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IDL - Bozeman eNEWS - April 2013 - Vol. 6 No. 4


Climate Design Tools

IDL-Bozeman is pleased to announce the latest addition to our website, a set of climate design tools originally created by IDL Boise. They can be found under the Software Tools, Climate Design Tools tab on the menu bar. With the permission of IDL-Boise, IDL-Bozeman has adapted these tools to reflect six reference cities in Montana. These include Billings, Bozeman, Great Falls, Helena, Kalispell, and Missoula. The creation of these tools was funded by the Idaho Power Company and was developed into two generations of spreadsheet calculators that are capable of analyzing building loads and the energy consumption impacts of a range of different design strategies. Currently, there are seven different calculation spreadsheets that span across two different generations of tool development. 


Climate Design Tools

IDL-Bozeman is pleased to announce the latest addition to our website, a set of climate design tools originally created by IDL Boise. They can be found under the Software Tools, Climate Design Tools tab on the menu bar. With the permission of IDL-Boise, IDL-Bozeman has adapted these tools to reflect six reference cities in Montana. These include Billings, Bozeman, Great Falls, Helena, Kalispell, and Missoula. The creation of these tools was funded by the Idaho Power Company and was developed into two generations of spreadsheet calculators that are capable of analyzing building loads and the energy consumption impacts of a range of different design strategies. Currently, there are seven different calculation spreadsheets that span across two different generations of tool development.



Heat Gain Calculations:

Heat gain is the heat added to the conditioned space by infiltration, solar radiation, occupant respiration and lighting. This tool calculates the heat gain rate of a building, and is measured in Btus/hr/square foot. It will determine the cooling capacity requirement of either the building’s passive or active systems.   The amount of heat gain is calculated based on multiple factors including heat gains through the building envelope, air infiltration, ventilation, and the internal gains of a building from inhabitants and other types of equipment.  The heat gain calculation tool must be completed prior to the following three tools.


Cross Ventilation:

Cross ventilation is driven by wind and is dependent on operable windows. Once you have established the heat gain rate of the building, the cross ventilation tool can be used to establish a building’s cross ventilation cooling capacity.  These calculations are based on location and size of operable windows, average wind speed, and the temperature difference between outdoors and indoors.


Stack Ventilation:

Stack Ventilation relies on the principal that hot air rises, and depends on low openings to admit outside air and high openings to exhaust air. The stack ventilation tool is very similar to the cross ventilation tool and also requires the heat gain rate to be established first. This spreadsheet tool also utilizes opening sizes as well as stack height to determine the buildings stack ventilation cooling capacity. Stack ventilation is not as effective as cross ventilation. However one can input the cross ventilation capacity in this spreadsheet to determine the combined cooling capacity of a building.


Night Ventilation Thermal Mass:

Night Ventilation strategy maintains a building at temperatures lower than those outside by day and flushes the building with fresh air at night. This tool analyzes the volume and Btu storage capacity of the thermal mass within a building combined with an equation that utilizes hourly data from an average summer day.   Combining night flush ventilation with a thermal mass strategy can be one of the most effective forms of passive cooling.   




Balance Point Calculation:

Balance point is defined as the outside temperature at which the indoor heat gains balance building heat loss to maintain a desired indoor temperature. Like the heat gain tool, this calculation is driven by infiltration rate, solar radiation, occupant respiration and lighting. The key difference with this tool versus the heat gains tool is that weather data, including hourly information from TMY3 weather files, are embedded into the calculations based upon each reference city. The balance point calculated in this spreadsheet will be used in subsequent design strategy calculators to determine how much natural ventilation is possible, how much energy passive solar will save, etc.


Passive Solar:

Passive solar design is perhaps one of the oldest and most popular passive strategies utilized in contemporary practice today. The balance of design parameters within a passive system requires much forethought to truly optimize both heating performance without sacrificing cooling performance in a project. While there are many types of passive solar systems, i.e. Trombe wall, sunspace, roof pond, etc., this spreadsheet tool focuses on direct gain systems coupled with thermal mass. Critical design parameters explored through this tool include: load reduction measures, thermal mass amount and distribution, and glazing parameters and area.


