Does Radiant Floor heat make sense

[Doubled33]

A few key notes
building is for profit and not a hobby shop
16’ from slab to underside of metal deck
about 10,000 SF 70x135
4.5k sf bays with lifts, 1k sf break room/parts/ equipment storage/office 2.5k sf tool/lathe/milling area 1.5k sf storage/indoor overflow parking
building located in central MS
natural gas is at the site
building will have AC As well.

I have read a lot of posts here that discuss the amount of time needed to bring it up to temperature and the fact that it is better off to leave it running all the time which brings up the cost issue of natural gas. most of these comments come from people in habitually colder climates. The temperatures at this location very seldom get into the 20s. so I am thinking the Delta T I am trying to achieve would not be that bad as related to the natural gas cost. am I correct in this thought or is that just not how this system works?

The other question I have relates to the insulation below slab which it seems 2 inches is what is recommended. in this climate in this location, would the 2 inches still be a recommendation or would 1 inch suffice?

The slab will be around 6 to 8 inches at most locations. Does this play into the viability of radiant heat?

The exterior walls will be metal studs have at least 6 inches of insulation and the roof will also be insulated with polyiso.

how quickly does this system dissipate the heat once it is turned off. The reason I ask there are times where the temperature may be 30 in the morning and warm up to the 60s during the day. Basically, I am worried about the system, making the building too hot.

since I am planning on putting in AC, am I better off using gas heat and a ducted system?

 

[HoosierBuddy]

I have radiant heat in my garage and part of my house. Have had for over 20 years now. Put it in myself and feel qualified to answer your questions.

The only advantage of radiant floor heat in your situation (and your situation is perfect for it BTW) is comfort. It's more comfortable than forced air heat in three ways. It's essentially noise free. It's not drafty. It's even heat with no swings in temperature and basically no issues of "now I'm hot because I'm standing under the vent."

It's more expensive to install especially if you are putting in AC anyway.

We used forced air heat at work, and I would urge you to at least consider the noise issue. We are using NG hanging unit heaters (Modine Effinity) and those suckers are loud. Monday morning safety talk? You have to have someone go over and turn off the heat so the speaker can be heard. However, a ducted system running from an actual NG furnace would be significantly quieter than that.

I really like my in floor radiant, and I'd do the same thing again maybe. In your situation, where everthing has to payback? I would look hard at insulating the slab and the hell out of the walls and ceiling and going with mini splits (ductless). If you are wanting to do a major turn down on temp nights and weekends, also put in a NG heat source (unit heaters or furnace) to allow the heat to recover as the mini splits are going to **** at that.

But to answer your actual questions.

2" insulation can't be much more expensive than 1" and it's twice the R value. Why not go 2"?

Thicker floors would work even better with radiant.

I've never had a situation where my in floor radiant has overrun my temp setting due to outside temperature swings. Your winter weather is similar to our shoulder seasons in November early December, and Late March April. No issues. You will not have a problem.

Radiant would work great, and if having a super quiet system makes sense for your business.....maybe you should go that route. But, it's going to cost more and will not generate a direct payback to put those $ back into your bottom line. Also? If you have to put any tapcons into the floor in the future, or similar....remember that those heat loops are subject to damage in those types of jobs and difficult to repair.

 

[theoldwizard1]

building is for profit and not a hobby shop

For profit, meaning you are going to sell it, or are you going to run a business from it ? If you are selling the building, just go with gas forced air.

I am thinking the Delta T I am trying to achieve would not be that bad as related to the natural gas cost. am I correct in this thought or is that just not how this system works?

Recovery time has a lot to do with how cold the interior got ! Use a set back thermostat and don't go below 55°F.

The other question I have relates to the insulation below slab which it seems 2 inches is what is recommended. in this climate in this location, would the 2 inches still be a recommendation or would 1 inch suffice?

2" will slow down heat loss when the system is set back. Probably worth the investment.

