Ceiling Insulation

[superal]

58 minutes ago, NorthernRyland said:

I can think of restaurants that have low ceilings and metal roofs. Even if I like their food I simply can not eat there during most times of the year because it feels like an oven. If they spent a few thousand baht to put in some 1CM foam that would make just enough difference to survive with a  fan on you.

My lady has an enclosed restaurant that is 9 x 18 meters . Flat roof and ceiling at about 2.8 meters average  height  . Outside on the roof top is cladded with Blue Scope profiled panels with foil back insulation . It did get hot in there and noisy when it rained so this year I had the roof over cladded again with the same materials that formed an air gap .  Result is much cooler and quieter . The ceiling is plasterboard with foil back . We also have 2 high level air extractors  , plus 2 Aircon units which make dining comfortable . However running 2 aircons can be expensive and use mostly when customers are coming . Problems are , the outside ambient temperature will  

get in , especially when doors are left open and the Aircon is running ( makes me angry ) . Will not be so bad in a months time when this extreme heat subsides .

[NorthernRyland]

9 minutes ago, superal said:

My lady has an enclosed restaurant that is 9 x 18 meters . Flat roof and ceiling at about 2.8 meters average  height  . Outside on the roof top is cladded with Blue Scope profiled panels with foil back insulation . It did get hot in there and noisy when it rained so this year I had the roof over cladded again with the same materials that formed an air gap .  Result is much cooler and quieter . The ceiling is plasterboard with foil back . We also have 2 high level air extractors  , plus 2 Aircon units which make dining comfortable . However running 2 aircons can be expensive and use mostly when customers are coming . Problems are , the outside ambient temperature will  

get in , especially when doors are left open and the Aircon is running ( makes me angry ) . Will not be so bad in a months time when this extreme heat subsides .

just an air gap? I have to assume some insulation material would have higher R value than air but maybe that would good enough. 9*18 is a big space though, would probably cost 20k+ baht for something basic.

[superal]

2 hours ago, NorthernRyland said:

just an air gap? I have to assume some insulation material would have higher R value than air but maybe that would good enough. 9*18 is a big space though, would probably cost 20k+ baht for something basic.

Air gap yes plus the double layer of Blue Scope cladding which both have the foil and insulation backing .  On top of the plasterboard ceiling is another foil/insulation . So , in total 3 layers of foil/insulation . It has certainly made quite a difference. The only downside is that the restaurant has windows on both 18 meter flanks and the end flank of 9 meters and glass being a conductor of heat , does not help . 

 

[superal]

On 4/16/2024 at 9:57 AM, tomster said:

Hi,

 

I need to insulate a roof on a bar as cheaply as possible.

 

I'm not sure what the roof type is called, but it's very common here, this is what it looks like underneath:

 

 

When the sun is on it it's literally too hot to touch the underside and this heat is radiating down into the area below, making it crazy hot in the space.

 

I would rather deal with this with something from underneath as it would save the headache of working on it from above, weight issues etc.

 

Is there something I can stick or paint on the underside that would block a decent amount of the heat out, it doesn't need to be 100% effective, 80--90% would be good enough.

 

Thanks in advance.

       Looks like you have a cement board ceiling/roof which are prone to cracking around the U bolts and also leaking in heavy rain . You do not tell the size of the room nor access to the outside of the roof . Reason is that your cement board could be over clad with zinc coated insulated roof panels that can be ordered to your required length . A lightweight Thai guy would take only 1 or 2 days to install .

Polystyrene ceiling tiles or simply insulation tiles  could be glued under the cement board for a cheap fix but without a level surface it would not look great . 

[khunPer]

Heat reflective foil reduces a lot of the heat radiation, which has also been suggested in earlier posts.

 

Even better would be when it's combined with a lowered ceiling  and mineral wool between the foil and the ceiling plates. You can even get mineral wool mats covered in reflective foil.

[sometimewoodworker]

15 hours ago, Luuk Chaai said:

Most common insulation materials work by slowing conductive heat flow and -- to a lesser extent -- convective heat flow.

I agree

15 hours ago, Luuk Chaai said:

Radiant barriers and reflective insulation systems work by reducing radiant heat gain.

No they don’t. You missed the full information in your physics classes, or you’re really confused in your wording.

