How efficient is in-floor heat?

[TRITOON]

For two evenings a week, you will be throwing money and comfort away trying to do infloor heating. Hot air will warm up the area faster and save you quite a bit of money in the long term.

 

[finn]

Don’t know the answer………but………the question is: if your system was just the hanging Beacon Morris* would the heating cost and heating effectiveness change for better or worse, knowing what you know would you spend the extra cost for in floor radiant ?

* given a larger btu unit 150k for the building size and climate

Hanging heaters like the BM are typically ~82% efficient.

The condensing boiler I am using is 95 or 96% efficient, and has the capability of heating water for domestic use, so I can eventually get rid of the small electric water heater, if I choose.

The slab w/ insulation and tubes was there when I bought the shop. I scrapped the old, troublesome cast iron oil fired boiler, and the power company rebate program paid for new high efficiency Taco circulator pumps to replace the old Taco energy hogs.

My other garage has an insulated slab with pex, and insulated walls and ceiling, but I choose to go with a hanging heater instead of completing the radiant installation. I don’t do enough work there to justify heating it full time.

 

[Copymutt]

Just an additional comment. Anything that is in contact w/ a heated slab gets heated via conduction. That being cabinets, furniture, tool chests, stands for grinders, polishers, vices, anvils etc. they all become convective heat generators. This may sound minor, but it does add significantly to the comfort fact of the space.

 

[cfk]

Hanging heaters like the BM are typically ~82% efficient.

The condensing boiler I am using is 95 or 96% efficient,

Thats what prompted my original post.. I would think that keeping the shop at 45 degrees all winter would be cheaper to do with in-floor heat than with a hanging heater. And then heating the air up to working temp would be easy after that for the evenings I want to work in there..

And with in-floor heat, do I maybe only need to heat the up to 60 degrees with the hanging heater since the slab and objects will be more comfortable?

All the pros of in-floor are making me lean toward it... Not exactly sure what the payoff is on it, but I suppose I could run the hanging heater only for a year or two and then hook up the in floor later and see what happens to my propane use. And the fact that propane is more expensive than NG means that the more efficient system will pay off faster.

One other thing keeps playing through my mind....I have yet to meet a single person that regrets running the lines in the floor - but I've met plenty that wished they would've because they can't go back and do it now.

 

[Showkey]

Alternative plan ?
95+ Propane ( NG) furnace for about $1000-$1500 DIY install. NOT run and or install two systems.
Enjoy the saving for 90 plus efficiency, set the your required temp, fast recovery from 50— 70*.
Shop duct work could be minimal to none.
Typical Hanging furnace $300-700, venting $200-500 estimate DIY install likely double for pro install ?
Yes, 90 plus furnace can not freeze and you have deal with condensate…….but…..same for 90 plus boiler as well.

I have a Beacon Morris 45k hanging heater in very well insulated 1000 sqft shop……..if I had to do over I would consider the high efficiency furnace. I estimate my NG cost to heat the shop to 55-60* in the coldest months is about a $1/day. Not outrageous by any measure. The 90 plus furnace is a demanding install ……often easier than hanging units.

Given the trend in energy cost …….currently we are likely at the lowest cost in years. The trend will be up and in some areas up quickly. Insulation and high efficiency are going to pay off in years to come.

There are many brands and HVAC a supply house selling units in the market, delivered to your door.
They can be pro installed as well. Some pros might not be real enthusiastic as they lost the sale and profit on the unit.

 

[finn]

Alternative plan ?
95+ Propane ( NG) furnace for about $1000-$1500 DIY install. NOT run and or install two systems.
Enjoy the saving for 90 plus efficiency, set the your required temp, fast recovery from 50— 70*.
Shop duct work could be minimal to none.
Typical Hanging furnace $300-700, venting $200-500 estimate DIY install likely double for pro install ?
Yes, 90 plus furnace can not freeze and you have deal with condensate…….but…..same for 90 plus boiler as well.

