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In the summer of 2009 my wife and I purchased a home in a small community outside Boulder, Colorado named Niwot. Niwot was named after a 19th century Arapaho Indian chief by that name. It means “left hand”. Consequently, there are a lot of local “left hand” this and “left hand” that. Continue Reading →




Things are different when you are over a mile above sea level. There’s less air at this altitude. The density of the atmosphere at sea level is 0.075 pounds per cubic foot. That means that every cubic foot of air weighs 0.075 pounds. In Denver, Colorado with an elevation of 5,280 feet above sea level, the air density is 0.0617 pounds per cubic foot. That means that there is only 82.3% of the air in Denver as there is at sea level locations. The air density in the Colorado mountains is even less. The altitude of Aspen, Colorado is 7,928 feet above sea level.  Consequently, the air density there is just less than 0.0554 pounds per cubic foot, or about 73.9% of that found at sea level. The reduced air density experienced at high elevations does not just make it more difficult for individuals to breathe; it impacts the operation and performance of all sorts of mechanical equipment. This article will focus on the impacts of altitude on the sizing of natural gas piping. Continue Reading →



It seems that there is always one room in a house that is coldest in the winter and warmest in the summer. I know – I had that room for a while as a child.

Airflow is “self-balancing” in all air handling distribution systems. That is not to say that the proper amount of airflow gets delivered to each room, but the pressure drop of each zone from the source of flow is exactly equal with each branch and/or air device. Residential air distribution systems rarely have balancing devices installed within the supply ductwork. Consequently, the airflow delivered to each room within the house, or the zone in larger systems, is equal to the proportional share of airflow based upon equal pressure drop from the fan. The pressure drop from the fan to each supply air device (grille or diffuser) will be exactly the same. This occurs automatically by the system adjusting the airflow in each branch duct such that the resultant pressure drop in that branch is equal to all the rest of the branches. Continue Reading →


David R. Olson, PE, LEED AP
Most thermostats utilized in commercial applications include one or more operating functions. They all can control to a heating or cooling setpoint, or both. Some thermostats include manual changeover from heating to cooling and visa-versa, and some have a setting which will permit the thermostat to determine if heating or cooling operation is necessary. Most thermostats sold today include automatic set-back features which promote energy savings during unoccupied time periods. Many commercial thermostats have an “on-auto” fan switch. In my experience, I have seen numerous examples of this control feature being mis-understood. I will attempt to clarify this confusion in this article. Continue Reading →


David R. Olson, PE

I was recently asked to consider the difference between “Engineering” and “Design”. The following represents my thoughts about this important distinction.

State of Colorado Definitions of Engineering

The licensing requirements for professional engineers are defined by statute in each State. In Colorado, Statute 12-25-114 defines the minimum requirements for registration as a Professional Engineer. This statute requires that an individual first be registered as an EIT (Engineer-in-training). To obtain EIT status, and individual must have completed a 4-year engineering curriculum and successfully complete an 8-hour Fundamentals of Engineering examination. Following four additional years of progressive engineering experience, an individual may apply for admission to a second 8-hour Principles and Practice of Engineering examination. Within this application, the individual shall prove technical competence prior to admission to the examination. Upon satisfactory completion of both exams, the individual may be licensed as a Professional Engineer. Continue Reading →


David R. Olson, PE, LEED AP, FASHRAE August 15, 2018

Throughout my career I have conducted HVAC and plumbing design for many new and remodel projects, on virtually every sort of building type imaginable. When I am doing a re-adaptation of an existing building the first step for me is to conduct a thorough survey, focusing on HVAC, plumbing and fire sprinkler components. As part of that work, I document model numbers and serial numbers for all the existing equipment. Sometimes there are equipment installations with specific components that are less familiar to me. I wonder, is this equipment installed the way the manufacturer intended it. Wouldn’t it be nice if there was a copy of the original installation manual available for me to look at? Continue Reading →

Cleanouts – Who Needs ‘em

Cleanouts – Who Needs ‘em

David Olson, PE

When I consider the cost of a properly installed plumbing system, I feel that the cost of installing adequate floor and wall cleanouts is negligible. I have been told by building engineers that more cleanouts is always better – it allows them to maintain their plumbing waste and vent system more effectively. Unfortunately, when we introduce solid material into a plumbing system, sometimes it gets clogged up. Perhaps there is a section of pipe that is installed too steep. Consequently, the liquid waste quickly runs down the pipe, and the solid waste tends to stay behind. The presence of a properly located cleanout won’t correct the pipe slope issue, but it will make dealing with it much simpler. Continue Reading →

Horizontal Offset of Sanitary Vents Below Flood Rim Elevation

David Olson, PE

I did my first building code plan review in 1991, a grocery store in Brighton, Colorado. I worked as a sub-consultant to an architect who had a good relationship with the local building official. I took on the project with a little anxiety, never anticipating that 24 years later I would still be doing code reviews. At that time, most building departments in the State of Colorado were enforcing the Uniform Code’s – Building, Mechanical and Plumbing. Today’s International Code’s are quite similar in content and organization, with some noticeable variations. For example, Chapter 9 of the UPC was entitled Vents, and Chapter 9 of the IPC is called…Vents. Go figure. The International Code Council also saw fit to break fuel gas piping into its own code document, and has supplemented the Uniform codes with numerous specialized code books such as the Private Sewage Disposal Code, the Residential Code, the Existing Building Code and the Property Management Code to name just a few. Continue Reading →





I believe that if you ask this question to practicing attorneys and experts involved in construction defect litigation activities, 9 out of 10 would say no. However, I have witnessed many professionals who seem to disregard professional ethics on behalf of their clients on each case they work on. Each time I have testified, either in depositions or in a courtroom, it seems that I have encountered individuals who will say anything for the benefit of their clients, and void of engineering proof, regardless of how preposterous their statements may be. I have asked myself, do they really believe this?? And, pondered, do they really not understand what they are saying?? My conclusion…of course they know better, the truth is just inconvenient. Continue Reading →