Attic radiant foil worth it?

[Viper98912]

Hello folks!

In the attic, is it worth putting in those 1/4" bubble foil reflective panels between the roof joists? We have the standard setup inside our house - sheetrock on the ceiling in the living space, then blown in insulation on top of that in the attic, and some plywood in certain areas for small storage.

Of course, it gets hotter than heck up there in the summer, and I'd like to see if there's a way to slightly reduce the temps up there for our storage items. It's not a big deal, but if it helps, it helps.

I previously had a house that had foam between the roof joists and it always felt a nice and cool 75 degrees up there (incredible honestly...) but after watching a few stories about bad foam jobs causing major health issues, I'm a little unsure about doing it now.

So while I know that this thin foil radiant barrier won't make that big of a difference, is it worth it at all to help bring the temps down?

 

[NUTTSGT]

I wanted to try using it, foil faced OSB, for roof decking of my addition but it wasn't in stock and wasn't waiting 2 weeks.

However, I previously used it on the exterior walls before siding it. I stood in front of a corner with the morning Sun on my back and the reflection on my front. I felt like I was getting cooked internally.

 

[cvairwerks]

One thing to reduce the heat up there, is make sure you have adequate ventilation and air exchange.

 

[TonyG109]

Several years ago I installed a bubble style radiant barrier on the bottom of the top chord on my attic trusses. It runs from the eaves to the ridge forming a channel for hot air to escape out of the ridge vent. The attic is definitely much cooler during the summer.

A couple years after installing the barrier, we had a couple of inches of snow. I noticed that there was a distinct vertical line of snow the exact width of the truss spacing that was slightly shallower than the rest of the snow on the roof. It turns out that the barrier had fallen in that area. This allowed the heat from the house to warm the roof resulting in the snow melting slightly and giving it a depressed appearance. So, not only does the radiant barrier help keep heat out in the summer, it helps to prevent heat loss during the winter.

Just make sure to have a means of exhausting the hot air that forms between the radiant barrier and the roof sheathing. Failure to do this can result in the sheathing and shingles being overheated.

 

[Viper98912]

Several years ago I installed a bubble style radiant barrier on the bottom of the top chord on my attic trusses. It runs from the eaves to the ridge forming a channel for hot air to escape out of the ridge vent. The attic is definitely much cooler during the summer.

A couple years after installing the barrier, we had a couple of inches of snow. I noticed that there was a distinct vertical line of snow the exact width of the truss spacing that was slightly shallower than the rest of the snow on the roof. It turns out that the barrier had fallen in that area. This allowed the heat from the house to warm the roof resulting in the snow melting slightly and giving it a depressed appearance. So, not only does the radiant barrier help keep heat out in the summer, it helps to prevent heat loss during the winter.

Just make sure to have a means of exhausting the hot air that forms between the radiant barrier and the roof sheathing. Failure to do this can result in the sheathing and shingles being overheated.

Thank you for this reply! One thing I was thinking about was the overheating of the shingles; I'll need to look into the airflow in that area of my attic.

 

[nadogail]

My opinion is "Any Insulation is Better Than None"

 

[Vintage Veloce]

If you do it, leave a strip out as a test and please report back!
Not sure on your location, but in the winter maybe you will see differences in the snow on the roof.
In the summer, maybe you can go up and see if you feel a difference in the radiant heat from that section.

 

[Firebrick43]

Tony G sort of alluded to it but you have to leave an airgap for the reflective barrier to reflect into. It is useless if put directly against the roof deck. And should be applied to the bottom of the top cord just as TonyG did.

I personally dislike the reflective bubble as the bubble part is snake oil and they are lying on the R value. They make just reflective sheet specifically for attic radiant barrier

 

[Viper98912]

I've seen the reflective sheet, but I was a little concerned at how fragile it might be when trying to install it. I can just imagine myself cursing up a storm as it tears and rips while trying to install and trying to staple. I figured the bubble thickness would add some rigidity to the foil to make it easier to not tear or rip.

Thoughts?

 

[DeeDubz]

I have it in my wifes garage. Theres a noticeable difference when its hot af out side. Wifes garage is attached to the house it helps with the house temp as well. My fridges couldn't keep my beer cold after the foil was added the mountains are always blue.

 

[musgofasta]

Yes I've used it now in two attics and have seen good improvement in reducing attic temperatures. Like others said, don't attach directly to the plywood, it needs to be attached to the truss or roof framing to create an air gap between the plywood(under the shingles) and the radiant heat barrier.

I bought some 1,000 square foot industrial rolls on Amazon and they are thick and do not tear easily. But easy to cut with scissors.

An infrared heat gun will be the proof and show you the temperature difference between the radiant heat barrier and plywood.

 

[FTG-05]

I did it to my last house in north AL and the house I'm in now. Definitely made a difference in summer!

As people have said, ensure you have adequate attic air ventilation and make you don't install directly on the roof deck; it needs a couple inches separation to work.

 

[MatBirch]

I made an inquiry of Ecofoil brand. The response I got from them was to use the perforated material without bubbles, and lay it directly on top of my blown-in insulation. I live in Southern Idaho- very hot and dry in summer, and cold COLD in winter. He explained that attaching it under the rafters would indeed lower my attic temp, and reduce cooling cost in summer, it would do nothing for me in the winter as my attic would still be ambient outside temps, due to the venting. By placing the foil low, it wont lower attic temps, but will still keep it out of the house...

 

[Firebrick43]

Matbirch, from a pure performance standpoint that is a valid installation. Issue is how do you do anything in the attic afterwards? I would question how much even then it provides in the winter, as if the insulation is of sufficent thickness (should be R60 in your local) the radiant barrier would have to reflect what little heat back through all insulation.

 

[duneslider]

You might see a slight improvement in the cooling season, you don't list your area so its hard to say how long your cooling season is. In my area it is roughly 3 months-3.5 months. So, for those few months it MIGHT help with your cooling costs but it will do basically nothing for you the other months of the year.

Adding attic insulation to get closer to r60 will give you benefits all 12 months of the year. Working on the interior air sealing will also provide better returns for all 12 months of the year.

Radiant barriers are typically not the best money spent. Air sealing and sufficient insulation will yield better results. If you have all the air sealing done and the insulation done then you could do a radiant barrier but you wouldn't at that point because you wouldn't need it.

 

[Dumber than lumber]

No!!

 

[Viper98912]

Thanks for the responses everyone. We live in the southeast US, so there's no snow here

In the future I might try this to see if it helps keep attic temps down in the June-July-August super hot months of the year.

 

[Daves69]

I just did this to my house this spring. https://atticfoil.com/

Also air sealed any areas there was air leakage. Was easy to spot since the insulation was dirty where the air was penetrating. Added some more blown in insulation. Hoping to see better cooling bills this summer.

 

[cpowelld]

I just did this to my house this spring. https://atticfoil.com/

Also air sealed any areas there was air leakage. Was easy to spot since the insulation was dirty where the air was penetrating. Added some more blown in insulation. Hoping to see better cooling bills this summer.

I know this was 3 years ago when you wrote this, but i was thinking about doing the exact same thing. I live in Tuscaloosa, AL and Im getting cooked in the summer. Did your upgrades help at all?

 

[ycgoat]

I used the double sided perforated foil no bubbles in my shed style garage and the temps stay ambient