Design Concepts – Daylighting Part 1

What is Daylighting?

The simplest definition is – the light that comes from the sun. In this post we will examine a very basic overview of daylighting. In other posts we will take a more in depth look at design strategies and building case studies to develop a greater understanding of why daylighting is so important and effective.

When talking about daylighting, think of it as natural light vs. artificial light. Daylighting design is more than just large windows and skylights. Careful thought and consideration must be made to optimize natural light for stimulating and comfortable spaces.

The use of daylighting creates a pleasing and productive environment. By creating a direct link to the outdoors a designer can deliver a pleasing distribution of natural light. In addition, proper use of daylighting can influence the mood of occupants within an environment.

Why is Daylighting Important?

Artificial lighting accounts for about one quarter of the energy consumption in the United States. In commercial buildings alone, lighting accounts for one third of the energy consumption. Daylighting reduces the amount of lighting fixtures needed, as well as reducing the amount of time fixtures are on.

There are also the indirect factors of artifical lighting that contributes to electrical loads. Heat from lighting fixtures add to the cooling needs of a building. Also, the production and transportation of lighting elements and fixtures consumes energy. All of these factors add cost, time for construction, and maintenance to the design and building process.

Also, study after study has shown that natural light has positive psychological impacts. Natural light makes people more productive, happier, and less stressed. Utilizing proper daylighting techniques saves money, energy, and increases productivity.

Examples of Daylighting Design

Daylighting involves the thoughtful implementation of various building elements. Design strategies must account for glare, depth of light, heat gain, climate/weather factors, and light intensities at various times. These issues are addressed with elements such as shading devices, opening sizes, opening spacing, glass propoerties, building materials, and glazing reflectance.

Daylighting design is not just putting in as many windows as possible. Dayighting design is about maximizing the effects of natural light in a building environment. Also, the design must minimize the undesirable effects of natural lighting. We will examine the design factors and techniques in Part 2.

You are more than welcome to contact us regarding any questions you may have regarding how to incorporate Daylighting into your design or if you would like Gustin Design Services to give you a more in depth information session please contact us –

Sound Control – Part 1 – STC and NRC


Today we are going to discuss the technical factors to consider when thinking about sound control. When thinking about acoustics, we want to focus on two major ways that sound moves – how sound travels within a space, and how sound travels from space to space. Once we understand how sound travels we can design systems to control the impact that sound has on the space.

In trying to determine the ways that acoustics can be controlled, architects looks at a number of factors. The most common ways to think about sound control is with understanding the Sound Transmission Class (STC) of a material and the Noise Reduction Coeffecient (NRC) of a material. There are other ratings of materials and assemblies that give the designer information about sound control, such as the Impact Isolation Class (IIC), and your designer will have to consider such information in order to design the best system. However, in most cases the greatest impact of noise control will come from understanding the STC and NRC, and when each one is important given the situation.

Sound Transmission Class (STC)

STC (Sound Transmission Class) is a rating that represents a material or product’s ability to block sound from travelling through assemblies (wall, ceiling, floor or other building assembly). In other words, how well a product or materials stops airborne noise transferring from place to place. 

The higher the STC rating, the better a material’s ability to block sound.

A limitation of STC, however, is that it only measures certain frequencies. This means it doesn’t accurately capture how well a material blocks low frequency sounds such as common noises that come from airplane engines, large trucks, and heavy equipment.

Noise Reduction Coefficient

NRC (Noise Reduction Coefficient) is a rating that measures the amount of energy absorbed when it strikes a particular surface. It’s how well a product or material reduces the echo into the space’

An NRC rating of 0 indicates complete reflection, meaning a material bounces 100% of the sound back into the room. An NRC rating of 1.0 indicates perfect absorption, meaning a material soaks up 100% of the sound and no echo is put back into the room.

While STC and NRC differ, both deal with airborne sound, however, vibrational sound must be taken into account as well, and that is where Impact Isolation Class (IIC) is examined.

Impact Isolation Class (IIC)

IIC (Impact Isolation Class) is a rating that measures impact noises. Impact noises are erratic sounds caused by footsteps, dropped objects, equipment vibrations, etc. The impact causes vibrations in construction assemblies and those radiate sounds to other locations.

The IIC rating is represented with whole number. A larger number means more impact sound is being blocked.

Blocking and absorbing airborne and impact sounds are key to designing sound control systems.

Which One is More Important?

Well, which rating, NRC or STC, is more important for controlling sound. Unfortunately, the answer is – it depends. Remember, STC measures how well a product keeps sound from escaping the room to an adjacent space. NRC is a measurement of how well a product makes the room you are in quieter.