Radiant barriers function by NOT radiating heat, they can be hot (very hot) but they don’t radiate heat well.

Reflective barriers function by being good reflectors of heat so don’t get hot.

15 hours ago, Luuk Chaai said:

Dust accumulation on the reflective surface will reduce its reflective capability.

Correct 

15 hours ago, Luuk Chaai said:

The radiant barrier should be installed in a manner to minimize dust accumulation on the reflective surface.

You are confusing the 2 different functions (this is not helped by the double sided silver film sold in Thailand)

a radiant barrier needs a relatively clean surface the reverse side has no effect on the functioning of the radiant barrier.

15 hours ago, Luuk Chaai said:

When installing a foil-type barrier, it's important to allow the material to "droop" between the attachment points to make at least a 1.0 inch (2.5 cm) air space between it and the bottom of the roof. 

This is only if you have double sided film and want to allow reflection back to the roof surface. 
 

You can use single sided silver faced plywood boards with the silver face down and they will be as effective.

 

I used single sided foil in my install as it was half the cost, as effective and I did remember my physics lessons 😉 

[sometimewoodworker]

13 hours ago, Muhendis said:

I'm going to backtrack on this a bit. 

The plywood is still a reasonable idea but, having gained some more knowledge I would supplement that with aluminium foil arranged to have free air on both sides.

I changed my idea because I read this:-

https://radiantbarrier.com/blogs/news/how-radiant-barrier-works-heat-gain-loss-in-buildings#:~:text=Most aluminum insulation has only,strikes its air-bound surfaces.

Regrettably that post very much glosses over the difference between using aluminium foils as a reflective barrier and using them as a radiant barrier.

 

Given that in Thailand the heat is virtually always from the roof, a radiant barrier with the high gloss surface facing down in contact with the underside of the roof is extremely effective, there is a need for the underside to face an air space, the topside doesn’t need an air space.

[sometimewoodworker]

On 4/16/2024 at 11:47 AM, 4MyEgo said:

 

I studied roofing for years and the only way your going to reduce heat penetrating below your roof is to:

2. Put cement tiles on

It seems that your studies did not include anything to do with night storage heaters! If it did you would know that cement is a good storage medium for heat. The mass of the cement tiles will nicely absorb the heat from the solar furnace AKA the sun, and then radiate that through the night keeping you nice and toasty warm.

 

So in fact metal roofs are far better than cement, as they don’t store anything like the amount that cement does.

[Bday Prang]

On 4/16/2024 at 11:13 AM, Muhendis said:

What I would do would be to screw some thin plywood or cement board to the underside of those, what look like, 30mm x 30mm steel roof panel supports.

This would create an air gap which would reduce heat significantly. If you could also fill that air gap with fibreglass insulation, that would be even better.

 

I would avoid using wood, it's too tempting for termites and other such pests

[sometimewoodworker]

FWIW There is a very simple experiment you can do to demonstrate the effectiveness of a radiant barrier.

materials required; black surfaced frying pan, a spatula and aluminium cooking foil. NB insulation foil will not work

 

method 

1. heat the frying pan to just under the smoke point of peanut oil
2. hold your hand a close to the surface of the pan as you can for at least a minute (without burning yourself) this will be several to many cm above the pan surface (is it isn’t the pan is not hot enough or you have no nerves)
3. take a piece of aluminium foil that is at least 5cm large on all sides than the pan, place it dull side down, using the spatula (don’t use a plastic one) press the foil down to the surface of the pan
4. hold your hand a close to the surface of the pan as you can for at least a minute (without burning yourself) this will be Very much closer than in number 2.

You can avoid the use of the spatula by forming a bowl shape to fit into the frying pan before heating the pan.

 

The foil can be touching the frying pan’s surface so at or close to the same temperature as the pan. This demonstrates that a polished aluminium surface is a poor radiator of heat, while a black surfaced frying pan is not.

 

A demonstration of a reflective barrier is a rather more complex process.

 

[4MyEgo]

On 4/17/2024 at 12:01 PM, CharlesHolzhauer said:

Cement tiles to reduce heat penetration?

