[Bldg-sim] MRT Tool
Varkie C Thomas
thomasv at iit.edu
Wed Apr 22 07:45:12 PDT 2009
I assume that this MRT discussion is about residential buildings with no dedicated perimeter heating and cooling system to maintain the temperatures of the inside surfaces of exterior walls and windows near the space temperature; and the supply locations of heating and cooling systems are well away from envelope.
Modern office buildings, even in extreme hot and cold climates, tend to be 70% glass today because of the low first, construction, and maintenance costs and also because they create a pleasant indoor environment. Today's glass efficiency is such that both heating and cooling systems of the perimeter zone (1' to 3") is by supplying conditioned air from the ceiling. Baseboard radiation, even in Minneapolis where temperatures drop to -30F, is not necessary. This frees up prime living space right up to the envelope without obstructions by HVAC units on the floor. The effect of solar radiation through the glass on MRT comfort inside is dealt with blinds. If the systems serving the perimeter fail, then the occupants have to leave the building since the windows are fixed shut to maintain inside pressure for fire and smoke control. MRT is not a factor inside these buildings if the Std90 Wall and Roof U-factors apply and the glass U-factor is about 0.3.
I have had to look at the MRT conditions inside such buildings in order to determine how inefficient the envelope could be made and still maintain comfort conditions inside based on MRT. This is a trial and error or iterative effort. In DOE2.1E you can get hourly report for EXTERIOR-WALL, Variable List Number = 6 (outside surface temperature). This information is not available for windows so an approximate value for outside surface temperature is the outdoor temperature assuming the glass outside surface is light-colored, smooth and low-heat absorbing. Transfer this information to an Excel file and calculate inside surface temperatures and MRTs at different distance. Surface temperatures of Space interior wall are assumed to be the Space design temperature. Some programming is required and extreme theoretical accuracy is not required.
Varkie
----- Original Message -----
From: Simon Rees <sjrees at dmu.ac.uk>
Date: Wednesday, April 22, 2009 3:28 am
Subject: Re: [Bldg-sim] MRT Tool
To: "bldg-sim at lists.onebuilding.org" <Bldg-sim at lists.onebuilding.org>
> You may also be interested in the work reported in an ASHRAE paper
> thatappeared at the last Chicago meeting:
>
> "Predicting Local Thermal Discomfort Adjacent to
> Glazing (NY-08-053)
> Simon J. Rees, Ph.D., Member, Kevin J. Lomas, Ph.D. and
> Dusan Fiala, De Montfort University, Leicester, UK
>
> In this work a multi-segment dynamic comfort model has
> been employed that incorporates recently developed models
> of local thermal comfort response. The work required the
> development of simulation methods able to predict the detailed
> long-wave and convective exchanges to the surrounding
> space and the absorbed solar irradiation. This has been done
> in an effi cient and generic manner so that parametric studies
> of local comfort responses have been possible. Such studies
> have been used to examine the relationships between local
> discomfort and room and window temperatures as well as the
> role solar irradiation and clothing may play in determining
> satisfactory winter environmental conditions."
>
> The main points to note are that the model uses a local rather than
> global comfort model i.e. effects on particular body parts are
> considered. Direct solar radiation and shading of particular body
> partsare calculated. View factors for each body part are
> calculated for a
> particular body position relative to the room rather than calculating
> the MRT.
>
> Regards,
> Simon
>
> ________________________________
>
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Timothy
> Moore
> Sent: 22 April 2009 04:19
> To: JRR; Peter Simmonds
> Cc: bldg-sim at lists.onebuilding.org; Vikram Sami
> Subject: Re: [Bldg-sim] MRT Tool
>
>
>
> Regarding asymmetrical thermal comfort and that involving transmitted
> short-wave radiation, the following link will get you an excellent
> (lengthy, detailed, and very helpful) paper on thermal comfort in
> proximity to windows. It discusses the effects of glass surface
> temperatures and transmission properties, along with possible options
> for including a rating of thermal comfort performance on NFRC window
> labeling.
