Busting R-value insulation MYTHS

R value is the standard by which all insulation products are typically measured in the US. In the metric system, the equivalent is RSI. Everyone involved in the construction industry relies on R values because there’s no other standardized way to measure insulation performance.

Chapters
0:00 Introduction
0:28 What is R value?
1:19 ASTM C518 R-value test
2:10 Artificial lab environments
2:50 Air movement
3:39 Steady-state differences
4:00 Effect of water
4:14 Installation issues
4:38 Vapor drive thermal drift
4:52 Thermal mass
5:24 Thermal briges
5:52 Conclusion

EDIT: At 4:29 I meant to say R3.5 not R35. I was tired. Age is catching up.
R-value is the measure of how well a barrier, typically insulation, can resist the conductive flow of heat. It is measured by multiplying the temperature difference between 2 sides of a barrier, the area of the sample and how long the measurement took place, divided by how much heat is lost through the sample. In a multi-layered wall, the total R value is the sum of the R values of individual layers.

The American Society for Testing and Materials or ASTM created a C518 Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus. This test establishes the R value of different materials. A sample is placed between a cold plate and a hot plate in a container that’s set at 75F or 24C with no surrounding air movement and no moisture. The test measures the transfer of heat by conduction, convection and radiation.

R values are determined in artificial lab environments, which are nothing like the real-world. The test prioritizes resistance to conductive flow of heat. Most homes are not air-tight, so in winter, the stack effect will cause convective loops through the home as warm air under pressure rises and escapes through the top, requiring an equal amount of cold replacement air to enter at the bottom. In summer, the exterior of a home absorbs UV rays from the sun and transfers it indoors through radiation.

Also, since most homes are not completely sealed off, there are holes in the exterior siding that allow air to be sucked inside. Air movement within walls, in attics and around insulation completely changes the R value. I’ll link a study in the description which showed that a home with R12 foam insulated walls used half as much energy as an identical home with R20 fiber insulated walls.

Another issue is that the R value test does not start until the materials reach “steady states”. This occurs when a material becomes thermally saturated so that for every single unit of heat entering on one side of the materials, a single unit of heat exits the opposite side. Fiberglass insulation reaches steady state within a few hours, but foam insulation can take about a day. Foam has a much greater ability to collect and store heat but this isn’t taken into account in the testing process.

R value numbers do not consider the effect that water has on them. If fiber insulation isn’t fluffed up enough and is squashed into wall cavities, it will not perform the same as it did in the lab. For example, an inch of fiberglass is supposed to have an R3.5 value, but if it’s squashed to .5”, the R value is lowered. The resistance to vapor drive is also ignored in the R value test. Thermal drift is the gradual loss of R value over time when a material slumps due to age or gravity, or loses trapped air.

Thermal mass refers to a structure’s ability to slowly absorb ambient heat, then store and radiate the heat. It can help regulate indoor temperatures and lead to energy savings. This is not considered in the test, so people have resorted to using an “equivalent” R value. Finally, a thermal bridge is a component of a wall, like wood or metal studs and windows, that has a much higher conductivity than the materials around it, like insulation. Thermal bridging can result in a 15% drop in overall thermal performance. Just because you use R30 batt in a stud framed wall, doesn’t mean that you get an R30 performance. 20% of that wall is made of wood that extends from the interior to the exterior which has an R value of only 5 or 6.
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#rvalue #constructionscience #mythbusting #construction #architecture #design

[buildshow]

FANTASTIC VIDEO! Well said. This is going to be required watching for all my young builders. (but old guys like me need a refresher too!)

[patrickcarey]

Just jumped down the Belinda Carr rabbit hole, her videos are very informative and much appreciated

[GiSoldier]

Straight to what I wanted to hear. No gimmicks, or clickbait. Liked and subscribed.

[CitEnthusiast]

Air movement is a big problem, Holmes helped me recognize that. So a few years ago my SO and I took apart the walls of the small sun room at her house, mainly to switch from panelling to drywall. With the walls open we saw lots of evidence of air leaks within the wall. So I put silicone sealant at all the joins between the siding and the studs, all for sides in each cavity, then put back the oribinal fiberglass insulation.

