When Contractors Fail to Understand the Dynamics of Building Science

When Contractors Fail to Understand the Dynamics of Building Science, the results can mean long term headaches for unsuspecting home owners. Consider this bathroom vent thru a flat roof on a DC home renovated and put on sale for over $1M.



slightly better bathroom exhaust vent

Seems rather innocent to the untrained. However, the contractor has failed to consider the fact that this is intended to exhaust warm humid air from a bathroom. When this metal pipe is exposed to warm humid air on the inside, during freezing winter temperatures or 2 feet of snow, the inevitable condensation occurs. That condensation will flow back to the exhaust fan, ruin the fan, possibly cause an electrical short and damage the interior ceiling. The buyer thinking, ‘oh I need a new fan’, will replace the fan never thinking the cause has to do with the contractors bad decision to run a metal exhaust to the roof.

Unfortunately trade schools that used to teach this stuff no longer exist. It is very easy to become a “licensed contractor” in most states with little to no knowledge of building science. Far too often, we here, “the work was done by a licensed contractor” as the justification or proof that the work was done correctly.

Corrugated Stainless Steel Tubing (CSST) Bonding

The following is taken from CSST Safety website. Corrugated Stainless Steel Tubing (CSST) is a flexible, stainless steel pipe used to supply natural gas and propane in residential, commercial and industrial structures. CSST is often coated with a yellow, or in some cases, a black exterior plastic coating. CSST should NOT be confused with flexible gas appliance connectors – the product that joins a moveable appliance to your home or building’s gas supply line.

Bonding is provided primarily to prevent a possible electric shock to people who come in contact with the gas piping and other metal objects connected to the grounding system. Nearby lightning strikes can result in an electrical surge that can potentially puncture a hole in CSST and cause a fire. Proper bonding and grounding will reduce the risk of damage and fire from a lightning strike.

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The Importance of Proper Venting of Orphaned Water Heaters

The importance of proper venting of gas appliances cannot be understated. With the increased efficiency of today’s furnaces and water heaters, venting into older masonry chimneys designed for low efficiency furnaces and water heaters, can create unsafe conditions. In many older homes, new high efficiency furnaces are being installed which no longer use the old masonry chimney, leaving the orphaned water heater to vent into a flue that is over sized. This condition can result in exhaust fumes entering teh home each time the water heater is used. For more on this we have attached a report from WSSC.

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