I have a Beacon Morris 45k hanging heater in very well insulated 1000 sqft shop……..if I had to do over I would consider the high efficiency furnace. I estimate my NG cost to heat the shop to 55-60* in the coldest months is about a $1/day. Not outrageous by any measure. The 90 plus furnace is a demanding install ……often easier than hanging units.

Given the trend in energy cost …….currently we are likely at the lowest cost in years. The trend will be up and in some areas up quickly. Insulation and high efficiency are going to pay off in years to come.

There are many brands and HVAC a supply house selling units in the market, delivered to your door.
They can be pro installed as well. Some pros might not be real enthusiastic as they lost the sale and profit on the unit.

The cons to any high efficiency boiler or heater in an outbuilding include disposal of the condensate in extreme temperatures. You need some sort of drain that won’t freeze, which may be an issue.

It is for me. My condensate goes into a slop sink, then into a drain connected to the septic. Not ideal, as the line runs under a slab in an enclosed, but unheated 16’x60’ lean to, and freezes solid by late February.

A couple of 4x8’ sheets of blue 4” foam on the floor provide enough insulation to prevent freezing, so far, but that’s not a very elegant solution, and is far from permanent. I may do up tearing out part of the floor to bury he line deeper, and reroute it from the septic.

A high efficiency boiler or furnace also pretty much commits you to heating 24/7, even if you are away for weeks or months, which may or may not be an issue

 

[finn]

Thats what prompted my original post.. I would think that keeping the shop at 45 degrees all winter would be cheaper to do with in-floor heat than with a hanging heater. And then heating the air up to working temp would be easy after that for the evenings I want to work in there..

And with in-floor heat, do I maybe only need to heat the up to 60 degrees with the hanging heater since the slab and objects will be more comfortable?

All the pros of in-floor are making me lean toward it... Not exactly sure what the payoff is on it, but I suppose I could run the hanging heater only for a year or two and then hook up the in floor later and see what happens to my propane use. And the fact that propane is more expensive than NG means that the more efficient system will pay off faster.

One other thing keeps playing through my mind....I have yet to meet a single person that regrets running the lines in the floor - but I've met plenty that wished they would've because they can't go back and do it now.

It takes perhaps a half hour to bring my shop from the low to mid forties with the hanging heater. The floor is relatively warm, from the radiant, so the low sixties, for me, is adequate.

I will be the first, and maybe the only, person to say or regret installing tubes in my other garage floor.

Put up the building in 2003 and never installed the boiler.

I have a wood stove and hanging heater in that building. The wood stove, if fired every couple of days, keeps the slab relatively warm, and the inside well above freezing. The hanging heater takes a while to bring the temp up if I don’t keep the wood stove regimen up and allow. the slab temp drop below freezing, though. Relatively warm slab gets you faster air temperature rise.

It’s all about managing thermal inertia / thermal mass.

 

[65ranchero]

That is what I said here last week, I'm in Minnesota in a pole barn house, garage is at 67° all winter and floor is 68°-70°

Same here, I keep my radiant at 58F and the ambient is better that than that in the surrounding air.
Keeps it warm enough to defrost the snow blower and utv after use and still warm enough for breakdown repairs if needed

 

[That1Guy]

I keep my shop slab at 55 - 65 degrees which is about 50 +/- room temp and is warm enough for me to be comfortable when I'm working. If I'm not working or if the wife or grandsons are out there with me, I go with plan B. I left one pex circuit out of the concrete and instead routed the pex to a large water-to-air heat exchanger (basically looks like a 20 x 30 truck radiator) with a fan. When I power the fan, it's as good as any forced air hanging unit I've ever had and it brings the room temp up really quickly. No need for a second heater or more plumbing of gas and exhaust. It was super simple to set up and it works great.

 

[Sumboodie]

I live in a pole barn house, in floor heat in the house in floor heat in the garage, all winter long my garage is at 68° if I use my infrared heat gun the floor is at anywhere from 65° to 70°

Exactly.
10-20* heat loss would be horrible. Like doors and windows open situation.

 

[Ak Jim]

1300 sqft using a simple Emerson thermostat and radiant heat. I’ve never ever seen the temp of the room overshoot the thermostat setting in the wall. You live in a pretty mild climate. Just do the radiant and leave the temp set to 60.

 

[finn]

1300 sqft using a simple Emerson thermostat and radiant heat. I’ve never ever seen the temp of the room overshoot the thermostat setting in the wall. You live in a pretty mild climate. Just do the radiant and leave the temp set to 60.

My house has radiant. The overshoot is a big issue in the shoulder season when it gets cold a night but there is a big sun induced thermal load by late morning. It’s hot in the house and the floors are still emitting heat.

Not an issue in mid winter when it stays cold all day and it’s overcast.

 

[Jackfre]

Look up “the half plan” on the Internet.
Engineer guy wanted to cut his utility costs in half and had radiant heating system so he built solar collector/solar heating system.
Large box with black tubing in it, built onto the side of a shed facing the primary sun direction.
He was in show country so the angle was to shed the show. He bolt a solar collecting box painted black inside with black piping. Idea was to have the sun heat the water in the tubes part of the way and then let the furnace heat it the rest of the way as needed for the radiant system. For your system you likly only need the solar part of it and then add the space heating to bring the temp up for when you are working

Thermal solar cannot compete against PV solar. Also, the costs of the storage tank, which has to be quite large and pumps, etc make it impractical. Thermal solar is ideal for radiant heat as your collector efficiency is so high due to the lower temps, but again, you get solar benefit only in the heating season. PV works yr round.

 

[yeldogt]

My house has radiant. The overshoot is a big issue in the shoulder season when it gets cold a night but there is a big sun induced thermal load by late morning. It’s hot in the house and the floors are still emitting heat.

Not an issue in mid winter when it stays cold all day and it’s overcast.

You can get a duel temp control with a floor sensor. it's stop the floor from getting to hot ..... it.s a work around but will often help

 

[finn]

You can get a duel temp control with a floor sensor. it's stop the floor from getting to hot ..... it.s a work around but will often help

Already have a floor sensor.

Easier to just use the mini split in the shoulder season, or get a small fire going in the wood burner for chilly mornings.

 

[yeldogt]

Already have a floor sensor.

Easier to just use the mini split in the shoulder season, or get a small fire going in the wood burner for chilly mornings.

It would be a rare house built in the past 30 odd years w/o AC and radiant heat. Replacing the straight AC with a heat pump solves the shoulder season problem.

Mini splits are great problem solvers -- They are often the ticket for AC in hot water houses and the ability to give that hit of heat on a cold morning is really nice.

Building new it's all a question of needs and cost. On the last couple houses I have done it made sense for me to do a furnace rather than just a HP in the ductwork. All have had propane and not full time residences .. so I was looking for options. Gone for a month in the winter -- you can turn down the radiant and have the furnace for faster warm ups. It's over kill but the cost of the furnace vs just the air handler is not all that much more when you look at the radiant budget.

Now with internet control ..maybe not needed?

My current project actually had to use mini-splits in a few areas due to the fact I had no room for ductwork -- so having the hit of heat from them is a bonus.

 

[86turbodsl]

Already have a floor sensor.

Easier to just use the mini split in the shoulder season, or get a small fire going in the wood burner for chilly mornings.

I had this problem. I added outdoor reset to my system and it helped a bunch.

 

[TRITOON]

In floor heat is good for drying up water that’s on your floor. The problem with
It is regulating your air temperature with it. If your thermostat is wall mounted, by the time the slab warms up enough to make the stat turn off, it is hot enough that it will keep warming up the air and makes it too hot. You are better off going with a stat operated by a temperature probe in the floor itself. I would still go with radiant tho. My brother heats his whole house with in floor heat and he complains all the time, he wishes he had a forced air system.

