There are limits where this applies that most taxpayers wont reach. Unless you do really well on your home sale and have a high annual income of > $200,000. Only then will you pay 3.8% tax on the capital gain. (Your profit on the house)
Not many people have capital gains on their house anymore. The 3.8% applies to rents and other income from some investments if you have a annual income > $200,000.