How to Look

at a House

A blog with answers
to your questions about

More blog posts about heating and air conditioning:

  1. How can I find out the size of my air conditioner?

  2. How can I find out the age of my air conditioner or furnace?

  3. The coils on my heat pump are covered with ice on cold mornings. What’s wrong with it?

  4. What is the SEER of my old air conditioner?

  5. What is the difference between the “ON” and “AUTO” settings on my thermostat?

  6. What is a “ton” of air conditioning?

  7. What is the best air conditioner for a mobile home?

  8. How do I find the right size air conditioner for my house?

  9. What is an HVAC system?

  10. What is the difference between the SEER and EER of an air conditioner?

  11. What does an ultraviolet air treatment system do?

  12. The coolant line to the outside unit of my air conditioner is frozen. What's wrong?

  13. What size air conditioner is right for my mobile home?

  14. What is the minimum SEER rating for a new air conditioner?

  15. What does the “AFUE” rating of a furnace mean?

  16. How much life is left in that air conditioner?

  17. Why is there mold around the air conditioning ducts?

  18. What is a geothermal heat pump?

  19. What is the difference between a heat pump and a cooling air conditioner?

  20. Is it alright to close the air conditioning vents in unused rooms?

  21. What is the right MERV number for my air conditioning filter?

  22. Should I move my air conditioner into the attic?

  23. What are the minimum requirements for bathroom ventilation?

  24. What is an air conditioning heat recovery system?

  25. When should I switch the thermostat to “EMERGENCY HEAT” for my heat pump air conditioner?

  26. Why does the air conditioner condensate drain line need a trap in it?

  27. What is the average lifespan of an air conditioner?

  28. Should I remove an old whole house fan or keep it?

  29. How can I find out the SEER of my air conditioner?

  30. Is it acceptable for an air conditioning condensate drain line to terminate under the house?

  31. My air conditioner won’t turn on What’s wrong?

  32. What is the purpose of the vent grille over the bedroom door?

  33. Should I have a return air vent in the master bedroom?

  34. Will closing doors reduce my heating and cooling costs?

  35. How much will I save on my utility bill if I get a new higher SEER air conditioner?

  36. Why is there a wall switch next to the furnace or indoor unit of the air conditioner in the garage?

  37. When does the ban on R-22 air conditioning refrigerant take effect?

  38. Why do the lights dim when the air conditioner turns on?

  39. Why is my air conditioner not cooling enough?

  40. Why does it take so long to cool a house when the air conditioner has been off for a while?

  41. What are the right words to use when talking about a heating and air conditioning system?

  42. What is a FanRecycler and AirCycler?

Photo - U.S. Department of Energy
Diagram - U.S. Department of Energy

Welcome to our blog!
We want you to be an informed homebuyer, and each blog post is a question that we have answered for our friends and customers over the years. Hope they help you make a good choice for your next home.

    Ideally each room of a home should have both a supply and return air register for a system that is perfectly pressure-balanced. But that adds major dollars to the construction cost and can create a maze of ducts in the attic. So a simpler alternative is a ceiling register in rooms with a closable door, like bedrooms, that simply connects to another register on the other side of the wall in an open room. That’s a “jump duct.” also sometimes called a “jumper duct.”  It’s a passive duct that works like the old louvered transom vents over doors in South Florida houses of a bygone era, to create an air flow connection between two rooms. The photo at the top of this page shows a jump duct installed into the framing of a home under construction, before the drywall has been hung, and the diagram below also illustrates the concept.

    Newer mobile homes and budget site-built homes often have a small louvered vent through the wall over each bedroom door, called a “transfer grille.” It is similar to a miniature transom vent, and is an even less expensive alternative than a jump duct for a return air connection to the open area of the house.

    A minor disadvantage is that sound also travels through both a jump duct and transfer grille, so privacy within the room is somewhat reduced. But energy efficiency for the heating and air conditioning system is increased, and jumper ducts also help to reduce the incidence of rooms that are noticeably warmer or colder than the rest of the house.

    To learn more about jump ducts, we suggest visiting the U.S. Department of Energy’s webpage about them at:

While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
©2015 - McGarry and Madsen Inspection. -


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