Holy smokes, what a difference that made! I don't have empirical data, but now that room is quite easy to heat in winter and cool in summer. That's been a big lesson for me, and like TheBuildShow talks about all the time, stop air movement from inside to outside, or outside to inside, this makes a massive difference. So your point about spray foam is on-point! But if joins are sealed fiberglass, rockwool, etc. will perform far better than they do now.

Several years ago the Washington Post had a story about a house built for energy efficiency, and every join, even between suds and plates, were first given a bead of silicone, so all air penetration was stopped. Air leaks steal energy!

[Ikantspell]

The biggest issue with this is building codes recognizing the difference. Blower door tests, and other things are only now working the way into building codes. Building performance is a system made up of parts and understanding the sum of the parts is as important as understanding the how one part compared to another in a test

[override]

I have to say you have a sincere, direct, non-hyperbolic style that is very refreshing on youtube

[screwydrewy]

This has to be one of the most though out and accurate assessments of r value and energy ratings in general I’ve ever heard or seen and I’ve been a carpenter and general contractor most of my life. It’s just explained so well

[lvitntnmrcls]

I’m sure this channel is going to take off. Every video is so informative

[tkmad]

Hard to imagine a test that can take into account all of the properties an insulation can affect. People need to educate themselves about which insulation will do a better job for the situation they have. Thank you for the help with the education!

[princeseroze]

I’m here to say I’ve noticed you’ve been uploading more frequently and some of your recent videos have been more personal and ever since I’m subscribed your subscriber count has grown 10-fold. I just wanted to remind you’re doing great and that I love your constructive arguments. Thank you for the work you’re doing!

[John-tqbf]

I like that you use the word performance and take us to a different level of expectation for savings of energy.
There is also a relatively new product in the stud feature and it is insulated studs that more or less eliminate the thermal transfer of a standard wall.
The studs have a foam core component to achieve this.

[gibbodive]

I have just discovered Belinda Carr presentations... Clear, concise, facinating, engaging and hghly informative.
Thank you

[southeastcleanairsolutions]

I’m very appreciative of this video!! I own a duct cleaning business in Virginia, and we commonly refer spray foam insulation to our clients that have HVAC systems located in attics and crawl spaces. Your video answered so many questions I had about the performance of insulation under realistic non-lab conditions - particularly in our humid Southeastern US climate!! Ill be sure to save and share your video with all of my future clients that I recommend spray foam insulation for in their homes!

[AlaynaValdez]

This video was so helpful, the breakdown was thorough without being overcomplicated. I am doing research and I have no construction background or training so these videos like these are extremely helpful without being too lengthy.

[grizzly_xavier]

Great video, very informative. Very important point re wind hitting the walls of the house and impact on insulative performance. We recently swapped out fiberglass in walls and ceiling with open cell spray foam in a room with three exterior walls...huge difference in comfort and draft reduction. Might be similar to R13, but the sealing qualities of spray foam really made a difference.

[kmcroes]

This was such a helpful video. Insulation R Values have been so confusing to me. I will be able to use this to help explain to clients why choosing hempcrete is going to make such a huge difference in their energy efficiency.

[ReasonablleDoubt]

You are building an amazing channel. This is so necessary. I was just looking up this info on polyiso foam board.

[thesonsofissachar]

Have watched 2 of your videos now. Your approaches to problems are both insightful and surprizingly comprehensive. Very impressive young woman you are Belinda. God bless

[lukejohnson]

Belinda just busted the Fiber-Glass ceiling

[fotostuf]

Just found your channel and I am so very impressed! We are in the process of having a Class B RV built (supply chain issues notwithstanding!), and have had to research, amongst other things, toilets, batteries, building systems, and insulation/R-value. You hit everything it took me months to figure out! Wish I had found your channel sooner!
Be seeing you!