The Building Envelope – All the Marbles
Spartan Building Scientists utilize the latest in AutoCAD and Building Information Management (BIM) Software to perform the two main functions of energy modeling that calculates the expected annual energy use for any house design, and utilizes built in optimization and a database of exiting home types similar to the one our customers want to build. Spartan consultants will identify the least expensive way to build the envelope of a net-zero energy house.
The BIM software programs includes a database of user-modifiable construction cost data. This feature allows Spartan Scientists to determine (for example) whether a house with 8-inch-thick SIP walls and double-glazed windows will cost more or less to build than a house with 6-inch-thick foam, and triple-glazed windows. It will also determine which of these options will perform best in your climate area.
Spartan Scientists and Architectural designers show different design scenarios of zero-energy homes how to improve envelope specifications, and lets them know the right point to quit making envelope improvements. After all, including energy-efficiency measures in a new home reduces the total cost to the homeowner for utilities and mortgage payments compared to a code-minimum house — up to a point. As more and more improvements are included in the design specifications, energy costs get lower and lower, until a point is reached that is optimal from a cost perspective. Beyond this optimal point, the designer may be able to achieve further energy savings, but the monthly costs to the homeowner for utilities and the mortgage begin to rise.
THE POINT OF DIMINSHING RETURNS IS KNOWN
It’s a useful program, even if you aren’t building a zero-energy house
Once envelope improvements start costing more than a photovoltaic (PV) array, they become a poor investment. Most homeowners don’t want to pay $5,000 for extra insulation if the investment yields lower annual savings than a $5,000 PV system. By identifying the point at which envelope improvements stop making sense, Spartan designers arrive at the least-cost envelope for a zero-energy house.
Even if you aren’t interested in including a PV system, Spartan Analysis can still be useful. After all, it always makes sense to design a house with the lowest combination of utility bills and mortgage payments — even if it isn’t a zero-energy house.
If you assume that energy prices are likely to increase steeply in the future, you can input your assumptions about energy price inflation into BIM software. It’s possible to enter different rates of inflation for four different types of fuel: electricity, natural gas, propane, and fuel oil. Spartan Designers take into account actual energy prices, and prevent the design of homes with more insulation than designers who assume that energy prices will stay steady.
The Spartan design analysis method involves searching all categories such as wall type, ceiling type, window glass type, HVAC type, etc. for the most cost-effective combination at each sequential point along the path to zero net energy. Starting with the base-case building, simulations are performed to evaluate all available options for improvement (one at a time) in the building envelope and equipment. Based on the results, the most cost-effective combination is selected as an optimal point on the path and put into the Final Spartan Building design description.