[Equest-users] Floors F- factor to Uvalue for equest input

[Nathan Miller]

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<http://www.rushingco.com/>

From: Equest-users <equest-users-bounces at lists.onebuilding.org> On Behalf Of Konstantina Kalliakoudi via Equest-users
Sent: Tuesday, July 23, 2019 7:18 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Floors F- factor to Uvalue for equest input

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 Μ.Sc.
www.khmoe.gr<http://www.khmoe.gr/>
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