Blower Door Basics
Leaky homes are hard to heat and hard to cool. The only way to know whether your home is leaky or tight is to measure its air leakage rate with a blower-door test. An energy-efficient house must be as airtight as possible. Many older homes are so leaky that one third to one half of the home’s heat loss comes from air leaks.
Nick Hanson of R-Value Construction, LLC donated his services to perform a blower-door test on the new FloydFest headquarters. With our donation of structural insulated panels and our crew putting up the shell for the headquarters, we were able to get them out of an ancient mobile home into a green building. This test proved that the building, made with ACME structural insulated panels, is 48% MORE energy efficient than an equivalent new structure made with traditional stick-built framing!
There are at least two reasons to conduct a blower-door test on an existing house: to determine how leaky it is, and to help locate and fix the leaks.
How does the blower-door test work? It’s actually fairly simple. The professional home energy auditor (Nick in our case) will set up a blower door in your home. In most cases, the blower door will be placed in the front doorway area.
The purpose of the blower door is to pull out all of the air from the inside of the house (a process more formally known as depressurizing the home). What does this do? Well, when you pull out all of the inside air, the outside air will rush into the house through any leaks that exist, exaggerating the leaks and making them easier to locate and measure.
Once the blower door is running, the energy inspector will go from room to room. What he’s doing is checking for these leaks. He’ll make a note of all of the areas where outside air is coming into the house. He’ll be able to analyze what needs to be done to seal up the leaks in the most efficient manner.
This type of energy check allows your home’s air-leakage rate to be calculated which determines exactly how much damage your home is suffering from air leakage. This will give you a clear picture of how much energy is lost to these leaks.
Our blower-door test came out great with a score of 0.33 ACH (air changes per hour). When you tighten a house more than 0.25 ACH, you have to add a mechanical air exchanger to ventilate the house – these take the stale air out, recover the heat or cold from it, and transfer it to fresh, clean filtered air from outside. So why would you want to first tighten a house and then turn around and ventilate it with a fan? For several reasons:
- Leaky homes don’t provide dependable volumes of fresh air. In a leaky house, air infiltration rates are very high in some conditions (when it’s cold outdoors and when it’s windy) and very low in other conditions (when outdoor temperatures are mild and there is little wind).
- Leaky houses tend to be over-ventilated in zones that are leaky and under-ventilated in zones that are relatively tight.
- Air leakage through wall and ceiling assemblies can lead to condensation, mold, and rot.
- Leaky homes are uncomfortable.
- Tight homes use much less energy than leaky homes – even taking into account the electrical energy used for ventilation.
The blower-door test is just one of many tests that R-Value Construction can perform. However, it is one of the most crucial tests that can be done. Sealing up the leaks in your home is one of the more significant things that you can do to make sure that you have the most energy-efficient home possible. Building your new home or addition with ACME structural insulated panels is another sure way you can get a home that uses 50-60% less energy for heating and cooling.
A blower-door test can cost anywhere from $500 to several thousand dollars, depending on the size of your structure, and will pay for itself. There are multiple quality energy auditors in the New River Valley including: R-Value Construction and Energy Check.