 

The thickness of the cement tiles on a gable roof (height in attic/ceiling) assists in reducing the heat penetration into that space, coupled together with the thermal reflective sissolation under the roof tiles, plus R38 insulation ceiling batts will reduce the heat further coming through till at least 2pm, plus the whirly birds to suck any excess heat trapped in the attic/ceiling during the 40 degree temps is the only way to go in my opinion, proof in the pudding so to speak.

 

Just ask yourself what time you put on the air conditioner in these 40 + temps, as mentioned, ours goes on at 2pm, one at the front of the house and one at the back of the house, floor ceiling fan at each end of the house in front of the air conditioners to help push the cool air to both ends of the house which is about 30 metres long.

[4MyEgo]

On 4/17/2024 at 12:11 PM, IvorBiggun2 said:

Too heavy.

 

Not if you have a steel roof frame, only way to go, plus no termite problems, ever. 

[4MyEgo]

On 4/17/2024 at 12:27 PM, CharlesHolzhauer said:

Weight or heaviness does not influence the penetration of heat.

 

I actually tested how long it took for the heat to penetrate the cement tiles vs the Thai conventional fibro tiles and metal deck sheeting, cement tiles took the longest.

 

I don't know how you believe it to be any different, nothing to do with weight or heaviness, it's to do with the thickness of the tile and what it's made of.

[4MyEgo]

On 4/18/2024 at 1:17 AM, sometimewoodworker said:

It seems that your studies did not include anything to do with night storage heaters! If it did you would know that cement is a good storage medium for heat. The mass of the cement tiles will nicely absorb the heat from the solar furnace AKA the sun, and then radiate that through the night keeping you nice and toasty warm.

 

So in fact metal roofs are far better than cement, as they don’t store anything like the amount that cement does.

 

Your entitled to your opinion.

 

I am not going to argue with people who think differently, fact of the matter is, as stated in my original post reply, 1 to 5 works fine for us and our place.

 

You believe what you like, that said once the air cons kick in at 2pm on 40 + degree temps for a few hours, then turned off, the house remains cool until we go to bed around 10pm, and we usually turn on the air cons on at around 9.30pm in each room that we sleep in and turn them off at 10pm, whereby a floor fan takes over in each room till we awake, so your theory of our house being nice and toasty throughout the night is incorrect, suffice to say you come to your conclusion without knowing how our house is designed and if sun hits any of our cement rendered brick walls.

 

Sometimes it's best not to assume, as I mentioned, I studied roofing for years, not to mention which way our house was going to face, what construction materials we were going to use, what side of the house our bedrooms, living rooms, kitchen were going to be on and how they were going to be shaded from the sun. The roof design, cement tiles, sissolation, insulation batts, whirly birds, cross ventilation, and eaves were the easiest part as was parting with the 10% of what it would have cost me to do back in the old country.

 

It helps when you lived in a similar climate, and have an understanding of buildings, construction materials and designs, like I said, having I studying roofing before I went down the path I did and if anyone has a different way to reduce the heat in their roof space, then hats off to them, but I doubt it, and your statement that metal roofs are better than cement roofs just goes to show you have no idea what you are talking about IMO. 

 

At the end of it all, if your house is cool without you having to put the air conditioner on in 40 + degree temperatures till after 2pm, you win....lol

.

[4MyEgo]

On 4/17/2024 at 12:33 PM, NorthernRyland said:

Yet very common. What's a better solution? I guess you can do foam insulation metal sheeting but that's kind of ugly if nothing else.

 

Not heavy if you have a steel roof.

[NorthernRyland]

On 4/17/2024 at 9:50 PM, sometimewoodworker said:

I used single sided foil in my install as it was half the cost, as effective and I did remember my physics lessons 😉 

 

this goes over my head I guess. The reflective part is facing DOWN? I thought it was supposed to face up towards the sun?

[NorthernRyland]

Summarize this for me, so the debate with ceramic tiles is that while they block heat penetration they retain heat and will radiate heat during the night after the sun is down, therefore ventilation is extra important as compared to some lighter material. Is this correct?

[Fruit Trader]

52 minutes ago, NorthernRyland said:

this goes over my head I guess. The reflective part is facing DOWN? I thought it was supposed to face up towards the sun?

 

You are not alone when it comes to understanding shiny side up or shiny side down because logic tells us we should reflect those bad rays back in the direction from which they came.

 

When it's not practical to add a reflective surface on the sunny side we can limit heat emitted inside by changing the surface facing into a room. 