>
>
>
> Huizenga, C., H. Zhang, P. Mattelaer, T. Yu, E. Arens, and P. Lyons,
> 2006. Window Performance for Human Thermal Comfort
> <http://www.cbe.berkeley.edu/research/pdf_files/SR_NFRC2006_FinalReport.
> pdf> . Final Report to the National Fenestration Rating Council,
> Centerfor the Built Environment, University of California,
> Berkeley, February.
>
>
>
> You do not need an open window to have comfort issues associated with
> transmitted short-wave radiation, nor does it have to be direct-beam
> radiation-any window permitting occupants to receive a good dose of
> transmitted diffuse and/or direct solar radiation is reason enough to
> care about this effect. The paper at the CBE link above provides a
> veryuseful means of estimating the contribution of both direct-
> beam and
> diffuse solar radiation. The discussion of the impact of diffuse
> radiation begins on page 44 and the discussion of direct radiation
> starts on page 49.
>
>
>
> CBE's Advanced Thermal Comfort Model
> <http://www.cbe.berkeley.edu/research/briefs-thermmodel.htm>
>
> This tool can used to study the effectiveness of energy saving design
> strategies, such as facade designs and advanced HVAC systems, in terms
> of occupant comfort.
>
>
>
> In addition, the CBE has an Advanced Thermal Comfort model that they
> will be happy to run for you as consultants to your project (and which
> their industry partners also have direct access to) which takes into
> account short-wave radiation striking a human subject, along with
> numerous very detailed thermal comfort parameters. This tool was used
> for several key sections of the paper linked above, so you can see
> examples of the model and results there. Not only does this model
> account for occupant attributes like body mass (along with the usual
> comfort parameters), it actually models 16 different human body parts
> and the constriction and dilation of blood vessels that accompanies
> different thermo-physiological states. This model, which is not really
> all that difficult to work with, has been used for CBE consulting
> to the
> automotive industry and a in-house by handful of large A&E firms.
> If you
> want to learn more, the following link takes you to the section of the
> CBE web site describing this tool:
>
>
>
> Cheers,
>
> Timothy
>
>
>
>
>
>
>
>
> Timothy Moore
> Senior Consultant
> Special Projects
>
>
> Office: 415 983-0603
> timothy.moore at iesve.com <mailto:timothy.moore at iesve.com>
> www.iesve.com <http://www.iesve.com/>
>
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>
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>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> From: JRR [mailto:energy.wwind at cox.net]
> Sent: Tuesday, April 21, 2009 7:44 PM
> To: Peter Simmonds
> Cc: Vikram Sami; Timothy Moore; Karen Walkerman;
> bldg-sim at lists.onebuilding.org
> Subject: Re: [Bldg-sim] MRT Tool
>
>
>
> JRR wrote;
>
> Good Point !! Do you take the radiation temperature at the virtual
> surface of the open window ??
> NO. It is the wrong answer, but now you need to know things like
> the RT
> of an adjacent building,
> background sky RT, luminosity...
>
> Peter Simmonds wrote:
>
> Ah, another can of worms. MRT is probably the least understood and
> certainly the least calculated of space thermodynamics. ASHRAE RP 1383
> was specifically set up to calculate MRT for spaces, even having
> unusualconfigurations. It should be ready in about 18 months or
> so?
>
> So Vikram, with reference to your analogy, how about this one?
>
> Imagine a space that is naturally ventilated through an open
> window, at
> this certain time of the day the occupant is in such a position
> that the
> suns rays reach the occupant through the open window. What would
> the MRT
> be in the space and how would this affect the occupants comfort.
>
>
>
> Peter Simmonds. Ph.D.
