?

In a cold area you really want to insulate under an on grade slab if you want to condition the space. In my area of PA you can get away with not doing in a deep basement if not doing radiant. Radiant needs that insulation so you are not trying to heat the ground under the slab.

Most people spend the few K doing the tubing on new builds because you can't go back. Yes a boiler can be set up to do hot water as well -- and a couple different ways. Again -- what is logical depends on the use and the amount .... will you have a shower? Washing hands with a sink and bathroom close does not require much water and can be done with a 5 or 10 gallon 120v electric tank unit. Shower changes the formula. Kitchen and bathroom far apart changes the formula.

You can make a comfortable shop with ducted forced air. I always recommend an insulated slab and making sure you have at least one duct coming down to blow along the floor (two is better) . I will say -- rarely do you hear regrets putting in radiant.

 

[jmdirk]

You probably want to insulate your slab regardless. I paid $.170CAD/sq ft for rigid insulation under my slab. Could be up to about $2.30 depending on the psi of the insulation.. I spend about another$1000CAD on o2 barrier PEX.
Probably another $1000CAD on the pump, manifold, valves etc. If you consider that you'll insulate anyway. The extra cost of pex is minimal. Install the tubing, if you don't use it fine. But it's very expensive to try and retrofit later.

The boiler is the big cost. It's all going to depend on how many BTU you need. and that's going to vary based on the design of your building (insulation, doors, windows), your location and your desired set temp. Minimum boiler prices were about $1500CAD for a 10-11kW electric putting out ~34,000BTU. It goes up from there.

Propane vs, electric. you'll have to compare your local prices. Earlier this year, propane would have been cheaper. But prices have risen about 30% over the last year and it's now pretty much equal. you'll also have to consider if the electrical service to your property and garage can handle the increased electrical load.

Minerals etc. in the system shouldn't really matter. Your going to (or should) run distilled water or distilled water and glycol mix. The glycol is good insurance if you ever think your building might freeze such as being left unattended/unheated for long periods of time.

 

[HoosierBuddy]

I agree with the above. You definitely need to insulate the slab if installing in-floor hydronic, but it would be a good investment regardless.

I do not like your idea to have both in-floor heat and forced air heat. It's not necessary and negates the benefit of having hydronic heat to begin with. The floor would end up being cooler, you'd have the noise of the air handler, and you'd have the draft of forced air blowing around. In that case, you'd be better off just going with forced air and not putting floor heat in at all.

For my 3-car with attached breezeway and bonus room above, I went with a fully condensing, modulating wall boiler. It will modulate the burner between 20,000 and 150,000 BTU based on the return water temperature. It has enough "umph" that it will bring my garage up from 50 degrees to 65 degrees within a couple of hours. I would have no need for any auxiliary heat source.

All that being said....for you situation, I'd likely be looking at a heat pump solution to save money vs propane. If money is any concern at all, you don't want an electric boiler or any form of electric resistance heat....but a modern heat pump or high quality mini-split would likely beat propane on a cost to operate basis 9 times out of 10 AND would provide you with AC during the summer months. I'm fortunate that I have NG available, so that was the obvious choice for me.

Phil

 

[yeldogt]

I agree with the above. You definitely need to insulate the slab if installing in-floor hydronic, but it would be a good investment regardless.

I do not like your idea to have both in-floor heat and forced air heat. It's not necessary and negates the benefit of having hydronic heat to begin with. The floor would end up being cooler, you'd have the noise of the air handler, and you'd have the draft of forced air blowing around. In that case, you'd be better off just going with forced air and not putting floor heat in at all.

For my 3-car with attached breezeway and bonus room above, I went with a fully condensing, modulating wall boiler. It will modulate the burner between 20,000 and 150,000 BTU based on the return water temperature. It has enough "umph" that it will bring my garage up from 50 degrees to 65 degrees within a couple of hours. I would have no need for any auxiliary heat source.

