The Home Owner's Guide to HVAC: The Envelope and Green Technologies

By Rob Turner P.E.

How green is green? The average homeowner is usually well-informed about which products and concepts are considered “green,” but they seem to have less of an understanding of how they compare, and which things work the best for the lowest investment. Did you know that 40 percent of the average home power bill is dedicated to air conditioning in warm climates? Further, energy is spent on cooking, hot water, clothes dryers, and such. Did you know that solar hydronic panels are way more efficient than solar voltaic panels? How about instantaneous water heaters? Are they good? Homeowners need to make dozens of decisions about which products or services they need in order to make their home the most efficient it can be for the given budget. Do you have mold or humidity problems? If you want to learn about things like the home envelope, HVAC, hot water, and electrical systems, this book is for you. It is written in plain English, and covers all the bases. Also, given are tips on saving the environment from an engineer’s perspective. The author is a big fan of the environment, but does not like “greenwashing.” The generic definition of greenwashing is the practice of making an unsubstantiated or misleading claim about the environmental benefits of a product, service, or technology. Pros and cons of various “green” products are discussed so that the homeowner can understand the smartest purchases and practices. One of the things you will learn is that the envelope of the home is just as important as the HVAC. You have to understand both to be successful. The envelope is thoroughly discussed as well as HVAC, plumbing, electrical, and the various green technologies.

• Language: English
• Publisher: Page Publishing, Inc.
• Release date: Aug 4, 2021
• ISBN: 9781662440113

Book preview

Chapter 1

Introduction

My name is Rob Turner, and I am a registered professional HVAC Engineer. I have a mechanical engineering degree from Clemson University, 1995, and got my license in 2000. I worked for ten years in Spartanburg, South Carolina, where I was trained by the two best engineers in the state of South Carolina. For the last fifteen years, I have been in Charleston, South Carolina. I am an owner/partner with Charleston Engineering where we design HVAC, plumbing, electrical, and fire protection systems for buildings via stamped drawings. Charleston is in the heart of the South and has a hot, humid environment. I have designed HVAC systems for all types of buildings, including historic buildings, theaters, office buildings, schools, labs, restaurants, and high-end homes, among other types. I have experience with all HVAC concepts including split systems, VAV (variable air volume), geothermal units, packaged units, VRF (variable refrigerant flow) like Mitsubishi City Multi systems, and chiller and boiler water systems. I regularly inspect homes and office buildings with humidity problems where I look at the HVAC systems and the envelope to identify problems and recommend solutions. I have been an expert witness for a number of legal cases for homes and buildings in a lawsuit over humidity damage. I won an honorable mention in an international competition for ASHRAE for my high-efficiency design of a lab hood facility (in the hot, humid, South). Finally, I have volunteered regularly as an ACE Mentor in local high schools for students interested in engineering since 2012.

In talking with homeowners and business owners over my career, I have found that the majority of people I deal with do not fully understand HVAC and/or the building envelope. I will use the word envelope quite often, so I need to define it. The home envelope is the exterior insulation system of the home which protects the inside from humidity and heat or cold.

Figure 1: The envelope of a home.

So the envelope includes the attic with insulation, the insulated walls and windows, and the slab, basement, or crawlspace with insulation. The envelope must be continuous around the home like a cooler around drinks and ice. This book will focus on cooling air conditioning concerns as opposed to heating concerns. It is intended for homes in cooling-dominant locations which are hot and humid. These are most of the southern states from Texas to North Carolina, particularly in the Warm-Humid zone.

Figure 2: ASHRAE map showing the warm-humid zone.

It is my goal to describe the equipment and the science without fancy equations and complex diagrams. I will focus on providing honest and experience-based information to help the reader understand and make wise choices.

There are many falsehoods, wives’ tales, and incorrect information out there regarding MEP (mechanical, electrical, and plumbing). There are even more bogus products out there that claim to save energy, provide free energy, or save 40 percent, 50 percent, and even 75 percent on your power bill. The salespeople for these products are very good at what they do, but I will tell the truth about the various concepts and products so the reader can make good decisions for their home without being manipulated.

Cost is a very important item to discuss when talking about the best MEP concepts for the home. I can’t give exact costs for everything because labor rates and material costs change. Having said that, I can provide good relative costs, payback considerations, and general advice about the costs of various levels of equipment. For example, air conditioners come in different efficiency ratings with a full range of costs from budget models to ultrahigh efficiency. The ratings are described by the SEER rating (Seasonal Energy Efficiency Rating). Think of SEER like miles per gallon in a car (higher numbers are more efficient). As of today the SEER for the typical home air conditioner ranges from 14 SEER to 21 SEER and sometimes higher. What is the best choice for the homeowner? You have to look at funds available and the payback. The payback is basically the number of years it will take for the higher energy efficiency to save enough money on your power bill to recoup the extra money spent on the higher efficiency units. This will be discussed in further detail later.

There are many things the homeowner can do or change in the home that will save money and/or improve the conditions. The goal is to do as much as you can yourself. However, I do understand that contractors must be called in many cases. If you are buying or building a house, many wise decisions can be made if the homeowner is properly educated. Education is more than knowing which products are said to be very green. How green is it? What is the payback? What are the pros and cons? Hopefully, this book will give the reader a good comfort level to make the best decisions on purchases and renovations.

Did you know that it is typical for 40 percent of your power bill to be dedicated to air conditioning? Why is air conditioning so expensive? First of all, it can be really hot and humid outside. An air conditioner uses energy to lower the temperature in the home, and it uses further energy to lower the humidity. In the early life of the air conditioning industry, 78 degrees in the home was luxury. Nowadays, most people set their air conditioner on 72 or 74 degrees. Every degree costs money, and probably more money than you think. Secondly, most homes have a lot of windows. Even the highest efficiency window is vastly less efficient than an insulated wall. Next, you have more equipment in homes. Equipment like computers, lights, refrigerators, and large flat-screen TVs produce heat. This equipment heat has to be overcome by the air conditioner. Exhaust adds cost to air conditioning. Every bathroom has an exhaust fan. The newer kitchens have larger and larger exhaust hoods for the range oven. Exhausting this air basically removes air conditioned air from the home and pulls in hot humid air from the outside to replace it (which is called make up air). The air conditioner will be taxed every time you use the exhaust. People give off body heat and humidity themselves. Did you know that the average person produces 100 watts of heat energy per hour just walking and sitting in the home? So the air conditioner has