Typical Attic bypass locations are often hidden under insulation.
A Blower door is the only sure way to tell how drafty a home is or if ventilation is needed.
Recessed lighting looks great until you view it in an infrared camera.
Air Sealing
The most effective energy-conservation measure a weatherization contractor can apply to a client’s home is to assure that the home is properly sealed. Air sealing includes tightening the building envelope by using caulk, foam, weather-stripping and other materials to prevent cold winter air from coming into the heated space and preventing warm, heated air from escaping. Additionally, air carries moisture, which can degrade building components and create a persistent mold or mildew problem. Based on a U.S. Department of Energy study, homeowners can expect air sealing to lower their space-heating consumption around 18 to 30 percent.
Infiltration is outside air that enters a house uncontrollably through cracks and openings. Exfiltration is inside air leaking outside of the building envelope. Air leakage is greatest during hot, cold and windy weather. When you feel a draft, the air entering the building is naturally balanced by an equal amount of air exiting. Think about it: when you feel a draft, the rush of cold air entering the home is matched by an equal amount of heated air, which you paid to heat (or cool), escaping. The recommended strategy both in new and old homes is to reduce air leakage as much as possible and, if need be, provide controlled ventilation. Determining if ventilation is necessary requires a contractor to determine the volume of the structure and then apply a mathematical formula to determine what the building airflow standard is. The only way to measure air leakage effectively is through the use of a blower door. At Murtha Construction, we test, not guess!
Although windows, doors and outside walls contribute to air leakage, the biggest holes are usually hidden from view. Most homeowners are aware that air leaks into their houses through what seem to be small openings around doors and window frames and through fireplaces and chimneys. Air also enters the living space from other unheated parts of the house such as attics, basements or crawl spaces. These holes and pathways (sometimes called bypasses) connect the house to the attic, crawlspace or basement.
Air travels through openings in walls, floors or ceilings, such as cracks where two walls meet and where the wall meets the ceiling, or near interior doorframes. Other openings are gaps around and through electrical outlets and switch boxes, recessed lighting fixtures, recessed cabinets, pull-down stairs, false ceilings such as kitchen or bathroom soffits, behind bathtubs and shower stall units, floor cavities of finished attics adjacent to unconditioned attic spaces and plumbing connections. These often overlooked leaks between the living space and other parts of the house can be much greater than the obvious leaks around windows and doors. Since many of these leakage paths are driven by the tendency for warm air to rise, the attic is the first place to stop the leaks. It’s imperative to stop these leaks before adding attic insulation because the insulation may hide them and make them less accessible. Many types of insulation will not stop these leaks and you won’t save as much as you expect because of the air flowing through the insulation. The R-Value of insulation subject to airflow can be reduced by up to 50%. Fiberglass insulation is especially prone to this phenomenon, called “wind wash.” Ventilated soffits and cathedral ceilings are areas of the building envelope greatly affected by wind wash.
Another problem created by uncontrolled airflow through a building is condensation, which can lead to mold and mildew. Basements are a great example of this phenomenon during the hot and humid Long Island summers. Thousands of homes across our area experience “musty” basements in the summer. Typically, this is caused by hot and humid air entering the house from outside, coming in contact with a cool basement wall and causing condensation. Condensation in the summer, when mold spores are typically most prevalent, is a recipe for disaster.
Treat your home holistically. Treat the cause of problem, not the symptoms. Contact the building scientists at Murtha Insulation today!
Air Sealing Links