[CNM Design]

Placing hot water heat behind drywall in ceiling.
Can I use ultralite drywall or will the air in the plaster insulate the heat from getting radiated into the room underneath?

Floor joist/rafter then .5 in OSB then .75 foam board then drywall with screws through the drywall, foam board and into OSB.

If I can use Ultralite drywall, can I use 3/8th in. Ultralite drywall for ceiling?


Thanks

 

[joecaption]

None of that makes any since to me.
Heat rises, why would try and heat from the ceiling?
This idea was tried long ago with electric heating in the ceiling and it never worked out.
You want to add 3 layers of items that all add R value, then try and defy physics and make the heat go down and through it all, HMM.

 

[de-nagorg]

I agree with Joe, sounds like a dumb idea,

As Scotty was prone to say, You can't change the laws of Physics.


ED

 

[CNM Design]

None of that makes any since to me.
Heat rises, why would try and heat from the ceiling?
This idea was tried long ago with electric heating in the ceiling and it never worked out.
You want to add 3 layers of items that all add R value, then try and defy physics and make the heat go down and through it all, HMM.

The only layer blocking would be the drywall.

https://www.doityourself.com/stry/effectiveness-of-radiant-ceiling-heat

 

[CNM Design]

I agree with Joe, sounds like a dumb idea,

As Scotty was prone to say, You can't change the laws of Physics.


ED

The only layer blocking would be the drywall.

https://www.doityourself.com/stry/effectiveness-of-radiant-ceiling-heat

 

[Missouri Bound]

Interesting.
Are you using tubing with reflectors as used in floor heating?
The drywall will most likely be fine, but usually ceilings are 5/8".
Drywall, being 'sheetrock" will most likely act as a heat sink so it will take a while to warm up...and also take a while to cool down. If you can keep the heat from going up into the space above, whether attic or upper level it should work fine.
Many people think that heat automatically rises....well hot air does, but radiant heat does not. Infared heaters used in outdoor spaces and often garages are proof of that. I would be more concerned about the energy needed to get the drywall or for that matter any ceiling covering up to temperature. But once it is there you should be fine. I will assume that the drywall will be against the radiant surface and all insulating materials will be above the radiant heat to keep it from traveling up.

 

[ClarenceBauer]

Hydronic Radiant heating was used in plaster ceilings for many years & some are still in use they work very well. When installed in the plaster ceilings the gypsum board was installed than a sanded plaster was used to cover the tubes.
As for todays radiant heat most use the cable system. In the newer systems the insulation is above the heat & will direct the heat into the Gypsum panel.
Provided the water temp. is not to high the Gypsum will hold the heat & release it over a period of time. Very high temps will break down the Gypsum product & cause failure of the Gypsum.

 

[CNM Design]

Interesting.
Are you using tubing with reflectors as used in floor heating?
The drywall will most likely be fine, but usually ceilings are 5/8".
Drywall, being 'sheetrock" will most likely act as a heat sink so it will take a while to warm up...and also take a while to cool down. If you can keep the heat from going up into the space above, whether attic or upper level it should work fine.
Many people think that heat automatically rises....well hot air does, but radiant heat does not. Infared heaters used in outdoor spaces and often garages are proof of that. I would be more concerned about the energy needed to get the drywall or for that matter any ceiling covering up to temperature. But once it is there you should be fine. I will assume that the drywall will be against the radiant surface and all insulating materials will be above the radiant heat to keep it from traveling up.

Reaction time for heat change is less then 10 min.
Water temp range inside pex 80-90 degrees. A water temp of 88 degrees can carry just over 55btus/sq. Most homes today require less than 30btus/sf.

https://www.pmmag.com/ext/resources/PM/2014/June/016-020-0614-Siggy.pdf

 

[CNM Design]

Hydronic Radiant heating was used in plaster ceilings for many years & some are still in use they work very well. When installed in the plaster ceilings the gypsum board was installed than a sanded plaster was used to cover the tubes.
As for todays radiant heat most use the cable system. In the newer systems the insulation is above the heat & will direct the heat into the Gypsum panel.
Provided the water temp. is not to high the Gypsum will hold the heat & release it over a period of time. Very high temps will break down the Gypsum product & cause failure of the Gypsum.

