Building Envelope Analysis

May 19, 2023 by

Building Envelope Analysis

Today’s topic is Building Envelope Analysis, but before we start …

“In life you need either inspiration or desperation.”

~ Tony Robbins

Webster’s dictionary defines INSPIRATION as “something that makes someone want to do something or that gives someone an idea about what to do or create; a force or influence that inspires someone.”

DESPERATION is defined as “a strong feeling of sadness, fear, and loss of hope.”

You are at a point in your career where you have:

  1. Been supported, encouraged, mentored, and positively influenced – INSPIRATION, or
  2. Been left to fend for yourself, learning to be an engineer on your own – DESPERATION

Although in any endeavor, there is a certain amount of learning-by-experience and trial-by-fire, the best way for someone to realize and reach their full potential is to have a mentor. Better yet, have more than one mentor who teaches, guides, and encourages.

Unfortunately, the sad truth is that most engineers who run their own business, or who ascend to a position of leadership in an already established firm, learned what they know on their own. Either they didn’t have positive, knowledgeable, and encouraging role models, or they arrogantly shunned available support and are now passing these traits on to the next generation of engineers.

However, there are alternatives.

EngineeringDesignResources.com‘s goal is to help, inform, encourage, and support those working in building design and construction. Our sole purpose and passion is to be the “something that makes someone want to do something or that gives someone an idea about what to do or create” through information, resources, and community. Take what you need from these posts, ask for help when you need it, and then, we can then pass that knowledge and INSPIRATION on to others.

BUILDING ENVELOPE ANALYSIS

As a building designer, one of your charges is to design and specify heating, ventilating, and air-conditioning systems for buildings. These systems can be as simple as ventilation fans for air movement or indoor air quality up to highly specialized air treatment systems. In addition, you may be required to provide input into the building design, especially when it comes to building materials.

Both of these functions require knowledge and mastery of Building Envelope Analysis. By learning these skills, you make yourself a valuable part of the whole Design Team. You will gain the respect of Architects, Owners, and Contractors as well as other Building Design professionals.

For your Test-Prep Resource Library©*, you want to find and include the following Building Envelope Analysis information – density, conductivity, conductance, and resistance or U-values – for:

Building Materials

Load Calculations for Building Envelope Analysis:

  • For roofs, walls, and glass conduction: q = U x area x CLTD
  • For glass solar: q = area x SC x SHGF x CLF
  • Conductivity = k in BTU per (hour)(square foot)(temperature difference)
  • Conductance = C in BTU per (hour)(square foot)(temperature difference)
  • Resistance (R) = 1/k or 1/C in (hour)(square foot)(temperature difference) per BTU
  • U-value = 1/R in BTU per (hour)(square foot)(temperature difference)
  • Available from ASHRAE or search online:
    • Cooling Load Temperature Difference (CLTD) tables
    • Shading Coefficients (SC) tables
    • Solar Heat Gain Factor (SHGF) tables
    • Cooling Load Factor (CLF) tables
  • Weather Data

NOTE: As per the NCEES Examinees Guide, books, notes, notebooks, etc. are no longer permitted in the testing room. This does not diminish the importance of a Test-Prep Resource Library© as a method of study and preparation. Taking the time to assemble your own library will naturally help you categorize and document your study materials, help you determine what’s essential to pass the exam, and keep all your resources in one easy to access tool.

In conclusion, using this Building Envelope Analysis information and a few quick calculations, you can be a driving force in the overall building design and system selections – building skin, structural, and HVAC. Set up a model on a laptop computer or tablet prior to a design meeting in order to quickly change and modify building dimensions, directions, and materials. You will assist the Design Team and Owner in making decisions, and you have made yourself a valuable part of the Project Team.

Building Envelope Analysis

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Heating and Air Conditioning Loads

May 18, 2023 by

Heating and Air Conditioning Loads provide the design engineer with rates of heat transfer through the building materials and surfaces – walls, floors, roofs, windows, etc. – and the contribution to the heating or air conditioning systems by various building components – people, lighting, equipment, etc. With this information solidly in hand, the engineer can proceed to design the multiple components of the building’s HVAC system.

