April Lutheran
Thermal Resistance
Having two different temperatures on each side of an area creates energy transfer. The U-Value characterizes the amount of energy that can be transferred by a material. The lower the U-Value, the greater the material resists to heat flow and its insulation properties are better. The U-Value unit is W/m2.K.
Another Unit to characterize the same property of a material is the R-Value. The R-Value is the inverse of the U-Value. R-Value = 1 / U-Value (as well U-Value = 1 / R-Value). The higher the R-Value is, the greater a material resists to heat flow and its insulation properties are better.
Roof and Wall types
The choice of roof and wall material determines the thermal mass of these components, and thus, the building. A high thermal mass reduces the daily swings of heat gain and loss within the building.
A wall or roof with higher thermal mass provides a damping effect against temperature swings. A building with lower thermal mass responds quicker to outdoor temperature changes.
In the Web Application, you can choose from a list of common roof and wall types. Here is a schematic description of the construction layers of each wall choice (outside to inside):
- Curtain walls: spandrel glass, insulation board, gyp board
- Stud walls: metal wall panel, sheathing, batt insulation, gyp board
- EIFS: EIFS finish, insulation board, sheathing, gyp board
- Brick walls: brick, insulation board, sheathing, gyp board
- Concrete block wall: lightweight CMU, batt insulation, gyp board
- Precast concrete: lightweight concrete, board insulation, gyp board
And this is a schematic description of the construction layers of each roof choice (inside to outside):
- Slope frame: gyp board, batt insulation, metal roof
- Wood deck: membrane, sheathing, insulation board, wood deck
- Metal deck roofs: membrane, sheathing, insulation board, metal deck
- Concrete: membrane, sheathing, insulation board, LW concrete
Floor type
Floor finish determines how heat is radiated back into space after it has entered the building. Carpeted floors have lower thermal mass and therefore re-release heat sooner than tiled floors.
For our office designs we like to work with raised floor systems. In those cases the ceiling has the exposed concrete (and so the benefit of the thermal-mass) is there a way to include this in the calculations as well ?
Thanks
Jan
Hello Jan,
Great question! To capture the thermal mass effect for the analysis, set the Core Structure to 'Heavy' in the Structure category.
Here is our Knowledge Base article on thermal mass effects for more info: http://support.sefaira.com/hc/en-us/articles/202285959-Thermal-Mass-and-Transient-Effects
Best,
Alyson
Does the "Stud" wall assembly type include the effects of thermal bridging? If so, does it assume wood or steel studs?
How. Am I approximate a glass roof? Glazing does not compute as a horizontal plane.
How does wall and roof colours affect thermal gains on Seifara? Apparently assigning different colors in Sketchup has no effect on energy use ou internal temperature, which is counterintuitive. So, how does Sefaira handle envelope reflectance properties, as regarded to thermal gains?