## Why we have to upgrade existing houses.

Low leakage windows, better insulation, and more efficient heating and cooling systems are among the many wonderful energy saving products and techniques that allow us to build very efficient houses.

Houses built to the high standards of a passivhaus , can use as little as 10% of the energy required to run the average U.S. single family house. For so many reasons, reducing energy use is critical to our society’s future. So….. let’s build a bunch of new passiv houses with an American flair. Well…..here’s the problem.

In a typical year, the housing industry produces about 1.5 million new housing units per year. This is within a base of approximately 128,000,000 existing housing units. (source census.gov). So, it would take about 85 years (with no population growth) to replace all of our existing houses.

This leads us to the conclusion that we must devise a way to make our existing housing stock efficient users of energy. It’s not a simple task. Standards must be developed and a process must be implemented. Oh, and by the way, perhaps government (good government) should direct this. I think we’re not even going to ask the finance industry to be involved in this one ðŸ™‚

## What is a cubic foot and a CFM?

OK, first the boring defintion. A CFM stands for cubic foot per minute. This term is used as a measurement of airflow rate for ventilation systems. The cubic foot refers to a (mythical) cube of air 1 foot x 1 foot x 1 foot. CFM becomes a flow rate since we measure how many cubic feet are flowing by per minute.

Now, let’s get some perspective on what a cubic foot and CFM represent:

• It takes about13.5 cubic feet of air to weigh one pound. A 2,000 square foot house will contain 16,000 cubic feet of air. The weight of all that air is only 1,185 pounds.
• Warming or cooling air is “low calorie”. To warm all that air in your house up from 50 degrees F to 70 degrees F takes about 5,688 BTU’s . The smallest house furnace puts out 40,000 BTU’s per hour. So how come it takes so long to heat up the house on a cold morning?
• An unsealed door jamb, leaking 50 CFM would over the course of 24 hours, leak out 72,000 cubic feet of air – not “low calorie”