# feasability of replacing AC flex ducting by myself?



## Queequeg152 (Dec 2, 2011)

so apparently the ducting in my attic is substantially leaky... to such a degree that i can actually feel cool air flowing down the attic and out the soffits that i was in process of replacing. from what i can tell several joints branching from a main rectangular duct are leaking, i suspect that they are responsible for the majority of that cold air i felt. i was aware of the poor condition of the ducting prior to this point... but honestly i had not thought it was as bad at this. 

what concerns me however; having spent the last few days reading and researching proper residential hvac installations, is that the attic ducting is just garbage. nothing is strapped, the ducting runs over each other... theres alot of slack in the smaller ducts, and there are dozens of fairly bad kinks that ive been able to observe. i havent seen any mastic used anywhere, just tape and zip ties. 

i had an HVAC company(apparently they only install trane products) come out last year to adress some minor issues. while they were there i asked if they could service the coil in the attic, at the time i was under the impression they needed cleaning somewhat regularly, it was my understanding at the time that it had not been cleaned in like 5 years. anyway they didnt seem to want to clean it, they actually said it appeared to be in OK condition along with the rest of the ac system. i asked if could give me a quote for just servicing the ducting. he hem'd and hawed for a while and i got the general impression that he didnt want to do it, but thought i personally should do something with it. 

my question is simply... can a grown fat man about 300lbs 6'3" feasibly replace a small single story homes entire poorly constructed AC ducting with something far more appropriate for a 14 cent/kwh electrical service? its a fairly small single story cheaply built tract home built in the 70's , i think there are only 19 registers? 
im mostly worried about what i should use to replace the main trunk line with and how to get it back into the attic, it looks like the existing one is just sheet metal? is that even possible? it seem like it would sweat badly..which is didn't appear to be doing. i cant actually get to it without hands and knees crawling and probably cutting some drywall. i understand that there is something called duct board that sounds like a suitable replacement, but can i work with it without specific tools? i have at a table saw and all the typical power tools, but nothing specific for sheet metal working. 

anyway back to the original question. should i even bother trying? should i just fix what i can get to? if i can actually just blow out all the old duct work, is there anyway to do it in phases such that i can basically keep the ac functioning while i replace sections of the duct. 
im going to buy the manual D and J books regardless so hopefully what ever i end up doing is done correctly. 

thanks in advance for what ever advice you can give me.

edit: bad spelling, grammar etc.


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## Doc Holliday (Mar 12, 2011)

I'm not certain ow physically fit you are. Just off the top of my head I've never seen anyone over maybe 200 pounds work an attic and even then they only do the equipment, not the ducts. One slip and you'll be on the living room floor not to mention if you become too hot and you can't get out in time, say you're in a tiny crevice on the back of the home and away from the staircase, and you're all alone and have a heat stroke up there than that's it, game over. You don't have to be thin or fat to have a heat stroke, many people have 'em in attics. 

Infortunately, and please don't take this the wrong way, attic work is a thin and hopefully athletic man's game. 

Your metal trunk line is insulated internally, why it's not sweating. 

Duct board is very easy to work with but you may need to practice on some before actually attempting the entire trunk.

You don't neccessarily have to mastik all collar/duct connections as long as the liner is taped to the collar and the insulation is pulled all the way up to the trunk line take off and the entire thing is properly zip tied with duct zip ties at the collar. You do need to at the very least foil tape or mastick the collars to the trunk line to prevent air leaks there, but not the duct to the collar, that's what I should've said the first time around.

Your ducts on the floor are a no no. They should be strapped up.


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## kilosos2 (Oct 14, 2010)

It's fairly easy to replace ductwork. You just need a good plan and get some books from ADC or NAIMA to see how ducts should be installed. Manual D is very good to do and it will help you design your ductwork accordingly to your equipment and the required cfm for your cooling needs. If you have alot of space in the attic and you can move in and out easily then go ahead! But if you feel you may have trouble and stuff then just hire a company but you tell them what to do so it can be done properly. The only thing suks is the cost is very high if you hire a company. So that is something you might want to keep in mind. (especially with 19 registers!) The pro's on this forum can help guide you on your ductwork. I changed almost 80% of my ductwork and it wasn't that hard at all. I even suggest if you can get some help from some friends or hire a local handy for the day will help install your ducts even faster! It won't be the actual work that will take that long but it will be the planning part. good luck


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## Doc Holliday (Mar 12, 2011)

Ask any hvac technician on here or any other forum or in real life, the minute a home owner "tells" us what to do as if we don't know our own job and you're on your own, we're out of there. 

Talking to us, informed with the recently studied knowledge that we as well have and have had for years, discussing a plan of action together is alright. That way you can tell from conversation who is on the same page. 

