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Ceiling Insulation Types? Recommendations please?

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5 hours ago, GarryP said:

I want a comfortable house in which I can sit in the living room and watch TV without the need for aircon, but my fear is that this would be so much more difficult in a bungalow than a two storey house.    

So, you need natural ventilation for the un-conditioned spaces, which would tend to require low thermal mass, good overhangs, and a way to bring air in low and exhaust high.  There are several ways to do that; the traditional Thai stilt house with high open ceiling and gable vents (possibly augmented with fans) works pretty well with a radiant barrier.  

 

If you want a 2-story concrete box, you will be forced to have the bedrooms upstairs and the “un-conditioned” spaces below.  But, in reality the cooling upstairs is also cooling the lower floor.

 

Personally I am not a fan of the ground-coupled style @willi2006 is looking at; I think the ground temperature is optimistically closer to 26-27C, and that will end up with too much thermal mass at the wrong temperature.  However, the wrap-around veranda makes tremendous sense here; normally the biggest pain point is really the solar heat gain especially when that continues to radiate back into the space at night.  Humidity is seasonally painful, and is most economical to address with air conditioning and transfer-exhaust or direct ventilation of latent heat sources.

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8 hours ago, tjo o tjim said:

...

Personally I am not a fan of the ground-coupled style @willi2006 is looking at; I think the ground temperature is optimistically closer to 26-27C, and that will end up with too much thermal mass at the wrong temperature. 

...

Completely  agree.

I meant a suspended slab as it is used here, not a slab-on-grade, but didn't make it clear in my posting.

As far as I know the average ground temperature here is 27 °C or even higher. But EnergyPlus doesn't accept a value higher then 25 °C. So I used that. Also not made clear in my posting as many other details.

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11 hours ago, sometimewoodworker said:

There are 3 recommend ways (US department of energy) of fitting a radiant barrier in a new build. They are equally effective. The choice of fitting method is dependent on the construction process.

Please give a reference, preferable an internet link.

Edited by willi2006

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2 hours ago, willi2006 said:

Completely  agree.

I meant a suspended slab as it is used here, not a slab-on-grade, but didn't make it clear in my posting.

As far as I know the average ground temperature here is 27 °C or even higher. But EnergyPlus doesn't accept a value higher then 25 °C. So I used that. Also not made clear in my posting as many other details.

We will be building our house between 1 to 2 meters off the ground. 

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4 hours ago, willi2006 said:

But EnergyPlus doesn't accept a value higher then 25 °C. 

I’ll see if I can get someone to talk to Martyn. I don’t think EnergyPro has the same limitation, and it is the same code base IIRC. 

 

 

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5 hours ago, willi2006 said:

Please give a reference, preferable an internet link.

Why? You can do your own research, as I did.

 

The information is there if you want it. The graphic I posted is from the US DoE I highlighted no. 3

Edited by sometimewoodworker

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1 hour ago, sometimewoodworker said:

Why? You can do your own research, as I did.

 

The information is there if you want it. The graphic I posted is from the US DoE I highlighted no. 3

Because I did my research before already and did it again to be sure. The sources tell a different story.

E.g. U.S. DOE:

"To be effective, the reflective surface must face an air space."

https://www.energy.gov/energysaver/weatherize/insulation/radiant-barriers

Or Wikipedia:

"Thermal radiation occurs through a vacuum or any transparent medium (solid or fluid or gas)."

https://en.wikipedia.org/wiki/Heat_transfer#Radiation

I would be glad to learn how radiation from the roof deck to the attic is reflected with "METHOD 3" where the "radiant barrier" is clued to the roof deck, as shown in posting  #30. Or is this just a thin foam insulation:
https://forum.thaivisa.com/topic/1123874-ceiling-insulation-types-recommendations-please/?do=findComment&comment=14651293

 

Edited by willi2006
typo

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1 hour ago, willi2006 said:

Because I did my research before already and did it again to be sure. The sources tell a different story.

No they do not, you have just misinterpreted the information. Or it explained poorly, unfortunately a not unusual case, which is confusing you.

 

1 hour ago, willi2006 said:

To be effective, the reflective surface must face an air space.

If you are using a REFLECTIVE barrier yes

 

 

However 

 

Quote

All materials give off, or emit, energy by thermal radiation as a result of their temperature. The amount of energy emitted depends on the surface temperature and a property called the "emissivity" (also called the "emittance"). The emissivity is a number between zero (0) and one (1). The higher the emissivity, the greater

the emitted radiation.

Silver foil has a very low number around 0.02 ~ 0.05

 

 

 

Reflective, reflects heat

 

Radiant, does not radiate much

 

Quote

A closely related material property is the "reflectivity" (also called the "reflectance"). This is a measure of how much radiant heat is reflected by a material. The reflectivity is also a number between 0 and 1 (sometimes, it is given as a percentage, and then it is between 0 and 100%).

Silver foil is about 0.95~0.98

Edited by sometimewoodworker

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1 hour ago, willi2006 said:

I would be glad to learn how radiation from the roof deck to the attic is reflected with "METHOD 3" where the "radiant barrier" is clued to the roof deck, as shown in posting  #30.

