Can air handler supply lines be laid in insulation below the attic floor deck

Specific Inspection Topics Inspecting HVAC Systems
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Not sure if this is the best place to post, but here goes. The issue is: I have an air handler in the attic and I am remodeling the attic so that new insulation is being added; floor joists are being beefed up and an OSB decking will be laid down. The question is how to deal with the copper lines that run to the air handler. Bury them in the insulation below the floor vs leave them above the floor?

Here is the overall picture.

  1. The tallest attic floor joists are 2 x 10’s (approx 5 joists). The remaining floor joists are only 2x6’s. The solution has been to add 2x4’s to the smaller joists to bring the entire attic joists up to 2x10 dimensions.
  2. The existing powder insulation is being removed due to dust conditions, irritation to skin and eyes. It is impossible to breath this stuff. In fact, I am using a respirator.
  3. The new insulation consist of rolls of batts rated at R-30, laid down on plastic vapor barrier, facing the sheetrock below.

To gain better access to the attic, I had a carpenter remove the old house fan and install an attic ladder in the upstairs hallway and added ceiling lights in the attic. This will make servicing the air handler soooooo much easier.

Construction has gone good so far. We are now working in the area of the air handler with its two copper lines; 220 volt electrical line, and the 2 low voltage thermostat lines (for for the wall thermostat and the other for the outside A/C).

My preference would be to carefully re-route all of these lines in the same floor joist cavity so that the OSB decking can be screwed down and thus cover up the lines surrounded with insulation batts. I would not need to cut into any of these lines to accomplish this because the lines are generally in the same path.

Is this a good idea and does it make any difference if the lines are at the bottom of the joist cavity (measures approx 14 x 9 inches)? Or should they be positioned near the top, directly below the OSB decking? Naturally, as the lines approach the air handler cabinet, they will need to be above the decking and I plan to run them up a vertical 2x4 for protection before they enter the cabinet.

Thanks. Bob :slight_smile:

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Put them in the middle. This will protect them from nails-screws of future insertion and being in contact with either material (ceiling or decking) which will prevent cooling the materials below dew point temperatures causing water condensation.

Make sure all butt connections for the insulated refrigerant line are glued together. Often water will condense at the air handling unit and flow down the insulation till it finds a loose joint and then floods the ceiling. This condition will happen whether it’s enclosed below the attic flooring or not. You just don’t want to have to tear things apart after you close them up if it happens.

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Thanks, David ~ Your suggestions make sense. :slight_smile: