Need Help Finding Suppliers for My New Garage - Radiant Heating

[Frank R]

Add foam insulation below the slab. Heat goes to cold. Heat does not "rise", warmer fluids rise in cooler fluids.

My ex-brother in-law installed heat tubing in the slab of a house he and my sister built. I told him to install 6-inches of blue foam below the slab. He and his buddy the plumber decided that I was wrong, and heat rises. No, insulation under the slab. $1700/month propane bill.

Sometimes us dumb ol' engineers know what we're talking about.

Hmmmm . . . . I thought I was pretty clear in my post that I was planning on putting foam under the concrete.

 

[Frank R]

Finished floor

Thanks for the photos.

Wow, you put tile in your pole barn? Never seen that before.

Do you have a finished photo?

 

[Frank R]

Here's a post for a barndominium Barndominium/Shop or "real" House? in Upstate NY using the Heat Sheet system. Appears to be installed on top of the gravel/grade with a moisture barrier underneath, then the heat sheet, then the tubing in the heat sheet. Then the wire mesh and standoffs on top of this.

You want one contiguous run of the tubing under the floor to a manifold (probably 2-3 runs for your size) and either electric or gas water heater run at a low temp. If you have solar plans, run your conduits now to the roof, as you might want AC in the summer. The thing about radiant it does best at a constant temp - its not immediate.

Also make sure you have big enough doors 9' high x 10' wide, and a lift is nice too!

Thanks Carl.

I thought you were implying that the AC would run through the floor tubing. That is not recommended due to condensation issues.

 

[Frank R]

My shop has it and used only once as I find the year round temp just about perfect without heat or cooling.

Brother installed in his home and never used it… both of us SF Bay Area.

Just a thought when you pencil out the numbers.

You are fortunate. My current unheated garage is very uncomfortable in cold weather.

 

[kennyd]

Wow, you put tile in your pole barn? Never seen that before.

Do you have a finished photo?

Yes, it's called 'clinker' tile, using in many auto dealers, auto shops, factories and breweries now.

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More pics, shops are never 'done' right? LOL.View attachment IMG_4741.JPG

 

[quicksandfarmer]

First, it's a huge mistake to assume that radiant systems are automatically effective. I see cases all the time where people made that assumption and now are looking for fixes to make their ineffective system effective. There aren't easy fixes, it's much better to design a system from the get-go to be effective.

The key to a heated floor being effective is for it to provide enough heat to match the heat loss of the room that it's in and keep the room comfortable. The heat loss of the room is determined by the construction of the room and the climate. This can easily vary by a factor of ten, there are no useful rules of thumb and be suspicious of anyone who wants to design using rules of thumb rather than measuring the room, analyzing its construction and looking at climate data.

The amount of heat that a floor puts into a room is entirely determined by the difference between the surface temperature of the floor and the air temperature of the room. There are two common extremes that lead to dissatisfaction with the comfort. The first is if the heating load is so high that in order to meet the heating load the floor has to be so hot that it is uncomfortable to stand on. This problem will be exacerbated if the floor is made from a material that doesn't conduct heat well, because then the floor will have hot and cold spots. The hot spots will be uncomfortably hot and the cold spots won't be putting out any heat.

The other issue is less serious, it happens when the heating load for the room is so low that the surface temperature of the floor has to be so low that it is not perceptibly warm. In the past 20 years or so there has been a dramatic improvement in what is considered acceptably insulated and air-sealed in residential construction, new houses built to the latest standards use a lot less energy to heat than in the past, and this situation is not uncommon in new construction.

Since the floor temperature controls the heat output, you want the floor temperature to be able to change as quickly as the heat load changes. If you have a room with a lot of solar exposure the load can drop precipitously when the sun comes out, and fall just as quickly when it goes away. A floor with low heat capacity will give better comfort.

Concrete conducts heat well, but has fairly high heat capacity. A system like Warmboard combines a layer of high conductivity aluminum with lower heat capacity, to give even heating and better responsiveness. (I'm not specifically promoting Warmboard, it's just the best known brand.)

 

[Frank R]

First, it's a huge mistake to assume that radiant systems are automatically effective. I see cases all the time where people made that assumption and now are looking for fixes to make their ineffective system effective. There aren't easy fixes, it's much better to design a system from the get-go to be effective.

The key to a heated floor being effective is for it to provide enough heat to match the heat loss of the room that it's in and keep the room comfortable. The heat loss of the room is determined by the construction of the room and the climate. This can easily vary by a factor of ten, there are no useful rules of thumb and be suspicious of anyone who wants to design using rules of thumb rather than measuring the room, analyzing its construction and looking at climate data.

The amount of heat that a floor puts into a room is entirely determined by the difference between the surface temperature of the floor and the air temperature of the room. There are two common extremes that lead to dissatisfaction with the comfort. The first is if the heating load is so high that in order to meet the heating load the floor has to be so hot that it is uncomfortable to stand on. This problem will be exacerbated if the floor is made from a material that doesn't conduct heat well, because then the floor will have hot and cold spots. The hot spots will be uncomfortably hot and the cold spots won't be putting out any heat.

The other issue is less serious, it happens when the heating load for the room is so low that the surface temperature of the floor has to be so low that it is not perceptibly warm. In the past 20 years or so there has been a dramatic improvement in what is considered acceptably insulated and air-sealed in residential construction, new houses built to the latest standards use a lot less energy to heat than in the past, and this situation is not uncommon in new construction.

Since the floor temperature controls the heat output, you want the floor temperature to be able to change as quickly as the heat load changes. If you have a room with a lot of solar exposure the load can drop precipitously when the sun comes out, and fall just as quickly when it goes away. A floor with low heat capacity will give better comfort.

Concrete conducts heat well, but has fairly high heat capacity. A system like Warmboard combines a layer of high conductivity aluminum with lower heat capacity, to give even heating and better responsiveness. (I'm not specifically promoting Warmboard, it's just the best known brand.)

Thanks for the analysis.

I guess I should have added this to my plans: This radiant heating system in my shop floor will probably only be used to keep the shop area above a certain temperature, say 50 degrees. I will then have a vented ceiling furnace that I can turn on when I am working in the shop.

I looked at the Warmboard website. Seems like a lot of their products are for heating residential wood floors.

 

[quicksandfarmer]

Thanks for the analysis.

I guess I should have added this to my plans: This radiant heating system in my shop floor will probably only be used to keep the shop area above a certain temperature, say 50 degrees. I will then have a vented ceiling furnace that I can turn on when I am working in the shop.

I looked at the Warmboard website. Seems like a lot of their products are for heating residential wood floors.

That doesn't really change anything, it just reduces the heating load.

Let me ask this: what benefit do you see from the heated floor as opposed to just leaving the furnace you're already paying for on a low thermostat setting and turning it up when you're there?

 

[Carl_NH]

Yes - I was referring to AC using Mini Splits - in fact, you could use the Mini Splits in the summer and bridge seasons when its 40-50 degrees for heat, then the radiant for the deeper cold winter months.

 

[not2old]

Thanks Carl.

I thought you were implying that the AC would run through the floor tubing. That is not recommended due to condensation issues.

My shop is not finished yet and I've needed to work out there in the summer. I ran cold water through the floor and through an old a/c condenser with a fan and lowered the temperature inside more than 20 degrees Celsius. It has a duroid roof and no ceiling yet. The plywood on the underside was 55C, well over 100F. It made the air temperature around me bearable with no sign of moisture around.