How does your home perform in energy usage compared to your neighbors or any other home? If you are having a home built or are buying an existing home, shouldn’t this be a consideration? Buying or building a home and knowing the energy costs can help you pick the home you are getting. The only way to know what you are looking at is if it is rated. The rating is arrived at by plugging in R-value numbers and U-value numbers for each component in an outside home assembly. (Walls, attic, basement, windows, etc.) Then there is input on type of heating/air conditioning, lighting, ventilation, and other things. A major component of a rating is how much does the home leak. The air leakage of a home to the outside greatly impacts the energy usage, indoor air quality, comfort, and the structural integrity of the home. The only way to measure this air leakage is with a blower door test. A blower door is a temporary door installed in an outside door opening. The door has a fan in it, the fan sucks air out of the home and there is a gauge that measures how much air is going out. Air going out is equal to air coming in, so you would know what amount of leakage your home is at. With an infrared camera, you can see where the leakage is coming from, so it can be fixed.
The most commonly used rating system is a HERS rating. (Home Energy Rating System). This system was developed by Resnet and the people using this system are Resnet Raters. This system is fairly complex and is used across the country as the standard for most efficiency programs. It does have some areas of building science that are not addressed. A HERS score is based on the 2006 IRC code. A HERS 100 is based on this code. A new home in Wisconsin for the Focus On Energy new homes program has to be 20% better than the base 100, which means it is 80 or lower. This means it uses 20% less energy to live in than a 100 home. There are a lot of homes in the country much less than HERS 80. There are some homes in the country that are at HERS 0, which means they produce as much energy as they use. There are even a few homes that make more energy than they use. A zero energy home uses renewable energy to get to 0.
There are some other rating systems out there, some are less detailed than HERS. There is legislation pending at the federal level that will, in short, put a MPG sticker on every home sold in the country, new or old. This is called the SAVE Act, Sensible Accounting to Value Energy. This bill has bi-partisan support and is supported by the mortgage industry and almost everybody in the building industry. One of the questions of this act is what rating system they will use. This act will pass at some time, it is only a matter of when. The DOE has been looking at coming up with their own rating system to be used for this act, stay tuned.
Another interesting thing that will happen in the next 2 years, all states will have to adopt a new building code, which means every new home will be blower door tested. This test is the basis for a rating, so it will be interesting to see if ratings are what is going to happen.