Insulating the air handler

[helmetheadbob]

Got a question. Would it be beneficial to me to insulate my air handler with some type of foil insulation? It just sits in the open attic with nothing around it. I am planning on taping (mastic?) the joints, but should I go one step further and just insulate the whole thing?

Thanks

[RoBoTeq]

I always insulated air handlers in unconditioned areas.

[gonekuku]

All plenums & air handlers I looked at had about a 1" or 4.3R internal insulation. For sake of simplicity, lets say your entire system is 2' x 2' x 12' in the unconditioned space with a max 60F internal to attic differential temp. You would be losing 1451 BTU, or .12 tons.

I.E. On a 5 ton system this is a 2.4% loss at the air hanldler.

Add an R8 blanket, your losses are 507 BTU, or .04 tons. You now have a 0.8% loss on a 5 ton system.

On this 5 Ton example, if you spend $300 / mo in heating or cooling, you may save $4.80 per peak heat/cool month. Payoff may be 5+ years, just like with many other improvements.

This is my theoretical opinion.

What ever material you may use - Make sure it is code compliant for your application.

[coolguysfl]

While re-insulating the air handler at 1st blush makes a ton of sense ---- I would strongly discourage it:

1) By most interpretations of the electrical code it is a violation as you can't see the data plates, or access the doors. They frown on any modification that could impact the EXACT conditions that UL tested it under.
2) You will trap moisture on the skin of the unit & it will be rust bucket in short order.
3) The insulation belongs on the INSIDE, not the outside of the air handler.

Just a side note: It's a sad testimonial that mfg's can get away with R4.2 in the air handlers (just happens to be the coldest part of the system) when the mechanical code for the attached duct work is R6.