Changes between fuel source and/or efficiency rating can greatly impact the HERS rating.
Be sure to match the “SEER” rating of a heating unit or “EF” of a domestic hot water heater to the values that were modeled in your preliminary HERS rating. If changes are being made, be sure to contact us so we can update the model and head off any potential problems at final commissioning.
Sealed Combustion Water Heater or Boiler – These are not affected by pressure changes in the building.
Naturally Drafting Oil Burner – These rely on convection to exhaust flue gases out the roof. Bathfans, range hoods, and poorly sealed air handlers can cause these to backdraft
Naturally Drafting Flue – These include boilers, furnaces, and any fireplace or wood stove that draws air from the building rather than being sealed airtight.
Mechanically Vented Water Heater – These are not affected by pressure changes in the building.
Naturally Drafting Water Heater Hood – These tend to have extremely poor drafting and are the most likely to backdraft in a well sealed home. These are not appropriate for new residential construction under any circumstances.
