[Equest-users] Parametric runs for under slab insulation

[Bishop, Bill]

I think the answer I needed basically is: use F-factors.
To simulate various thicknesses of continuous (fully insulated) slab insulation for a slab-on-grade building with heated (radiant heated slab) and/or unheated slabs:

1.) Find the F-Factor for the R-value of the insulation you want to simulate in ASHRAE 90.1, Table A6.3.1.
2.) Determine the perimeter length by adding the widths of all exterior walls.
3.) Multiply the F-Factor by the exposed perimeter length.
4.) Divide this value by the total floor area of the slab.
5.) Take the inverse of this value. You now have a number with the same units as R-value. Use this to edit the R-value of the insulation material in the underfloor layers, which is used in the underfloor construction for all the slab surfaces included in the area and perimeter calcs above. (Don't just use it for slab surfaces with perimeter exposure. Use it for all slab surfaces within the boundary of the exposed perimeter.)

Suggested edits or clarifications to this methodology are welcome.

Thanks all!
~Bill

________________________________________
From: David Eldridge [DEldridge at grummanbutkus.com]
Sent: Friday, May 01, 2020 12:00 PM
To: Bishop, Bill
Subject: RE: Parametric runs for under slab insulation

>From the IBPSA-USA SimBuild 2010 archives:
http://ibpsa-usa.org/index.php/ibpusa/issue/view/34

ENERGYPLUS VS DOE-2 : THE EFFECT OF GROUND COUPLING ON HEATING AND COOLING ENERGY CONSUMPTION OF A SLAB-ON-GRADE CODE HOUSE IN A COLD CLIMATE
Simge Andolsun, Charles H . Culp, Jeff Haberl

This topic is one that I have always considered EnergyPlus may have some new capabilities for modeling that aren't in DOE2.2 or DOE2.3. (or 2.1). Anyway - you may enjoy this paper by Andolsun, Culp, Haberl or some of the Winkelmann references for DOE2.1 maybe can be applied to eQUEST.

Not sure specifically about the insulation compoent - did you check with PHIUS? I can e-introduce you to Katrin if you haven't already met her. https://www.phius.org/about-passive-house-institute-us/phius-staff

David



David S. Eldridge, Jr., P.E., BEMP, BEAP, HBDP, GGA
Associate

Direct: (847) 316-9224 | Mobile: (773) 490-5038

Grumman/Butkus Associates | 820 Davis Street, Suite 300 | Evanston, IL 60201
Energy Efficiency Consultants and Sustainable Design Engineers

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-----Original Message-----
From: Equest-users <equest-users-bounces at lists.onebuilding.org> On Behalf Of Bishop, Bill via Equest-users
Sent: Friday, May 01, 2020 10:37 AM
To: equest-users <equest-users at lists.onebuilding.org>
Subject: [Equest-users] Parametric runs for underslab insulation

Hello, WFH equesters!



I would appreciate any insight on modeling underground surfaces from anyone that has tried modeling continuous insulation as is common on Passive House projects, especially in radiant slab heating applications.

I want to compare alternative thicknesses for continuous horizontal underslab insulation for both radiant slab heating and non-heated slab applications. Continuous underground insulation is becoming more common, particularly in Passive House projects or from passive-house-inspired architects. DOE-2.2 and 2.3 emphasize slab edge effects in the documentation and seem to ignore potential heat transfer from surfaces that have a path of travel greater than 4' between the surface and ambient air conditions. The wizards have only one option in the dropdown menu for continuous slab insulation - R10 continuous. Any underground slabs that have no exposed perimeter are given an R-100 insulation layer that results in near-zero heat transfer in the simulation.



All tips, musings and even non-sequiturs will (likely) be appreciated.

~Bill



William Bishop, PE, BEMP, BEAP, CEM, LEED AP Senior Energy Engineer

T: (585) 698-1956                      F: (585) 325-6005
bbishop at pathfinder-ea.com        www.pathfinder-ea.com<http://www.pathfinder-ea.com>
134 South Fitzhugh Street
Rochester, NY 14608
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