All that being said....for you situation, I'd likely be looking at a heat pump solution to save money vs propane. If money is any concern at all, you don't want an electric boiler or any form of electric resistance heat....but a modern heat pump or high quality mini-split would likely beat propane on a cost to operate basis 9 times out of 10 AND would provide you with AC during the summer months. I'm fortunate that I have NG available, so that was the obvious choice for me.

Phil

With his -20 for two months .... I'm not sure I would love the heat pump. No problem if it dips into the single digits ....

 

[Onebean]

Just for clarification, the temps don’t get to -20 very often, maybe a handful of nights per year. Typically in the dead of winter we see around zero at night, and 20’s during the day. I won’t be working in this workshop every day, at least not for quite a few years. I’m really temped by the floor heat, but I also need the ability to draw moisture out of the air for finishing wood working projectS and comfort in the heat and humidity of Nebraska summers.

Insulating the slab before pouring the concrete seems to be the one thing everyone agrees on. At that point, I may as well spend a bit more and put down the Pex pipe too. That gives me some options down the road. It sounds like if I want A/C, I’m going to need 2 different systems. I’d rather not do window A/C units. Does Geothermal heat pump make any sense? I’ve heard in the past they are very cheap to operate once installed. Is that true? Is Geothermal the most expensive up front? Does it run out of efficiency when it gets below a certain temp, like air to air heat pumps do?

 

[walrus]

In Maine geothermal requires wells to be drilled. You use that water generally about 45-50 degrees to "pump heat" out of, water goes back into wells. I know a guy who put pipe in the ground and circulated water/antifreeze thru the pipe, he froze the ground. Not sure how much pipe he had but it wasn't enough. Wells are expensive. The better air to air(mini split type, ductless) heat pumps will work at low temps but like you say efficiency drops off. I'm heating my house right now with 2- 12k units, but I'm about to go to wood. Last nights temps in 20s and they are blowing hot air right now

 

[finn]

Listen to Yeldogt.


I have said this many times, but in floor radiant is best for a building that is used every day. Heating a building 24/7 to shirt sleeve temperatures in a cold climate is crazy. You’re burning propane and only using the heat for comfort maybe 10-20 hours per week.

I ended up adding a supplemental hanging heater and set the in floor boiler thermostat for freeze protection only, then bump the temperature only when I am working.

Propane beats electric unless you have really low electric rates. Do insulate the slab, including the perimeter.

No need for a 1000 gallon tank. I have a 300 gallon tank to supply fuel for a 48x75x16 foot building. I prebuy from a long term locally owned, reliable supplier, with a keep fill plan.
They refill my tank about every six weeks or so in the cold months.

 

[Jackfre]

Pay attention to the orientation of the shop for the addition of solar PV on the roof. My 30x30 8/12 pitch allowed 7.5kwh of panels and I zeroed my electric bill and then some. That is a big deal with out electric rates. I did all the roof work myself and only hired the electrician to terminate the panel. Cost about 50% of what the pro shops wanted. Radiant is the “be$t” heat, or as YD says, best comfort. I wear real shoes in the shop and am not uncomfortable with a propane wall furnace. If you have the resources for radiant and want to do it, then by all means go for it. Pay close attention to your slab edge insulation detail if you go forward on this. We are beginning to see air to water heat pumps hitting the market. You are a ways out on the build so don’t overlook the option. the solar will pay. The radiant will cost. i lived in Lincoln and spent a winter working on a powerhouse in Bellevue. It was fun up at the 325’ level with the breeze off the Missouri.

 

[jmdirk]

Just for clarification, the temps don’t get to -20 very often, maybe a handful of nights per year. Typically in the dead of winter we see around zero at night, and 20’s during the day. I won’t be working in this workshop every day, at least not for quite a few years. I’m really temped by the floor heat, but I also need the ability to draw moisture out of the air for finishing wood working projectS and comfort in the heat and humidity of Nebraska summers.

Insulating the slab before pouring the concrete seems to be the one thing everyone agrees on. At that point, I may as well spend a bit more and put down the Pex pipe too. That gives me some options down the road. It sounds like if I want A/C, I’m going to need 2 different systems. I’d rather not do window A/C units. Does Geothermal heat pump make any sense? I’ve heard in the past they are very cheap to operate once installed. Is that true? Is Geothermal the most expensive up front? Does it run out of efficiency when it gets below a certain temp, like air to air heat pumps do?

