Leaky houses have their own set of problems ranging from drafts, blistering paint, ice dams and frozen pipes to a house that won't adequately heat or cool. While in the past airsealing efforts concentrated on the easy to find air leaks around windows and door, we now know that the most important leaks in a house are the hard to find leaks in the attic, crawlspace, attached garage and other framing connections. These hidden leaks are responsible for most of the air leakage in typical houses, and are often the cause of performance and durability problems.
Blower Door Test
The easiest way to measure building airtightness is with a diagnostic tool called a Blower Door. The Blower Door consists of a powerful, calibrated fan that is temporarily sealed into an exterior doorway. The fan blows air out of the house to create a slight pressure difference between inside and outside. This pressure difference forces air through all holes and penetrations in the building envelope. Blower Door tests are typically performed at a pressure difference of 50 Pa (0.2 inches of water column).
By simultaneously measuring the air flow through the fan and its effect on the air pressure in the building, the Blower Door system measures the airtightness of the entire building envelope. The tighter the building (e.g. fewer holes), the less air you need from the Blower Door fan to create a change in building pressure.
Airtightness measurements are presented in a number of different formats including:
- Square inches of leakage area
- Air flow needed to generate 50 Pa of pressure difference (CFM50)
- Air changes per hour at 50 Pa of pressure difference (ACH50)
In addition to assessing the overall airtightness level of the building envelope, the Blower Door can be used to estimate the amount of leakage between the conditioned space of the building and attached structural components such as garages, attics and crawlspaces. And because the Blower Door forces air through all holes and penetrations, these problem spots are easier to find using chemical smoke, an infrared camera or simply feeling with your hand.
Finally, Blower Door measurements can be used to estimate the natural infiltration rate of houses. While the Blower Door doesn't measure infiltration rates directly, test results can be used along with mathematical models to estimate annual average and design infiltration rates for the purposes of evaluating indoor air quality, the need for mechanical ventilation, and to help with proper sizing of heating and cooling equipment.
Assisted Home Performance Program with ENERGY STAR
Assisted Home Performance with ENERGY STAR offers two incentives for eligible New York home owners: (1) a subsidy for up to 60% of the total cost of the approved efficiency improvements (“Assisted Subsidy”) in a 1-4 family home, and (2) low interest rate financing for the balance of the cost of the efficiency improvements through selected Lenders (“financing”). Eligible New Yorkers include borrowers in 1-4 family homes that have household incomes at or below 80% of the State Median or Area Median Income (whichever is greater).
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