Heating and Air Conditioning Loads

Central Plant:

  • Chillers
  • Cooling Towers
  • Boilers
  • Pumps

Air Side:

  • Air Handling Units
  • Ductwork
  • Exhaust Fans
  • Outside Air Systems
Summer Heating and Air Conditioning Loads

The peak – or highest – cooling load during the summer is that amount of heat removed to maintain the room’s design temperature. Factors that contribute to a building’s cooling load are:

  • The sun, which heats up the building exterior and then transfers into the building through walls, roofs, windows, etc.
  • Items within the building that produce heat such as people, lighting, equipment
  • The building’s geographic location
  • Maintaining the interior design temperature
Winter Heating and Air Conditioning Loads

The peak – or highest – heating load during the winter is the amount of heat added to maintain the room’s design temperature. Factors that contribute to a building’s heating load are:

  • Heat lost to the outdoors through walls, roofs, windows
  • The building’s geographic location
  • Maintaining the interior design temperature

The loads calculated for both heating and cooling are necessary to accurately size the equipment – heating and cooling systems, the air distribution systems – ductwork, diffusers, terminal boxes – and the ventilation system. A Heating and Air Conditioning Loads system that is incorrectly undersized will not be able to keep the building at the desired indoor temperature as required in the design. And a Heating and Air Conditioning Loads system that is incorrectly oversized will constantly cycle on/off and will be unable to maintain the proper humidity levels within the building. This can lead to larger problems such as equipment damage, occupant discomfort, and mold growth.

Calculating Heating and Cooling Loads

Heating and Air Conditioning Loads are mostly calculated using computer programs such as Elite Software’s CHVAC and RHVAC programs, Carrier Corporation’s HAP program and Trane’s TRACE program. These and many other programs on the market are highly specialized, can require an extreme amount of data input, produce large quantities of output, are very accurate in terms of Heating and Air Conditioning Loads, and are usually quite expensive. These programs are often necessary when it comes time to perform the actual equipment sizing, selection, and specification.

A design engineer who didn’t spend the time manipulating wall construction, roof construction, occupancies, equipment loads, and lighting configurations would not be providing the building owner with professional service. In designing the building’s HVAC systems, it is imperative to use the most realistic and accurate computer model of how the building will function in both heating and cooling environments and at different times of the day, week, month, or year.

But there are times when this accuracy and time/effort investment are not fiscally reasonable. For example, in the early stages of the design process, when the owner, architect, and engineer are meeting to determine the best course of design to pursue, it is important to understand the impact of the HVAC system on the overall design especially as it relates to space requirements. It becomes convenient to have a method by which the engineer can estimate these space requirements by quickly sizing the equipment required based on the current architectural design and extrapolating out to come up with mechanical room sizes, access into/out of and overall location within the building.

Load Calculation Worksheet

The Heating and Air Conditioning Loads Calculation Worksheet is one-page “snapshot” design tool based in Microsoft Excel utilizes psychrometric equations to solve and provide data for heating and air conditioning designs. The simplicity and unique compactness allows the design engineer to input, change, and manipulate multiple HVAC load variations, altering and adjusting on the spot, with the output immediately available on screen. The benefit to the engineer, architect and owner is in the speed of decision making. If the design team can quickly arrive at the most beneficial building design with respect to building materials, site orientation, occupancies, hours of operation, etc., this saves the overall project budget in terms of time – meetings, phone calls, design – money and frustration.

Air Handling Unit Selection Worksheet

The Air Handling Unit Selection Worksheet is designed to be used in conjunction with the Heating and Air Conditioning Loads Calculation Worksheet, although it can stand alone. The Air Handling Unit Worksheet uses parameters such as sensible load, latent load, and total load to provide the remaining variables needed to select and specify air handling units. The worksheet also allows the design engineer to input known static pressures to get a more realistic estimation of the overall Internal and Total Static Pressures for the units.

Heating and Air Conditioning Loads

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HVAC Load Calculations Worksheet

May 18, 2023 by

HVAC Load Calculations Worksheet

HVAC Load Calculations Worksheet specifically accelerates initial design decisions and system selection. The simplicity and unique compactness allows the design engineer to input, change, and manipulate multiple HVAC load variations on the spot, with the output immediately available on screen. The output is a one-page form showing all the pertinent data and design conditions needed to accurately select the proper heating, ventilating, and air-conditioning equipment to satisfy the space conditions.

