My Mylar notification for you and a question

[paradisePhysicist]

TL;DR

mylar

my home is over 100 degrees in the ceiling. the engineers who built this palace put the lightbulbs in an open cavity so that the 105, 110, 120? degrees ceiling pours into the room. I thought mylar would be a good material to insulate this since it would allow some light to pass through while insulating. however, i started to notice an odor after many days, and began to feel ill. this post is meant as a notification to be careful of using mylar as insulation. Idk if there are online articles. Do not take this as a 100% absolute peer reviewed fact but just a notification. There are many different types of mylar materials.

hutchpd also told me that mylar balloons alter sound. I tried this and didn't notice any change. I am looking for an online website or video which instructs me on these matters. I am also looking for a cheap alternative to mylar insulation.

 

[berkeman]

Summary:: mylar

this post is meant as a notification to be careful of using mylar as insulation. Idk if there are online articles.

You DK because you didn't look?

 

[berkeman]

Summary:: mylar

the engineers who built this palace put the lightbulbs in an open cavity so that the 105, 110, 120? degrees ceiling pours into the room.

Can you post pictures please to make the situation more clear? Could you just use glass panes instead of Mylar for the downward-facing light bulb fixture windows? Also, do you have an attic fan that comes on during warm days? They are relatively inexpensive, depending on how available an electrical tap is near that location in the attic.

 

[russ_watters]

IDK what your setup looks like so ICH design a better insulation system (FYI, mylar doesn't really even count as "insulation"). The obvious solution is to insulate above the lights, not below them.

Ok, seriously though; stop using text speak. Use complete sentences.

 

[paradisePhysicist]

You DK because you didn't look?

I looked into mylar earlier to see if it was safe, the information I found was vague.

The glass panels are a good suggestion.

IDK what your setup looks like so ICH design a better insulation system (FYI, mylar doesn't really even count as "insulation"). The obvious solution is to insulate above the lights, not below them.

I guess technically it "could" be done but it would be impractical. Idk if lightbulb glass is insulated or not, the temp would flow through the lightbulbs and out of the base also. One of the benefits of putting it underneath is it will also insulate the heat from the lightbulb itself.

Ok, seriously though; stop using text speak. Use complete sentences.

Alright.

 

[russ_watters]

View attachment 286625

That doesn't show what is above.

I guess technically it "could" be done but it would be impractical. Idk if lightbulb glass is insulated or not, the temp would flow through the lightbulbs and out of the base also. One of the benefits of putting it underneath is it will also insulate the heat from the lightbulb itself.

Are you using incandescent? I thought the problem here was heat flow into the house through "holes" in the insulation? If the real problem is heat from light bulbs, get more efficient light bulbs.

 

[paradisePhysicist]

That doesn't show what is above.

I am not sure if it is even possible to get into the roofceiling of the house.

Are you using incandescent?

Most likely but I am not entirely sure. They give off a yellow tint.

I thought the problem here was heat flow into the house through "holes" in the insulation?

Presumably so, but I am not sure if it is possible to get into the roof ceiling to verify. I measured the temperature in the light cavity and it is much hotter than the main ceiling. Heat generally rises upward but in this case it is pouring downward into the room, standing underneath the hotspots feels hotter than other parts of the room.

If the real problem is heat from light bulbs, get more efficient light bulbs.

I rarely use the lights ever, but in the rare event I did, bottom insulation would stop the heat of the bulb. I read online that CFLs still produce heat. The surface of CFL is only 100 degrees but the surface of an incandescent ranges from 150 to 250 degrees. Fluorescent gives me headaches so maybe the answer is LED lighting. Anyway the main source of heat seems to be the sun originally, trapping heat inside the roofceiling itself. Looking into improving the roof ventilation but don't have the budget for that right now.
https://www.razorlux.com/light-bulb-heat-temperature-chart.html

 

[berkeman]

I guess technically it "could" be done but it would be impractical. Idk if lightbulb glass is insulated or not, the temp would flow through the lightbulbs and out of the base also. One of the benefits of putting it underneath is it will also insulate the heat from the lightbulb itself.

Can you post a picture? One thing to be careful of is cutting down on the airflow through the light fixture (especially if they are hot incadescent bulbs). If you cut down on the airflow (by putting Mylar or glass over the opening), that will result in the fixture and bulb running even hotter and cutting down on the lifetime of the bulb.

If you look inside the fixture housing, is there a little sticker that gives the maximum wattage bulb that is allowed (even before cutting down the airflow with a transparent covering)?

 

[paradisePhysicist]

Can you post a picture? One thing to be careful of is cutting down on the airflow through the light fixture (especially if they are hot incadescent bulbs). If you cut down on the airflow (by putting Mylar or glass over the opening), that will result in the fixture and bulb running even hotter and cutting down on the lifetime of the bulb.

I will draw a 3d picture.

I looked at the bulbs again I think some are incandescent but I have a mix of bulbs. One solution I am thinking of is just get larger bulbs that completely enclose the area, however, based on your post, this could result in the bulb running too hot. But since I don't use the bulbs that often maybe that is not that much of an issue.

If you look inside the fixture housing, is there a little sticker that gives the maximum wattage bulb that is allowed (even before cutting down the airflow with a transparent covering)?

Not sure.Also was wondering does anyone know about the mylar balloon topic as well?

 

[russ_watters]

Most likely but I am not entirely sure. They give off a yellow tint.

It's tough for me to wrap my head around not knowing the answer to that, and I think we really need to know. Can't you look at the label on the bulb? I'm not even sure there is a real problem to be solved here.

