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

Entries in energy efficiency (13)


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.


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.


Rehau Eco Smart House Construction Completed in Bozeman

The Rehau Eco Smart House is a project sponsored by Rehau, an international manufacturer of polymer based innovations and systems.  The Creative Research Lab (CRLab) of Montana State University in Bozeman assisted in the design and is monitoring the house, utilizing the lab supervisor and several students from the university to gather comparative research data from the experimental house.  The project uses numerous sustainable systems and materials throughout the house, aiming to compare these different options and use the comparisons to expand the knowledge base of the industry regarding environmental and human sustainability.  In addition to sustainable mechanical systems and products, the house incorporates the concept of human sustainability with elements such as telemedicine and advancements in human comfort and accessibility. 

Technologies throughout the residential construction include geothermal ground loop heat exchange, ground-air heat exchange, solar thermal and photovoltaic panels, vinyl window and door design, hybrid curtain wall, radiant heating and cooling, and tambour cabinetry for accessibility.  Sunlight responsive thermo-chromic glazing was also installed, having innovative technology to automatically tint the window glazing when in the path of direct sunlight, but adjusting to no tint and allowing full daylight to be brought in on cloudy or overcast days.  A thermal storage heat sink was also installed, capturing heat throughout the year and storing it under the patio in the ground to then use for winter heating and snow and ice melting.  The construction of the residence utilized insulating concrete forms (ICFs) on the first floor and structural insulated panels (SIPs) on the second floor and roof.  Together, these systems create a tight building with limited air leaks, providing better occupant air condition and less heat transfer through materials.  Multi-generational living was also a primary design consideration to accommodate three generations in one house.  To achieve this, the team designed an elevator, no door thresholds, smooth flooring materials, and telemedicine communication technology throughout the house so that accessibility was not an issue for the family.  

For more information about the various technologies mentioned or any other information regarding the Rehau Eco Smart House, click here.


Daylighting Guide for Commercial Offices - Part 1

Benefits of Daylit Offices

Providing a daylit space creates a healthier and higher quality interior environment.  Increased individual productivity and human comfort is also found with daylit spaces.  Natural daylight allows for mental and visual stimulation necessary for proper regulation of human brain chemistry.  In addition to health benefits, allowing daylight to enter the space shows substantial energy savings throughout the building.

Design Inquiries for Designing Daylit Offices

Before you begin the spatial programming of the building, a few items should be in the forefront of your mind when deciding.  These inquiries include interior surface design and selection, shading for glare control, and shading for thermal comfort and heat gain control.  Interior surface selection has the opportunity to increase the daylight appearance dramatically, while shading control allows the building to effectively take advantage of natural daylight.

Best Practice Foot Candle Levels

Another thing to keep in mind when designing daylit spaces are the common lighting levels for different spaces.  The following footcandle levels describe the “best practice levels,” or in other words, the goals to achieve as opposed to the average level attained. 

            Reception Area:  5 fc   

           Working Spaces for Simple Visual Tasks:  10 fc

            Performance of Visual Tasks of High Contrast and Large Size:  30 fc

            Performance of Visual Tasks of High Contrast and Small Size or Visual Tasks of Low Contrast and Large Size:  50 fc

            Performance of Visual Tasks of Low Contrast and Small Size:  100 fc

Programming Criteria

When spatially programming the space, ask the following of each space:  Is daylight important for this space?  Are views to the exterior important?  How frequently is this space used?  What time of the day and time of the year will the space be occupied?

An example spatial programming might include the following:  Open Office Space – Daylight and view desired, occupants have individual glare control.  Private Office Space – Daylight and view desired, occupants have individual glare control.  Support Spaces – Minimal daylight or view opportunities required.  Building Core Spaces – No daylight or view opportunities are necessary.

After you have specified the spaces that desire daylight, ask the following of each of the daylight spaces:  What are the minimum daylight requirements?  How crucial is direct sun control?  What is the minimum footcandle level for the task that is performed in this space?  What might be the ideal solar orientation?  What might be the best strategy for providing daylight?  Side lighting?  Top lighting?  Are there maximum light levels required?

