Enough heat?

birch

I'm remodeling a 19x16ft livingroom. It currently is heated with boiler baseboard heat. The floor is an on grade slab and Two walls are about 50 % glass and there is a skylight. I will be finishing with tile so I want to eliminate the (ugly) baseboard and go with radiant. I have been researching...a lot...and am told that the radiant will not produce mouth heat as a sole source. I had a contractor give me an estimate and he said the radiant would produce plenty of heat to heat the space. I would hate to spend $4g+ to have it installed and find out I need to reinstall baseboard. Any thoughts would be greatly appreciated. Will it be enough?
Cheers
Birch

delta T

Radiant can supply enough heat...if installed and designed properly. Whether or not it will depends on the heat loss of the room (you can guess all you want, but the only way to be sure is to do the math), the manner of installation, and the designed floor temp. Unless all this is actually figured out up front, you won't know until its too late to fix.

Anyone who says that radiant can't possibly heat the space, does not know what they are talking about.

Did the contractor perform a heat loss calculation for the room, or if not is doing so part of his bid? If he did (or had someone do it for him) he should have a designed floor temperature and supply water temperature. Ask him and make sure. doing this without proper design is asking for trouble.

If you have baseboard in the rest of the house, there will have to be some kind of temperature control for the radiant zone to prevent 180 degree water from running through the radiant floor. This would most likely be a thermostatic mixing valve dedicated to this zone.

KC_Jones

Some of the pros will be along soon enough, but was a heat loss calculation done of the space? That is the only way to know if you will be able to get the output. Does that slab have insulation under it? I am guessing no. Just a few basics I am sure will be asked.

Gordy

First step is a heat loss for the room in question. This will dictate tube spacing, flow rates, and water temps need to to off set the heat loss of the room in question.

What type of radiant floor heat method is the contractor offering? There are different methods that require differing water temps. Sandwich, warm board,staple up, suspended tube? Heat transfer plates?

And yes there are situations where radiant may need supplemental heat. Those are with limited floor areas, high load rooms. Don't forget there are other radiant surfaces besides floors, and that is walls, and ceilings. Those surfaces can have higher surface temps than floors thus creating higher btu outputs.

SWEI

Is that room slab on grade? Is there any slab edge insulation? Find someone who knows what they are doing, please.

ChrisJ

For my own curiosity can someone tell me how many btu/h a typical 19x16' floot can radiate into a room at the warmest setting for radiant heat? Assuming typical furniture etc.

SWEI

Most of us would probably say 30 BTU/ft²

ChrisJ

SWEI said:

Most of us would probably say 30 BTU/ft²

So, 9,120 btu/h for 19x16?

Gordy

Typically with floors. You can get more output with radiant walls and ceilings due to higher allowable surface temps. Floors are limited to 85 for comfort reasons, and some flooring materials in particular wood floorings.

birch

Wow..can't believe how many replies! I will answer a few questions and go back to see what I missed..
1. There was NOT a heat loss test.
2. He suggested tiring tubing to mesh and muddling over. ($3500) I suggested warmboard ($4500) and he said that is another option.
3. He mentioned a temp control to lower the water temp. It will be on its own zone.
4. The slab is on grade. Don't think there is any edge insulation.
5. Finding a "guy who knows what he is doing" is tough. I got this guy through a home advisor site. Any other places to get "qualified " names? Long Island ny
I will search "heat loss test". Is it something I can do?

4Johnpipe

Before even performing a heat loss...What type of boiler do you currently have? Cast iron will not play nice with radiant water temps. A possible solution exists...

Gordy

Why not john? it's been done for decades with proper control. Unless of course the poster needs a new boiler there are better options, and efficiencies.

To the op since this is a slab detail you need insulation as been covered by swei.

ChrisJ

Slant fin has an Android app for doing a heatloss.
It'll take some time and be as accurate as you can.

birch

My boiler is older and runs on oil. I will check out the app and try to do heat loss.
Edit..I downloaded the app. How do I know which boiler I Have?

Gordy

Your boiler is a cast iron. You need a mixing valve to service the radiant loop. Your guy at least knows this. Is oil your only fuel option?

This is not all that important to do your heat loss right now.

When you do the heat loss for giggles do the slab on grade with, and with out proper insulation. Just so you see the difference.