Other HVAC Worksheets

Not only are there are many HVAC Load Calculations Worksheets on the market that are highly specialized, require an extreme amount of data input, produce large quantities of output, are very accurate in terms of HVAC loads, but they are usually quite expensive. These programs are often necessary when it comes time to perform the actual equipment sizing, selection, and specification. A design engineer who doesn’t spend the time manipulating wall construction, roof construction, occupancies, equipment loads, and lighting configurations would not be providing the building owner with professional service. It is imperative to use the most realistic and accurate computer model in designing the building’s HVAC systems. This will determine how the building will function in both heating and cooling environments and at different times of the day, week, month, or year.

Stages

However, there are times when this accuracy and time/effort investment are not fiscally reasonable. For example, in the early stages of the design process, when the owner, architect, and engineer are meeting to determine the best course of design to pursue, it is important to understand the impact of the HVAC system on the overall design especially as it relates to space requirements. It becomes convenient to have a method, such as the HVAC Load Calculations Worksheet, by which the engineer can estimate these space requirements by quickly sizing the equipment required based on the current architectural design and extrapolating out to determine mechanical room sizes, access into/out of, and overall location within the building.

At this stage of the design, the owner, architect, and engineer make preliminary decisions and select the type of system depending on the total load, the desired system control, the required space setpoints, etc. Further information and design considerations on the HVAC Load Calculations Worksheet topic are available on the HVAC Loads page.

HVAC Load Calculations Worksheet

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EngineeringDesignResources.com prohibits the use or reproduction of this material by any means, graphic, electronic, or mechanical, except in the case of brief quotations embodied in critical articles and reviews. This includes photocopying, recording, taping, or by any information storage retrieval system.

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Air Handling Unit Design Worksheet

May 18, 2023 by

The Air Handling Unit Design Worksheet compliments the HVAC Load Calculation Worksheet. This worksheet assists the design engineer in accelerating initial design decisions and system selection. The simple and straight forward worksheet layout allows the design engineer to input, change, and manipulate multiple AHU variations to arrive at a suitable selection. The output from the worksheet is a one-page form showing all the pertinent data and design conditions needed to accurately select the proper air handling unit equipment to satisfy the space conditions.

Air Handling Unit Design Worksheet

Other AHU Programs

There are other Air Handling Unit Design Worksheet programs on the market that require more data input, produce large quantities of output, are very specific in terms of air handling unit selection. These programs are either manufacturer specific or are very expensive. The use of these programs is often necessary and beneficial when it comes time to perform the actual equipment sizing, selection, and specification. A design engineer who doesn’t spend the time manipulating air handling unit configurations would not be providing the building owner with professional service. It is imperative to design and select the most realistic and accurate systems and equipment for the building so that the owner receives the most economical and functional building possible. However, due to budget or time constraints, there are times when the more sophisticated unit selection programs are not fiscally reasonable.

For Example

In the early stages of the design process, when the owner, architect, and engineer are meeting to determine the best course of design to pursue, it is important to understand the impact of the HVAC system equipment on the overall design especially as it relates to space requirements. It becomes convenient to have a method by which the engineer can estimate these space requirements by quickly sizing the equipment required based on the current architectural design and extrapolating out to come up with mechanical room sizes, access into/out of and overall location within the building.

It’s also at this stage of the design when the owner, architect, and engineer make preliminary decisions about the type of systems that will be used. The team can narrow down or select the types of systems, depending on the total load, the desired system control, the required space setpoints, etc. Further information and design considerations on the Air Handling Unit Design Worksheet can be found on the HVAC Load Calculation Worksheet.

Air Handling Unit Design Worksheet

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EngineeringDesignResources.com prohibits the use or reproduction of this material by any means, graphic, electronic, or mechanical, except in the case of brief quotations embodied in critical articles and reviews. This includes photocopying, recording, taping, or by any information storage retrieval system.

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Any resemblance in the images in this material to actual people or locations is merely coincidental. EngineeringDesignResources.com prohibits reprinting, copying, changing, reproducing, publishing, uploading, posting, transmitting, or using in any other manner images in this material.

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