The slab will be around 6 to 8 inches at most locations. Does this play into the viability of radiant heat?

Only in cool down/recovery time. You will need to "tune" the set back temperature so that it is not to cold when you come in. Or get one of those fancy thermostats that change set temp at a given time.

since I am planning on putting in AC, am I better off using gas heat and a ducted system?

This is ALWAYS the big debate ! The big win for radiant floor is COMFORT ! If your feet are warm, you are warm !

In other parts of the world, there are heat pumps that can supply cool air (with appropriate air handlers) AND hot water. I am not certain if any of those are sold in the US.

 

[Doubled33]

I have radiant heat in my garage and part of my house. Have had for over 20 years now. Put it in myself and feel qualified to answer your questions.

The only advantage of radiant floor heat in your situation (and your situation is perfect for it BTW) is comfort. It's more comfortable than forced air heat in three ways. It's essentially noise free. It's not drafty. It's even heat with no swings in temperature and basically no issues of "now I'm hot because I'm standing under the vent."

It's more expensive to install especially if you are putting in AC anyway.

We used forced air heat at work, and I would urge you to at least consider the noise issue. We are using NG hanging unit heaters (Modine Effinity) and those suckers are loud. Monday morning safety talk? You have to have someone go over and turn off the heat so the speaker can be heard. However, a ducted system running from an actual NG furnace would be significantly quieter than that.

I really like my in floor radiant, and I'd do the same thing again maybe. In your situation, where everthing has to payback? I would look hard at insulating the slab and the hell out of the walls and ceiling and going with mini splits (ductless). If you are wanting to do a major turn down on temp nights and weekends, also put in a NG heat source (unit heaters or furnace) to allow the heat to recover as the mini splits are going to **** at that.

But to answer your actual questions.

2" insulation can't be much more expensive than 1" and it's twice the R value. Why not go 2"?

Thicker floors would work even better with radiant.

I've never had a situation where my in floor radiant has overrun my temp setting due to outside temperature swings. Your winter weather is similar to our shoulder seasons in November early December, and Late March April. No issues. You will not have a problem.

Radiant would work great, and if having a super quiet system makes sense for your business.....maybe you should go that route. But, it's going to cost more and will not generate a direct payback to put those $ back into your bottom line. Also? If you have to put any tapcons into the floor in the future, or similar....remember that those heat loops are subject to damage in those types of jobs and difficult to repair.

Thanks. I should have added a few things. I had radiant in my bathroom in my CA house And yeah it was amazing. That’s what is driving this thought but this shop is 100x larger.
I forgot about the noise of those old Modine heaters as I worked under those many many years ago.
insulation such as formulae has gotten expensive and the 1” is close to half the cost of 2” at about 1.50 a sf.

 

[Doubled33]

For profit, meaning you are going to sell it, or are you going to run a business from it ? If you are selling the building, just go with gas forced air.


Recovery time has a lot to do with how cold the interior got ! Use a set back thermostat and don't go below 55°F.


2" will slow down heat loss when the system is set back. Probably worth the investment.


Only in cool down/recovery time. You will need to "tune" the set back temperature so that it is not to cold when you come in. Or get one of those fancy thermostats that change set temp at a given time.


This is ALWAYS the big debate ! The big win for radiant floor is COMFORT ! If your feet are warm, you are warm !

In other parts of the world, there are heat pumps that can supply cool air (with appropriate air handlers) AND hot water. I am not certain if any of those are sold in the US.

Do you have the name of a manufacture of the above mentioned units. A google keeps showing me heat pump residential water heaters.
I will own And run the business.

 

[Stuart in MN]

If it's a business that's occupied every day I think radiant is a good choice. Where it can fall flat for many people here on the board, is they have a home shop they'll be in a few evenings during the week and maybe on Saturday, and they want to turn off the heat other times.

 

[theoldwizard1]

Do you have the name of a manufacture of the above mentioned units.

Mitsubishi Ecodan

I'm not sure if it is sold in the US.