Do Radiant Barriers Work & How Much Energy Will it Save: Real Home Owners Experience (Before/After)

The next stop on our quest to make our cookie cutter house more energy efficient lead us to install a Radiant Barrier in our attic. We have watched many video about radiant barriers, but it is hard to know if they really work based on commercials and promo videos by manufactures. We installed a single bubble radiant barrier throughout our attic and we are excited to share the results. The goal of this video is to show the data gathered at our house to test if radiant barriers work. Watch to the end to see the temperature different the radiant barrier made in our attic.

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[PaulWhitelock]

You can't get an accurate temp reading when using an IR gun on metallic surfaces due to high emissivity. The reading displayed will be significantly lower than what it actually is. Try putting a small square if black electrical tape on the metal and then point the gun at that for a more accurate measure of the radiant energy.
I'm looking to do this barrier install to my house here in Australia soon. Thanks for the info.

[Berkana]

I have a comment about the tip you gave about leaving an air gap so the heat doesn't conduct straight through the radiant barrier.
Even if you have the radiant barrier pressed right up against the wood and the barrier itself gets hot, you still benefit because of an interesting bit of physics: shiny things, which are really good at reflecting radiant heat are intrinsically poor at radiating heat themselves. If you look for physics demonstrations of emissivity, you'll see demos where two metal cans filled with the same temperature water with the only difference being that one can is painted matte black and the other is polished shiny do not look like they're the same temperature when viewed with an infrared camera. The shiny one looks many degrees cooler even though the heat conducts right into the shiny part, simply because reflective surfaces are intrinsically poor at radiating heat.

You can actually get even better performance if you use multiple layers with gaps between them. Have one radiant barrier pressed up against the wood, and then have another with a gap between the two. Radiant barriers are not 100% efficient; a few percent of the radiant heat still makes it through. Suppose the leakage is about 4%. If you have two layers, then the first one lets through 4%, and the second lets through only 4% of 4%, which is 0.16%. This repeated attenuation of radiant heat is how the multiple radiant barriers of the James Webb Space Telescope are able to keep the shaded side at temperatures a few degrees absolute zero (Kelvin scale) while the sun-side gets to temperatures of about 230˚F (383K).

[SandmanUSAFA]

I'm sure you already know this, but an A/C system that "short-cycles" like this is the direct indicator that it is oversized for the conditions (home load compared to outside conditions).
If that every-15-minutes cycling is happening around your peak summer conditions, you'd really benefit from some measures to address this.
Eventually down the road when ready to replace your A/C, you can go cheaper and just get a one-size-lower capacity to better match, or invest in better answer, a higher efficiency unit that includes a VARIABLE or STAGED compressor at full size.
You'll have the capacity to retain the ability to address higher temperatures during hot spells, but gain the incredibly more efficient handling of your A/C during the rest of the year as it runs at lower capacity.
You'll get longer run-times at lower energy use, and it will properly dehumidify the air.
For now, there are also programmable thermostats that allow you to set a wider dead-band and other features, so that you can have it wait an extra degree above setpoint before activating the compressor, and run it an extra degree or two below the setpoint so that cycle times are extended and more dehumidification can be effected.
Also, be sure your thermostat location is away from sun exposure on an interior wall, and is NOT directly in the path of one of your supply air diffusers.
Side note: You've probably already gotten the advice that you cannot get an accurate spot reading of temp with your IR pistol on reflective or bare metal surfaces (paint a section matte black first?).
You may wish to add that installing the reflective radiant barrier like this does block a large chunk of the radiant solar load from being absorbed into the attic, but retains the full airflow from the soffit-vents up to the ridge-vent so that roof sheathing and structure is still fully vented and airflow will actually be better, minimizing any potential increase of temp to the shingles.
This concern about shingle temps goes away completely once you upgrade your roof to a metal one.

Keep up the information sharing!

[Inkling]

I've got attic foil on top of my blown-in cellulose insulation and it definitely helps. On a hot day the temperature under the foil is about 10 degrees less. Keep in mind that when it's placed on top the insulation on the floor of your attic the air gap is above it with only a small air gap provided beneath. When it is bouncing up is the radiant heat in hot the attic air. 
I have taken another step. To keep the heat radiating from my roof away from the floor of the attic I've also placed a wrap of 4-foot-wide attic foil around the base of my attic. That starts the heat radiating from the lower shingles moving up. On a hot day the air exiting up at the top of that foil is about twenty degrees hotter than the foil itself. That also creates a chimney effect as moving air moves other air up and out of the way. The one weakness is my house is that it lacks sufficient ridge venting, but at least I can push that heat upward where it eventually exits.
One final remark. The foil I'm using comes from Attic Foil, which has a website with that name. It is very heavy duty. You can walk on it repeatedly without tearing. Also, for humid climates you can get a foil from them with holes in it to keep moisture out of your insulation.

