[Equest-users] Wall insulation in multifamily buildings

[Joe Huang via Equest-users]

I'd say the message is that R-19 wall insulation has already "captured" most of the energy 
losses (or savings) for the wall.

(leaning heavily on my cane...) Back in 1986, I did a project in support of ASHRAE and DOE 
residential energy standards where I did what then seemed an endless number of DOE-2 
simulations (~ 20,000) for five prototypical residences in 45 US climates, from which 
using regression analyses I came up with the component loads (KBtu/ft2) for various 
components of the building (walls, roofs, internal loads, windows, etc.).  Just picking 
out the wall component loads for an apartment in Seattle, Miami, and DC, I get the following:

             Seattle             Miami            Washington DC
             HL        CL        HL        CL        HL        CL
R-0     28.8     0.8       1.1       4.7       23.1     1.5
R-11   10.9     0.4       0.3       1.5        8.9      0.8
R-19     7.1     0.3       0.2       0.9        5.9      0.5
R-34     3.9     0.2       0.1       0.5        3.2      0.3

So, by R-19, you're already on the flat part of the curve and more insulation buys you 
very little.

Incidentally, this data base of component loads was then turned into a PC program called 
PEAR (Program for Energy Analysis of Residences) that then multiplied the regression 
curves by the component scalar (ft2 of wall, e.g.), and added them up to derive the 
heating and cooling energy use of a house.
PEAR is now so out-of-date technologically that the display no longer functions, but I 
still think there's some good basic information contained in the data base.  David -  
maybe something that could be updated and maintained by IBPSA?  Or better yet, put it on 
the Web ?

source: "Technical documentation for a Residential Energy Use Data Base Developed in 
Support of ASHRAE Special Project 53", Huang, Ritschard, and Bull,
LBL-24306,  November 1987.

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

On 3/9/2017 2:07 PM, David Eldridge via Equest-users wrote:
>
> R-19 is not the worst starting point, I’d expect diminishing returns going from good 
> insulation to great insulation, but a much bigger jump in efficiency from poor to good 
> insulation levels.
>
> Make sure you are modeling the cavity insulation accurately including any equivalent 
> assembly resistance due to the studs. i.e. continuous insulation requirements are there 
> because the cavity insulation is de-rated quite a bit from the studs and which can be 
> important in colder climates.
>
> In terms of an overall percentage difference due to envelope changes you may also see 
> that window performance dominates if the WWR is relatively high.
>
> David
>
> __
>
> David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
>
> *Grumman/Butkus Associates*
>
> __
>
> *From:*Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On Behalf Of 
> *Nathan Miller via Equest-users
> *Sent:* Thursday, March 09, 2017 2:52 PM
> *To:* Michael Campbell <mcamp1206 at gmail.com>
> *Cc:* equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] Wall insulation in multifamily buildings
>
> Don’t know where your building is located, but on the Seattle area multifamily projects 
> we routinely model, envelope has very little impact on building energy use. DHW and 
> ventilation seem to be the items we have the most influence over that really can change 
> the energy consumption.
>
> FWIW, many of us in the Seattle market are starting to believe the standard plug/misc 
> load assumptions from the Energy Star MF High Rise Sim Guidelines (if you are using 
> them) overestimate that energy use, and result in more “free heat” in the building and 
> thus less sensitivity to envelope changes (among other implications).
>
> **
>
> *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 [mailto:equest-users-bounces at lists.onebuilding.org] *On Behalf Of 
> *Michael Campbell via Equest-users
> *Sent:* Thursday, March 09, 2017 3:44 PM
> *To:* equest-users <equest-users at lists.onebuilding.org 
> <mailto:equest-users at lists.onebuilding.org>>
> *Subject:* [Equest-users] Wall insulation in multifamily buildings
>
> Hello eQUEST Users,
>
> I've been working on a model for a multifamily building, 5 stories, approximately 
> 300,000 square feet.  I've been running a few iterations of the model to see how changes 
> to the wall assembly affect the model results.
>
> What I've found is that changes in the wall assembly seem to have a minimal impact on 
> the model results.  I just did a comparison where I took an assembly with R-19 cavity 
> insulation and 2" rigid insulation and compared that to the same assembly but without 
> the rigid insulation.  This was applied to the entire building.  What I found was only a 
> 0.4% increase in total energy cost after taking out the rigid insulation.  I'm wondering 
> if others have found similar results in multifamily buildings?
>
> Any input is appreciated.
>
> Thank you,
>
> Mike Campbell
>
>
>
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