You'll probably pay more for a geothermal heat pump than you pay for your entire building. Seriously.

I have one in my house and had to replace it a few years back. I think it's a 1.5 ton unit and ran $16k CAD just for the heat pump.

Drilling the wells and or putting in the ground loops can easily double-triple that cost.

 

[kelpaso1]

Geez some of you guys suggesting the most expensive ways to heat. Get a minisplit and be done with it. My 18KBTU costs me an extra $30/month to keep my attached 24X24 at 62 degrees 24/7. Keeping a space warm all the time instead of heating only when your out there does not save you anything unless you go months without heating it.

 

[theoldwizard1]

My current plan is to use tube heat in the floor ...

Be careful of your terminology. When some people see "tube heat" they will immediately think of gas fired ceiling mounted tube heaters. Clearly not what you want.

... and I will have an HVAC system to bump up the temp if needed while I’m working.

Good. Radiant floor heat does not shift from low temp to high temp quickly.

Is Propane an effective fuel for the boiler? I will not have access to natural gas, and I’m concerned electric will be much more expensive to run.

Propane is much more cost effective than a electric boiler.

Is tube floor heat the least expensive way to keep the space warm 24/7?

Probably not, but it is the MOST COMFORTABLE form of heat.

A properly designed and install mini-split heat pump system is probably the cheapest to operate. Expensive to install, no additional cost for AC. Not as comfortable as radiant floor heat because it is has basically forced air.

With any heat pump system you need a backup heat source unless the building and it's contents can survive without heat for several days during a power outage?

 

[HPRifleman]

The quotes I got for a turn-key in-floor heat system:

600 sq. ft. garage converted to living space: $8,775
1070 sq. ft. garage: $10,575
Both areas in same project: $11,750

 

[spudley]

A few years ago, I built a 24 x 40 two story garage with the intention of an upstairs wood shop. However up and down 16 stairs dozens of times daily during construction quickly got real old (as did I) and the wood shop stayed on the first floor.

My hanging heater works great to quickly bring up air temps but the floor stays cold until August. I should've at least installed pex during the concrete pour.

 

[Juiced06GTO]

The most costly part of prepping for the floor heat is the insulation, especially right now. I think I paid $34/ sheet of 2" XPS last spring,it used to be possible to find reclaimed foam board, but I'm sure the supply is short right now. I got the pex tube pre cut to 300' for i think $99 bucks a length from amazon, and the manifold was maybe $150. The staples weren't cheap, maybe 40 bucks and I needed a box and a half to do 1200 sq ft. The tubing would have been cheaper in a roll, but much more difficult to handle and cut accurately.

I am trying to decide on the boiler now and am leaning towards an electric boiler right now, mostly because I am considering a large solar array on the south facing side of the barn to offset the cost and make up some of the bill on the house. I'm meeting with the solar company this Thursday to discuss that option, which will really determine what I end up with for a boiler.

 

[yeldogt]

The most costly part of prepping for the floor heat is the insulation, especially right now. I think I paid $34/ sheet of 2" XPS last spring,it used to be possible to find reclaimed foam board, but I'm sure the supply is short right now. I got the pex tube pre cut to 300' for i think $99 bucks a length from amazon, and the manifold was maybe $150. The staples weren't cheap, maybe 40 bucks and I needed a box and a half to do 1200 sq ft. The tubing would have been cheaper in a roll, but much more difficult to handle and cut accurately.

I am trying to decide on the boiler now and am leaning towards an electric boiler right now, mostly because I am considering a large solar array on the south facing side of the barn to offset the cost and make up some of the bill on the house. I'm meeting with the solar company this Thursday to discuss that option, which will really determine what I end up with for a boiler.

I was a bit shocked at the cost of foam last summer as well .... needed two sheets of the pink 2" stuff. It was a lot! I just thought it was my local yard charging a lot because it's really just a curtesy item for them ...

Some times you just have to bite the bullet and move on