Attic Insulation Question - Woodworking Talk - Woodworkers Forum
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post #1 of 14 Old 07-16-2017, 02:20 PM Thread Starter
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Attic Insulation Question

I know, I know, not exactly a woodworking question...

Background: My attic is framed with run of the mill 2x4 trusses. There is an air handler in the attic. To support the air handler, there are 2x4's laid on edge and fastened to the top of the lower chord of the truss. On top of those 2x4's is a piece of plywood. There's a pan on top of the plywood and then the air handler.

I'm repairing the ceiling in the room below. When I took down the old ceiling, of course all the insulation fell down. I know I should replace the blown in insulation in the rest of the area, but I'm wondering if there should be insulation in the space between underside of the platform the air handler sits on and the ceiling below, or if air circulation should be allowed. A drawing below describes the scene of the crime. Thanks.
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post #2 of 14 Old 07-16-2017, 03:03 PM
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Assuming you are working from the room underneath I think I would use the paperback insulation so you can staple it in place.
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post #3 of 14 Old 07-16-2017, 04:40 PM Thread Starter
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Paper backed is what I'd use, but I was wondering if there should be insulation under there, or if I should allow for airflow.
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post #4 of 14 Old 07-16-2017, 05:17 PM
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I don't see any reason not to use insulation. I don't know what benefit there would be for air to pass under the plywood.
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post #5 of 14 Old 07-16-2017, 05:58 PM
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Insulate under the air handler (actually a fan coil) it doesn't need any airflow under it, but make sure you don't get any in the auxiliary drain pan, at some point in the units life it will leak condensate and that is why the pan is there

Also if you ever see water dripping from some odd place like on the patio or by a window, get the main drain cleared ASAP

I have been to so many homes where the owner said that was was dripping where it shouldn't have been, then the aux drain plugs up and then they get to do a ceiling repair or replacement
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post #6 of 14 Old 07-16-2017, 08:21 PM
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Quote:
Originally Posted by Catpower View Post
Insulate under the air handler (actually a fan coil) it doesn't need any airflow under it, but make sure you don't get any in the auxiliary drain pan, at some point in the units life it will leak condensate and that is why the pan is there

Also if you ever see water dripping from some odd place like on the patio or by a window, get the main drain cleared ASAP

I have been to so many homes where the owner said that was was dripping where it shouldn't have been, then the aux drain plugs up and then they get to do a ceiling repair or replacement
Keeping that drain clear cannot be over emphasized. Also be certain that the fan does not blow any spray outside the pan area. I know this because when I lived south of Houston I had this type of unit in my attic. One morning as we are ready to leave for Lubbock the ceiling in a closet fell in.

Check it frequently. Once a week is not too often.

George
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post #7 of 14 Old 07-17-2017, 05:12 PM Thread Starter
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It's sage advice about making sure the drain from the auxiliary drain plan is clear. It's also important to make sure the auxiliary drain pan doesn't leak. That's why I'm working on a ceiling!
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post #8 of 14 Old 07-18-2017, 11:18 AM
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It's sage advice about making sure the drain from the auxiliary drain plan is clear. It's also important to make sure the auxiliary drain pan doesn't leak. That's why I'm working on a ceiling!

I was kind of wondering about that

I think they should shoot the A$$ hole that came up with the idea of putting an evaporator over a sheet rock ceiling, over my 40+ years in HVAC/R I have seen many caved in ceilings form a leak waiting to happen
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post #9 of 14 Old 07-18-2017, 11:38 AM
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Quote:
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I was kind of wondering about that

I think they should shoot the A$$ hole that came up with the idea of putting an evaporator over a sheet rock ceiling, over my 40+ years in HVAC/R I have seen many caved in ceilings form a leak waiting to happen
It works when it's new. That's as far as an engineer can think.
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post #10 of 14 Old 07-18-2017, 01:56 PM
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For sure you want to insulate. The air handler should not need circulation from below. You are right that this is not finish carpentry job but it is a fun question anyway. Thanks for asking it.

Ron
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post #11 of 14 Old 07-19-2017, 05:55 AM Thread Starter
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I think the design flaw may have less to do with being above a ceiling than accessibility and serviceability. In my case, the air handler is hard to access and out of sight (out of mind). The filter, which was the cause of my problem is hard to get to and it's the kind you clean, not the kind you replace, so not a welcome task. It's also in a hot attic, so who wants to go up there? Other than that, it works great, especially for AC because it's dropping the cold air from above.
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post #12 of 14 Old 07-19-2017, 11:37 AM
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Quote:
Originally Posted by Quickstep View Post
I think the design flaw may have less to do with being above a ceiling than accessibility and serviceability. In my case, the air handler is hard to access and out of sight (out of mind). The filter, which was the cause of my problem is hard to get to and it's the kind you clean, not the kind you replace, so not a welcome task. It's also in a hot attic, so who wants to go up there? Other than that, it works great, especially for AC because it's dropping the cold air from above.

That is another problem with them in an attic, the filter doesn't get cleaned and then the return static goes negative, and it will suck the drain water back down the pipe and floodola

You might want to put a deeper trap where the drain comes out of the unit
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post #13 of 14 Old 07-19-2017, 01:57 PM
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I see no reason not to insulate right up to the bottom of the plywood under the air handler. But unlike others suggested I would forgo the craft backed insulation an use blown in. Way easier, similar cost and more efficient because there will be no gaps. Be sure not to block any air flow from eves or gable vents.
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post #14 of 14 Old 07-19-2017, 03:47 PM
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I moved both of my units to the attic, drains are checked regularly, and there are float switches that disable the units if there is water in the pan.

My filters are at the intakes, not sure why someone would put them at the unit in the attic, makes them un-serviceable for the most part.

I thought the general ROT was no vapor barriers on ceiling insulation, or on ceilings for that matter. With that in mind I would use unfaced batt insulation, pretty easy to hold in place with some sections of coat hanger cut just a bit longer than the opening.
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