Fellow eQuest users,
I am brand new to equest and I am attempting to model a baseline ASHRAE
building per the 2004 90.1 standard and am curious if there is any
specific wall, roof or window constructions that other users are
entering as their baseline constructions. I have noticed several
things:
1. Simply entering a resistance (such as an R-value of 11.9) I get a
"WALL has no heat capacity. U-VALUE used" error (see attached)
2. Defining a layer-by-layer construction does not allow any
improvement through EEMs. In other words the options to increase the
amount of insulation are grayed out.
3. It is impossible to determine the actual total U-value of one of the
"cookie-cutter" constructions provided by eQuest.
As a side note, I'd be curious to know what computer specs others have
to run eQuest, as I have developed a model with over 3,000 components
and it takes about 6 minutes just to open the file on a computer with
the following specifications:
* Intel Pentium D 2.99 GHz
* 1 GB RAM
* ATI Radeon X600 - Video card
* 29 GB HDD
The specs on this computer are terrible in my eyes, and it really shows
when I try to run eQuest but I'd like to see what other PCs run this
program effectively.
Thanks,
Paul Skelton
12300 components - 6.5 minutes to open
Intel Pentium 4, 3.4 GHz
2 GB Ram
120 GB hard drive
Radeon X700 video card
I suspect equest would open the file faster if
you could turn off the progress bar. All that
GUI reporting likely doubles the time to open.
>> Christopher Jones, P.Eng.
> Hi Paul
--
Graduate Student, MSBE
School of Architecture and Landscape Architecture
Arizona State University, Tempe
I have never used the specify resistance option in creating a custom construction. I have always input the actual building materials used (either in the main menu if they are available, or in the layer by layer construction if I need to add air gaps and things of that nature). Im not sure why you are inputting a specific value but I played with it for a minute to see what was going on and I got the same error. If you go under layer by layer construction in the wizard and pick new construction you need to put atleast one building material to get rid of the error. For example I picked library entry from the first drop down menu for the first layer and then chose brick, brick common 4 inch. This gives an R-value of 0.8. (you can see the cumalitive r-value in the bottom left hand corner as you create your construction.) Then for the second layer I chose specify resistance and input an r-value of 18.2. This gives the specific r-value of 19 your looking for as well as gets rid of your error. I think the program is looking for some type of physical building material and that is why its giving the error. You could maybe even try adding another layer of gypsum board or something (whatever your assuming your actual interior building material is) and then changing your specified resistance on the middle layer once again to give you exactly 19. I believe the program also needs that outer layer to calculate solar absorbance. After using this method I went to detail mode to check the u-value and it showed the construction I made as having a u-value of 0.053 which is rounded off and coinsides with an r-value of 19. And most importantly it gets rid of your error. Make sure when specifying your layers you pick vertical exterior wall from the upper right drop down menu or else it will re-calculate your r-value when running or coming out of the wizard to match the construction location type.
Im not sure what EEMS are but if your talking about the layers in the custom layer by layer construction menu its because you haven't chosen a category for the first construction to allow you to create the next. (either library entry or specify resistance)
I hope this helps.
ASHRAE 90.1 section G is very specific about the wall construction details.
See G3.1(5). All walls should be Light weight steel framed and roof should
be insulation above deck per your climate zone. A3.3 details the actual
layers that are used to make up a steel frame wall(see similar sections for
roof and below grade walls). Remember equest adds the exterior air film
during the simulation, so you won't see the equivalent U value until running
the simulation. All of my baseline models are done in detailed data mode so
I'm not sure how to accomplish this with the wizard.
If you layers are too light, you need to add mass or use the U-value
construction method.
Also, we max out the ram on our machines and use dual core processor. The
dual core doesn't help the modeling speed but allows for multitasking during
simulation and frees up the whole processor for simulation.
Thomas Serra