radiant heating ?

[PAGUY]

Anybody know anything about radiant heat that is an electrical pad in the ceiling? My sister recently bought a house built in 1973 and my understanding is that this is a pad that supposedly heats from above. Now I always have been under the opinion that heat rises so how can this be an efficient way to heat a bi-level home? She is having the ceilings repainted and the walls due to previous owners being heavy smokers and the resulting yellow tint to everything in the house. Her painter said he can just paint over with one or two coats and there should be no problems with the stained ceilings and walls. Any thoughts about this.

 

[davedj1]

We built condos in the eighties with radiant electric in the ceilings. They were sheetrock panels that fit in between the floor joists. I never liked it as I am tall and I could feel it on my head. We built quite a few of them and it seemed to work fine. I think part of the theory is that if your head is warm your body will be warm. I suppose that once the building is up to temp and insulated properly that you would hardly notice it. I think painting over it will be fine.
Of course you would have rely on the painter to use the proper sealer to cover the smoke.

 

[KubotainNH]

I lived in an apartment with this type of heat for 2 winters. Absolutely hated it. We were on the 1st floor over an unheated basement. Our feet were always cold but our heads were warm. I like it the other way around, radiant in the floor is great. The folks who lived on the 2nd floor probably liked our heat on their feet though. Sitting at the kitchen table was brutal because the heat does not get underneath it. The electrical bills were staggering. I think we had one month over $350 in a small 2 bedroom apartment almost 20 years ago. I can't imagine what that would cost now in an average sized house.

 

[Raspy]

That ceiling electric radiant was the cheapest way to add heat and it required no ducting or equipment. But it's terrible and a lot of it doesn't work anymore.

Don't ever make a hole in the ceiling to hang something, as you might cut the wire and finish it off.

I've never heard anyone who has used it, say they liked it.

If she ever remodels she might consider an electric system in the bathroom and kitchen floor where there is tile.

By the way, the painter may have to put a coat of KILZ on to seal the oil stains before any coat of regular paint will cover.

 

[PAGUY]

Thanks guys. Your comments are appreciated. I will pass them on to her.

 

[Jay4200]

Now I always have been under the opinion that heat rises so how can this be an efficient way to heat a bi-level home?

Common misconception. Heat does NOT rise, it radiates equally in all directions. Hot air does rise, but that is fundamentally irrelevant.

JayC

 

[Scotty Dive]

I have a house with it....I removed all of the thermostats and turned it off and installed forced hot air....I will tell you that - at my grandparents house, they had it and over the years (40+) a couple of their ceilings cracked due to the weight of the electric pad. Craziest thing I have ever seen.

 

[PAGUY]

Scotty Dive - They are installing two propane fireplaces that will have blowers to supplement the radiant heat.

Jay4200 - I always believed that heat rose so it is interesting to hear I was wrong like I imagine others also think that way.

 

[Raspy]

Heat doesn't rise.

Warm air, which is less dense than cold air, floats up in an atmosphere of cooler air, because it weighs less. Warm air rises the same as warm water rises in the ocean, or the same way helium balloons rise.

The heat from the sun gets to the Earth by radiation, it travels through the vacuum of space without convection or conduction. Radiant heat warms objects, like the Earth, people or walls, then air in the vicinity of the warm object warms up by conduction and rises because of gravity. The rising air is called convection. This transfers energy to cooler objects that are higher up. So it seems as though heat rises. Actually, warm air rises in the presence of gravity. But radiant heating is all about heating objects to begin with, and then the room gradually warms through convection and conduction.

This is why you can be in a cool room with radiant heating and feel perfectly comfortable. It's also why radiant is more efficient. Because you don't have to heat the entire space and all its massive walls, etc. in order to feel comfortable. That's why ceiling radiant is ridiculous, it only warms people's heads in a cool room. But leaves their feet, or anything out of the line-of-site of the ceiling unaffected.

At least with floor radiant you get warm feet first. Then the convection takes over, from the lowest point in the room, and the whole environment becomes comfortable. Much better than forced air heat, because a draft is not comfortable and a draft promotes evaporation. Evaporation is cooling. So forced air is also evaporative cooling that is overpowered by so much heat that it feels warm.

 

[BeezFun]

This is why you can be in a cool room with radiant heating and feel perfectly comfortable. It's also why radiant is more efficient. Because you don't have to heat the entire space and all its massive walls, etc. in order to feel comfortable. That's why ceiling radiant is ridiculous, it only warms people's heads in a cool room. But leaves their feet, or anything out of the line-of-site of the ceiling unaffected.

I agree with everything you said except this. Your body radiates heat to any surface that's colder than it is, so if you're in a house that has cold walls, you feel cold because your body is radiating heat to warm the cold walls. So while the ceiling is radiating heat to your body, your body is radiating heat to the cold walls and windows. So it is necessary even with radiant heat to keep the walls and windows at a temp as close to your body as possible to be comfortable. It may be a small temp difference, but radiation goes with the fourth power of temperature difference, so it can be a significant effect.

