Adobe Thermal Performance
- question: I am trying to find the r-value on 9" thick adobe brick. I live 12 miles from Oklahoma in texas. 75 miles north east of dallas in the sherman/denison texas area.I do a/c for a living and need to figure a heat load on two houses. any help would be appreciated.
That's a mighty tough question. Adobe has about 140 Effective U-Values according to tne NM Energy Conservation Code Applications Manual. I am looking at 10-in adobe walls in Zone 9 which is Clovis and Roswell which is as close to the Dallas/Dennison area as we are going to get minus some of the humidity. For a Medium Colored Wall the U-Values are North: 0.227; East: 0.198; South: 0.160: West: 0.204 For dark colored walls the values go down 10 to 30%. For light colored walls the values go up 8 to 15%. The ASHRAE Steady State U-Value is 0.263
R-factor is the reciprocal of U-Value. ( R = 1/U )
Because adobe is a storage device rather than a resistance device it performs well beyond predictions based on steady state numbers. The NM numbers are based on the Tesuque Thermal Study Project of the 1970's which used full-sized adobe test cells and computer numbers to mimic adobe's dynamic performance. Adobe often performs better than even the predictions using the NM numbers.
I do know that there was an entire school district built in the Dallas area with adobe in the 1930's.