Earth Tube:

Earth tubes are earth-to-air heat exchangers that capitalize on the moderate temperatures below ground to help reduce the heating and cooling loads of a building. They can be used to provide cooling in residential and commercial applications, or be used to pre-treat outdoor air for the ventilation requirements of commercial buildings. As air moves through a pipe, it transfers heat or couth to the surrounding tube material and soil before connecting into an HVAC system or being delivered directly to a space. The amount of heat transfer is contingent on the following critical design parameters: temperature difference between the ground and air, soil conductivity, pipe material, pipe diameter, tube length, and air velocity through the system. This spreadsheet calculator will help guide you through testing the effect of these parameters on heating and cooling performance.


These Climate tools are geared toward the conceptual phases of design and contain robust calculations that are quick and easy to use. They are designed to provide quick feedback loops that make direct correlation between design and performance apparent through instantaneous outputs in an intuitive spreadsheet input format. The 2nd generation of tools utilizes hourly TMY3 data for calculations specific to the six different reference cities in Montana. This detailed level of weather data provides a robust climate-specific analysis while opening the door to more advanced calculations for balance point, passive solar capacity, etc. The seven total spreadsheets provide many useful outputs which range from peak cooling load reduction, to heating energy/cost savings, to the quantification of natural ventilation hours for various design strategies.

We hope to offer some interactive workshops on the use of the climate tools in the near future, so stay tuned.

For more information about the production of these tools, please visit the Integrated Design Lab Boise.

Click here to download the climate tools for your region in Montana.


USGBC MT Chapter's 2013 Annual Summit

Building Performance for a Changing Environment

May 10th-11th in Billings, MT

The annual summit is an opportunity to participate in an educational workshop and four educational breakout sessions on Friday, May 10th.   Speakers include Jacob Dunn and Lauren Hemley from IDL – Boise and Tom Wood of IDL – Bozeman.  On Saturday, May 11th, there will be a Billings green building walking tour.

IDL – Boise’s Jacob Dunn and Lauren Hemley are teaching a climate design workshop.  This workshop introduces analytical climate design tools to implement passive design strategies and ensure optimum building performance for specific climates.  The following analyses and strategies will be covered during the workshop: peak cooling calculation, heating energy use, balance point calculation, cross and stack ventilation, night flush ventilation, and passive solar analysis.

IDL – Bozeman’s Tom Wood will be giving a presentation on advancements in LED lighting. Tom’s course will provide a history and basic anatomy of this lighting strategy, and overview the performance characteristics of LED’s verses standard light sources.  He will then describe the system components that are necessary for proper operation and control, as well as an overview of the appropriate application and the unique design considerations of LED’s.

These are just two of the many presentations at the summit.  Check out the USGBC Montana Chapter Website for more information about registration and events.


Register Now for AIA Convention and Meeting in the Mountains!

Looking for a networking opportunity to mingle with other architects? Needing to catch up on some of your continuing education credits? Spring is here, and so are the AIA National Convention and Meeting in the Mountains!

2013 AIA National Convention

June 19th – 22nd in Denver, Colorado

The AIA National Convention offers a wide range of guest speakers, sessions, workshops, and events to attend during your stay in Denver. Pre-registration is recommended for sessions as seating will be limited.

Registration is currently open, with the Early Bird Discount deadline on April 10th.

Fees for the convention are categorized based on your registration date, and range from free events to total convention passes ($575 max. for AIA members, $945 max. for nonmembers.) Students, AIAS members, and young professionals under age 40 will be eligible for discounted passes, and new AIA members can attend the convention for free! The complete breakdown of prices and fee deadlines can be found on AIA National Convention website.