Has he tried turning down the thermostat to a range where it's comfortable at should height?

I love radiant heat but get that if you try to run it at 72 you are going to be hot and miserable

 

[Firebrick43]

My 1450 square foot addition is radiant, as is the 850 garage. The existing house was 2x6 walls with fiberglass and r60 in the ceiling, tight for the time in 2001 when built. The original house is 72 degrees, the addition with radiant is 67 degrees with 69-70 slab temp. It feels much more comfortable than the existing house. The garage is set at 55 and is quite comfortable. A buddies building with hanging heater feels colder at 72 degree air temp on the thermostat due to the cold slab.

I have fallen asleep a few times on the creeper.

 

[Root'N-Rumble]

I live in a pole barn house, in floor heat in the house in floor heat in the garage, all winter long my garage is at 68° if I use my infrared heat gun the floor is at anywhere from 65° to 70°

I am building a pole barn home as well, what zone do you live in? Im in 6 in Western MT. The guy that I'm using to build my pole barn just did a pole house as well. He heats in floor and says his second story is heated only about degrees less than his lower level. I am building on the second level of mine not lower and considering heating with the in floor heat from the shop to the second story. What ya think.

 

[kj_mustang]

My building has a second floor with no heat and is near the border between zones 4-5. It stays about 3-4 degrees cooler than the lower level with radiant floor heat. I keep the thermostat around 58 F since I only work out there occasionally. When we lived in the building for 1.5 years, I kept the thermostat at 70F. I would recommend that you plan on some heat upstairs for your climate. I would consider radiant panels or better floor heat using some kind of warmboard product. And insulate the best way possible.

 

[HoosierBuddy]

Good advice from kj_mustang above. I have living space over my shop with in-floor hydronic. I keep the shop 55 or 60 and the living space 70 so obviously I have 2 zones. I didn't use warmboard, just loop pex loops stapled to the subfloor and fiberglass batt insluation under that....and it is marginal. I should have used the warmboard, litecrete or similar to get better heat transfer out of the pex and into the upstairs.

My upstairs space has fairly large windows on all 4 sides and vaulted cielings, which doesn't help anything as far as keeping it warm. Some spaces are going to be easier to heat than mine and that would help too.

 

[Rc_Guy]

I am building a pole barn home as well, what zone do you live in? Im in 6 in Western MT. The guy that I'm using to build my pole barn just did a pole house as well. He heats in floor and says his second story is heated only about degrees less than his lower level. I am building on the second level of mine not lower and considering heating with the in floor heat from the shop to the second story. What ya think.

I’m in zone 6 but real close to zone 7, but I don’t have a second floor. Climbed ladders all the time at work and didn’t want stairs when I retired.

 

[CHRISTOPHERMK1989@GMA]

25 yrs. w/ exactly the combo you’re thinking about. Never looked back. NG makes the most economical choice. I keep it at 50*, turn on the Modine when I’m out there and very comfortable in a few minutes. Did have to replace the Grundfos pump cartridge once. That’s been it. Zone 5. Well insulated slab w/ thermal break between slab & stem wall.

Well insulated slab w/ thermal break between slab & stem wall. You said this 4 years ago...what exactly does this mean ? Can you break it down for a layman?

 

[Copymutt]

Well insulated slab w/ thermal break between slab & stem wall. You said this 4 years ago...what exactly does this mean ? Can you break it down for a layman?

Slab is poured on top of 3” of polystyrene. Then the in floor tubing is laid.
2” of polystyrene against the inside of the stem walls. This leaves a 2” edge end of the insulation on the perimeter of the slab & totally isolates conduction of slab heat to the stem wall. To deal w/ that difference in materials some taper the the insulation thickness to a smaller gap. I just overlay the slab perimeter w/ wood flooring as its an insulator.
Two examples: