I scheduled an “energy audit” with an organization that promotes energy efficiency. I am not sure exactly the backing and purpose of the Center for Energy and the Environment (CEE), but I think it is a collective effort funded by energy companies trying to meet the state legislated requirements for energy generation. Minnesota is a forward-looking state that actually has made a plan in anticipation of its future energy needs. They include changes from the current model of energy generation and delivery, and provides for incentives and requirements to ease the transition.
Since I intend to use This Odd House as a personal experiment in energy use, I thought it would be beneficial to obtain a snapshot of its energy efficiency and losses before making any structural or functional changes. So I made an appointment with CEE for the day after closing. The house would be empty and easy to identify leaks, drill test holes to assess insulation, and other issues that could help guide my construction choices.
I was told that two technicians would be visiting, making measurements, and interviewing me for two hours. I was expecting two men with clipboards, but instead, at the appointed time, two women with iPads showed up. Corrie and Stacy conducted an extensive check of light bulbs, shower heads, air flow in and out of the house, furnace ventilation, and insulation detection. It is a measure of how far we have come that there should no longer be a gender expectation in the delivery of these technical services.
One can imagine that there could be a tremendous savings in light bulb replacement. Unfortunately, nearly every light is connected to a dimmer switch (and there were dozens), disqualifying them for compact fluorescent bulbs. One of my future tasks is to remove the dimmers.
The boiler that runs the gravity heating system (i.e. radiators) is very old. Inefficient (50%), but so reliable it is unlikely to fail any time soon. The water heater on the other hand is past its warranty, and is likely to need replacement in the next few years. Both send their exhaust up the chimney, a penetration of the roof, and in need of repair. Modern heating plants are over 95% efficient, so high that the exhaust gasses are not hot, and do not need special protection by a chimney. Typically, they vent out the side of the building.
In a departure from the otherwise discouraging findings, the house was insulated and fairly well sealed. Cellulose in the walls, ten inches of fiberglass in the attic (the attic in this house is a 12-inch space between the second floor ceiling and the flat roof). A blower door test measured 2640 cubic feet per minute air flow (at their prescribed 50 pascals pressure difference, a 20 mph wind effect). The volume of the house is approximately 20,000 ft^3, so this represents about 8 air changes per hour (ACH).
The air change rate has two consequences:
1. High rates represent high energy loss rates, since the conditioned air leaves the house and new air must be taken in and heated to replace it.
2. Low rates have health impacts; we need some ventilation to bring in fresh air and get rid of contaminants.
So we need to find some balance between staying healthy and consuming energy.
Modern, highly energy efficient new construction takes the approach of making the house as tight as possible, and then managing the ventilation with controlled active elements- fans and vents. Here are some comparative values of ACH (from http://www.bae.uky.edu/energy/residential/guide/guidehtml/guidep20.htm)
airtight construction: 1.5 – 2.5
standard new home: 7 – 15
standard existing home 10 – 25
older, leaky home 20 – 50
So This Odd House compares favorably with new construction methods! Now to decide on the fate of that old reliable, but inefficient furnace.