For more information about the conventional, as well as housing and travel information, check out the AIA National Convention website.


Looking for something a little closer to home? Meeting in the Mountains is happening in Billings this year!

2013 Meeting in the Mountains

April 25th – 27th in Billings, MT

The three day event includes guest speakers Patrick Tighe, Jonathan Segal, and Craig Hodgetts, workshops, and sessions - all of which count towards continuing education credits and offer the latest information about a wide range of topics.

IDL – Bozeman’s very own Tom Wood will be giving a presentation on advancements in LED lighting, so you don’t want to miss out!

Registration is currently open, with fees listed as $100 for members and $35 for students. Some meals are included within registration fee.

Check out the Billings Architectural Association website for more information about registration and events.


Simple Steps to Improving the Energy Efficiency of Historic Buildings

Within the realm of energy efficient design, building professionals deal not only with new construction, but also with existing and historic buildings. Whether it is a retrofit or a preservation undertaking, these projects have great potential to extend the life of a building and encourage sustainable attitudes towards existing buildings in society. Yet, working with historic buildings can be a challenging process. Historic buildings are defined by key features in their construction and architectural style as well as in their historical significance; thus, when those features need repairing, replacing, or retrofitting, the methods and manner in which those features are handled are critical to the historic integrity of the building.

These issues often arise with windows and other elements that significantly affect the energy efficiency of the existing building. While the initial thought may be to alter or replace these elements, the building should first be evaluated for its current energy saving potential. Many historic buildings were designed to be inherently energy saving due to their lack of reliance on mechanical systems. Window shading, natural ventilation and circulation, light reflecting surfaces, local materials, thick insulated walls, and operable windows and shutters are often part of the original fabric of the building and could thus be utilized for their continued energy saving characteristics.

After identifying these features, it is critical to determine what type of work will be completed due to the restrictions and suggestions that are unique to each treatment category. It is important to note that a qualified historic preservation professional such as a Historic Preservation Officer should be consulted early in the design process to ensure adequate interpretation and execution of the treatment standards based on the agreed treatment category. Guidelines and standards vary to some degree between the different organizations and institutions, but the most widely accepted and trusted information comes from the National Park Service. They oversee the National Register of Historic Places Program and its various branches, which include the Secretary of the Interior’s Standards for the Treatment of Historic Properties. These standards outline the different types of work and the subsequent methods of treatment that could be done to a historic building. The standards divide the work into the four categories of Preservation, Rehabilitation, Restoration, and Reconstruction. According to their website…

“The Standards for the first treatment, Preservation, require retention of the greatest amount of historic fabric, along with the building's historic form, features, and detailing as they have evolved over time. The Rehabilitation Standards acknowledge the need to alter or add to a historic building to meet continuing or new uses while retaining the building's historic character. The Restoration Standards allow for the depiction of a building at a particular time in its history by preserving materials from the period of significance and removing materials from other periods. The Reconstruction Standards establish a limited framework for re-creating a vanished or non-surviving building with new materials, primarily for interpretive purposes.”*      

* www.nps.gov/history/hps/tps/standguide/overview/using_standguide.htm


While some treatment methods are unique to a particular category, there are a few guidelines that consistently apply to all four categories:

  1. The most important and emphasized standard is that it is always preferable to repair damaged elements as opposed to replacing or retrofitting. The introduction of new materials and styles can do irreversible damage to the historic integrity of the building, especially when dealing with windows. For example, wood windows that were installed prior to the 1950’s have a greater chance of containing very valuable old growth wood that, if removed, are essentially impossible to replace and will compromise the value of the building’s historic significance.
  2. Any new materials or elements must match the appearance of the original element, and if possible should match the original material. A few examples would include not changing the glazing color in a repaired window, replacing wood windows with wood, not vinyl windows, etc.
  3. All changes to the historic building must meet the specified code requirements based on either the existing building code (Preservation, Restoration, Rehabilitation) or new building code guidelines (Rehabilitation, Reconstruction.)



