Dear equest users,

I am using equest for LEED projects.

In table 5.5-1of ASHRAE 90.1-2010 the F factor is given for floors.

How can F- factor be used in order to get Uvalue, which is needed in equest

for floors?

Thank you

Konstantina Kalliakoudi

Mechanical Engineer ?.Sc.

www.khmoe.gr

You can search the archives for the thread titled ?Slab on Grade Floor Heat Loss? but here is how I personally handle F-factor to U-factor conversions:

In the past I?ve done a conversion of F-factor (perimeter based) slab-on-grade heat loss to U-factor (area) and input that in on a zone-by-zone basis if I really wanted to nail down SOG heat loss.

Example- Space is 20? x 30?, but the exposed perimeter is only two of the faces (20? + 30?). Let?s say it is uninsulated SOG.

F-factor from 90.1: F = 0.73 Btu/(hr*ft*F)

Perimeter based heat loss: 0.73 Btu/(hr*ft*F) * 50 ft = 36.5 BTU/(hr *F)

Then we can back-calculate the U-factor to assume for the whole floor to equate to that heat loss: 36.5 BTU/(hr *F) = 600 SF * X BTU/(hr*SF*F) -> U = 0.0608 BTU/(hr*SF*F)

You can create a custom floor construction for each space to provide the U-factor to produce equivalent heat loss that the F-factor calcs are telling you lose. For purely core zones (no exposed perimeter), I guess the F-factor calcs are telling us were not really losing heat through that slab (doesn?t? seem right, but it probably is relatively small) .

Nathan Miller, PE, LEED AP BD+C ? Mechanical Engineer/Senior Energy Analyst

RUSHING | O 206-285-7100 | C 207-650-3942

www.rushingco.com

You can also use the approach in Ashrae Fundamentals Chap 18, p. 39, or from Ashrae 90.1-2010 Appendix C (C.6.10.1).

Shaun Martin LEED-AP, BEMP

Principal

Shaun Martin Consulting

ph. 604-789-1095