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I just moved into a house made in 1969, it gets really hot during the sunny days and cold during the winter. I'm living close to the rocky mountains just so you have an idea how cold and hot it gets. I then got a contractor to let me know what was the problem and told me that I have about 6 inches of fiberglass insulation in my attic and that I need to have about 15 inches.

He told me the next process is to add insulation with a blower machine and then I could add the needed insulation to solve the problem. I looked online to see how easy/hard is to do that and I found out that it's not an easy job, and of course not pretty cheap. I was planning to do it myself to save some dollars but I'm pretty sure that the current insulation in the attic might have some asbestos, so I just don't want to deal with that.

Then I was looking for alternatives to insulation and I found the reflective insulation to be an effective way (it claims that it can get the temperature down to up to 10 degrees) to insulate a home with a possibility of doing it without having to hire a contractor for the job.

First question here:

If is that effective, cheap and easier to install than other methods is that great as they clam it to be? It sounds good to be true.

After watching some youtube videos on how to install this kind of insulation, I noticed that when you install it inside your attic on the ceiling of it, there will be a gap between the ceiling and the reflective layer, since it has be stapled to the studs, so I was wondering how hot could that get and if would affect the roof in any way?

Thank you!

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    I found that DIYing the blown-in insulation was easy. I did have full and easy access to the entire attic space.
    – brhans
    Aug 28, 2019 at 20:38
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    You might want to research pros and cons of reflective insulation. From my own 5 min research, I see that it's not good for cold climates and the "R" ratings are subject to various caveats.
    – computercarguy
    Aug 28, 2019 at 20:39
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    Sure - but more is better, and blowing in another 9" worth of fiberglass or cellulose should be fairly cheap & easy.
    – brhans
    Aug 28, 2019 at 21:34
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    I can only speak from my experience with the blown cellulose stuff, and it turned an old 1900 cottage in North-central GA with no insulation in the walls and only about 3" on the ceiling which no amount of heating or cooling effort from the central AC/furnace could make comfortable, into a very nicely livable space. I added an extra 6-8" in the attic and filled all the wall cavities (old 2x4 studs, so only 4" thickness of insulation there). I'm almost certain that the amount I paid to rent the blower and buy the insulation has already paid for itself in reduced heating & cooling costs...
    – brhans
    Aug 28, 2019 at 23:47
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    "If it sounds too good to be true, it probably is." Put in actual insulation. Based on my research I prefer the cellulose to the fibeglass product for blown-in (less air circulation in the insulation itself.)
    – Ecnerwal
    Aug 29, 2019 at 12:42

2 Answers 2

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Something I didn't see mentioned is that along with proper insulation depth to get yourself to a minimum of R-36 also ensure your attic has proper ventilation. Attics need to breath to let hot air out in the summer and keep your roof cold during the winter (prevent ice dams). Windows have really bad R factors so if you only have single pane and cant get to double, consider storm windows. If your walls are "sweating" during the winter then they don't have enough insulation in them as well. For your wall ensure all your exterior gang boxes are sealed. A single can of foam spray can seal up almost all in a 2400 sq ft house.

As for the reflective insulation, it works well but only in hot climates as it acts a radiant barrier but there are numerous factors to ensure it works well. Doesn't do anything for cold.

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  • Agreed, ensuring good ventilation of the attic is important. Don't forget that there are two parts to this equation: air exits through roof or gable vents, but where does enter? Usually through eave vents. When blowing insulation into an attic, take care to identify where air will enter and avoid blocking the inlets.
    – Greg Hill
    Aug 29, 2019 at 18:56
  • Thank you Micah, just a question, what exactly do you mean by "walls are sweating"? my exterior gang boxes are indeed sealed, I have a storm door, so I don't understand what you mean by a single can can seal up all in a 2400 sq ft house, you mean if I didn't have the exterior outlets sealed?. I have noticed though that during winter, on the lower part of the windows, there's usually a little bit of ice. The windows are double.
    – VaTo
    Sep 3, 2019 at 17:16
  • Also, yesterday I went up in the attic with a respirator, goggles bots and a long sleeve shirt, but I was sweating in the first 2 minutes. Also another thing is that since there's already cellulose all over the attic so I can't see where I can stand and where I can't, so I went down and I just thought I have to have a better strategy to do this myself, one to address the heat issue and to avoid stepping where I could fall from the ceiling.
    – VaTo
    Sep 3, 2019 at 17:19
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    @VaTo Summer is not the best time to be doing this. Best to do it when it's in fall. If anything like where I grew up in the rockies, it's already around the low 50s in the mornings so that would be the best time. Wait a month and it may be even better. Also, just lay wood planks across the rafters where you want to walk. Don't worry too much about the insulation. You can fluff it back up once you remove the plank. 'Sweating' I mean is if you find condensation on the wall in winter. Yes, I meant if you didn't already have the gangs sealed then you could use a can of sealant.
    – Micah Montoya
    Sep 3, 2019 at 18:39
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Conduction, radiation, and convection are the three mechanisms of heat transfer. For typical buildings, they are listed from least to most important. Most ordinary building materials create low conductance losses in practice. The prevalence of forced air systems for heating and cooling (plus wind) makes convection the front line mechanism of heat loss and gain. Radiation sits in between in most building applications.

“Silver” insulation (radiant barrier) mitigates heat flow by radiation. A simple analogy is it reflects heat back toward the source while low mass limits the amount of heat it reradiates toward the cool space as it heats up.

Ordinary batts and blown insulation reduce convective heat movement by slowing air movement. This makes batt/blown insulation a good compliment to forced air climate systems. They keep the heated/cooled air inside the conditioned space.

Without addressing convection, a forced air system will simply force air around a radiant barrier. The conditioned air blown outside is replaced with unconditioned air sucked from outside...nature abhors a vacuum.

Going further, air movement affects human comfort. A cold draft feels worse than still air at the same temperature. Another reason conventional insulation and weather sealing are the convention.

Radiant barriers are not a silver bullet. They are better than nothing and can improve the performance of reasonably performing buildings. In ordinary circumstances batt/blown insulation and weather sealing is likely to be a better investment of time and effort.

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