[Equest-users] Wall insulation in multifamily buildings
Maria Karpman via Equest-users
equest-users at lists.onebuilding.org
Tue Mar 14 09:52:35 PDT 2017
To David’s comment about infiltration (“Lower infiltration will save you
more energy than any other envelope ECM.”), there are a few caveats.
a) To document infiltration-related savings in App G models (e.g. for
LEED), the baseline air leakage would be modeled as 0.4 CFM/SF *@ 75Pa*
(90.1 2013 G3.1.1.4). 90.1 2013 Table G further requires that infiltration
inputs in the simulation tool are adjusted to account for factors such as
weather and “…. HVAC system operation….“. 90.1 leaves these adjustments to
the modeler, but PNNL’s Infiltration Modeling Guidelines for Commercial
Building Energy Analysis
<http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.510.8703&rep=rep1&type=pdf>
mentions in passing (Note 2 on p.6) that “The total building infiltration
schedule fraction will be 1.0 when all heating, ventilation and air
conditioning (HVAC) systems are off and 0.25 when the HVAC systems are in
operation.” (It’s good that they used Energy Plus for the study, so results
must still be accurate in spite of this seemingly arbitrary assumption
J.) Since
HVAC systems are operating 24/7 in multifamily, infiltration schedule in
the baseline and proposed design would have to be set to 0.25 of the peak
if we follow the PNNL study, which very significantly reduces
infiltration-related heating load in the model. (The infiltration load is
shown in LS-F report.) As a side note, with LEED v3 and v4,
infiltration-reduction credit can be claimed via exceptional calculation
methods, or by using LEED pilot credit
<http://www.usgbc.org/credits/new-construction-core-and-shell-schools-new-construction-retail-new-construction-healthc-110>
which is based on 90.1 2016 Appendix G modeling rules with the appropriate
adjustment to performance targets and point scale. (I recommend that you
check out this credit, as it simplifies the baseline model.)
b) Potential savings from infiltration reduction should be considered
in conjunction with the specified ventilation strategy. In North East, it
is overwhelmingly common to have 100% OA units serving multifamily
corridors with no exhaust, and continuously running rooftop exhaust fans
serving kitchens and bathrooms in apartments on one vertical stack with no
make-up. Both supply and exhaust rates are often grossly oversized compared
to the minimum CFM required by code, and since the relevant code
(summarized here
<https://buildingscience.com/sites/default/files/document/ba-1507_ventilation_guidance_final_measure_guideline.pdf>)
requires that apartments are compartmentalized and envelope is air-tight,
it creates an interesting conundrum for air J. Balanced ventilation is
still a rarity in NE even in high performance buildings. Old editions of
ASHRAE Fundamentals had a way of taking into account this dynamics (see
below), which was crude but better than “one size fits all” approach in the
PNNL study. So I’d use ASHRAE’s method in lieu of PNNL’s to model
infiltration savings for LEED, and to decide whether tighter envelope
should be pursued for a given project.
Nathan, thanks for clarifying your plug load observations. Your explanation
makes total sense. On the related note, the latest LEED EAc1 template
includes the following info (based on ASHRAE Applications handbook) for the
impact of occupant demographics on HW usage. Perhaps you can reference this
data (also used in EPA HRMF program) to justify modeling lower plug loads
for certain projects. But I can also see that rating authorities may reject
this logic and insist on using “typical” plug loads in the model,
recognizing that occupant demographics may change over the life of the
building.
*From:* Nathan Miller [mailto:nathanm at rushingco.com]
*Sent:* Tuesday, March 14, 2017 9:38 AM
*To:* Chris Jones <Christopher.Jones at RWDI.com>; David Griffin II <
DGriffin at archnexus.com>; Maria Karpman <maria.karpman at karpmanconsulting.net>;
Michael Campbell <mcamp1206 at gmail.com>; Joe Huang <
yjhuang at whiteboxtechnologies.com>
*Cc:* equest-users at onebuilding.org
*Subject:* RE: [Equest-users] Wall insulation in multifamily buildings
I can’t think of the last high-rise project I worked on that stayed
anywhere near 25% WWR. 40-50% is very much the norm in Seattle (climate
where I do most of my modeling work). Owners want 60%+. Mid-rise resi (and
mixed use), I do tend to see 25-35% WWR as typical.
When we do the envelope sensitivity analysis on high rise multifamily
projects, honestly the glazing percentage isn’t as bad a penalty as you’d
think. Like on the order of 0.1-0.25% energy penalty for each 1% increase
in glazing when we are already in the 40%+ glazing band, meaning we are
comparing extra glazing to opaque wall. This is with a WSHP system serving
residences. If it is more of a traditional hydronic job, that penalty seems
to go up a little, but still isn’t a killer.