> Senior Associate, Advanced Technology Group
>
> IBE Consulting Engineers
> 14130 Riverside Drive Suite 201
> Sherman Oaks, CA 91423
> p: (818) 377-8220 ext. 246
> f: (818) 377-8230
> m: (818) 219-1284
>
> This e-mail message, including any attachments, is for the sole
> use of
> the intended recipient(s) and may contain confidential and privileged
> information. Any unauthorized review, use, disclosure, or distribution
> is prohibited. If you are not the intended recipient, please
> contact the
> sender by reply e-mail and destroy all copies of the original message
>
>
>
> ________________________________
>
> From: Vikram Sami [mailto:VSami at lasarchitect.com]
> Sent: Tuesday, April 21, 2009 12:02 PM
> To: Peter Simmonds; Timothy Moore; Karen Walkerman;
> bldg-sim at lists.onebuilding.org
> Subject: RE: [Bldg-sim] MRT Tool
>
>
>
> It's an interesting conundrum that the times that MRT becomes a
> significant player in the comfort calculation is when there is an
> unevenradiant field (hot or cold window; fireplace; thermal mass
> wall). In
> such a situation, is it fair to average out the MRT for an entire
> room?Don't your view factors change drastically depending on your
> position in
> the room?
>
>
>
> Does one person too hot near the window and another person too
> cold on
> the inside equal thermal comfort?
>
>
>
> Vikram Sami, LEED AP
> Direct Phone 404-253-1466 | Direct Fax 404-253-1366
>
> LORD, AECK & SARGENT ARCHITECTURE
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>
> From: bldg-sim-bounces at lists.onebuilding.org [
> mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Peter
> Simmonds
> Sent: Tuesday, April 21, 2009 1:36 PM
> To: Timothy Moore; Karen Walkerman; bldg-sim at lists.onebuilding.org
> Subject: Re: [Bldg-sim] MRT Tool
>
>
>
> I do not think the thermal comfort tool calculates the MRT it is a
> userinput.
>
>
>
> Peter Simmonds. Ph.D.
> Senior Associate, Advanced Technology Group
>
> IBE Consulting Engineers
> 14130 Riverside Drive Suite 201
> Sherman Oaks, CA 91423
> p: (818) 377-8220 ext. 246
> f: (818) 377-8230
> m: (818) 219-1284
>
> This e-mail message, including any attachments, is for the sole
> use of
> the intended recipient(s) and may contain confidential and privileged
> information. Any unauthorized review, use, disclosure, or distribution
> is prohibited. If you are not the intended recipient, please
> contact the
> sender by reply e-mail and destroy all copies of the original message
>
>
>
> ________________________________
>
> From: Timothy Moore [mailto:timothy.moore at iesve.com]
> Sent: Tuesday, April 21, 2009 10:00 AM
> To: Karen Walkerman; bldg-sim at lists.onebuilding.org
> Subject: Re: [Bldg-sim] MRT Tool
>
>
>
> Karen,
>
>
>
> The ASHRAE-55 Thermal Comfort Tool created by the UC Berkeley
> Center for
> the Built Environment and available from ASHRAE publications (if I
> recall correctly) includes a very easy-to-use MRT calculator for
> rectangular rooms. It allows for MRT at a particular position in that
> room, separate surface temperatures and dimensions for surfaces, and
> also the inclusion of a "panel" or other area within one of the walls
> (such as a cold/hot window, heating panel, etc.) that has a distinct
> temperature. This is part of a very handy tool for determining
> PPD, etc.
> based upon the typical range of human thermal comfort variables (clo
> value, activity level, air temp, MRT, humidity, air movement).
>
>
>
> Cheers,
>
> Timothy
>
>
>
>
>
>
>
>
> Timothy Moore
> Senior Consultant
> Special Projects
>
> Mobile: 415 810 2495
> Office: 415 983-0603
> timothy.moore at iesve.com <mailto:timothy.moore at iesve.com>
> www.iesve.com <http://www.iesve.com/>
>
> **Design, Simulate + Innovate with the <Virtual Environment>**
>
> Email Disclaimer <http://www.iesve.com/disclaimer.html>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> From: bldg-sim-bounces at lists.onebuilding.org [
> mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Karen
> Walkerman
> Sent: Tuesday, April 21, 2009 9:50 AM
> To: bldg-sim at lists.onebuilding.org
> Subject: [Bldg-sim] MRT Tool
>
>
>
> Hello,
>
> Is anyone aware of a simple Mean Radiant Temperature calculation tool?
> I'm looking for something that will calculate MRT for a basic
> rectangular room.
>
> Thanks!
>
> --
> Karen
>
>
>
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