[EcoFoil]

We are glad that you were able to use the Radiant Barrier, and thank you for the shoutout! DIY projects are the best 😉

[lawrencegolba]

Good info. It works! Just installed 2-sided foil- backed bubblewrap (pressure fit, no air gap) inside a couple of kitchen cabinets against the back wall. Did this because our coffee cups would need to be heated with hot tap water to prevent cooling our morning cup of coffee. After a cold 25 degree F night, a cup located inside the newly insulated cabinet was just as warm (same temp by feel) as a cup that sat on the counter overnight in a 68 degree F kitchen.

[CCCC-tqyo]

No one ever compares there bills on here before and after

[ahnilatedahnilated]

As a side note, it is much hard to heat/cool very humid air. You can heat/cool less humid air very easily. As an example, look at deserts, their temps go up and down drastically with their low humidity.

[christos]

What an informative video! I use that same stuff in car restorations - awesome barrier inside the car, on the front bulkhead (to reduce engine heat transmission). I also use that stuff for custom car shades.

[markchristensen]

It's not only the heat from the roof, and attic. it's, also, 3 more things that heat up your home..
1, holes in the ceilings, from, , The can lights, the ceiling fans, and the heating and cooling, registers. The heat from the attic in summer, comes through the holes. The cold in winter comes through the same holes. I sealed the space between the sheet rock, and fixtures. No air movement.
3, a gable fan that is thermostat controlled. It blows the hot, attic air out.
2, My home came with blown in insulation, no good home got hot. You could feel the waves of heat coming down from the ceiling. I added R13 in the attic. It slowed down the waves of heat, not enough. I then added R 25, for total of R 38, what a difference. No more waves of heat. Yesterday it was 112° outside, our home inside got up to 72°. We have no air conditioning. What we also have is a whole fan. We turn it on at night, when the outside temperature is less than the house temperature. Most mornings the house temperature starts at 64°. We not only cool the house down we coolthe attic temperature as well. The whole house fan cost about .06 cents per hour to operate. At the time of writing this, it's 1 pm, and, 100° outside, and a cool 68° inside, we started the morning, at 64° inside the house.

[waterbug]

I live in Phoenix, have lived in other climates. My biggest improvements has been insulation and using mini split AC. I furred inside walls so 8" and max attic insulation. The mini split AC allowed for controlling every room separately, no ducts in attic and returns grills.

[Peter-pizo]

Very interesting video. I was hoping you had a follow up video. It would be great if you did one In peak summer heat to do a comparison to this one.

[RevngeFold]

I could not believe the difference it made with the method I tried. I found white highly refractive roof paint at the hardware store and painted my flat roof with that. It made a MASSIVE difference. Easily 5-10 Degree Celsius cooler than ambient in the house now. I left a small section uncoated on the roof close to where the ladder was for comparison and the white roof feels as cold as the steel of a pot you took out of your kitchen cupboard and the old paint(Dark grey) is scolding hot.

[dpool]

Been a bit since this was posted, seen your channel is not making many videos anymore. I would highly suggest using a FLIR (even if you buy it, check the areas, and return it soon after) to see if there are air leaks around your fixtures in the walls and ceiling, and even pull apart some of the insulation around the ducting to ensure that there are no leaks in the ducting itself. Checking you have enough soffit vents to ensure no air is being pulled into your house from outside by the heat rising to the top and pulling some air from your house into the attic. I also believe from what I have seen here on Youtube it is better to have it directly over the insulation. They are made to be vapor permeable, however, if you have it over the insulation itself you ensure no air movement over the insulation that could reduce the R value by blowing through the top few inches. Hope all went well with this as I don't see really an update on it after 3 years.

[mikegrok]

I had a similar with the air conditioner cycling, and found that it was due to one of the vents pointing at the thermostat. Turning that register fixed the short cycling issue.

Later in the year when the 40k btu air conditioner was on 14 hours a day continuously, I installed a gable vent fan, and the interior temperature dropped 8 degrees even though it was 6 degrees hotter outside when I took the second measurement. Btw peak daily humidity is about 85%.

[larrynone]

I put it in mine, and it made my atti and house cooler. I haven't reblown insulation yet, but hopefully, in a few months before summer gets here.

[Alphasig]

The air gap between sheathing radiant Barrier the insulation. Installed by radiant barrier on my remodel and the space above radiant barrier was 125 degrees and 80 degrees below it. With only a single layer of vapor permeable vapor barrier. With adding 800 Sq ft. Contractor said I’d need a new HVAC. It’s running better than before remodel.

[mikeyfoofoo]

Thanks for putting this up. Did you see drop in the ambient temperature in your attic? And comfort in your house over the last two years?

[EasyLiving]

WOW! Great video thanks so much for sharing and taking the time to do this video. Hmmm looks like your last video was 2 years ago, are You all OK?

[justaguy]

Very informative, nice job. I've been researching this, hence how I got here. Thank you.