[Equest-users] Green Roof - eQuest style

Nick Caton ncaton at smithboucher.com
Fri Mar 2 08:38:57 PST 2012


Karen,

Thank you very much for the feedback.  I personally don't have the cross-platform experience necessary to share such perspective, and it is not my goal to pretend that I do, just trying to keep our community's mutual efforts to help each other constructive =).

As well as I can predict the weather, I see myself adding EnergyPlus to my toolbox sooner or later as well.  UI issues and other items collectively affecting the time-efficiency of EnergyPlus are what I see as the greatest hurdle for myself and others... more easily dismissed if you have the time to burn, but harder to do so where time is a scarcer resource.

In the meantime, myself and others are in the camp of needing to make do with the tools we are able to use with both accuracy and speed.  I do not mean to argue against learning new tools by sharing suggestions/means to approximate.

Thanks again for the input!

~Nick

[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: Karen Walkerman [mailto:kwalkerman at gmail.com]
Sent: Friday, March 02, 2012 8:21 AM
To: Nick Caton
Cc: Nathan Miller; CleanTech Analytics; John Aulbach; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Green Roof - eQuest style

Nick,

I used eQuest intensively for a time and recently moved most of my modeling to EnergyPlus.  In addition to having more capabilities and being more flexible, EnergyPlus gets regular updates and bug fixes.  EnergyPlus is also a total bear, runs slowly compared to eQuest and doesn't have a fully functional user interface.  I wouldn't recommend it to everybody.

eQuest is very good at modeling buildings that use fairly normal constructions with fairly normal HVAC systems.  I have run into problems when modeling water to water heat pumps, central ventilation systems (with heat recovery), high thermal mass buildings, and dessicant wheels, to name a few.  While I've run into problems with EnergyPlus, I've either been able to resolve the issue with help from the EnergyPlus helpdesk, or, when my issue illuminated an underlying problem with source code, a bug fix was incorporated into the next version.

I understand that eQuest/DOE2 is not receiving funding for updates and bug fixes of eQuest.  A few years ago I tried to start a conversation around updates, bug fixes and feature improvements, and also suggested that we in the modeling community fund some of this effort.  There were quite a bit of responses from users to the "modeling wishlist," but few if any responses to the funding idea.

To extend your carpentry analysis, I think that the eQuest community needs to face the fact that the eQuest saw just isn't capable of cutting some of the species of wood coming into the shop these days.

--
Karen
On Thu, Mar 1, 2012 at 7:03 PM, Nick Caton <ncaton at smithboucher.com<mailto:ncaton at smithboucher.com>> wrote:
Jeremiah,

While dumping eQuest entirely and (re?)starting a project using different software may certainly be a viable solution, I think it's reasonable to assume someone posting a "how do I do this in eQuest" question in forum titled [Equest-users] is probably not looking for such answers first!  I personally understand EnergyPlus is often the tool-of-choice for green-roof specific research, but let's avoid telling a carpenter to throw away his hand saw just because power tools exist ;).

John,

eQuest can certainly *approximate* green roofs, to varying degrees of accuracy.  There were a couple long, informative, and unfortunately disjointed conversations on this exact topic held over the [bldg-sim] list some time ago.  I'm attaching those messages including various attachments and white papers here in a zip file - if you can move these into a folder in outlook or similar you may find it easier to follow the flow of the conversation...

Read up on what's been discussed so far, and I'm certain you'll be able to decide for yourself how comfortable you are using eQuest for your current project ;).

Regards,

~Nick
[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036<tel:913.344.0036>
fax 913.345.0617<tel:913.345.0617>
www.smithboucher.com<http://www.smithboucher.com>

From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of Nathan Miller
Sent: Thursday, March 01, 2012 10:18 AM
To: 'CleanTech Analytics'; 'John Aulbach'

Cc: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Green Roof - eQuest style

I suppose there is probably some benefit to a green roof, but I've never tried to claim credit for it.

At least in Seattle's damp climate, when you would most benefit from the additional insulation of a green-roof-layer (winter) is the same time of the year the growth medium will be saturated, and likely provide you with the least insulative value. In the summer, when you would actually want the heat to escape, the medium will dry out (unless you are irrigating it).

Soil has an insulative value of only around R-0.104/in (at least according to a table in the Seattle Energy Code), so even ignoring moisture levels, it doesn't seem like there is much benefit there.

I suppose in a heavy cooling climate the reflectivity of the plants might get you some benefit, as well as the evaportative cooling effect if you are irrigating. Is that where the credit would be? Is there a thermal mass benefit?

Nathan Miller, PE, LEED AP BD+C
Mechanical Engineer/Senior Energy Analyst
O 206-285-7100<tel:206-285-7100> | D 206-788-4577<tel:206-788-4577>
www.rushingco.com<http://www.rushingco.com/>

From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of CleanTech Analytics
Sent: Thursday, March 01, 2012 7:08 AM
To: John Aulbach
Cc: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Green Roof - eQuest style

John,
I advise you to use a more modern software that has the ability to correctly simulate the effects of a Green Roof rather then some wacky eQuest work around. Professor David Sailor of Portland State University developed the Green Roof object for Energy Plus that uses a a finite difference algorithm and works well. The problem with eQuest/DOE2 is that it is based on a conduction transfer algorithm, and can not really emulate the effects of a Green Roof. If you need the easy to use inputs, I suggest Design Builder to generate the Energy Plus file.

Best of luck, and feel free to ask if you need more about EP/DB..

On Thu, Mar 1, 2012 at 6:04 AM, John Aulbach <jra_sac at yahoo.com<mailto:jra_sac at yahoo.com>> wrote:
OK, my fellow Raiders of the Lost BTU..

What would be your advice for developing a green roof in eQuest? I am sure some of you have gone through the USGBC with hopes of getting this approved.

I eagerly await your suggestions with thanks.

John Aulbach
Partner Energy

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--
Jeremiah D. Crossett
CleanTech Analytics
503-688-8951<tel:503-688-8951>
www.cleantechanalytics.com<http://www.cleantechanalytics.com>


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