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Air Sealing and Weatherization
Energy Efficiency, Comfort, and Health | Function and Optimal Operation | Components | Ducts | Caulk and Weather Stripping | Mastic | Tape | Spray Foam | Attic Hatch | Attic Vents | Can LightsQuick Facts
- Thorough air sealing is vital to proper functioning of insulation and should be undertaken before addition of insulation
- While it may seem simple to run a bit of caulk in a few obvious cracks, only testing a home for leaks before and after sealing will thoroughly identify and eliminate all wasteful leaks in the building envelope since most leaks are nearly invisible
- Air sealing will have modest positive effects on its own and works best in conjunction with other components of the building envelope to best improve energy efficiency and indoor air quality
- Air sealing will reduce the number of natural air changes in a house (how often outside air replaces inside air) and can create combustion safety issues when not conducted by properly trained personel
- Air sealing should be conducted to a calculated target level, otherwise mechanical ventilation may be required to ensure healthy indoor air quality
Energy Efficiency, Comfort, and Health
Air leakage, or infiltration, occurs when outside air full of moisture, drafts, noise, and dust enter the living space through cracks and openings. Properly sealing such cracks and openings in your home can significantly reduce heating and cooling costs (reducing CO2 emissions), improve building durability, and create a healthier more comfortable indoor environment.
To avoid accumulation of pollutants and irritants in the home, as well as to ensure sufficient fresh air, air sealing should only be done to a level which allows enough fresh air to enter the home (air changes per hour). Air sealing beyond this level can increase energy efficiency even more, but should only be done in combination with a mechanical ventilation system, which constantly and actively draws in fresh outside air. This is a healthier solution than drawing in air through natural ventilation (leaks) because the air is brought in from outdoors and can be filtered, while natural ventilation is often from leak infiltration of dirty attic or crawlspace air.
Function and Optimal Operation
Properly identifying and sealing leaks in the home’s building envelope is not only vital to the proper functioning of insulation, it also prevents infiltration of allergens and pollutants from unconditioned spaces and the wasteful loss of conditioned air.
Components
Ducts | Caulk and Weather Stripping | Mastic | Tape | Spray Foam | Attic Hatch | Attic Vents | Can Lights
All systems are made up of functional components. These air sealing materials are useful for insulating different spaces and situations in a home. It is vital that all surfaces of the building envelope be thoroughly sealed (particularly floors in conjunction with ceilings), since heat will always gravitate towards the least insulated portion of the building envelope, creating a high pressure system which pulls cold air in the winter, and out in the summer. Using the following types of air sealing materials conjointly for the varying applications throughout the home will assure all corner of the building envelope are properly sealed.
Ducts
Homes with a forced air ducts system typically suffer significant air leaks in the duct system which should always be replaced or properly sealed with duct mastic (NEVER duct tape!). [+] MORE
Caulk and Weather Stripping
These are the most well known tools in the air sealing system. They can be used to seal narrow leaks throughout the home from windows and doors to electrical boxes and vents in the attic (heat resistant caulk and professional expertise should always be use to properly seal around furnace or flues).
Mastic
Mastic is mostly used to seal ducts, but it can be used in other applications, such as around heating registers. Leaky ducts lead to unconditioned waste of air escaping to unconditioned areas and the intake of harmful particles and gases from attics and crawlspaces being pulled into the living space to be breathed by the occupants.
Tape
In most cases mastic is a more effective sealant than tape. However, some applications need more heat resistance or tidy installation than mastic can provide. NEVER use duct tape; there are a variety of tapes appropriate for a variety of tasks, but duct tape, despite its name should never used anywhere in a duct system as it is ineffective and will soon fall off.
Spray Foam
Spray foam insulates and air seals in a single step. It is quite versatile and has several types and application. [+] MORE
Attic Hatch
It is counter effective to thoroughly seal and insulate and attic without assuring that the threshold to the attic is also sealed and insulated. The most effective choice is to have a well insulated and tightly locking attic hatch installed.
Attic Vents
Depending on the location of the home (pertaining to local building codes and climate) an attic may either be entirely sealed and insulated (to eliminate heat loss and moisture infiltration), or the bottom few feet only may be insulation, taking care the upper space in the attic is sufficiently vented to the outside so that condensation does not create moisture problems in the attic.
Can Lights
This is another common source of air leakage. Before insulating an attic all recessed lighting cans need to be sealed and preferable upgraded to airtight ICAT (insulation contact) cans so that insulation may be installed flush to the cans (spray foam requires an extra air barrier between itself and the can lights).