Busting R-value insulation MYTHS
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3 سال پیش
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R value is the standard
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.
Link to my Patreon page: Patreon: Belinda_Carr
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.
https://www.cufca.ca/docs/R-Value%20F...
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.
--------------------
SOURCES:
Video
--------------------
Fluffy by Smith The Mister https://smiththemister.bandcamp.com
Smith The Mister https://bit.ly/Smith-The-Mister-YT
Free Download / Stream: https://bit.ly/stm-fluffy
Music promoted by Audio Library Fluffy – Smith The Mister (No Copyrig...
---------------------
Disclaimer: This video was created for educational/informational purposes and qualifies as Fair Use. If you are the creator or own the footage featured in this video and have reservations please notify me via Youtube comments or email and I will accommodate you
#rvalue #constructionscience #mythbusting #construction #architecture #design
Link to my Patreon page: Patreon: Belinda_Carr
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.
https://www.cufca.ca/docs/R-Value%20F...
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.
--------------------
SOURCES:
Video
--------------------
Fluffy by Smith The Mister https://smiththemister.bandcamp.com
Smith The Mister https://bit.ly/Smith-The-Mister-YT
Free Download / Stream: https://bit.ly/stm-fluffy
Music promoted by Audio Library Fluffy – Smith The Mister (No Copyrig...
---------------------
Disclaimer: This video was created for educational/informational purposes and qualifies as Fair Use. If you are the creator or own the footage featured in this video and have reservations please notify me via Youtube comments or email and I will accommodate you
#rvalue #constructionscience #mythbusting #construction #architecture #design
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