4Johnpipe

Gordy...The solution I was referring to was of course a mixing valve. However you would also be better served with boiler protection from below 140 degrees with another mixing valve. I've ripped out too many relatively new CI boilers that rusted away to pieces well before normal life...It is a lot of piping on this old boiler...

Is the tankless coil piped into the electric water heater?

hot_rod

How much baseboard fin tube is in the room? Did it keep the room comfortable? If so that would get you an idea of the heatload until you get an accurate number.

If it is bare concrete, well insulated below and around the edges, 30 btu/ft. is a high output number. considering furniture, possibly floor coverings will be added. Mid 20's is more realistic for btu/ sq. ft. output.

One rule of thumb is 2 but/ ft for every degree difference between floor temperature and ambient. Only with a consistent 85° floor surface temperature could you expect 30 btu/ ft.

6" on center tube spacing with the tube in the center of the pour is a best practice for high load radiant floors.

Ceiling radiant an option? That is a good, unencumbered surface area to turn into a radiator.

Rooms with a lot of glass, especially leaky glass, can be a tough go with just radiant floors.

Gordy

When I heard sky light I figured a vaulted ceiling.

birch

After reading all of the info, I decided to pass on then radiant ht. the cost is not worth hoping or enough heat. I a appreciate all of the help and informative responses. I will def. return to this forum for future projects.
Cheers
Birch

Gordy

Neutral tile is much nicer than cold

jonny88

I see you have two top notch companies who work on your boiler.How are your bills?

birch

Oil bills are normal.

jonny88

Always have the option of propane.....BTW there is a rule here about pricing.

birch

Sorry about the pricing

spoon22

BTW that is a steel dry base boiler looks like a newyorker

Mark Eatherton

Birch, before you disappear, please give us more of an explanation as to why you think radiant won't perform well in your scenario. It is obvious that you are doing your homework, and it is also obvious that you have been exposed to some less than qualified pro's, all whom have different ideas as to what will, or may work.That is a REAL problem within our industry, and we are working over time trying to correct that situation, but it has taken many years to get where we are, and it's going to take some time to get it all under control.

What we pro's do is well practiced and well thought out. Members of the RPA have access to 20 plus years of field experience, and many of those members are responding to your requests for information, and in my opinion, are heading you in the right direction.

Tell us more about the bad feeling you have about whether or not it will work in your case or not. As the director of the Radiant Professionals Alliance, your opinions and actions/reactions tells a story, but it isn't telling the whole story.

The only "problem" with a properly designed and installed hydronic radiant system (pick a surface, walls, floors or ceiling) is that it is physically addicting, and your spouse, once she has experienced radiant comfort, is going to DEMAND that you put it in the rest of the home....

Talk to us please. We are listening.

ME

birch

ME
I am a homeowner who performs 95% of the upgrades on my home. I try to educate wisely to all options before attempting myself or hiring a professional. Even with the project of radiant floors I feel that I could confidently install using some sort of flooring system such as warmboard. Unfortunately my knowledge is completely Internet based. I don't know anyone who has it. Therefore I couldnt physically get the "feel" of their too and compare it to mine or ask their thoughts on what they would do differently. I also am unable to get a recommended name...my only option was a Google search. The 2 guys who came were both professional but didn't offer many options until I started mentioning things and asking questions. They wanted to lay the tubes and mud. Here are the other main issues that make me hesitant:
1. The cost with too much of a question mark of wether it would be enough to heat. I have no prob. Spending the $ but would hate to have to add 2nd source later.
2. Since it would be on an existing slab, I figure the heat loss down would be too great.
3. Raising the height of the slab about 3" would be an issue for my French doors
4. Mathematical calculations of existing btu heat output with baseboard compared to the estimated from radiant floor. The numbers that I was given with current baseboard were 3 x what was estimated for radiant (per another site).
5. Would the windows, doors and skyline eliminate the ability for it to heat this room.
6. It is an extension w/o a floor above...may reduce heat containment?
6. Would my boiler be able to handle it? This was not a huge concern but one non the less.
For me just too many question marks. If I had a guy come and say "yup, this will be plenty of heat" it would be done. Yes they did say that but after me asking questions, both guys' confidence seemed to drop.

I do intend to revisit it in other rooms I am working on ( less windows and heated level above) and I will def be back to pick the brains of the experts.
Cheers
Birch

Gordy

In the future use find a contractor here. Not Google see if some one is close to your area.