 

 

 

 

 

 

[Fruit Trader]

1 hour ago, NorthernRyland said:

Summarize this for me, so the debate with ceramic tiles is that while they block heat penetration they retain heat and will radiate heat during the night after the sun is down, therefore ventilation is extra important as compared to some lighter material. Is this correct?

 

There are so many factors to consider in the roof tile versus sheet material heat absorption and reflection argument.

Not easy to summarise, and unless a particular roof design, location and style is used, the argument could go on for many pages.

[NorthernRyland]

19 minutes ago, Fruit Trader said:

You are not alone when it comes to understanding shiny side up or shiny side down because logic tells us we should reflect those bad rays back in the direction from which they came.

 

In fact I have a roll of single sided foil foam insulation I bought from HomePro. It says to point the reflective side UP towards the sun too.

[sometimewoodworker]

1 hour ago, NorthernRyland said:

this goes over my head I guess. The reflective part is facing DOWN? I thought it was supposed to face up towards the sun?

You are getting confused by the difference between a reflective barrier, where the reflective side goes up

And a radiant barrier where the non radiant (shiny side) goes down.

 

There are 2 different laws of physics involved radiation (shiny side down) and reflection (shiny side up)

 

The silver film sold in Thailand is either shiny on one side (cheapest) where it is important to have it shiny side down on the underside of a roof as it is a good radiant barrier. Or shiny on both sides where it can act as a reflective barrier on one surface and a radiant barrier on the other surface 

 

The problem with reflective surfaces is they quite quickly get dirty/dusty so loosing effectiveness 

The benefit of non radiant surfaces is they face down so dirt and dust has little effect so maintaining effectiveness

[sometimewoodworker]

8 minutes ago, NorthernRyland said:

In fact I have a roll of single sided foil foam insulation I bought from HomePro. It says to point the reflective side UP towards the sun too.

That goes to show that the information printed on it is not enough as you must have an air gap between the silver side and the roof, it could be completely correct if it is designed to lay on a ceiling.

 

[sometimewoodworker]

1 hour ago, NorthernRyland said:

Summarize this for me, so the debate with ceramic tiles is that while they block heat penetration they retain heat and will radiate heat during the night after the sun is down, therefore ventilation is extra important as compared to some lighter material. Is this correct?

 
my post got eaten 

Quote

Ideally modern buildings should be constructed in such a manner as to minimise temperature build up in the room space during warm weather and yet prevent the loss of this excess heat in cold periods. To achieve this, a combination of insulation to exterior walls is required for colder weather and a high thermal mass to act as a heat sink for hot weather. Concrete has a high thermal mass with properties similar to brick and stone. It is possible to absorb heat from the atmosphere in warm weather and release it during cooler periods, e.g. overnight. This is known as the ‘thermal flywheel’ effect. In a passive concrete design the cooling capacity of concrete can be up to 25W/m² and with an active system, e.g. by ducting of air through a concrete slab, up to 40W/m² can be absorbed.

 

[KannikaP]

1 hour ago, NorthernRyland said:

this goes over my head I guess. The reflective part is facing DOWN? I thought it was supposed to face up towards the sun?

Very little sunlight will penetrate your roofing.

[sometimewoodworker]

2 hours ago, 4MyEgo said:

It helps when you lived in a similar climate, and have an understanding of buildings, construction materials and designs, like I said, having I studying roofing before I went down the path I did and if anyone has a different way to reduce the heat in their roof space, then hats off to them, but I doubt it, and your statement that metal roofs are better than cement roofs just goes to show you have no idea what you are talking about IMO.

It actually shows that while you may have studied roofing you neglected, forgot, or never learned basic physics and are attributing statements to me that I never made.

 

Quote

Concrete has a high thermal mass with properties similar to brick and stone. It is possible to absorb heat from the atmosphere in warm weather

Also from the sun in the usual Thai weather.

Metal roofs do not store heat (or at least the thermal mass is so small the heat storage is minimal) 

Metal roofs will quickly transmit heat.

 

in direct sun A metal roof with sufficient insulation will not heat up the interior at any greater speed than than a properly insulated concrete (cement tile) roof

 

With no sun and a low air temperature (Thailand after sunset)

The metal roof will almost instantly (in a few minutes) be at ambient air temperature.

