Pages > Project Pages > Load Calculation > Construction Tightness Descriptions

The Infiltration page let you choose between five levels of construction tightness. Below are the descriptions of these levels from Manual J's recently published Addendum D.

Tight	All structural panels, corners, cracks, joints and penetrations are sealed by meticulous workmanship using some combination of air barrier (film), taping, packing and caulking. Window and door assemblies are rated at less than 0.25 CFM per running foot of crack at 25 mph (wind speed). Bath exhaust fans, kitchen exhaust fans, and dryer vents are equipped with backdraft dampers. The home does not have ceiling recessed light fixtures or, if so, there is a negligible amount of leakage around the fixture. No combustion equipment (furnaces, water heaters, dryers, etc.) are contained within the conditioned space, or, if so, they are to be of the direct-vent variety. The house does not have powerful (i.e., 150 CFM or greater) range hoods (acceptable is a high-power hood that has its own source of makeup air). Fireplaces, if any, receive combustion air from the outdoors and have tight glass doors.
Semi-Tight	Envelope conditions are approximately between Tight and Average.
Average	All structural panels, corners, cracks, joints and penetrations reasonably sealed by adequate workmanship using some combination of air barrier (film), taping, packing and caulking. Window and door assemblies rated between 0.25 and 0.50 CFM per running foot of crack at 25 mph (wind speed). All bath exhaust fans, kitchen exhaust fans, and dryer vents are equipped with backdraft dampers. The home does not use ceiling recessed light fixtures or, if so, there is a minor amount of leakage around the fixture. No envelope openings (per National Fuel Gas Code) are required for combustion air. The house does not have powerful (i.e., 150 CFM or greater) range hoods (acceptable is a high-power hood that has its own source of makeup air). Fireplaces, if any, receive combustion air from the indoors but, have tight glass doors and a chimney damper.
Semi-Loose	Envelope conditions are approximately between Average and Loose.
Loose	There has been no effort or inadequate effort (regarding methods, materials and workmanship) to seal the structural panels, the associated corners, cracks, joints and penetrations and/or there is a large amount of ceiling recessed light fixture (or light-can) leakage. Window and door assemblies are not rated; or are rated at more than 0.50 CFM per running foot of crack at 25 mph (wind speed). Some, or all, of the bath exhaust fans, kitchen exhaust fans, and dryer vents are not equipped with backdraft dampers. Envelope openings (per National Fuel Gas Code) are required for combustion air. Powerful (i.e., 150 CFM or greater) range hoods are used that do not have their own source of makeup air and requires powered air-makeup, an open window for make-up air, or a negative pressure relief. Fireplaces, if any, receive combustion air from the indoors and do not have glass doors or chimney dampers.

General Notes:

1.Ignore duct system leakage when evaluating envelope tightness. The Manual J duct load tables (for duct runs routed through unconditioned spaces) include a penalty for induced envelope infiltration (or exfiltration) caused by duct leakage. (Envelope performance and duct system performance are evaluated separately because a tight envelope may have a leaky duct system or a leaky envelope may have a tight duct system - or some other combination of an envelope leakage scenario and a duct leakage scenario.

2.Ignore intermittent bath and kitchen exhausts when making an envelope leakage evaluation.

3.If a kitchen is equipped with a powerful range hood (150 CFM or more), provide powered makeup air, or open window, or pressure relief damper. (Operation of the range hood shall not cause any combustion appliance to backdraft.)

4.Table 5A is applicable to multi-story applications, but is based on a single-story construction and Class IV shielding.

5.Table 5B is applicable to multi-story applications, but is based on a two-story construction, an exposed ceiling and Class III shielding.

6.Tables 5A and 5B are based on a 15 MPH wind for heating and a 7-1/2 MPH wind for cooling.

7.The fireplace adjustment is for an inactive fireplace. Operation of the fireplace shall not cause any combustion appliance to backdraft. (When in use, provide powered makeup air, or open window, or pressure relief damper.)

8.The incremental CFM adjustment for additional fireplaces decreases as the number of fireplaces increases because the airflow is limited by the size of the cracks and penetrations in the building envelope.