# Modeling a Townhouse

Hi everyone!

I am learning TREAT, so perhaps this is too simple of a question for you guys but I am kind of stuck... when TREAT asked me about the building I choose attached, considering that one wall of the building is attached to the neighbor's house, but when I check walls, all of them are set up to the outside, and so far I have not found the way to change the setting for that attached wall. Just for me to learn, is that attached wall considered towards living space? -considering that there is a firewall separating both units.

Luis

Views: 110

### Replies to This Discussion

Hi Luis,

This is a great question that points to a fundamental tenet of energy modeling: we don't worry about surfaces (walls, floors, etc.) where there's no energy transfer.  We assume that temperatures between adjacent units (or between conditioned bedrooms) are essentially the same, so UA∂T = 0 (the delta-T is zero), and there's no point in modeling the boundaries between them.

In other words, don't model walls between adjacent units, floors over conditioned spaces, ceilings under adjacent units, etc.  You've already discovered that TREAT doesn't give you the option to specify conditioned space adjacency.

So, unlike detached single-family homes, that will have at minimum 4 walls, a floor, and a ceiling, attached units will often have fewer.  The most "minimal" case is an inside apartment unit on a middle floor, which might have only one surface, a wall, on the Walls/Surfaces screen.

I hope this helps clarify.  Remember, energy modeling is not the same as architectural modeling -- we don't need to worry about surfaces that are there for structural or aesthetic reasons, but that have no thermal transfer.

- Ethan

Just curious, exterior walls have negative energy transfer (energy loss), heat gain from sun exposure, wind, etc, so when modeled as adjacent to the outside, with the R value of all materials, there is a calculation of that lost energy. I am thinking that the firewall should be pretty energy neutral and so I was thinking it should be represented as wall adjacent to condition space; even though I understand that walls from inside the condition space are not modeled. But the other Townhouse is not part of this condition space....  maybe I am seeing this the wrong way...  hmmm, love building science!

Luis

Exactly right, Luis.

The other unit is conditioned also, so there's negligible energy transfer between them, so the common walls don't provide a heating or cooling load, and there's no reason to enter them in the model.

And to simplify it, there's no way to enter them in TREAT.

If you created this model with the New Building Wizard, you probably have at least one wall that you just need to delete from the model -- the one that would have been adjacent to the other unit.

- Ethan

Great Ethan!

I am going to give it a try!!! I know that what you say makes sense... it just feel silly modeling 3 walls

Luis

## Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy, under the American Recovery and Reinvestment Act) and brought to you in partnership with Home Energy magazine.

## Latest Activity

"Pics are hopefully attached this time. As for details\specs I have not as of yet.  The…"
4 hours ago
"Thanks, I did find that out. In weatherization we deal with some really old furnaces, so sometimes…"
6 hours ago
"Ernst, You mentioned oil, but the replies seem to all be for gas, unless I didn't read…"
7 hours ago
"Thanks for all the comments plus the link. I think based on them I have enough information…"
8 hours ago
"As there are a few different types, impossible to answer without some pics & more specs -…"
10 hours ago
"Waiting for the pictures, Bud"
11 hours ago
rodroc and Gary Fisk joined Home Energy Pros
19 hours ago
Tony Ramirez posted a blog post

### A Shout out to Creative Marketers

A Shout out to Creative Marketersby Tara TafferaDecember 3rd, 2013A Shout out to Creative…See More
19 hours ago
Patrick Michaelyan posted a discussion

### Insulating the "walls" of a mansard-style roof.

Hello pros.Please see the attached pictures.Any insights on how you would insulate the 2nd story…See More
21 hours ago
"For propane, you can look at the burner orfice size.  there are charts that give the btu…"
22 hours ago
scottscontracting shared Greg Labbe's blog post on Twitter

### Air Leakage Testing a New Off-Grid High Performance House

23 hours ago
Everblue's video was featured

### Blower Door Training Part 1: Basic Set Up

Everblue's Blower Door tutorial will teach you everything from understanding equipment to detailed set up a blower door frame. For BPI certification and more visit us at www.everblue.edu or call us at 1(800)-460-2575.
yesterday

© 2013   Created by Lawrence Berkeley National Laboratory.