 

[ozley]

The ceiling heat would give me a headache. I had to wear a hat when working in apt. that had it.
Back before the panels the the guys installing it just ran a wire back and forth then they would but a skim coat of plaster over it. Well they would write words and after a time they would show up on the ceiling.

 

[Raspy]

Beez,

Except that we usually have clothes on, which reduces the radiant loss from our bodies, and the fact that we conduct heat from the warm floor with our feet directly, not through radiation.

It's all a matter of difference in radiation rates and temperatures.

It's not fair to say we "can't" be warm if the walls are "cold". Define those temps first. But it is true that we can feel comfortable in a cool room within certain parameters. Those parameters are what we use for reference in programming the thermostats and designing the temperatures. At what point does a warm floor compensate for a cool wall, etc., and can we use that info to get comfortable without heating the entire space.

Here is an important point: It is NOT important to keep the walls at a temperature as close to our bodies as possible, in order to be comfortable. Not true. 70-75 degrees is much closer to a realistic max for general living areas. If the floor gets to 87 degrees in a well insulated and stable room, where the walls are close to that but a bit less, people can't stay there for very long without overheating. If the temp needed to be equal with our bodies, we'd be most comfortable in a place with 100% humidity and 98.6 degree temperature. Sitting around in that kind of heat is oppressive and trying to sleep in it is very uncomfortable. See what I mean?

The reason it's important to find that comfortable situation is that it is much more efficient and even more comfortable than just heating until the thermostat says 70 degrees or whatever. It prevents overheating later, overshooting and heating when no one is home etc.

Unlike with forced air, we have to anticipate and time the system a bit to get the maximum comfort. But at least we don't have to put up with the draft, the noise and the mixing of all the air in the house as we do with forced air.

 

[V1Rotate]

I like my hot water baseboard radiators. They are located around the perimeter of the outside walls so the warm air that they produce warms the walls above them. Also, they are not noisy or drafty.

 

[KubotainNH]

I've lived in all of them, current house is hot water radiant in the floor which is the best so far. My only complaint is slow to heat up. Next is hot water & electric baseboard. After that it all sux. Radiant in the ceiling was awful and forced hot air blows too. FHA is dry, dusty and only comfy at the midpoint temp. Wood heat is way too dry. Haven't lived with a pellet stove but seems to be a good way to make a room comfy.

 

[BeezFun]

Beez,

Except that we usually have clothes on, which reduces the radiant loss from our bodies, and the fact that we conduct heat from the warm floor with our feet directly, not through radiation.

Rule of thumb for HVAC design is a resting human (with clothes) produces 400 BTU/hr. Of that, about 100 is through evaporation (perspiring and breathing), 100 is through conduction/convection, and 200 is through radiation. I didn't expect that the walls would be kept at a temp above the room temp, but the body is very sensitive to the difference between a 40deg wall and a 70deg wall. It's not uncommon in old homes to see frost in the corners, very common to see frost on windows even in new homes. That means the temp there is 32deg or colder, which has a big effect on comfort. So you can install any kind of heat you want, but if you don't build the place well enough to keep the envelope warm, grandma is going to turn up the thermostat.

In the summer the wall temp is probably in the 80s on a hot day, which is so close to your body temp that radiation is no longer significant in your comfort level. Instead evaporation dominates the heat exchange and if the AC isn't designed to remove the moisture, you'll feel hot.

 

[PAGUY]

Ok guys, with this being a bi-level would it make sense to keep the downstairs (family room) temperature setting higher than the upstairs (parlor) as the ceiling radiant heat downstairs should effect the flooring upstairs? I'm thinking it has to be a matter of controling temp settings to find comfort level in occupied rooms.

 

[Raspy]

Paguy,

You'll probably find you don't need to run the upstairs heat at all and the downstairs ceiling radiant might make the upstairs floor pleasantly warm.

Since warm air rises, and unless you have some sort of fan system, the upstairs will be warmer just from the warm air accumulating upstairs.

I usually find it best to only run the upstairs radiant systems for an hour or so in the morning, before people get up, and to limit how late the lower one runs, in the evening, in order to prevent overheating upstairs at night.

Most people prefer to sleep in a cooler upstairs bedroom, but like a nice comfortable living room for lounging around in the evening. This is where timing and careful settings make the most out of multi story systems. Also, closing the upstairs bedroom door helps.

 

[PAGUY]

John - I believe we are on the same wave length with thinking how to get it to work the best it can. The propane fireplaces (0ne up and one downstairs) would be supplemental heat for those really cold days in PA.

Again TY to all who offered their 2¢.