If you are in a noisy room, like a daycare classroom or school gymnasium, you want products with a higher NRC on the walls or ceiling to absorb the sound, making the room less noisy.  If you are in a office or medical clinic where you are talking about sensitive topics that you don’t want people in adjacent rooms to hear, then you should focus on a product on the wall with a high STC. In certain cases, such as hotels and multi-family units housing, both NRC and STC will play a big role in determining the design and product selection.

Similarly, in Sound Control – Part 2 we will discuss and examine examples to maximize acoustical design for sound control.

Remembering I.M. Pei (April 26, 1917 – May 16, 2019)

As the tributes and memorials are pouring in, the architecture world remembers the life and career of I.M. Pei, who passed away on May 16th, 2019. He was a major influence within and outside of architecture. There are an abundance of articles and features that highlight his influential work and approach to design. The impact that Pei had on future generations can not be undersold. Pei’s work and legacy made him a celebrity that very few from the design world can ever realize.

Favorite Work

Perhaps his most famous design is the pyramid at the Louvre in Paris, which is elegant and artistic in it’s own right. However, the Kennedy Library is the most accurate representation of the architectural process that architects encounter. The design process was contentious and frustrating for Pei. Multiple changes to the scope of work, delays, and jurisdictional interference derailed Pei’s early concepts.

Originally, he wanted to create a giant glass pyramid, similar to the Louvre, but opposition to how the style and forms related to the nearby buildings led to that vision being scraped. As the years passed, many designs and re-designs proposed, more delays occurred, and conflicts dragged the project into the territory of weighing Pei down. Eventually, the library was approved and constructed even though the final design was far removed from his original vision. Pei admitted he was unsatisfied with the final product, but his talent and expertise created a beautiful building that marks what Pei still considered “the most important commission” of his career. Only a talent like Pei is able to create this striking of a library with all the problems and baggage that accompanied it.

There is no way to do justice to his life and career in tributes, articles. or blog posts. However, every working or aspiring architect should pay tribute to such an important figure in our industry. As cliche as it may sound, the architecture community lost a legend when Pei passed away. But, his work and influence will live on.

Navigating the Building Code – Part 4 (Occupant Load)

This installment of Navigating the Building Code examines Occupant Load, how to calculate the Occupant Load, and how that calculation can affect the building design.

What is Occupant Load?

Occupant Load is defined by the International Building Code as “the number of persons for which the means of egress of a building or portion thereof is designed.” So, what does that actually mean?  In the most general terms, it means it is the maximum amount of people that can occupy a space so that each person can safely exit the space as required.

How is the Occupant Load Determined?

In order to determine the occupant load, you first must calculate the area of the space in question.  Typically, you must breakdown the project as a whole into smaller parts and determine the area of each individual part.  Each individual part would then be classified by the function of the space.

For example, if within a library there were reading rooms and library stacks, the floor plan would need to be viewed in terms of each space.  So, if you had 2 reading rooms that are 30’x40′, you would have 2,400 sf of reading rooms (2X30X40).  Then, if the library stacks area was 50’x100′, you would have 5,000 sf of library stacks.  After determining the area of each space then you would reference the load factor in the code, in the IBC it is shown in Table 1004.5 (figure 1.1).  Then you simply divide the area by the occupant load factor with the result being the occupant load for that space.  Finally, continue determining the the occupant load for each space and then add all of the occupant loads together to determine the occupant load for the project.

Occupant Load TableFigure 1.1

From our example above, we can determine the library stacks occupant load by finding the load factor in the table above (100 gross) and the known area (5,000 sf).  So our occupant load for the the stacks area would be 5,000 sf/100 = 50 Occupants.  Then, we would just continue with each space for the entire project and add all the occupants together.

One thing to keep in mind is whether the load factors are calculated using gross or net.  Gross is the total area of a space, where as net is calculated using only occupiable space.  The determination of whether a space is considered net, gross, or any other special cases are laid out in the code, but is more detail then we need to explore at this time.

How Does Occupant Load Affect the Design?

Occupant Load is the driving force of many aspects of design.  Some of the elements that are directly tied to the number of occupants are the required number of exits, required number of restroom plumbing fixtures, the width of stairs, the clear width of doors, the width of the clear egress path, types of door hardware, corridor fire-resistance, and a number of other items to ensure the health, safety, and welfare of people within the structure.

You are more than welcome to contact us regarding any questions you may have regarding Occupant Loads or if you would like Gustin Design Services to give you a more in depth information session please contact us –

Navigating the Building Code – Part 3 (Required Plumbing Fixtures)

This installment of Navigating the Building Code examines pluming fixtures and the role they play in planning and space layouts.  Required plumbing fixture counts are the number of each fixture that the code prescribes as necessary.  The number of fixtures directly relates to the size and square footage allocated to restrooms and the plumbing systems.  In the code there is a chart that gives the plumbing fixture calculation factors to determine the number of required fixtures.