Upon taking a closer look at the four categories, each category has outlined a set of steps for design professionals to take towards completing a project without compromising the building’s integrity. When working within a Preservation project, the goal is to preserve as much of the existing building as it is in its current state.

The Steps for Preservation:

Identify, Retain & Preserve, Stabilize, Protect & Maintain, Repair, and Limited Replacement in Kind.


Restoration projects are similar to Preservation projects in that they attempt to retain a large amount of the historic fabric of the original design. However, Restoration allows for the removal of elements that did not exist during the period to which the project is being restored.

The Steps for Restoration:

Identify, Retain & Preserve, Protect & Maintain, Repair, Replace, Removal of Existing features from Other Historic Periods, and Recreation of Missing Features from the Restoration Period.


Rehabilitation Projects are commonly known as adaptive re-use projects where a building is reworked to better accommodate a current use while still retaining its historic features. It is important to note that with Rehabilitation Projects, new additions to the building cannot alter the appearance of the existing features of the building such as adding a mezzanine whose floor plate crosses through window planes, or lowering the ceiling below the top of the windows. However, windows can be added to party walls and non-dominant facades if they are compatible with the building design while not matching windows on character defining elevations.

The Steps for Rehabilitation:

Identify, Retain & Preserve, Protect & Maintain, Repair, Replace, Design for the Replacement of Missing Historic Features, Alterations/Additions for the New Use.


Reconstruction Projects constitute a reconstruction of a demolished or missing historic building and/or feature based upon reliable documented evidence.

The Steps for Reconstruction (if any features remain):
Identify, Protect & Preserve.

To learn more about the restrictions and suggestions identified above, visit the Secretary of the Interior’s Standards for the Treatment of Historic Properties’ website.


With these four categories outlined, there are several ways in which all of the project types can be updated to improve their energy efficiency:

  1. Additional Insulation may be added in out-of-site areas such as attics, unheated cellars, crawlspaces, etc. It is important that added insulation avoid high moisture content areas to prevent damage of historical elements and features, and it must not affect the interior or exterior appearance of the building.
  2. Original windows, louvered blinds, and exterior shading devices should be maintained to utilize their inherent energy conserving properties.
  3. Interior shades, blinds and, if appropriate, awnings may be added to improve efficiency.
  4. It is acceptable to recaulk windows and replace and/or add weather stripping to improve the thermal efficiency of the windows so long as it does not detract from the overall historic appearance.
  5. If a non-operable window is beyond repair and must be replaced, operable windows may be used to capitalize on energy conserving potential so long as the appearance of the window matches that of the original.
  6. Non-damaging exterior storm windows and shutters or interior storm windows “with air-tight gaskets, ventilating holes, and/or removable clips to ensure proper maintenance and to avoid condensation damage to historic windows” can be added to improve thermal efficiency. In many cases, they can be ordered with Low–E glass or laminated glass to further improve the performance of the windows.
  7. In Rehabilitation projects, additions such as skylights can be added to non-character defining elevations to help improve natural daylighting.

So how do you go about finding windows that meet all of the criteria in these categories? Window manufacturers have begun developing windows that meet the stipulations outlined in these guidelines to make is easier for designers to find quality windows that will work within these projects. Jeld–Wen and Kolbe Windows & Doors have created lines of historically designed windows, and Dynamic Architectural Windows and Doors are a custom order company that produces thermally broken steel windows to name a few of the options available for designers today.

So while working with historic buildings can be difficult, there is great energy saving potential to be found in many historic properties. As mentioned earlier, historic buildings are often inherently designed to be energy saving, and the guidelines for Preservation, Restoration, Rehabilitation, and Reconstruction allow some flexibility to accommodate additions and changes that can improve the energy efficiency of the building. To learn more information, visit the National Park Service’s website or contact your local Historic Preservation Officer to help you determine the best treatment method for your next historic project.