Using standard ESMFHRSG plug loads we see the conditioning load of the
buildings driven by internal loads, ventilation, and infiltration, not
envelope. Related to the previous comment in this thread from Maria:
“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.”
Her comment made me realize I’m suffering a bit from selection-bias. The
projects I tend to model are the newest multifamily projects to hit the
market. These projects in Seattle are almost all studios and 1 BR, with a
few 2 BR and penthouses sprinkled in. They aren’t serving as housing for
families, but more professionally-employed individuals, who don’t cook
much, who probably concentrate their electronics (laptop plus maybe a flat
screen) more than the typical American family, and certainly do less
laundry. Some of the trend on housing design seems to be minimal living
space and more amenities. That is probably why the national averages for
dwelling unit plug loads seem high for THE TYPE OF PROJECTS I WORK ON.
Hope that makes more sense (given some reflection).
*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 *Chris Jones via Equest-users
*Sent:* Tuesday, March 14, 2017 7:46 AM
*To:* David Griffin II <DGriffin at archnexus.com>; Maria Karpman <
maria.karpman at karpmanconsulting.net>; Michael Campbell <mcamp1206 at gmail.com>;
Joe Huang <yjhuang at whiteboxtechnologies.com>
*Cc:* equest-users at onebuilding.org
*Subject:* Re: [Equest-users] Wall insulation in multifamily buildings
My only comment is that developers and contractors like curtain wall
(window wall for high rise MURBS) because it is less expensive to install
and can be installed in any weather. This may be the main reason we see
glass towers north of the 49th.
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<http://www.rwdi.com/assets/logos/RWDI-logo.gif>
*Christopher Jones, **P.Eng. *| Senior Energy Analyst
*RWDI*
901 King Street West, Suite 400, Toronto, ON M5V 3H5 Canada
Tel: (519) 823-1311 ext 2052
rwdi.com <http://www.rwdi.com/>
*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org
<equest-users-bounces at lists.onebuilding.org>] *On Behalf Of *David Griffin
II via Equest-users
*Sent:* Monday, March 13, 2017 7:46 PM
*To:* Maria Karpman; Michael Campbell; Joe Huang
*Cc:* equest-users at lists.onebuilding.org
*Subject:* Re: [Equest-users] Wall insulation in multifamily buildings
I thought I might chime in on this discussion as well to drive a few points
home.
I have attached a file illustrating a graph to explain Joe’s comment below.
It shows diminishing returns from increased insulation. When it comes to
effective envelope ECMs for projects. I focus on two very important things:
1) Lower infiltration will save you more energy than any other
envelope ECM. However, it is hard to get an owner to buy off on this and
enforce the requirement with the contractor. Typically, an envelope
consultant will be brought in to assist the architect with details,
supervise the contractor during construction, and test the building (or a
portion thereof) to verify performance. You can see how something like this
is hard sell to an owner because it can be a costly process, and if the
building fails the blower door test, the contractor has a $$ issue and the
a lot of rework.
2) Window-to-Wall Ratio (WWR) reduction is great. On the curve
illustrated in the attached file, you essentially replace an expensive
window with a cheaper wall assembly and saving more energy! It’s a true
win-win-win. However, windows exist for more reasons than daylight
controls. Comfort and views are essential for occupants. Some architects
may also argue they are essential for aesthetics as well, so you have to
have a target in mind for the project you are willing to negotiate. On
commercial projects, I generally shoot for 25% WWR.
3) Window upgrades are next since they have the most potential to save
energy on the illustrated curve. Since you tried to minimize the WWR on #2,
this ECM will be cheaper than it would have been otherwise – always saving
the client $$ J This includes glazing and frames.
4) After all three of the above items are addressed, I start to talk
about added insulation in the walls, roof, etc.
Anyway, this is my approach on new construction. Is this what you guys see,
or am I missing something?
Let me know.
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DAVID W. GRIFFIN II
BEMP
ENERGY ANALYST
2505 E Parleys Way
Salt Lake City, UT 84109
*Office* 801.924.5028
archnexus.com <http://www.archnexus.com>
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*From:* Maria Karpman via Equest-users [
mailto:equest-users at lists.onebuilding.org
<equest-users at lists.onebuilding.org>]
*Sent:* Friday, March 10, 2017 9:24 PM
*To:* Michael Campbell; Joe Huang
*Cc:* equest-users at lists.onebuilding.org
*Subject:* Re: [Equest-users] Wall insulation in multifamily buildings
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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