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Single-Family Home Retrofit Basics

  • 1.  Single-Family Home Retrofit Basics

    BPA Staff Member
    Posted 07-15-2022 10:10

    The majority of single-family homes in the United States are older and they are often in need of a little help. There are many ways to make each of them more energy efficient and oftentimes more healthy. This article will discuss many of the options available for retrofitting homes. Not all of these will be viable for each home. Nor will they all be good options in every climate. 

    There are a couple of things we need to remember as we look at retrofitting single-family homes. Heat moves from hot to cold. Air moves from areas of greater pressure to areas of lower pressure. Moisture moves from areas of higher moisture to areas of lower moisture and from warmer areas to cooler areas. In general, stuff moves from more to less.

    We need to think of a home's shell or building envelope as having two components. The first is the thermal boundary. The thermal boundary is the insulation system whose purpose is to keep the heat inside and the cold out or vice versa. The air barrier is the second component of the building shell. The air barrier needs to be aligned with the thermal boundary for the building envelope to work right. Its purpose is to minimize infiltration of outside air into a home and to keep hot humid air out of insulation systems. This hot humid air can condense and cause mold, rot, and other nasty things to happen. 

    Think of the thermal boundary like a sweater and the air barrier as a wind breaker. If you're standing outside on a windy day, in order for the sweater to work well and keep you warm, you need something to stop the wind from whistling through it. 

    As you contemplate retrofitting a single-family home, you also need to be aware of the concept of interactivity of measures. For example, on a given home you may be able to retrofit the heating-and-cooling equipment and come up with, say, a 25% savings estimate. Looking at the building shell, you may also identify an additional 35% savings available. Does this mean you are going to manage to get 60% savings? You probably will not, because of how measures can interact and change overall outcomes. Fortunately there are many good options to help you estimate what the savings may be (see "How to Calculate Savings").

    Let's go ahead and take a look at the different opportunities we have when considering retrofitting a single-family home.


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    Macie Melendez
    Editor in Chief, Building Performance eJournal
    Building Performance Association
    Moon Township PA
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