Is in floor heat for me?

[jradtke920]

Hi all, I am planning on building a 48x56 garage at my cabin in northern WI. I would like to install in floor heat with an LP boiler, but I am not sure if it will give me the best result. I am only at this property on weekends. How does energy consumption compare when starting up and shutting down the boiler vs running it around the clock at a low setpoint when I am not at the property? Also how quick will the radiant heat up a building? Id appreciate any advice I can get. Thanks

 

[Bert_]

If you shut it down for the week, it will take a couple days before it starts to warm up.

 

[jblnut]

You’re going to get all kinds of people telling you not to do infloor because it isn’t designed to rapidly heat up, and it isn’t. BUT. If you have infloor heat you can set it to the minimum temp you want to keep the building and also have a cheap forced air heater of sorts to rapidly bring the air temp up to where you want it.

Infloor will not be inexpensive but it is sooooooooo nice to work on top of.

If you shut it down for the week, it might start to get warm by the end of the day on Sunday.

That’s a fairly blind statement not knowing any construction details other than size and location.

I have a very well insulated 54x72x18 building and the infloor heat system will take it from 56 to 70 air temp overnight. If I were doing that often I’d keep the floor at 56 and have a forced air topper.

I have a 180k BTU IBC boiler and it’ll drink over 10 gallons a day to keep it at 56-60 when it’s -20f and windy outside.


OP - will this be a space you want to work in on the weekends or just a heated storage space you may want to be in for a few hours on the weekend ?

 

[Innovate1]

As Bert said they respond very slowly due to the thermal mass of the floor. So not that good for a place that you want to heat up without a huge lag after being cold. A plus to floor heat is it can be set lower without issues with the equipment - in contrast a gas furnace if set to too low a temp will have condensation in the first heat exchanger and die an early death. I think 55 - 60F is the safe minimum. And the floor mass works great when the big door is opened briefly - the mass allows the space to be nearly the same temp as before quickly. Probably better choices for your situation, especially if you are going to shut it down completely when you are gone.

 

[HoosierMark]

Following. I built a 36x60 and chose forced air. Plumber and friend wanted in floor. Since I am out there randomly I thought FA would make more sense. And it has for me. I can take mine from 40 to 55 quickly. Often I am only out there for an hour or two and never know when to preheat it. I also turn my ceiling fans on to circulate hot air from ceiling.
it just depends how you will use the building. i Sometimes wish I had put the coils in the floor in case I changed my mind. But that ship has sailed. I don’t thing cost is that much to just put the lines in.

 

[jack stand]

My 40x64 slab will take 24 hours for the initial (early-mid December) heat up. The beginning slab temperature is in the low 40's and the thermostat is set at 60.
Hot air is not so great with 16' ceilings. Even with ceiling fans, a reasonable shop or storage setting of +/- 60* results in nothing more than a cold draft feeling across your skin.
My only experience with the gas tube radiant is at home depot, but I'd guess the this would be a better choice than FHA.
No matter what you decide, put 2" of foam under your slab! You may as well be standing on a frozen lake only heating it periodically.

 

[PoorUB]

Floor heat in concrete can take a couple days to heat to a expected temp. You want to set it at a temp and forget about it.
You could still do concrete with floor heat and run a slab sensor set at 60F. It would keep the cabin around 5-10 degrees cooler than the floor temp. Then use a second heat source to bump it up to 70'ish degrees. For a cabin, a nice wood stove comes to mind. A setup like this is nice because the floor is never extremely cold and more comfortable than a floor that isn't heated.

 

[lonestarky]

In floor heat is awesome for a building you're not at all the time, Imo. It will keep the air temp up, keep the thermal mass of the floor warm and give you piece of mind when you're not there nothing is freezing.

On the other hand, that means you DONT shut it down. It just runs at 55° all the time.

You won't see much of a difference in cost between running at 50 all the time, vs trying to heat it up from 40-60. But, it won't do it in a weekend when it's cold.

I would agree, aux radiant heat tubes from the ceiling and in floor is your best bet, with JUST ir tubes if you're on the fence.

Just prepare for lifts and anchors if you ever want to drill the concrete later.

 

[Denwood]

If you are only using it on weekends, I would install a hanging furnace and call it done. Nothing uses less energy then having the system completely off. If you insulate the building well, slab included, it will heat up quite quickly as needed and ultimately use far less energy than leaving it heated partially and then having a boiler run full tilt for 4-6 hours to heat it up. I did a radiant/insulated over-pour combined with air handlers in a 9000 square foot commercial building (very well insulated) and honestly regretted doing the radiant. The air handlers were far quicker and more efficient to warm the space when needed. I had nine ecobee stats in the building so tracked run times etc. between radiant and the air handlers over a few years. Insulate your slab yes, and run tubing if you want. It may make sense in the near future to use an air source heat pump, towards electrification and ASHP..but it makes no sense for your use case as described IMO.

