What is the different between U-value and R-value?

Question

They are both related with thermal insulation. Do you have any clue?

Answer 1

U-value is the inverse of R-value.

U=1/R

R-value is the standard way of describing how effective an insulation is. The higher the R-Value, the better the insulation.

An HVAC engineer will determine the total R-value for a given assembly by adding all the r-values of each component.

For example: outside air film + aluminum siding + plywood + air space + fiberglass insulation + drywall + inside air film.

The individual R-values are totalled and then the inverse is taken to calculate the total U-value.
But it is the U-value which is used in formulas to determine heat gain thru wall in summer and heat loss in winter.

R-value is used commercially because it is easier to explain to consumers that R-19 insulation is better than R-11 rather than telling them U=0.05 insulation is better than U=0.09

Answer 2

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RE:
What is the different between U-value and R-value?
They are both related with thermal insulation. Do you have any clue?

Answer 3

U = 1/R R value is what most people are familiar with in comparing insulation's ability to resist the flow of heat.

U value is thermal conduction rating of insulation

Answer 4

Essentially, in the study of heat transfer, Heat flux = (difference in temperatures) / (R which is analogous to resistance)

So, think about heat transfer problems as similar to Ohm's Law namely, current = potential difference / resistance. Note the similarities such as current cannot accumulate and heat always flow from a hot to cold (you can't contain it), temperature differences causes heat to flow and voltage difference causes current to flow, and resistance to current vs resistance to heat flux.

Once you get this idea, you should have a better understanding of the R value in terms of insulation. U just happens to be defined as a reciprocal of R and if you have studied basic electrical engineering, U value is analogous to conductance G.

I hope this helps in your understanding of R and U values conceptually.

Answer 5

BTU The amount of heat radiated from a heater or the amount removed by an air conditioner.

R-value is the insulation rating for insulators against heat radiation.

Answer 6

R Value To U Value

Answer 7

U Value To R Value

Answer 8

Here is a good explanation..

http://www.engineeringtoolbox.com/heat-loss-transmission-d_748.html