U values of typical building methods u values overall coefficient of heat transmission indicate the heat flow through materials the higher the figure the higher the heat loss.
U value of concrete wall.
The original cost of installing perlite loose fill insulation can be recovered quickly due to substantial reductions in heating and air condition energy consumption.
The lower the u value the more efficient the construction is at keeping heat flow through the structure to a minimum.
Therefore the overall wall element u value 1 r 1 4 16 0 24 w m 2 k.
Reference table for u values u value is the coefficient of transmission i e the transmission of heat through the materials which compose the building s envelope or outer shell.
A reasonable r value for a normal concrete slab can be estimated using an r value the thermal resistance per inch of thickness between 0 1 and 0 2 and multiplying it times the slab thickness.
For a 6 inch slab r value would be between 0 6 and 1 2.
Calculating the inverse of that 1 r would give you a u factor in the range of 1 67 to 0 83.
For example a building with material with an r value of r 11 converts to an u value of 0 09 1 r or 1 11 0 09.
F btu 1 23 m k w an estimate of the building envelope energy use for this structure is approximately 27 800 btu ft 87 7 kwh m as shown in figure 1.
Coverage charts for masonry units.
A concrete wall with thickness 0 25 m and conductivity 1 7 w mk is used for the default values in the calculator above.
U value 0 11w m2k 0 2w m2k.
So the lower the u value the better.
Wall 1 with u value of 0 3 w m2 k will lose heat at half the rate of wall 2 which has a u value of 0 6 w m2 k.
U 1 1 5 8 m 2 k w 0 25 m 1 7 w mk 3 13 w m 2 k.
U value has an inverse relationship to r value.
In addition perlite loose fill insulation cuts installation costs since it is lightweight and pours easily and quickly in place without need for special installation equipment or skills.
While the values do vary for each particular material and method of construction the following table gives general figures for some common modes of construction.
The insulation is typically expanded polystyrene and having insulation inside and out gives a u value of at least 0 2w m2k with a wall thickness of 250mm.
If this school is built using single wythe concrete masonry walls with cell insulation only and a resulting wall r value of 7 hrft 2.
Some systems offer the option to increase the internal insulation and can provide a u value as low as 0 11w m2k with a wall thickness of 335mm.
The inside and outside surface resistance is estimated to 5 8 m 2 k w.
Cellulose blown wall 3 70 vermiculite 2 13 air entrained concrete 3 90 urea terpolymer foam 4 48 rigid fiberglass 4 lb ft3 4 00 expanded polystyrene bead board 4 00 extruded polystyrene 5 00 polyurethane foamed in place 6 25 polyisocyanurate foil faced 7 20 construction materials concrete block 4 inch 0 80.
As calculation of u values can be time consuming and complex particularly where for example cold bridging needs to be accounted for numerous online u value calculators have been released.
If we increase the r value of the wall to r14 by adding additional insulation while holding the other envelope variables constant the building envelope energy use drops by only 2 5 which is not in.
The u value can be calculated as.