The only place radiant actually made sense in that building was the loading bay, which was left at about 8-10 C at all times and had a 10'x12' overhead door. I ran lots of tests given the rather unique situation of having both radiant and air handlers to manage the main floor heating/cooling. The Ecobee stats make data analysis pretty easy via web logging and reporting using beestat.io (highly recommended!). The slab was fairly quick to react as we insulated over an existing slab, and added just 2" of concrete for the radiant. It was expensive and ultimately we should have just stuck with the air handlers as they needed to be there for fresh air and summer AC anyway. As you're building a pretty massive garage, for a cottage, my guess though is that efficiency may not be your first concern here...

I leave my detached shop completely unheated except when needed. Outside temps here in winter can hit -35 C, but the shop never dips below -10. It was built sometime in the 70s and is structurally 100%.

 

[fitter30]

Air is easy to heat. Mass is another story have a lot of tools,cars and stuff will take a few days. When a purchased a second house in the country now it's full time winter come down on friday night leave sunday house would be 35° when we left at noon it just started to get comfortable. Cold air would still be in kitchen cabinets.

 

[Firebrick43]

You will feel more comfortable with a lower temp if you have in floor hear.

In my house the air thermostats are set to 67 and everyone thinks it feels warmer than the original house at 72. Original house is 2x6 weather tight house so it’s not drafty.

The garage floor is at 55 and it’s great with just a long sleeve t shirt as your feet are not freezing like my buddies occasional use pole building shops.

 

[HoosierBuddy]

If you want something you can only run while you're there....infloor radiant isn't it.

If you want something you can leave set back 20 degrees and turn higher for when when you're out there? Actually it might be great. You'd need one of those internet connected t-stats so you could turn it up in plenty of time to get it warmed up for you.

My garage can heat up a couple of degrees per hour...so 24 hours before you got there would be a good target time to set it up and see how it works for you.

 

[theoldwizard1]

Infloor will not be inexpensive but it is sooooooooo nice to work on top of.

And that is the BIG win !

The important thing about in- floor heating is insulation. 2" below the floor. 4" is better. You also need to install vertical insulation, down to the frost line, around the entire perimeter.

if you do a double layer and tape and stagger the seams, you do not need a vapor barrier.

You can always use some auxiliary heat for quick warm ups.

I have a very well insulated 54x72x18 building and the infloor heat system will take it from 56 to 70 air temp overnight. If I were doing that often I’d keep the floor at 56 and have a forced air topper.

Some mini-split companies are starting to offer air-to-water heat exchangers. The heat pump will heat the water, and provide forced hot/cold air. Quicker warm up and summertime A/C !

 

[txvwnut]

I'm in Texas and wish I would've done in-floor heating when I built my shop. Winter time cold concrete is not fun at all, as stated above set it to a minimum temp then use a forced air or other means to bring it to a comfortable working temp for you. It's cheaper to maintain a constant temp then it is to bring a building up to temp each time.

 

[Mr onetwo]

Hi all, I am planning on building a 48x56 garage at my cabin in northern WI. I would like to install in floor heat with an LP boiler, but I am not sure if it will give me the best result. I am only at this property on weekends. How does energy consumption compare when starting up and shutting down the boiler vs running it around the clock at a low setpoint when I am not at the property? Also how quick will the radiant heat up a building? Id appreciate any advice I can get. Thanks

First off, have you had an accurate heat loss study done on your design? What are your ceiling heights and openings in the building envelope?Post up a plan view if you have one.Denwood's comments above are very valid.I am a retired mechanical contractor having installed hundreds of thousands of ft of radiant over the years and yet I do not have it in my shop/garage. I have never been comfortable working on a heated slab...I keep my shop at 55 degrees and heat with a gas fired radiant tube heater.I definitely would install insulation,tubing and manifolds in the slab, if for no other reason than for flexibility and resale value in the future. Invest all your money in building insulation...the more the better.That makes your heating choice easier.

 

[Mr onetwo]

I love these things but you will have to build a much bigger building

 

[EricL]

I live in Iowa with a 72 x 60 x 20 building. Filled with cars, woodworking, and a bar area. I did in-floor heating. Its normally set at 56 unless I have an event then I bump the temp to 60. The cost is about 400 of LP per year. No change in temp from the floor to the ceiling. I am happy with it. I am different then you as I am in the building every day.

Questions for you -
Do you plan to have water in your building? Either a sink or a bathroom? This may influence your decision.
Do you plan to change from a weekender to full time working in the building?
Do you plan to sell in the future? What is the best resell option?

Good luck!

 

[Beemer]

Part of the topic I was interested in reading about but didn't see it is how much does it cost to run?
We don't have any and our electric bill is more than any car payment we ever had and heating oil is at $4/gallon .

 

[Firebrick43]

No one heating (or cooling) technology is going to trump another form if the building is not well insulated.

If the slab and envelope are well insulated and sealed in floor heat has the propensity to be the cheapest of continuous heat simply due to the fact that the human body deals warmer at a lower temp if their feet are warm.

And then there is energy cost itself.

Heating oil is not being installed in new builds and is quickly being replaced by natural gas or propane due to cost per btu.

Same goes with electric resistance heat.

This of course is all negated if your wife leaves a window open during sub zero weather so the cats can come and go as they please. And then actually wonder why the heat bill is 900$ for three weeks?