Retrotec Residential Pressure & Air Leakage - Manual (Page 8)

Page 8 of 75
©Retrotec Inc. 2014
The attic is a major (if not the major) place to find leaks. Plumbing stacks often have large holes around them, as
do chimneys. Beneath the insulation, a number of other leaks can usually be found. The top plate, and wire
penetrations are typically quite leaky. In many cases, a dark attic is brightened by spots of light from the room
below; each spot is a leak of air to the attic.
In a typical house, windows and doors occupy a very small percentage of the total leakage in a house. Where
the house sits on its foundation is another major source of leakage. Dissimilar materials, usually wood and
concrete, are in contact with each other, and are rarely adequately sealed. The bottom portion of the house is
also where there are penetrations for plumbing and wiring. These holes are very significant, since negative
pressure is usually greatest at the bottom of the house.
Figure 3: Houses typically experience common leak locations, including penetrations into the attic, and where dissimilar building
materials meet. (Source: InsulationSmart.com)
Duct systems can also be significant contributors to air leakage. In many cases, these leaks can be the hardest to
find and fix. Even small leaks in duct systems can be a major problem, if air is pulled in from polluted or
contaminated areas such as carports or damp, moldy crawlspaces.
1.3 Warm Moist Air does damage in walls
In a warm humid climate, even a 1 Pa depressurization can lead to moisture problems, as moist air from outside
is drawn into leaky duct systems and into the walls. This moist air then condenses and molds.
1.4 What Does Air Leakage Cost?
FanTestic software from Retrotec can calculate the annual cost for both heating and cooling associated with
measured air leakage. The software uses the established Lawrence Berkeley Lab calculation technique to
provide a reasonable estimate of typical air leakage.
To calculate annual heating cost
Use the following equation:
26 ×𝐻𝐷𝐷 ×𝐹𝑢𝑒𝑙 𝑃𝑟𝑖𝑐𝑒 ×𝐶𝐹𝑀50 ×0.6
𝑁 ×𝑆𝑒𝑎𝑠𝑜𝑛𝑎𝑙 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦
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HDD is the annual heating degree days (base 65° F) for the building location
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Fuel Price is the cost of fuel in dollars per BTU
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N is the Energy Climate Factor from the Climate Information Screen
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Seasonal Efficiency is the AFUE rating of the heating system