Reaction time for heat change is less then 10 min.
Water temp range inside pex 80-90 degrees. A water temp of 88 degrees can carry just over 55btus/sq. Most homes today require less than 30btus/sf.

https://www.pmmag.com/ext/resources/PM/2014/June/016-020-0614-Siggy.pdf

 

[Missouri Bound]

It's pretty clear you have done your research and study.
I'm not sure coming to this chatroom is going to enhance your knowledge very much. It appears you are on the right track.
Good luck with your project.:vs_cool:

 

[CNM Design]

It's pretty clear you have done your research and study.
I'm not sure coming to this chatroom is going to enhance your knowledge very much. It appears you are on the right track.
Good luck with your project.:vs_cool:

Thanks

Just can't find anything anywhere regarding the R-value of Ultralight vs regular drywall. No regular drywall at Home Depot now, all Ultralight. Looks like it may even be a special order now.

 

[de-nagorg]

There is a fella from Maine on here, that specializes in home weatherization, he probably knows the answer to that, If he don't chime in soon, I will PM him to take a look at your post.


ED

 

[Missouri Bound]

Thanks

Just can't find anything anywhere regarding the R-value of Ultralight vs regular drywall.

Go to the US Gypsum website. They have an 800 number to answer questions regarding their products. I would think you wouldn't be the first to ask about R value.

 

[Missouri Bound]

Regular 1/2" drywall has an r value of .45.....fairly insignificant.
In my humble opinion, I would think the mass of the board would be a more important factor than any insulation factor for your purposes.

 

[CNM Design]

Regular 1/2" drywall has an r value of .45.....fairly insignificant.
In my humble opinion, I would think the mass of the board would be a more important factor than any insulation factor for your purposes.

Thanks

Even the 5/8ths has a response time of less then 10 min.
Theoretically, (IMO) seeing the Ultralight is wiped and has air bubbles in it, it would function more like a foam board and insulate more then regular drywall.
I will give them a call.

 

[Bud9051]

Virtually no difference. Residential Energy (the bible for energy auditing) does not list the ultralight but shows Gypsum or plasterboard at 0.9 r-value per inch. As a source of radiant energy the emissivity of the ceiling paint will have far more to do with the transfer of radiant heat. A reflective surface like aluminum foil would radiate almost zero energy while a black paint would be close to 100%. The color and characteristics of the paint you choose are important. Unfortunately that would require some research but I suspect the mfgs of the radiant system would have that answer.

Short answer, not enough difference to be concerned about.

As for installing a radiant ceiling, the added heat loss through the ceiling would also be a concern. All improvements to a house add or subtract to its value. I suspect this one subtracts more than it adds.

Bud

 

[de-nagorg]

Virtually no difference. Residential Energy (the bible for energy auditing) does not list the ultralight but shows Gypsum or plasterboard at 0.9 r-value per inch. As a source of radiant energy the emissivity of the ceiling paint will have far more to do with the transfer of radiant heat. A reflective surface like aluminum foil would radiate almost zero energy while a black paint would be close to 100%. The color and characteristics of the paint you choose are important. Unfortunately that would require some research but I suspect the mfgs of the radiant system would have that answer.

Short answer, not enough difference to be concerned about.

As for installing a radiant ceiling, the added heat loss through the ceiling would also be a concern. All improvements to a house add or subtract to its value. I suspect this one subtracts more than it adds.

Bud

There you have it, from he who knows more than the rest of us.

About weatherization anyway.:devil3:


ED

 

[Bud9051]

Thanks ED, I think, a very limited specialty.

Bud

 

[CNM Design]

Virtually no difference. Residential Energy (the bible for energy auditing) does not list the ultralight but shows Gypsum or plasterboard at 0.9 r-value per inch. As a source of radiant energy the emissivity of the ceiling paint will have far more to do with the transfer of radiant heat. A reflective surface like aluminum foil would radiate almost zero energy while a black paint would be close to 100%. The color and characteristics of the paint you choose are important. Unfortunately that would require some research but I suspect the mfgs of the radiant system would have that answer.

Short answer, not enough difference to be concerned about.

As for installing a radiant ceiling, the added heat loss through the ceiling would also be a concern. All improvements to a house add or subtract to its value. I suspect this one subtracts more than it adds.

Bud

Thanks for your input.

Looking more at radiant heat coming into the room, not leaving.

https://www.pmmag.com/ext/resources/...0614-Siggy.pdf

 

[Bud9051]

Radiant heat transfer is line of sight and all surfaces emit it. So everything in the room below the radiant ceiling is radiating towards the ceiling while the ceiling is radiating back down. It is an exchange process that is constantly trying to equalize the temperature of the two surfaces. The greater the temperature difference in conjunction with the surface properties determines the net transfer of energy.

The r-value of the drywall or other materials below the radiant tubes determines how fast the heat loss can be replenished.

Bud