Radiant Floor Heat

Bobber · 06-16-2008, 08:26 PM

I'm looking at putting one of these in a detached garage I'm going to build. Does anyone know which system is more cost effective; electric or water? The electric system sounds like it would be easier to install, but not sure how the intial cost and ongoing utility bills would compare?

superdorf · 06-16-2008, 10:06 PM

Just curious... Why would you put this in a detached garage? I have always seen it as part of a furnished room. If you have a cement floor I don't think it would work.

Bobber · 06-16-2008, 10:12 PM

Originally Posted by superdorf

Just curious... Why would you put this in a detached garage? I have always seen it as part of a furnished room. If you have a cement floor I don't think it would work.

I have a pie shaped lot and not enough room for an attached garage. I want it heated to melt snow and ice off my cars in the winter and also to have a place to work when it's cold. You have to insulate well underneath and around it, but works very efficiently once that's in place. Just can't figure out which system is the better way to go?

superdorf · 06-16-2008, 10:15 PM

Hmm... I'm not sure... My gut would say a boiler type system for that type of application, but I'm definitely not an expert.

vanillathrilla · 06-16-2008, 10:15 PM

Where are you located? I know some knowledgeable people in Ames who can help you!

heyguy85 · 06-16-2008, 10:23 PM

I have heard good things about water as floor heat in garages and basements but have not heard any comments about electrical floor heat.

kingcy · 06-16-2008, 10:34 PM

Originally Posted by superdorf

Hmm... I'm not sure... My gut would say a boiler type system for that type of application, but I'm definitely not an expert.

In a small area I think you can used a 55 gal water heater. Either way be sure you know forsure where the lines are ran. It is an empty feeling when you drill through the cement and hear the sound of air becauase you just hit a water line.

vanillathrilla · 06-16-2008, 10:38 PM

You can do neat stuff with radiant floor heating.

Phaedrus · 06-17-2008, 12:14 AM

Radiant floor heating rocks, imo. I have it in both our bathrooms at our current house.

But if you are going to put it in your garage, you need to be able to get the garage up to 60 degrees, overnight. Reason is, if you constantly keep your garage at 45-55 degrees, you will turn them into rust magnets, because at those temps, rust thrives. It's warm enough to encourage corrosion, but not warm enough to remove all the moisture in the moisture traps.

clonefarmer · 06-17-2008, 09:30 AM

My semi-informed opinion would be: electrical installation is cheaper, operating costs though are higher. Every article I've read on radiant floors in outdoor buildings stresses one thing. The system needs to be professionally designed to work evenly and efficiently. Especially a hot-water system. Check with your electric company to see if they will give you a lower rate on this as some will.

Cybone · 06-17-2008, 09:38 AM

I spent two months living in a hotel during a trial over radiant hydronic heat about 5 years ago.

Who ever decided to put a lifetime warranty on rubber hoses embedded in concrete was an idiot.

Good luck with your search!

usedcarguy · 06-18-2008, 03:17 AM

The electric people will argure that electricity is 100% efficient, but what they won't tell you is that the power plant that produces it isn't. I don't have any concrete numbers for you - no pun intended - but in the case of comparing water heaters, electric ones are more expensive to run, which would explain why the utility companies almost give them away to encourage their use. I do know that gas radiant heating is quite a bit cheaper than electic radiant so I would assume that in-floor would be similar.

From what I've heard, a traditional water heater is only 70-75% efficient, although the newer power vent models are probably better. A boiler is more efficient, but more expensive.

I would think an electic heating element embedded in concrete would not handle cracks and shifting nearly as well as pex tubing.

usedcarguy · 06-18-2008, 03:57 AM

Originally Posted by Phaedrus

But if you are going to put it in your garage, you need to be able to get the garage up to 60 degrees, overnight. Reason is, if you constantly keep your garage at 45-55 degrees, you will turn them into rust magnets, because at those temps, rust thrives. It's warm enough to encourage corrosion, but not warm enough to remove all the moisture in the moisture traps.

I'm not sure that it is that big of deal here in the rust belt for the fact that the liquid brine which the governments are all addicted to acts as a moisture magnet anyway. It will absorb moisture at ANY temperature, which makes it great for dust control on gravel roads, but lousy stuff to have attached to your car at any time. Also considering that it is corrosive, it will do far more damage than humidity from a damp garage. Besides, cold air holds less moisture than warm air.

Also, in a radiant heated environment, the rust issue would be minimized because you are heating the objects inside the garage rather than heating the air. I've been in many shops heated to 50 degrees where there was a 30 degree difference between the floor and the ceiling. With forced air you've got to run it warmer to compensate for the less efficient heating at the floor level.

Any time I've had rust issues with stuff in a garage (unheated), it was a result of condensation due to a warm day, cold concrete, cold tool box, cold tools, etc.; and always in the spring. With radiant heating, this problem is minimized because the coldest objects in the space which create the condensation are warmer.

Phaedrus · 06-18-2008, 05:03 AM

Originally Posted by usedcarguy

I'm not sure that it is that big of deal here in the rust belt for the fact that the liquid brine which the governments are all addicted to acts as a moisture magnet anyway. It will absorb moisture at ANY temperature, which makes it great for dust control on gravel roads, but lousy stuff to have attached to your car at any time. Also considering that it is corrosive, it will do far more damage than humidity from a damp garage. Besides, cold air holds less moisture than warm air.

Also, in a radiant heated environment, the rust issue would be minimized because you are heating the objects inside the garage rather than heating the air. I've been in many shops heated to 50 degrees where there was a 30 degree difference between the floor and the ceiling. With forced air you've got to run it warmer to compensate for the less efficient heating at the floor level.

Any time I've had rust issues with stuff in a garage (unheated), it was a result of condensation due to a warm day, cold concrete, cold tool box, cold tools, etc.; and always in the spring. With radiant heating, this problem is minimized because the coldest objects in the space which create the condensation are warmer.

You know, the radiant nature of the heat never figured in to my calculations, but it is possible you are correct. The extent of my experiences is in long-term storage of military vehicles. And they use a large air conditioner, and pull air directly from the vehicle using a hose to do it.

Those are good points, sir.

CyinCo · 06-18-2008, 07:55 AM

The cost to operate the hot water system versus the electric system is just a matter of calculation. You need to figure out what you pay for 1 kWh of electric (check your next bill) and what you pay for 1 therm or 1 ccf of gas. Then, just calculate the $/BTU or $/MBTU for each arrangement taking efficiency into account. For the purposes of the calculation, assume electric to be 100% and hot water to be about 80% efficient. As someone pointed out above, the source efficiencies are different but for the purposes of figuring out YOUR operating costs, we don't care about that.

If you want to figure out your annual expense to run each system, you'll need an estimate of the heating load annually in BTUs.