“Why can’t we just remove that restroom to save space and make the circulation better?”  More often than you would think this question is posed by a client (typically in a commercial design situation), if there are more than two restrooms (one male and one female), clients tend to think of them as “extra.”  The typical answer is that the code requires it, and the architect tries to move the conversation along.  But, it is important to know what the code actually states and the options available to meet code in the most efficient and cost effective way possible and not view those required restrooms as “extra.”

Residential Applications

Residential fixture counts are more straight forward in their calculations.  Typically, fixtures for residential projects are calculated on the number of units in a facility.  In most cases, only 1 water closet (toilet), 1 lavatory (restroom sink), 1 bathtub or shower, 1 kitchen sink, and 1 washing machine are required per dwelling unit.  The fixture count requirements for residences is a way to prescribe and define that a home needs to have a restroom.  It is important to verify the requirements with the building department and/or authorities having jurisdiction for the project.

Minimum Number of Required Plumbing Fixtures

While the code doesn’t prescribe the number of restrooms in a facility it does state the required number of fixtures (water closets, lavatories, bathtubs and/or showers, drinking fountains, or other fixtures).  How the number of required fixtures are incorporated into the building is up to the architect and client to determine.

The required number of fixtures is based on the occupant load of the building (see Navigating the Building Code – Part 4 – Occupant Load).  Once the occupant load is known, the Plumbing Systems section of the code explains how to calculate the number restroom fixtures required.  In general the larger the occupant load, the more restroom fixtures the client will need in their facility.  When calculating fixture counts, any fractional amounts must be rounded up to the next whole number.  So if the calculation determines that 5.2 lavatories are required, then the facility would need 6 lavatories.  Each occupant classification (see Navigating the Building Code – Part 1 (Use and Occupancy)), will have different requirements for the load factors to calculate the total number of fixtures.

For example, if a facility is a restaurant (occupant classification – Assembly A-2), and the occupant load is determined to be 300 occupants, then the required amount of fixtures (based on IBC 2018 table 2902.1), would be 4 water closets, 2 lavatories, 2 drinking fountains, and 1 service sink.  In this case the client and architect could choose have 2 restrooms, each with 2 water closets, 1 lavatory, and 1 drinking fountain directly adjacent to each restroom (figure 1.1).  A second option would to be 4 single use restrooms, each with 1 water closet, 1 lavatory, and the drinking fountains located as best fits (figure 1.2).  In this second situation, 2 of the lavatories would be in excess of the required amount, but that might serve the functions of the spaces better.  Again, there are options available for the allocation of fixtures to best suit the project.

Restrooms Example 1Figure 1.1Restrooms Example 2.jpgFigure 1.2

Women’s and Men’s Fixture Counts

One major (and sometimes overlooked in the preliminary stages) factor in determining the number of fixture counts is that their needs to be designated water closets for men and women.  The code requires that half the water closets are designated for women and half are designated for men.

In the restaurant example above, 2 water closets and 1 lavatory would be required to be designated for women, and 2 water closets and 1 lavatory would be required to be designated for men.   The two allocations explained above would meet this requirement because of the equal distribution of fixtures.  The example would no meet code if the women’s restroom had 3 water closets and the men’s restroom had 1 water closet.  Even though the total number of water closets would be met (4), the distribution of women’s and men’s does not meet the code (figure 1.3).

Restrooms Example 3.jpgFigure 1.3

Restroom Locations

Another factor set forth in the code, that can play a major role in the space design and layout of a facility, is the need for access to restrooms.  Generally, the general public must be able to access the required restroom designated for the public.  So, a customer or visitor to a structure must be able to follow a safe path of travel to get to a restroom without passing through spaces such as kitchens, closets, storage rooms, and even private offices.  The code contains a few other rules regarding locations, for example restrooms are not permitted to open directly into a room used for food preparation, that are described in the Plumbing Systems section of the code that your architect needs to be familiar with from the onset of the project.

Exceptions and Variances

There are some instances where a project qualifies for exceptions from the required number of fixtures, or a variance can be requested.  Urinals in lieu of water closets for men’s restrooms is a typical exception.  In our restaurant example, a variance can be requested to not have the drinking fountain requirement.  The rationale behind that variance is that the restaurant would have clean, drinkable water available to serve as requested.  The variance would still need to be approved by the authority having jurisdiction.

You are more than welcome to contact us regarding any questions you may have regarding plumbing fixture counts or if you would like Gustin Design Services to do a plumbing fixture count analysis for you project –