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

[Shaun Martin]

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

 

 

 

From: Equest-users <equest-users-bounces at lists.onebuilding.org> On Behalf Of Nathan Miller via Equest-users
Sent: July 23, 2019 7:16 AM
To: Konstantina Kalliakoudi <kalliakoudi.k at gmail.com>
Cc: equest-users at onebuilding.org
Subject: Re: [Equest-users] Floors F- factor to Uvalue for equest input

 

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

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

 

From: Equest-users <equest-users-bounces at lists.onebuilding.org <mailto: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 <mailto: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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