It is not reflected of course neither is there any reflection in methods 1 and 2 if single sided radiant barrier is used

 

neither is it reflected in the pictures I show of my back kitchen.

 

it is not the reflectivity that is important. 

 

The hint is in the name RADIANT BARRIER it is the radiation that is poor the emissivity!!!

 

Quote

A radiant barrier reduces the amount of heat radiated across an air space that is adjacent to the radiant barrier.

 

So there must be an air space on the silver side for the radiant barrier to function, it emits (Radiates) very little heat.

 

do this demonstration at home. Heat a black frying pan to around 400 degrees C put your hand as close as you can, note the distance. Put a layer of silver foil in contact with the surface, shiny side up (no air gap between the foil and pan) repeat the test. The second time you will be able to get hour hand very much closer because the foil is a bad emitter.

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15 hours ago, sometimewoodworker said:

It is not reflected of course neither is there any reflection in methods 1 and 2 if single sided radiant barrier is used

 

neither is it reflected in the pictures I show of my back kitchen.

 

it is not the reflectivity that is important. 

 

The hint is in the name RADIANT BARRIER it is the radiation that is poor the emissivity!!!

Okay, guess now I understand there's a misunderstanding. Or better misleading use of terms.

Radiant barrier is, e.g. Wikipedia:

"A radiant barrier is a type of building material that reflects thermal radiation and reduces heat transfer."

https://en.wikipedia.org/wiki/Radiant_barrier

Emissivity is e.g. Wikipedia:

"The emissivity of the surface of a material is its effectiveness in emitting energy as thermal radiation."

https://en.wikipedia.org/wiki/Emissivity

In method 3 the bottom surface of the roof deck is covered with material that has a lower emissivity than the roof deck.

Searching for information about this method I found:

Thermal Proof That Foil Radiant Barriers Don’t Work Directly Under Roofing Shingles

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1 hour ago, willi2006 said:

Okay, guess now I understand there's a misunderstanding. Or better misleading use of terms.

Radiant barrier is, e.g. Wikipedia:

"A radiant barrier is a type of building material that reflects thermal radiation and reduces heat transfer."

https://en.wikipedia.org/wiki/Radiant_barrier

Emissivity is e.g. Wikipedia:

"The emissivity of the surface of a material is its effectiveness in emitting energy as thermal radiation."

https://en.wikipedia.org/wiki/Emissivity

In method 3 the bottom surface of the roof deck is covered with material that has a lower emissivity than the roof deck.

Searching for information about this method I found:

Thermal Proof That Foil Radiant Barriers Don’t Work Directly Under Roofing Shingles

OK you seem to understand that there are 2 different, but related, properties of silver (aluminium) foil. Both of them require an air space to function. (No airspace no radiated heat, as the example video explains) Both can function without an airspace on the reverse side. If you have double sided foil you can employ both properties. If you have the cheaper single sided then the most effective way (because of dust) is to use the low emissive property.

 

All factory installed foam insulation with foil uses the low emissive property of the foil. No factory installed insulation (in Thailand) uses the reflective properties. It all works, some better than others.

 

None/few of the explanations use terms that make clear which properties are functioning as they mix the terms (possibly scientifically correctly but leading to immense confusion) .

 

Yes radiation can be reflected (95%~98%), so technically you can term that function as a radiant barrier. However if you term that function as a reflective barrier (it is) and the low emissive function (0.02~0.05) as a radiant barrier NOT emitting radiation, things begin to be more understandable and less confusing, maybe 😉 .  You could also use the accurate but cumbersome terms "reflective radiant barrier" and "emissive radiant barrier" but good luck with that.

 

None of this is helped by marketing speak, ceiling insulation is often sold in foil bags. These have a single main benefit, to keep the insulation dust and moisture free. A secondary function is to reflect heat radiation back to the roof this will be compromised over time by dust. The fact that the bag is completely silvered just eliminates the chance of installing it the wrong way up

 

IMG_8475.JPG.bb8d3f62562b12326ea5d858b56da5b2.JPG

 

In conclusion due to the materials use in roofing in Thailand with a well vented roof space double sided foil may have a slight advantage if fitted in type 1 & 2 ways. This is borderline as you will have heated air being produced by the hot (hotter because of the reflected radiation) underside of the roof. [I postulate that where bitumen roof shingles are used you may cause them to fail due to overheating, I have no data and little interest in that as it's not a roofing material used in Thailand]

 

A not insignificant benefit is that you have 2 shiny sides so you will always have one effective side down however incompetent (or good) the people installing the foil are.

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2 hours ago, willi2006 said:

In method 3 the bottom surface of the roof deck is covered with material that has a lower emissivity than the roof deck.

In all methods that is correct and a rather massive understatement, as shown under.

IMG_8485.PNG.5ba39e32c0f615506ab082e2bc766aab.PNGIMG_8484.PNG.d8d0eed187ecbe57871a98f47069c8c1.PNG

 

You did note that single sided foil is acceptable in 1 & 2 didn't you?

Edited by sometimewoodworker

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