TIP for Programming Spaces  

“Daylight and view are typically preferred in areas that are most heavily occupied for extended periods of time, such as open office areas.  Corridors, circulation paths, break areas, copy/print zones or other short term gathering spaces may be tolerate of direct sunlight whereas fixed workstations or reception desks will almost never remain comfortable with the presence of direct sun.”

Space Planning

It is well known that open offices are typically occupied for almost the entire work day, while private offices are only occupied one-third of the time.  Also, since open office layouts are communal spaces, the shading blinds are not adjusted frequently.  This differs from private offices where the ownership is clearly defined, and the blinds are adjusted frequently.  The following values are the recommended distances from the glazing (illumination source) needed to provide adequate daylight and views to all spaces in need.

Locate open office areas within 18-20 feet of the perimeter zone (glazing wall) and at areas where direct sun penetration is limited (North) or less varied (South).

Position individual offices where low direct sun may otherwise be problematic (East and West), while allowing for individual control within the space with manual shading devices.

Top Lighting Strategies

Studies show that top lighting provides the most effective daylight into the building.  Designing them to be a diffuse light source easily takes care of any glare potential.  Compared to side lighting, top lighting covers a much larger area of the space.

Stay alert for part 2, discussing window coverings, shading and exposure tips, furniture influence, and daylighting controls.  For read the full article, click here.


Refining the Southern Window

Breaking down a southern window into components helps to design efficient windows.  These components can be arranged in multiple ways, to design a specific design detailed to the project. 

1.  The Daylight Window and the View Window

The Daylight window’s primary function is to provide a maximum amount of daylight deep into the space from the perimeter.  This window is located above the View Window, or generally above 7’-8’.  Glazing specifications are recommended to be a window glass with a high visible transmission value (Tvis 70% or higher), to allow the most light through the window.  Also, a low solar heat gain coefficient (SHGC .38 or less).

The View window’s primary function is to provide a view to the exterior from the interior.  This window is generally located within the view frame of the occupants, 3.5’ sill height and 6’-7’ head height.  This gives the occupants a view to relax their eyes, reducing eyestrain, while also giving a connection to the outdoor environment.  The glazing specifications for this window are generally tinted to a transmission value of 50%.  This reduction in light transmission reduces the contrast between the brighter window and the darker interior wall surfaces.

2.  Shade the View Window to Block Direct Sun, Eliminate Glare, and Reduce Solar Gain.

An exterior overhang that is about as deep as the window is high (1:1 ratio) will shade a south facing window during the summer months, which will dramatically reduce solar heat gain into the interior. 

In building types such as schools and offices, where the occupant hours are limited to the mornings through early afternoons (until 3 pm), this strategy can be used on the West Elevations.  By the time the sun comes around to the west side, with the sun altitude low enough, the building will be unoccupied.  Heat gain incurred after this time can be night flushed and the space will be cool by the next morning.

3.  Use an Interior Light Shelf to Provide Diffuse Daylight

Interior light shelves provide three major benefits, they block direct sun from penetrating the space through the upper daylight window, they reduce light levels at the perimeter, and they reflect diffuse daylight onto the ceiling plane.  All these benefits together combine to give the space a more diffuse, uniform lighting level.  Illuminating the surfaces such as the walls and ceiling plane makes the space look larger and brighter than it is actually.

A bright white or translucent, matte finish surface is recommended to provide the best light diffusing quality.  This material specification will have less contrast with the bright exterior also.

4.  Provide Adjustable Louver Blinds at the Upper Daylight Window

Interior louver blinds in the upper daylight window can provide direct sun control without significantly reducing the amount of diffuse daylight into the space.  They can be adjusted seasonally or when low sun angles penetrate the space.  They can be specified as mechanical units or manual.

5.  Use a Roll-Down Shade to Control Direct Sun in the View Window

An interior roll-down shade can control direct sun in the view window without significantly reducing the view to the exterior.  It is recommended to use a dark colored surface on the interior of the shade fabric.  This allows for a comfortable view through the fabric, while allowing room darkening capabilities.  Many newer fabrics provide a dark interior surface while maintaining a light exterior surface.  The bright light exterior surface helps reduce heat gain into the space. 

For more information and to read the full article with diagrams, click here.