[Equest-users] Wall insulation in multifamily buildings

Mon Mar 13 16:46:05 PDT 2017

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 $$ ☺ 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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From: Maria Karpman via Equest-users [mailto: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<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<mailto:yjhuang at whiteboxtechnologies.com>>
Cc: equest-users <equest-users at lists.onebuilding.org<mailto: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<mailto: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<mailto:yjhuang at whiteboxtechnologies.com>

http://weather.whiteboxtechnologies.com for simulation-ready weather data

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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><mailto:mcamp1206 at gmail.com>
Cc: equest-users at lists.onebuilding.org<mailto: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<tel:(206)%20285-7100> |C 207-650-3942<tel:(207)%20650-3942>
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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