Radiant heat in the fall

[Lakegeezer]

Its our first fall with radiant heat (water system, tacked up under subfloor). So far, we haven't turned it on. As the seasons change, we'd like to open windows when the day is warm, but that seems like throwing away stored heat. Yet, if we don't start up the system, the first nite it gets into the 40's, we're going to wish it had been going for days to warm everything up. What is the right approach to warm days and chilly nights with radiant heat

[dpg]

I'm missing something. If the day is warm (I assuming you mean like 60-70's) why would you lose much? If the inside and outside temp is close there's nothing to lose. Not real familiar with radiant so maybe I'm missing something.

[RLW]

Its our first fall with radiant heat (water system, tacked up under subfloor). So far, we haven't turned it on. As the seasons change, we'd like to open windows when the day is warm, but that seems like throwing away stored heat. Yet, if we don't start up the system, the first nite it gets into the 40's, we're going to wish it had been going for days to warm everything up. What is the right approach to warm days and chilly nights with radiant heat

One doesn't turn on the heat until November or later. I just throw on a log or 2 and then I have to open the windows. I have never turned my main floor heat higher than what I set it for when I'm not there (52). That is the good thing about a stove, great insulation and the proper Pella windows.:) Yes, I sell and install that brand. :)

[Bear Islander]

In the long run radiant heat is just plain heat. The sales pitch is that radiant heat makes you feel warmer because it is directed at you. Kind of like when you sit at a campfire and notice that one side of you is warm and the other is cold.

However when the radiant heat hits something in the room, like you or the walls, it turns back into plain old heat.

For instance about 90% of the energy that goes into a light bulb becomes heat. The other 10% is light. But when that light hits an object in the room, the light energy is turned back into heat. So a 100 watt light bulb heats the room as much as a 100 watt heater. Its just distributed differently. Actually a very little energy is lost if the light escapes out a window. The same is true of radiant heat.

[hazmatmedic]

Geezer,
What you want to hear is that radiant heats your floor and then radiates upward through the room. This makes your body feel warm and so the thermostat can be set at a lower temp. You will be happy with it, but it had to be installed correctly.

Where it becomes an issue is for second homes. When arriving on a Friday night in January with the temperature set at 55, it will take until Sunday for the rooms to heat up to a comfortable level.

In your case, the air temperature on those first cold nights are just that, air temperature. The floor is still warm, so turning on your radiant at that point would be fine because it wouldn't take much to heat your floor first and then the rest of the room. It is when the floor and everything in the room is cold that it will take time to reheat.

[Audiofn]

It will depend on your heater that you picked. My heater in my house is not a variable fired furnace and it only heats my floor up at one temperature. The place in Maine checks the temp outside and fires based on that. If it is cool it will only run the pipes at a lower temperature, if very cold it will run them at a much hotter temp. This stops the roller coaster ride that my primary house has at this time of the year. Yes you can just open the windows and you will not really loose much stored energy because when you close the windows the floor is still warm. Radient is by far the most comfortable and efficient way to heat a home when it is installed correctly. Most issues seen in homes are dues to the tubes being spaced to far, the temp being to high in the tubes, or poor insulation in the house.

Depending on what kind of flooring you have you will want the radient to be set to as low of a temperature as it can be. To hot on a wood floor will dry it out.

[HUH]

Radiant heat is the most efficient way of heating a dwelling. Heat loss is the most important factor. The beauty of radiant heat is that the floor structure itself acts as a heat sink and holds heat especialy if you have tile or stone flooring. On the other end of the spectrum, Hot air heat heats the air ( a very poor heat sink). The drawback with radiant is slow recovery..its usualy cheaper to leave it on than it is to cycle it.

[Sunbeam lodge]

Radiant heat is the most efficient way of heating a dwelling. Heat loss is the most important factor. The beauty of radiant heat is that the floor structure itself acts as a heat sink and holds heat especialy if you have tile or stone flooring. On the other end of the spectrum, Hot air heat heats the air ( a very poor heat sink). The drawback with radiant is slow recovery..its usualy cheaper to leave it on than it is to cycle it.

I have a problem:
I have a hot water system and blowers on a thermostat in my great room. A couple of years ago I added radiant heating under the greatroom hardwood floor but they connected it to the same thermostat. Now when the heaters go on first they warm the room and I am not sure this makes the radiant heat effective as the room warms from the heaters first and it shuts down the thermostat. Does this seem right?

[jeffk]

Sunbeam Lodge,

I would think that you want the radiant heat to be doing most of the heating and if is is the other system would hardly never come on. Since the radiant heat must first heat the mass of the floor I would think that if it only comes on while the air heating is on it will never actually get the floor heated up enough to be effective. Is the heat on in the house all the time or just during visits? As others have pointed out it could take quite a bit of time to heat the floor from a cold state.

