U Factor Of Roof

For example if you measure 4 inches the pitch of your roof is 4 12.

U factor of roof. And canada to express the heat flow through entire assemblies such as roofs walls and windows. The u value or u factor measures how much heat a window including the frame glass and insulating materials allows out of the house which is also known as its thermal transmittance. Q a δt u. 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.

The term u factor is usually used in the u s. Without knowing the u value of a wall or a floor or roof you won t know how energy efficient the whole building will be. The u factor is a measure of heat transmission in this case through a concrete slab either from the ground into the enclosed space or vice versa. U factor 1 sum of the r values.

Simply locate a roof rafter board place the end of the level against the bottom edge and measure from the 12 inch mark vertically to the bottom edge of the rafter. Calculate the u factor by using this formula. Ultimately selecting which product and value to use depends on many factors particularly thermal load. While windows are rated using both u factors and r values the u factor is used to express the insulative value specifically of windows while the r value is used primarily to rate the energy efficiency of insulation installed in other areas of the building envelope such as beneath the roof in the attic behind the walls and beneath the floors.

Step 3 check your calculations by reversing the calculation and determining 1 u factor. For example energy codes such as ashrae 90 1 and the iecc prescribe u values. It is expressed in btus per hour per square foot per degree fahrenheit referring to the temperature difference between the slab s upper and lower surfaces. For example when building in dubai a roof in a villa has a recommended best starting point of a u value of 0 30w m 2 k.

We all remember factors from the 7th grade right it is part of the well known heat loss formula used by builders to determine transmission losses through floors roofs and walls. U value has an inverse relationship to r value. 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. U factor is literally a factor it s part of a mathematical formula involving multiplication.

This will give you the rise over run or pitch. Using the previous example with an r value of 16 the u factor is one sixteenth or 0 0625.