# Radiant Floor Heat Systems **URL:** \ **Category:** Factual Questions\ **Created:** [March 12, 2005, 7:11pm UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219 "2005-03-12T19:11:17Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Blown\_Injected](https://avatars.discourse-cdn.com/v4/letter/b/a87d85/32.png) [@Blown\_Injected](https://boards.straightdope.com/u/Blown_Injected)\ **Post date:** [March 12, 2005, 7:11pm UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/1 "2005-03-12T19:11:17Z")
The systems that heat the floor are called radiant heating systems but I thought radiant heat is transmitted via electromagnetic radiation. If there is a radiation source that is strong enough to warm a body thru a floor, would it not injure the persons body? Thanks ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [March 12, 2005, 7:15pm UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/2 "2005-03-12T19:15:23Z")
In this case, _radiant_ means infrared. Infrared is readily absorbed by most things, and thus creates heat; this is why infrared is often referred to as radiant heat although that’s a misnomer. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [March 12, 2005, 7:21pm UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/3 "2005-03-12T19:21:56Z")
> [@Blown & Injected](#): > > If there is a radiation source that is strong enough to warm a body… would it not injure the person’s body? Ever sat around a campfire? ---
**Author:** ![Valgard](https://avatars.discourse-cdn.com/v4/letter/v/7feea3/32.png) [@Valgard](https://boards.straightdope.com/u/Valgard)\ **Post date:** [March 12, 2005, 9:27pm UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/4 "2005-03-12T21:27:53Z")
Radiant heating systems circulate hot water through plastic tubing under the floor. They emit about as much electromagnetic radiation as a hot water bottle 😃 ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [March 12, 2005, 9:34pm UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/5 "2005-03-12T21:34:00Z")
We’ve got radiant heat in our basement floor, and it’s wonderful. It feels very different than forced air heat. Very comfortable. And your tootsies stay warm. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [March 12, 2005, 9:35pm UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/6 "2005-03-12T21:35:00Z")
> [@Valgard](#): > > Radiant heating systems circulate hot water through plastic tubing under the floor. They emit about as much electromagnetic radiation as a hot water bottle 😃 By which you mean quite a bit, just not of a frequency capable of doing your cells very much damage. (Of course, we all know heat isn’t completely harmless. But it won’t cause cancer because the photons aren’t going to disrupt your genes.) ---
**Author:** ![zoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zoid/32/336_2.png) [@zoid](https://boards.straightdope.com/u/zoid)\ **Post date:** [March 12, 2005, 9:49pm UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/7 "2005-03-12T21:49:14Z")
> [@Derleth](#): > > By which you mean quite a bit, just not of a frequency capable of doing your cells very much damage. > > (Of course, we all know heat isn’t completely harmless. But it won’t cause cancer because the photons aren’t going to disrupt your genes.) OK - educate me, how does a hot water bottle emit EMR? I’m not saying you’re wrong, I’m just having difficulty wrapping my head around it. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [March 12, 2005, 9:56pm UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/8 "2005-03-12T21:56:40Z")
> [@Sam Stone](#): > > We’ve got radiant heat in our basement floor, and it’s wonderful. It feels very different than forced air heat. Very comfortable. And your tootsies stay warm. We had radiant floor heat in our previous home. It was great. I miss it. ☹ ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [March 12, 2005, 9:58pm UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/9 "2005-03-12T21:58:43Z")
> [@zoid](#): > > OK - educate me, how does a hot water bottle emit EMR? I’m not saying you’re wrong, I’m just having difficulty wrapping my head around it. If an object has a temperature above 0 K, it emits EMR. ---
**Author:** ![zoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zoid/32/336_2.png) [@zoid](https://boards.straightdope.com/u/zoid)\ **Post date:** [March 12, 2005, 10:03pm UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/10 "2005-03-12T22:03:55Z")
> [@Crafter\_Man](#): > > If an object has a temperature above 0 K, it emits EMR. Well there you go 😃 I’ve learned my one thing for the day, I can go back to bed now, right? ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [March 13, 2005, 12:02am UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/11 "2005-03-13T00:02:12Z")
> [@zoid](#): > > OK - educate me, how does a hot water bottle emit EMR? I’m not saying you’re wrong, I’m just having difficulty wrapping my head around it. To exapand on what **Crafter\_Man** said, infrared radiation is one frequency in the electromagnetic spectrum that includes visible light, ultraviolet, and the frequencies we use in radio, TV, and wireless computer networking. It also includes gamma radiation, the most penetrating form emitted by some radioactive atoms. The difference is the frequency, which is directly related to the energy level in each photon. (Frequency is a property of waves, (kinetic) energy is a property of particles. Photons have both, because photons act like both. It makes sense when you don’t think about it. ;)) Heat, however, is somewhat broady defined. It makes sense to speak of _any kind_ of radiation as heat, not just radiation within the infrared range. A radio station is giving off heat, just not of a form you can feel. In common usage, it’s common to equate heat with infrared because humans tend to perceive infrared as heat. ---
**Author:** ![Blown\_Injected](https://avatars.discourse-cdn.com/v4/letter/b/a87d85/32.png) [@Blown\_Injected](https://boards.straightdope.com/u/Blown_Injected)\ **Post date:** [March 13, 2005, 12:52am UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/12 "2005-03-13T00:52:14Z")
When around a camp fire one needs to only hold a piece of cardboard between themselves and the fire and the radiant heat is blocked. The air around the sides, and a several feet, back from the fire is not hot; the hot air goes up but the radiant heat travels thru the air, not significantly heating the air, and heats the solid objects that it hits. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [March 13, 2005, 1:35am UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/13 "2005-03-13T01:35:00Z")
Well, personally I think the term “radiant heat” is exaggerated. The floor is warm so it heats the air in contact with it by conduction. Some IR radiation is also absorbed by the air. The air heated by the floor rises by convection heating the room. ---
**Author:** ![Valgard](https://avatars.discourse-cdn.com/v4/letter/v/7feea3/32.png) [@Valgard](https://boards.straightdope.com/u/Valgard)\ **Post date:** [March 13, 2005, 2:13am UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/14 "2005-03-13T02:13:13Z")
> [@Derleth](#): > > By which you mean quite a bit, just not of a frequency capable of doing your cells very much damage. > > (Of course, we all know heat isn’t completely harmless. But it won’t cause cancer because the photons aren’t going to disrupt your genes.) Yeah, that’s what I meant. That’s it, that’s the ticket… I just got the impression that the OP didn’t quite understand how radiant heating functions and was trying to point out that it’s the same mechanism as a hot water bottle. Nothing mysterious about it and no need to be concerned (unless you crank the heat up so high that your feet start to smoke). ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [March 13, 2005, 2:21am UTC](https://boards.straightdope.com/t/radiant-floor-heat-systems/294219/15 "2005-03-13T02:21:00Z")
It’s just barely possible that I was a lttle hasty in dismissing the radiant part of the radiant heating system so casually. If the floor were a black body at 27 C (80 F) the total radiation would be equal to 145 Btu/hr/ft[sup]2[/sup]. This would give roughly 44000 Btu/hr for a 15 x 20 ft. room. The floor isn’t a black body but if the emissivity were even 50% of that there would still be a lot of radiant heat around.