Once the house is heated I guess I would shut off the air system and let the radiant system do the job. Otherwise, even with 2 thermostats you're going to be playing games trying to keep them balanced. If the air thermostat was set too high it would kick on and the warm air temp would shut off the radiant even though the floor wasn't up to the right temp. If you need a quick hit of heat, turn up the both systems and then then turn the air down again after the chill is gone. The radaint will catch up in a while.

[Sunbeam lodge]

Sunbeam Lodge,

I

Once the house is heated I guess I would shut off the air system and let the radiant system do the job. Otherwise, even with 2 thermostats you're going to be playing games trying to keep them balanced. If the air thermostat was set too high it would kick on and the warm air temp would shut off the radiant even though the floor wasn't up to the right temp. If you need a quick hit of heat, turn up the both systems and then then turn the air down again after the chill is gone. The radaint will catch up in a while.

Thanks, I will try it. I may also just disconnect the air system and try just using the radiant heat and see if it will do the job. The room is very big and tall and has a lot of windows facing the lake. But it does have heat in the two rooms on either side so the radiant heat might be able to do the job once the floor is warmed up.

[ApS]

"...Its our first fall with radiant heat (water system, tacked up under subfloor)..."
Yours sounds like a wood floor, so the start-up time shouldn't nearly be as critical as for a concrete floor. :coolsm:

Sidebar:
I'm fairly certain I was the first on this forum to live with floor-based radiant heat. :cool:

The system was very simple back then, with copper pipe buried in the ground floor (the floor being a poured concrete slab). An oil-fired furnace would circulate hot water through the concrete. We were never uncomfortable, even walking around barefoot in winter! (Copper is quite pricey today, so modern radiant systems rely on plastic tubing).

Thirty years later, we revisited that old homestead and found the system had continued to run flawlessly all that time! :)

[tis]

We have radiant heat under a marble floor, but it is electric. It was put in around '84. It got very pricy, like 1800$ a month (for the whole house though) which was a lot back then, so we installed oil heat. It is still there but we don't use it. You are right though, Acres, it feels wonderful under your feet.

[fatlazyless]

Ok, I heat my little two bed cottage with a couple of older, Rinnai 18000 btu, propane heaters which seem to work perfect, forever, with zero problems, and no maintenance or service needed. It's a 60 year old, wood frame cottage, built on wood supports,, over an enclosed dirt crawl space.

At temps below 20 degrees, the carpeted floors definately feel cold!

As a do-it-myselfer, could I install flexible plastic tubing on the underside of the wood floors, and heat it with a small hot water heater, and one circulator pump with its own zone thermostat?

Or, am I better to hook up a small Rinnai 6000 btu, non-vented, propane heater down in the crawl space. They sell these at Amerigas-Laconia for just $200, marked down from $400, right now, and they are Rinnai. It could be set on the lowest setting of 50 or 60 degrees, and controlled by simply unplugging/plugging its' 110 volt power cord, from upstairs, when the temps drop. There's got to be enough air leaks down there to keep it operating properly.

You know, that would be pretty easy to do....just one 3/8" soft copper propane line, plug the electric cord into a 110v outlet up in the house....and it is done. And, probably an eighteen dollar, carbon monoxide alarm would be smart. :):D:)


....anyone trying something like this....don't forget...no compression ferrules in a propane line...:confused:

[RI Swamp Yankee]

:offtopic:
.... As a do-it-myselfer, could I install flexible plastic tubing on the underside of the wood floors, and heat it with a small hot water heater, and one circulator pump with its own zone thermostat? ...
Yes, you probably could put PEX under the floor. Here are a couple of links to This Old House articles.

http://www.thisoldhouse.com/toh/article/0,,20163505,00.html

http://www.thisoldhouse.com/toh/article/0,,1548320,00.html

Sorry, this is a bit off topic from Lakegeezer's question

[ApS]

"...am I better to hook up a small Rinnai 6000 btu, non-vented, propane heater down in the crawl space. They sell these at Amerigas-Laconia for just $200, marked down from $400..."
Your Rinnai heater idea is not "radiant" enough. :emb:

In an ideal world, a whole-house radiant heater would be:

1) made out of huge block of concrete directly under living spaces,
2) heated by a recirculating solar water heater,
3) backed up with another energy source for cloudy days.

Since solar water heating is still an uneconomical concept in North America's upper latitudes, that "block" would have to be heated by a conventional energy source. For other ideas on radiant and passive heating, you could visit locations like the Hanover House (http://www.buildinggreen.com/hpb/overview.cfm?projectid=49).

For such a small heater, your crawl space floor would act like a giant "heat sink" and I doubt you'd notice any heat difference for the whole house.

Since the heater is on sale (and you already have propane plumbed to the house), you could enclose a portion of the crawl space below a single room to give it a try. I'd suggest enclosing the crawl space area below wherever the living room couch and TV is located.

[woodswalk]

Any unvented propane unit in a crawl space would be a major mistake.- way too much moisture is put out and the risk of turning your crawl into a moldy rain forest is almost guaranteed.