Homes built today may include a number of mechanical systems, and for each function that those systems serve, a number of choices in components are available. The primary systems used in most homes are heating, ventilation and cooling (HVAC) and water heating. Some homes employ onsite sewage treatment (septic) systems. Green homes may include rainwater and graywater systems. More high-performance homes are embracing new technologies in electrical energy management, including smart lighting and appliances, as well as onsite renewable energy production systems.
Certainly advances in technologies over the last few years have resulted in far too many brands, models and variations in component configurations for this website to offer any in-depth analysis of their features, benefits or appropriateness for every application. Depending on where you live, some of these systems might not be necessary, although with recent changes in climate across the country, historic applications may not be indicative of future needs. But the main consideration for not attempting to address specifics in this website is, of course, that as soon as any words are put to the page they are out of date, as new technology and product improvements are being introduced at such a rapid rate. Having said that, this website’s goal is to provide an overview of the general types of systems that you should investigate and consider for your project.
Spending money on high-performance systems will result in a minimal return on investment if your home is not designed for them to provide optimal performance. The envelope of the home is where efficiency is rooted and comfort is to be found. Many people setting out to build a house ask, “If we have limited resources, should we focus our funds on designing and building the best envelope or build a basic envelope and pour our limited funds into the best, highest efficiency equipment we can afford?” The answer that building science studies support is clear: design, build and test the best envelope you can afford and then buy the best downsized mechanical equipment you can afford with the funds that are left. Your bills will be lower and your comfort greater in a high-performance envelope with a 13-Seasonal Energy Efficiency Ratio (SEER) three-ton air conditioner with tight ducts and the correct airflow than with a 19-SEER five-ton unit in a standard envelope with average ducts and airflow.
Efficiency Ratings
It’s unfortunate that many green homes are built with expensive, high-performance systems that will never achieve their rated efficiency or deliver real comfort due to poor home or system design and sloppy installation. We cannot tell you how many homes we have seen dedicate good money to upgraded systems, only to hire an installer who is either uneducated in what it takes to achieve high-performance installations or is forced to try to install them in a home that was not designed and built for the system to operate efficiently. This is not to say that you should not invest in equipment with the highest performance rating that you can afford, it is just a caution to let you know how to prioritize your spending and set your expectations for return on investment according to your actual design conditions and the capabilities of the contractor. It is important to keep in mind that most system ratings were achieved in controlled laboratory conditions, so unless you design your home to that same standard, you should not expect that level of performance.
Equally important to mention here is the impact that the efficiency of these systems have on achieving the overall goal of net zero energy we discussed earlier. The common approach is to size your solar photovoltaic array (or other type of onsite power generation system) to cover the loads dictated by whatever your average kilowatt hour usage is. A better approach is to design and specify the home and its systems to meet the goal of reducing the total load to that capable of being managed by a reasonably sized onsite source. For this article, the systems are listed in the order that they might offer the greatest contributions toward that goal.
