Formulas - Building Systems

Question 1

CDD

Formula

Answer 1

sum of [^oF _{avg daily temp} - 65^o] for each day of the cooling season

Question 2

Measure of Heat Transfer Efficiency

_{<span>Conductance (C)</span>}

formula

Answer 2

C_conductance = 1 / R_resistance

or

C_conductance = k_conductivity / d_{thickness of material in inches}

_{What’s measured: Homogeneous or heterogeneous material of a given thickness}

Question 3

The formula for heat loss through conduction

Conduction (Q)

formula

Answer 3

Q = U_u-value x A_area x ΔT_{temp difference}

Question 4

Measure of Heat Transfer Efficiency

_{<span>Conductivity (k)</span>}

formula

Answer 4

k_conductivity = 1 / r_resisivity

What’s Measured: homogeneous material, per inch

Question 5

The formula for heat transfer rate

Convection (Q)

formula

Answer 5

Q = 1.08 x CFM_{cubic ft per minute} x ΔT_{temp difference}

Question 6

HDD

Formula

Answer 6

sum of [65^o - ^oF _{avg daily temp}] for each day of the heating season

Question 7

Measure of Heat Transfer Inefficiency

_{<span>Resisivity (r)</span>}

formula

Answer 7

r_resisivity = 1 / k_conductivity

What’s Measured: homogeneous material, per inch

Question 8

Measure of Heat Transfer Inefficiency

Resistance (R)

formula

Answer 8

R_resistance = r_resistivity x d_{thickness of the material in inches}

What’s measured: Homogeneous or heterogeneous material of a given thickness

Question 9

Measure of Heat Transfer Efficiency

U-value

formula

Answer 9

U_value = 1 / R_{value (R1 + R2 + R3 + …)}

What’s measured: A composite building assembly of multiple materials