Conversely it will take hours for the concrete (cement tile) roof to loose the heat it has gained 

 

I will use the option that is suitable for myself.

you are welcome to continue the your your night storage heater roof

Edited April 19 by sometimewoodworker

[freeworld]

1 hour ago, Fruit Trader said:

 

There are so many factors to consider in the roof tile versus sheet material heat absorption and reflection argument.

Not easy to summarise, and unless a particular roof design, location and style is used, the argument could go on for many pages.

The US dept of energy has this document for guidance.

 

https://www.energy.gov/sites/prod/files/2013/10/f3/coolroofguide.pdf

 

and from https://www.energystar.gov/products/cool-roofs

 

Cool Roofs

What are cool roofs?

A cool roof is made of a material or has a coating that can lower the roof surface temperature, decreasing the amount of heat transferred into a residential or commercial building.  In general, traditional roofs absorb sunlight during the day, heating the building and the surrounding air.  Roofs that are lighter in color or are reflective stay cooler than roofs that absorb sunlight.

There are two ways to help cool a roof. First, a cool roof can reflect away sunlight, so it stays cooler.  Such a roof is said to have a high solar reflectance. Second, a cool roof should also release or emit heat (infrared radiation) so it stays cool.  Such a roof is said to have high thermal emittance.  An ideal cool roof is a roof with both high solar reflectance (SR) and high thermal emittance (TE). While lighter color roofs tend to have the best SR and TE, new coating and material technologies now exist for other colors that have high SR and TE. 

Exterior building walls are exposed to only about half the amount of sun as roofs, but they can also absorb heat. The same basic principles apply to cool walls as to cool roofs. 

 

Edited April 19 by freeworld

[4MyEgo]

1 hour ago, sometimewoodworker said:

in direct sun A metal roof with sufficient insulation will not heat up the interior at any greater speed than than a properly insulated concrete (cement tile) roof

 

So what you are saying is that a metal roof with insulation will not heat up the interior at any greater speed than that of a concrete tiled roof. If it has a gable roof I will agree as it will have enough clearance in the attic for the hot air to be circulated, that said, I would assume that the noise from the rain would be noticeable at times, vs nil from the concrete tile on a gable roof.

 

https://www.linkedin.com/pulse/metal-vs-tile-what-better-roof-choice-cunmac-vietnam#:~:text=Both metal and concrete roof,has evolved through the years.

[sometimewoodworker]

1 hour ago, 4MyEgo said:

 

So what you are saying is that a metal roof with insulation will not heat up the interior at any greater speed than that of a concrete tiled roof. If it has a gable roof I will agree as it will have enough clearance in the attic for the hot air to be circulated, that said, I would assume that the noise from the rain would be noticeable at times, vs nil from the concrete tile on a gable roof.

 

https://www.linkedin.com/pulse/metal-vs-tile-what-better-roof-choice-cunmac-vietnam#:~:text=Both metal and concrete roof,has evolved through the years.

You did rather ignore the fact that a concrete roof will continue to radiate heat for a much longer period than metal one. And while insulation will reduce the amount radiated into the roof spaces it doesn’t eliminate it. 
 

The rain noise will be greater on metal than concrete but you will still get some.

[NorthernRyland]

9 hours ago, sometimewoodworker said:

With no sun and a low air temperature (Thailand after sunset)

The metal roof will almost instantly (in a few minutes) be at ambient air temperature.

Conversely it will take hours for the concrete (cement tile) roof to loose the heat it has gained 

 

If the ceiling is well insulated does it matter if the space above the roof is releasing heat slower?

 

So basically the trade off with the metal roof is you're taking on more heat during the day but releases faster at night. This all relies on the ceiling insulation being of the highest quality also.

 

What do you think about the metal roof panels with foam inserted in the middle? I guess that has the same problem of trapping heat though if it does pass through.

[SAFETY FIRST]

On 4/16/2024 at 9:57 AM, tomster said:

Thanks in advance.

These properties were not designed for AC to be installed. 

 

You are chasing your tail. 

 

It will be expensive to redesign the roof to insulate. 

 

It will be expensive to run an AC unit without adequate insulation. 

 

Buy an extra fan.

 

You will be throwing good money after bad.