[Equest-users] Wall insulation in multifamily buildings

Fri Mar 10 20:23:30 PST 2017

Few more thoughts on this:

1)     I agree with Joe and David that R-19 “…has already captured most of
the energy losses (or savings) for the wall”. R-19 is better than 90.1 2016
requirements for steel-framed wall in climate zone 4A, and since 90.1
requirements are set taking into account cost effectiveness, it is not
surprising that further improvement does not often pay off.

2)     Overwhelming majority of high performance multifamily projects have
efficient heating systems, often condensing boilers or VRF HPs, which
lowers heating costs and potential savings from envelope improvements.

3)     Most multifamily projects in North East have gas heating, and gas is
cheap compared to electricity. For example EPA EStar MFHR projects in NY
typically use $0.15/kWh and $1/Therm in performance rating calculations,
which effectively makes BTU of electricity ~4.4 times more expensive than
BTU of gas. This further shrinks contribution of heating toward the total
building energy $, and reduces potential savings from envelope
improvements. (Using source energy instead of $ in performance rating
calculations makes envelope improvements more appealing, because with EPA
PM site-to-source conversions BTU of electricity has only ~ 3 times greater
weight than BTU of gas.)

4)     I am curious about the reasoning behind Nathan’s comment that “…
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
overestimate that energy use”. EPA’s plug loads are 4 times lower than
COMNET’s for Multifamily/Residential, and are also lower than the loads in
PNNL High Rise Apartment prototype. Passive house protocols are the only
two sources that I know off that prescribe lower in-unit loads -
Passivehaus Institute (PHI) loads are less than half of EPA’s, and US
passive house off-shoot (PHIUS) loads are 15% lower than EPA’s. In general,
in-unit electricity consumption can vary significantly depending on
occupant demographics (by factor of 10 based on some papers), so both
COMNET and PHI may be correct for *some* apartments. We compared EPA
assumptions to the in-unit electricity usage in several apartment complexes
in NJ, and the numbers were in the right ballpark, so appear to represent
reasonable averages.

*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
Behalf Of *Michael Campbell via Equest-users
*Sent:* Thursday, March 09, 2017 9:55 PM
*To:* Joe Huang <yjhuang at whiteboxtechnologies.com>
*Cc:* equest-users <equest-users at lists.onebuilding.org>
*Subject:* Re: [Equest-users] Wall insulation in multifamily buildings

Wow, thank you everyone for the extremely helpful responses.

To answer a few of the questions... the project is in NJ, Climate Zone 4A.

I did account for the thermal bridging of the walls studs.  This project
has some metals studs and some wood studs and I accounted for both using
Appendix A of ASHRAE 90.1-2013.

Nathan, thanks for the input specifically regarding the Energy Star
Multifamily High Rise inputs values.  This particular project is
participating in the ESMFHR Program so I am using their guidelines for
equipment/plug loads.

On Thu, Mar 9, 2017 at 6:32 PM, Joe Huang via Equest-users <
equest-users at lists.onebuilding.org> wrote:

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 <(925)%20388-0265>

(c) (510)928-2683 <(510)%20928-2683>

"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
<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> <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 <(206)%20285-7100> |*C* 207-650-3942
<(207)%20650-3942>

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

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