Presumably so, but I am not sure if it is possible to get into the roof ceiling to verify. I measured the temperature in the light cavity and it is much hotter than the main ceiling. Heat generally rises upward but in this case it is pouring downward into the room, standing underneath the hotspots feels hotter than other parts of the room.

Heat rises, but incandescent lights radiate heat. They have to be high wattage and you have to be close to feel it though. But because heat rises, if the cavity the light is in is hot, that doesn't necessarily create a problem.

I rarely use the lights ever, but in the rare event I did, bottom insulation would stop the heat of the bulb. I read online that CFLs still produce heat. The surface of CFL is only 100 degrees but the surface of an incandescent ranges from 150 to 250 degrees.

Temperature isn't heat. I have one incandescent in my house, a floodlight that is in a similar recessed installation to yours (except on the first floor of a two-story). The surface temp is about 82C, which is less than I would have guessed. But that's not heat. The heat is 60 W. If I want to reduce the heat, I'll replace it with an LED of probably about 10 W.

For your main question/issue though, I think covering it with mylar is a bad idea because that would block almost all the light, and the mylar may melt (especially if it has a coating of another kind of plastic). I don't see what real benefit you get. In fact, it makes so little sense I'm wondering if I'm mis-interpreting: you do mean you put the mylar under the light, not above it, right?

 

[hutchphd]

Also was wondering does anyone know about the mylar balloon topic as well?

I think that had to do with my suggestion to use Helium-filled Mylar balloons as (negative) sound lenses?? I've lost the reference. In that case it was the gas not the Mylar.

 

[anorlunda]

You are asking about a high effort, high cost solution. The simpler and cheaper solution is simply to switch to LED bulbs that produce very much less heat in the first place. Then you don't need to worry about where the heat goes.

Pay attention to the label on the LED. You want the kind that is rated for use in a contained fixture.

 

[berkeman]

If you look inside the fixture housing, is there a little sticker that gives the maximum wattage bulb that is allowed?

Not sure.

It will look something like this, stuck inside the fixture where you can see it when replacing the bulb:

 

[paradisePhysicist]

I think that had to do with my suggestion to use Helium-filled Mylar balloons as (negative) sound lenses?? I've lost the reference. In that case it was the gas not the Mylar.

Hmm ok thanks. Next balloon I get I will be sure to try helium.

It will look something like this, stuck inside the fixture where you can see it when replacing the bulb:

View attachment 286672

Hmm I will use a flashlight and see if I can find that.

You are asking about a high effort, high cost solution. The simpler and cheaper solution is simply to switch to LED bulbs that produce very much less heat in the first place. Then you don't need to worry about where the heat goes.

Pay attention to the label on the LED. You want the kind that is rated for use in a contained fixture.

Alright thanks, LED it is then. Will it say the words "contained fixture" on the rating?

It's tough for me to wrap my head around not knowing the answer to that, and I think we really need to know. Can't you look at the label on the bulb? I'm not even sure there is a real problem to be solved here.

Heat rises, but incandescent lights radiate heat. They have to be high wattage and you have to be close to feel it though. But because heat rises, if the cavity the light is in is hot, that doesn't necessarily create a problem.

Temperature isn't heat. I have one incandescent in my house, a floodlight that is in a similar recessed installation to yours (except on the first floor of a two-story). The surface temp is about 82C, which is less than I would have guessed. But that's not heat. The heat is 60 W. If I want to reduce the heat, I'll replace it with an LED of probably about 10 W.

Hmm interesting, I thought temperature and heat were the same thing, I will look into some science vids about that.

For your main question/issue though, I think covering it with mylar is a bad idea because that would block almost all the light, and the mylar may melt (especially if it has a coating of another kind of plastic). I don't see what real benefit you get. In fact, it makes so little sense I'm wondering if I'm mis-interpreting: you do mean you put the mylar under the light, not above it, right?

I gave up on the mylar idea, in my opinion when it gets too hot it is a health hazard. I don't have 100% proof but just my opinion. Probably also depends on the brand and type of mylar also. Currently I am just going with the larger bulb idea to cover up the gap in the ceiling, unless the bulb is too expensive. Other than that I thought about covering it up with a bunch of paper but I don't think will be good insulation, it will also block the light. Actually I may just go with the glass plate idea if the bulb is too expensive. I am not sure if all glass plates insulate or if I need a specific type of glass, same with the bulb. I am not sure if all bulbs will insulate against parasitic heat paths around the outside of the glass. The material ideally should prevent heat movement from both flowing through the glass and around the glass imbetween the tiny micron gap between it and the ceiling rim. But probably any glass will do and improve the current situation.

 

[anorlunda]

lright thanks, LED it is then. Will it say the words "contained fixture" on the rating?

It has been a while since I shopped for bulbs in the hardware store. I think the correct language is "Lamp Rated for Enclosed Fixtures" . But each bulb package should say either "don't use in enclosed fixtures" or the opposite.

 

[paradisePhysicist]

It has been a while since I shopped for bulbs in the hardware store. I think the correct language is "Lamp Rated for Enclosed Fixtures" . But each bulb package should say either "don't use in enclosed fixtures" or the opposite.

Oh ok thanks.

Also with the helium balloon thing I'm pretty sure it has helium because it floats. I don't think hydrogen balloons are sold at stores so I don't know what else it would be filled with. Doesn't seem to affect the sound in any noticable way though unfortunately.

 

[hutchphd]

https://sciencedemonstrations.fas.harvard.edu/presentations/refraction-sound
Use sound of high frequency.
If all else fails attach weight to make the balloon neutrally buoyant and watch the air currents (and relative humidity) in your house. Or give it to a trusted kid for observation.