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.

Lighting for Large Spaces

Large open spaces, such as warehouses, industrial spaces, and big box retail stores, are difficult to light due to the tall and large bays.  There isn’t anything fundamentally different in large spaces compared to small spaces, but the specifics of each design needs to be assessed with much more detail and attention.

Lighting Issues

1. Glare.  High ceilings in large spaces are often accompanied by high brightness fixtures.  Excessive brightness makes working and shopping a challenge. 
2. Uniformity.  Improper lighting distribution creates unnecessary strain on the eye.
3. Vertical brightness.  Users assess the brightness of spaces through the amount of light on ceilings and walls.  Dark vertical surfaces create uninviting cave effect on large spaces.
4. Maintenance costs.  Many large spaces operate 24/7 and have very high ceilings.  Long burn hours on lamps make for more frequent relamping.  If the maintenance is deferred, the space looks neglected and ‘broken’.
5. Energy efficiency.  Lights mounted in tall spaces must produce lots of lumens to make the space feel well lit.  It is advised to use light sources with high lumens to Watt (lumen/W) ratings.

Lighting Options

1. More diffuse lighting.  Using luminaires that are more diffuse can help reduce unpleasant glare.
2. Uniformity.  Pay close to attention to the manufacturer’s spacing to mounting criteria of each luminaire.  When properly spaced, the lighting is much more even, reducing the amount of work the eye has to do when adjusting.
3. Distribution and reflectivity.  Placing luminaires so that more light is on walls and warehouse stacks creates an appearance of a larger, more inviting space.  Surfaces need to have lighter color values in order to reflect the light in the space.
4. Lamp life and lumen depreciation.  More light sources are on the market with longer life ratings.  Longer life and lower depreciation values mean that you get more light over the product life.
5. Energy Efficiency.  Many energy codes allow a watt or less per square foot in big spaces.  When good lighting distribution provides better uniformity, the eye does not need high footcandle levels to see well.  Daylight is an important tool for improving the efficiency of lighting in large spaces.  Skylight and clerestories bring in light during daylight hours, improving color quality, aiding in productivity, and integrates with other controls with the opportunity to shed many loads. 

Lighting for Better Color

1. Ceramic Metal Halide.  CMH lamps offer color rendering index ratings in the 80s.
2. Rare Earth Flourescent. Standard T8s offer CRIs in the 70s, but Rare Earth T8s offer 80s.  These provide better color and more lumens.

With this information, any big box store can be transformed into a vibrant, interesting place to be in.  For more information, click here.

10 Steps to Improving Your Lighting

Developing a single strategy or equation for lighting design is difficult due to the unique specifics of each project.  Following is a list of ten simple steps to improve any lighting design.

1. Switch from cool and warm white lamps to Rare Earth (RE).  Rare Earth lamps give better color quality and produce more light.
2. Switch from magnetic ballasts to electronic.  Electronic ballasts help eliminate flicker and hum, which are very common user complaints.
3. Put more light on ceilings and walls.  Brighter walls and ceilings make the space appear larger and uniform brightness can reduce glare problems, which lead to user eyestrain.
4. Add paint to your lighting tools.  Lighter color values improve the reflectance of the wall surface, improve the efficiency of your lighting design, and make spaces brighter.
5. Include daylight in your lighting design.  Daylight has many benefits, including better color than electric lighting, a connection to seasonal rhythms, and increased occupant health.
6. Illuminate architectural details and artwork.  This technique gives users a sense of depth, shadow, and contrast for visual variety, which is needed for the eye to stay interested and awake.
7. Determine who will use the space.  The age of the occupants changes the amount of light needed for seeing and the amount of glare that can be tolerated.
8. Determine what the users will be seeing.  Visual tasks are the first step to defining when, where, and how the light should be distributed.
9. Calculate the lighting performance of your designs.  Lighting software is easily available and manual hand calculations are not difficult to complete.  Good estimates of the lighting distribution in the space are critical in order to determine an adequate lighting design.
10. Know when to hire a lighting professional – and do so.  Good lighting designers offer a range of solutions, knowledge of equipment, creative applications, and comprehensive project management.

For the complete list, click here.  And for more information on specific questions or projects, please contact us at the IDL_Bozeman.

NEW ADDITION TO OUR WEBSITE!

Three new manuals have been added to our website. 

Two are eQUEST manuals; Module 1: Basic Energy Modeling and Comparative Runs, Module 3: Life Cycle Cost Analysis. These manuals can be found under the SOFTWARE tab, through the eQUEST section or click here.

The third manual is a design guide for daylighting in Montana and similar climates.  This manual gives the tools to optimize the building orientation, glazing specificiations, and window shading devices.  This can be found under the DESIGN GUIDE tab or click here.

Check back often for future design guide and software manuals.  An AGi32 and eQUEST Module 2: Intermediate Modeling will be added soon!

Reminder to complete Night Walks

Buildings are unoccupied during the majority of the year, likely between 5000-6200 out of 8760 hours.  That equates to more than half of the year.  How do buildings perform during this time?  “Night walks” are the key to finding out.  Night walks are walks that are done with a team of building engineers, checking for building systems that aren’t operating properly.  These are very important for the building; frequently the found problems are easily addressed.  This gives the opportunity for immediate energy efficiency and building performance improvements. 

Night walks are done primarily by the on-site building engineer or another member of the engineering or property management team.  The walks should not be solely by one person, as there are safety concerns associated with the walks. 

The walk should begin when the building is in ‘unoccupied mode’.  Many engineers recommend walks on a monthly basis.  At the minimum, walks should be conducted at least each quarter, with at least an hour dedicated to each walk.  The time is highly dependent upon the size of the building; in large buildings, it is about 15 minutes per floor.

Important spaces to walk through and check are mechanical rooms, areas near the top of the building, top of the roof and stairwells, main lobby and elevator lobbies, and a typical tenant space in each HVAC zone.

Feel for air movement, hot/cold temperatures, humidity, static shock, acoustic/physical vibrations, and hot electrical systems. 

Look for brightly lit areas, extremely dark areas, visible condensation, accumulations of dust on surfaces, blocked air diffusers, and water spots or standing water.

Listen for airflow, rattling, humming, high-pitched radio static, running or dripping water.

Smell for food, trash, or chemical odors, moldy odors, and overheated mechanical/electrical systems.

For additional information and specifics on what to look for, information can be found at the Better Bricks website.  The website also has four short videos, a brief, and a system diagnostic tool kit to provide the probable cause for the problems found.