Greetings. Long time lurker, first time poster.
The lowdown: Bought a 1984 built foreclosed 1.5 story home last year. Did an energy audit and found out the house leaks like a sieve. Had all new windows put in which helped tremendously now I need have the very leaky, old return ducting done. So far I have had two contractors come out and bid.
The equipment (existing):
Trane XB Downdraft Furnace (Model #TDE1B100A9451AB)
Trane Coil (Model #4TXCB048BC3HCAA)
Filter box: 3 - 10x30x1 filters
Trane 4 ton outside a/c unit.
Supply ductwork in slab, no dampers
1 - 16x32 return in central hallway that is nothing more than a joist cavity running back to a duct board end with two flex duct attachments, once which is broken loose. Can actually feel cold air come back once furnace shuts off.
1 - 12x12 return in upstairs master bedroom. Master bedroom takes up half the upstairs. Hallway from bedroom to master bath overlooks living room (22 foot vaulted ceilings) with 3 shutter doors.
(A) $$$ : 1st Contractor came out, stated that the return ducting from the box into the unit was fine. Would replace the box and flex duct and upgrade from 2 - 16" to 2 - 18" and fix broken attachment on return ducting. No calculations, nothing else but a visual.
(B) $$$$: 2nd Contractor came out. Inspected all the registers in the rooms, took measurements, used an Ipad with some sort of software on it to calculate and offered the following:
- enlarge the two returns to 20x30 and 14x14
- replace furnace return plenum
- run new 20" diameter metal ducting from plenum to roof rafters, split into two 16" diameter metal ducts to go around roof rafters (see picture 3) back to 20" and straight to return joist run. All insulated and hung properly.
- remove box and instead have master bedroom return "t" into main duct with damper
- for extra $$$ add two more returns to back two bedrooms feeding into main return duct.
The pictures of what I am dealing with:
1st picture is looking at the ductwork coming from the top of the furnace closet.
2nd picture is looking under the roof rafters to where the existing flex duct ties into the joist area. (Have to remove my cover front patio ceiling to get to this area, adding $$$ to the job)
3rd picture is looking at where the flex duct from the main return joins up with the master bedroom return. (yes it is noisy). To the right of that is where the roof rafters drop down to the top plate and tie in to the covered patio roof. No way they can mess with the rafters or top plate which is why they have to split the ducting. Only room enough for 16"-18" ducting, between the rafters and the top plate.
4th picture is a close up of the box.
5th picture is where the duct drops down into the unit.
6th picture is looking up inside the box that's on top of the filters.
Need to know if option 2 is a good enough deal to go with. Option 1, I know, from what I learned here, is not the answer. The hair on my neck (what little is left) stood up when I heard those words "I've been doing this for years".
Are there any other questions I need to ask? Anything anyone sees could be done differently ? I probably will end up getting a 3rd bid but I travel for a living and I don't have much time to deal with this, nor a ton of money to throw at it wastefully. (Windows are expensive!)
Next up is having the roof replaced along with the decking. Ugh.
I have appreciated all the information I have garnered from this site and all the amazing professionals here. Helps make informed decisions. You are all a credit to your profession. Yes, you are right, this stuff is NOT easy. Dont know how you guys do it.
Thanks again for any and all input!
Thank you for the pictures, they really help. I'm still not 100% sure I understand how the #2 contractor is going to do it exactly. The first contractor you can forget.
Let me give you some facts......a 30"x20" RA grille is good for 1200 cfm. A 14"x14" is good for 390 cfm. The total is 1,590 cfm, you need at the minimun 1,600, it's close enough for most. I alway like to design for more, but that's me.
16" rigid hard pipe wrapped with insulation is capable of 1,400 cfm. 12" rigid is good for 600 cfm.
I hope that helps alittle. What has me befudled is why the 20" to 2- 16" and back
I can't picture what he has in mind. But he's on the right track.
Thanks George for the reply.
The reason why he has to split the 20 into 2 - 16's is because of where the ducting goes to meet up with the return. My house is weird. The only attic space is over the garage due to cathedral ceilings throughout the house. To the right of the box where the two flex ducts converge is a roof rafter right in the way. where my roof over the garage meets up with the roof line from the front of the house. Between it and the roof sheathing leaves a space only big enough for about an 18" duct on both sides of the rafter. He explained to me that if he reduced it down to 18" to make it thru that gap and back up to 20" he would bottle neck the return air. It was better go around the rafter on both sides with the 16's. From what I remembered, he said he calculated not much of a flow loss by doing that.
I will get a picture taken tomorrow to make it clearer.
I'll ask about the return sizes. I have to say he was pretty thorough. He spent the better part of yesterday afternoon with me.
That was my guess for the reason for spliting the 20" duct, but like I said in my last post, it's not necessary. But he's on the right track.
Do you have filter grilles? Or is the filter at the furnace?
The filter box is at the furnace.
What he proposed makes sense with what little I know, as I do NOT want any of the structure modified in any way. This house is solidly built, although leaky and I dont want to upset the apple cart.
I think I have the only house that whistles during a blower test.
Picture 1 is showing how the existing garbage flex duct goes under the roof line. Yes the duct on the right is pinched. Shows why we can't mess with rafters.
Picture 2 is showing the roof deck on the front of the house and where the return line turns to go into the joist cavity.
Picture 3 is the filter box you asked about: holds 3 10x20x1 filters and I replace the pleated filters monthly. Its a downdraft furnace.
Not to hijack my own thread but other homeowners out there that might be considering doing an energy audit. Like Nike says JUST DO IT! Well worth the money to show you where you are losing money! The 2nd month after I replaced windows, put in recepticle and switch seals, caulked outside, had some other work done I dropped approximately $125 in monthly electric bills and so far this winter I have dropped $45 in gas usage.
If I can just get this return done correctly I know this will help tremendously. The second guy is coming out again Monday to discuss this even further, so any other things you can tell me to ask I would greatly appreciate it.
Third bid is coming on Wednesday.
Look at the wall in the third picture in post #1. I assume that is the wall to the house?
Would it be possible to put a RA on that wall which would eliminate the need for all the other work (except to "tighten up" the existing RA pipes)?
Thats the wall to the master bedroom. Where the silver box is - thats where the existing 12"x12" return is for the master bedroom.
told ya I have a weird house. I think this thing hates me.
No, that's good. Like I said, he can add another RA grille there (no prob) and omit all the other work (if the new one is sized properly.)
Originally Posted by Bald Because Of Her
Just a idea to throw at them.
Note: You'll need some distance in the (new) duct to make sure the new grille is quiet.
Yeah there was a concern since the top of the unit is just right around the corner approximately 25 feet.