As part of our recent addition/remodel, we had to put a secondary gas furnace & air handler in the attic above the new 2nd story living space. The ductwork runs across the attic floor, into the wall cavities below and to the vents in the various rooms.
The ducts are insulated/wrapped with about an inch or so of flexible fiberglass (aluminum foil faced). I don’t think this is sufficient, and the “heated” air coming into the living space does not feel especially heated during the cold winter months (we live in NY state). The attic space is vented, and not within the heating envelope, so it stays pretty cold up there.
I’d like to increase the insulation for the ducts without making a huge mess up there with piles of fiberglass batts wedged all over the place. I’ve thought of putting up plywood edges (maybe 12″ high) running parallel to all the duct runs on both sides, and then pouring loose fill insulation (cellulose?) between the plywood & around/over the ducts. Creating an extra 6-12″ of insulation around the ducts, keeping it contained within the plywood barriers on either side of the ducts.
Anyone have any other suggestions?
Replies
Greetings perswede,
As a first time poster Welcome to Breaktime.
This post, in response to your question, will bump the thread through the 'recent discussion' listing again which will increase it's viewing.
Perhaps it will catch someone's attention that can help you with advice.
Cheers
Peace out.
Your idea sounds good, but with the cost of loose fill, I would think it would be more effecient to just bring in the insulator and over-insulate the attic. Mounding it up around those ducts will help both the air in the duct and the room below. The cost of the ply and the time will be put into $$ that would produce a measureable return (lower energy bills)
By the way, remember that the air in the ductwork will be cool for the first 30 seconds or so when the fan comes on as the fan needs to push the unconditioned air thru before the warm air gets there. The further from the furnace the longer the time till warm air gets to you. HVAC guys will have some better input but those are my 2 cents worth.
I think your idea is novel, and it helps keep the attic cold, as it should be. You should see the ice dams in our area, and insurance companies are complaining about water leakage claims. These may be the same insurance companies who paid to replace thousands of roofs in this Wisconsin area after hail a few years ago and didn't force their clients to put in impermeable membranes at the eaves. I have them -- dry home, sweet home.
I like your idea. Just a thought that might work better. After you install the plywood channels on the insides of the plywood install 2" Styrofoam first. This gives you higher R value. I wound then foam the rest of the channel. This would help seal the duct which is a big concern in the attic and also provide a higher r value than cellulose. I would then apply a silver faced 1/2" board to the sides and top of the channel this would be beneficial mostly in the summer buy reflecting some of the heat that builds. Hope this helps. Jay
Additional I would apply mastic tape to all joints on the HVAC unit and the glue rigid insulation to the furnace and plenums.
Rather than plywood you can find other stuff that's much cheaper. If you can wait that long, political lawn signs will be free come November (and many much sooner). "Fan fold", the foam board used behind aluminum or vinyl siding on side-over jobs, is also quite cheap. Plain old corrugated cardboard is also a reasonable alternative.