First Pass - Chicken or Egg?

It is well known in the industry that energy analysis used to improve design has the greatest impact at the very earliest stages of a project.
One must add to this that the costs associated with making changes is least also at the earliest stages of the project. *

But the effort to push energy analysis to the front of the project has run into a couple of hurdles:

1) The analysis software in use may not be fully integrated with the design tools, which are often still a pencil and paper. The good news here is that the software industry is working very hard to improve interoperability all of the time.

2) The other hurdle is the amount of assumptions needed to begin an energy model. The accuracy of the simulation is improved by reducing assumptions, by designing the building in detail much earlier. By the time your details are defined your project is usually far enough along that the scheme can't change and the analysis can only have a minimal impact on the design process. **

Another Approach:
We try to avoid these problems associated with assumptions by focusing on the variables we have the greatest control over that enter into the building energy equation.

Thermal balance occurs when the sum of all the different types of heat flow into and out of a building is zero. That is, the building is losing as much heat as it gains so it can be said to be in equilibrium.
Thus:

Qc - Conduction Gains
Qv - Ventilation Gains
Qs - Solar Gains
Qi - Internal Gains
Qe - Evaporative Loss

To remain in thermal equilibrium our HVAC system kicks in gear and is inversely equal to the sum of the gains.

For our projects in hot climates we only have two gains which significantly impact design that we are able to modify during an investigation modelling period. Qs which includes solar heat gain through windows is often our greatest load. The other big one is the heat from lights (Qi) for spaces not utilizing daylighting. ***

Its very easy for us to take a project in a hot climate, forget about all of these other building assumptions and just start working to minimize solar heat gain through windows while maintaining adequate daylight. Later, when we have enough building assumptions to produce an accurate energy model, our design will be in much better shape than if we had held off on the analysis.

But in a hot climate it can become more complicated when taking into account peak loads. The largest cooling loads generally occur late in summer in the afternoon, and the strategy to minimize peak loads sometime works against the strategy to minimize total gains. Knowing closely when the peak occurs can influence wall orientation, shading strategies and daylighting strategies on the west facade. One should rely on a full thermal model to get as close as you can to the time of the peak load to effectively work to reduce it. ***

Even more complicated than this are buildings with both heating and cooling loads for which we will try to minimize solar gains in one season while maximizing them in another (while ensuring that our solar design decisions work with our daylighting strategy). ****

If the designer can utilize solar analysis during the concept stage the building will be much improved by the time accurate energy modeling can enter the process. But to accurately design for solar optimization in moderate and cold climates they must make assumptions about the hours of the day and the months of the year for which there will be heating and cooling loads.

To find the heating and cooling range we probably need one of three things:
1) Expert guidance from a local engineer.
2)"Target Finder" type information that includes monthly loads for heating and cooling.
3) Perhaps a first pass at an energy model before there even is a design. The Egg before the Chicken. A first pass can be done with any reliable analysis software, verified by an engineer familiar with both the software and the building type and location. This analysis could be done using simple boxes, but it would be great to see the architect and engineer jointly develop generic building "type" models, easily dropped into any climate for the first pass at understanding basic loads associated with type and location.


There is a quote about knowing your enemy, but I'd rather focus on enlightened designing, utilizing both technology and one's conscience to design and produce buildings that really work well. To this effect how can we improve upon our process?

Image Reference:
* ASHRAEs 2003 Green Guide with vertical axis notes added for clarity by Alex Hirsig**

**Hirsig, Alex. "Design by Simulation: Building Performance Modeling by Architects in the Conceptual Design Process." Masters Thesis, Design Studies: Design and Technology Concentration, Harvard Universtiy Graduate School of Design, 2008

***The ASHRAE Guide for Buildings in Hot and Humid Climates, 2008

**** Bedington Zero by Bill Dunster Architects