Tips

Bypass Surgery

In residential construction terminology a ‘Bypass” is a hidden path for conditioned air to travel in its quest to escape or invade your home.  If your home is insulated well, was built after 1975, and is still uncomfortable or has mold or condensation, then the cause of those issues is probably a bypass.  

Look around your home for hollow interior wall voids that extend from the floor to the ceiling of rooms or halls.  Visualize yourself as an air molecule.  You pass into an interior wall cavity through an electrical outlet, you are warm so you float up in the wall.  At the top of the wall there is no sheetrock on one side, but there is fiberglass.  Fiberglass is very porous to you though, so you fly into the attic.  This sounds simplistic, but most homes have this situation somewhere in their construction, and simply plugging up these leaks will significantly change the comfort level and fuel costs of these homes.  

If your home has an interior wall that is cold, or if you feel a draft from a partition in your home the likely cause is a bypass.  Here are a few of the most common bypasses, there are more, but these principals are usually evident in all bypasses. 

• Showers and Kitchens
• Split Level Homes
• Recessed Lighting

Showers & Kitchens

Frequently, builders will put a small dropped ceiling over a shower, kitchen cabinets, or a bathroom vanity.  This lowered ceiling is called a soffit.  Typically the surfaces you would see from inside the house when it is complete are covered with a finish.  However, the portion of the interior wall that is above the soffit usually is not covered in any way.  This results in a path for air to follow from the void under the tub and from electrical penetrations from the other side of the shower partition into the interior wall cavity and out of the partition into the attic or floor chases above the shower.  

Did you know that the wall along the sides of your bathtub probably does not extend from the ceiling of the bathroom to the floor of the bathroom?  Usually the wall covering extends from the tub rim to the ceiling.  This helps prevent water from getting between the tub rim and the wall finish and rotting the 
bottom of the partition wall.  However, under the tub there will be a large hole in the floor where the tub drain is.  If you have a ranch home and your tub is always cold, then air passing up into the hollow between the tub and the floor, then traveling up into the void space above the bathroom is probably taking away the heat from your bath.  If your bathroom happens to be over your garage this problem is much worse.

Split Level Homes

These homes are bypass heaven. 

There are two main problem areas in a split level.  First is the partition we have highlighted in red.  Usually there is a stairway and a bathroom along this partition.  The portion of the partition that butts up against the attic of the lower level usually has no sheathing on it.  The side that faces the upper level room is finished.  In this situation, heated air that enters the partition leaks into the lower level attic and can also invade the upper level attic by traveling along the ceiling of the stairway.  Moving air has no insulation value.  Fiberglass will NOT stop air movement. Fiberglass in this partition is useless.  

The other problem area is the garage ceiling.  Any bathroom over this garage will be cold.  By the time a tub or toilet drain is installed there is not sufficient room left for insulation.  If there is any insulation in the ceiling then it is fiberglass.  Fiberglass does not stop air movement.  If this home is heated with forced air, then there will be ducts in this ceiling.  At least one of those ducts will be a return duct.  If the owner decides to heat up his car inside the garage and the furnace is on there is a good chance he will unintentionally suck exhaust gas into the return ducts and then blow it into the house. 

These homes are frequently heated with forced air heat.  Some ducts are run in this partition or the garage ceiling.  Those ducts take the space usually filled with insulation.  Now the heating system is trying to blow hot air through uninsulated ductwork in the cold attic or garage to an upper level room to make heat.  In the end, the homeowner gets warm air at best.  Spraying foam on those ducts will both seal them and prevent heated air from blowing directly into the attic and insulate them resulting in increased temperature at the heat registers.  

The partition flaws are relatively easy to fix since they usually can be accessed from the lower level attic.  Removing the fiberglass and installing urethane foam will solve a vast majority of the problems here. 

The garage ceiling is another matter.  The ceiling finish needs to be torn down.  Then the fiberglass in the joist cavities needs to be removed.  Frequently the HVAC system utilizes the floor joist cavities as return ducts.  In that case the returns need to be ducted.  Then urethane can be applied to insulate and airseal the floor.  The urethane must be covered with a 5/8ths inch thick sheet rock to meet the fire codes.  Then a finish can be applied. 

Recessed Lighting

People like the effect and appearance of recessed lights, so they will be with us for quite some time to come.  Recessed lights are unfortunately not kind to houses though.  Think about it.  Warm air rises.  Warm air has a higher pressure than cold air.  Cold air sinks.  A recessed light is a hole in the membrane that stops the warm air from escaping into the atmosphere.

Moving air has no R value.  Fiberglass will not stop air movement.  The paper facing on fiberglass will detour air movement, but it will not stop air movement.  Simply throwing a fiberglass batt over the light will not stop convective heat loss.  There are two fixes for the recessed light holes. 

• One is to eliminate the lights.  This is frequently unacceptable to the owner. 

• Another is to use Airtight fixtures. 

There are three types of recessed light fixtures. 

• One is called an IP fixture.  These are the cheapest and they require no insulation be installed within 3 inches horizontally of the fixture, and that no insulation at all be applied above the fixture.  These fixtures should be avoided at all times in my opinion. 

• Another is an IC fixture.  These fixtures allow insulation to be installed around them.  They have a small protective circuit built in, they blink and then go off if they overheat.  These fixtures are OK in applications where they do not puncture the membrane between the heated portions of the house and the atmosphere.  If you inspect one of them though you will find that they have holes punched in them to allow for different adjustments to the bulb height.  These holes are highways for air to follow.  The air that moves through these fixtures is usually warm and moist.  When it gets into the cold environment above the light it will drop its water.  Spotted ceilings, mold, and roof rot are results of these flaws. 

• Finally there are AirTight units.  These are basically IC fixtures inside a “sealed” metal housing.  These housings usually have some holes in them, but these holes can safely be sealed with foam or caulk.  It is important to either seal the fixture to the sheet rock ceiling with a gasket or caulk them from the attic after the ceiling is up.  We will spray them from the attic as part of the insulation work. 

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