Tell us how to do our job? Do we tell you how to do yours as if we know more than you in your field? No. 

Just saying.


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## kilosos2 (Oct 14, 2010)

Doc Holliday said:


> Ask any hvac technician on here or any other forum or in real life, the minute a home owner "tells" us what to do as if we don't know our own job and you're on your own, we're out of there.
> 
> Talking to us, informed with the recently studied knowledge that we as well have and have had for years, discussing a plan of action together is alright. That way you can tell from conversation who is on the same page.
> 
> ...


Sorry , I worded that wrong. Yes your right , we should do our research and see if the contractor knows what they are talking about when making a bid for the job.


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## Queequeg152 (Dec 2, 2011)

Doc Holliday said:


> I'm not certain ow physically fit you are. Just off the top of my head I've never seen anyone over maybe 200 pounds work an attic and even then they only do the equipment, not the ducts. One slip and you'll be on the living room floor not to mention if you become too hot and you can't get out in time, say you're in a tiny crevice on the back of the home and away from the staircase, and you're all alone and have a heat stroke up there than that's it, game over. You don't have to be thin or fat to have a heat stroke, many people have 'em in attics.
> 
> Infortunately, and please don't take this the wrong way, attic work is a thin and hopefully athletic man's game.
> 
> ...


lol, as bad as this sounds, the attic is actually only 5-10 degrees hotter then the conditioned space i estimate, and were talking at about 2pm cst. the leaks i spoke of are pretty bad i dont know if i got that across. i dont think ill get anywhere near hyperthermic while up there untill the leaks are fixed. 
for what its worth, while i would never consider myself fit, im not some sort of asthmatic or diabetic or some kind of scooter bound fat guy. :laughing: 
i am worried about the smaller spaces tho, but there is really only one, and that's the stretch of attic that has the main duct, the roof is sloping down toward the edge at that point and is pretty low. i was hoping to just cut several access holes where necessary, in the drywall in between studs so i can get stuff;and get at stuff, in the attic space. 

if i were to replace all the ducting or atleast a good chunk of it, my goal would be to get it in such a condition that when i do actually replace the AC unit(within 5 years probably), id like to have done the job correctly, such that i could have it installed with this proposed ducting. is that reasonable? should i perhaps step up the quality of the materials i use in anticipation of maby installing a much higher efficiency unit later?(currently an 8 seer 4 ton i believe)
anyway ill reserve anymore questions untill i really dig into those manuals. 

kilosos2, its actually 13, including the tiny ones in the guest bathroom and laundry room. idk where i got 19. 

thanks for taking the time to reply, i really appreciate it.

edit: grammar


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## Doc Holliday (Mar 12, 2011)

I wasn't trying to be rude, you asked and so I told you what I thought. 

It gets well over 130f in the attics I'm in. In the middle of the day I can only go in for about 30 seconds and I have to come out and rest for 10 minutes, go back up for 30 seconds, come back down and cool off for 10 minutes and so on and so forth.

If you think you can do it than go for it. It's really not all that difficult. Once the science (manual j and d) is done with the labor can be leisurely seeing as how you don't absolutely have to do it all in one day as we would if you hired us. You can do one or two duct runs a day until the job is finished or however you want to tackle it.

For now you may want to simply concentrate on the existing metal trunk line, sealing it all up with aluminum tape and/or mastik (all the collars which are connected to the trunk line as well) and then only run new flex ducts. That is if the trunk line is repairable, not squashed and torn or flattened, and is simply leaking air at the seams which can easily be repaired.


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## beenthere (Oct 11, 2008)

Your sheet metal duct is lined duct. Which means its insulated on the inside. 

Duck board, is best when cut on a duct board machine. There are hand cutters for it, but the set isn't cheap.


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## Queequeg152 (Dec 2, 2011)

Doc Holliday said:


> I wasn't trying to be rude, you asked and so I told you what I thought.
> 
> It gets well over 130f in the attics I'm in. In the middle of the day I can only go in for about 30 seconds and I have to come out and rest for 10 minutes, go back up for 30 seconds, come back down and cool off for 10 minutes and so on and so forth.
> 
> ...


oh i wasn't offended in the least lol, if i was sensitive about being fat i wouldnt of mentioned it.sorry i shoulda made that clear :laughing:. i live in houston, so i suspect those temperatures are shared here as well... all the more to motivation to do it now and not in June-august. 

on another note, im looking at the ACCA store for the MANUAL J and D, and i see that they are 300+ pages? i thought i was getting some sort of booklet with charts graphs spreadsheets etc for calculating duct sizes, not a 300 page book. am i missing something?


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## Doc Holliday (Mar 12, 2011)

Coincidence? I live in Alief, Bellaire and Kirkwood, southwest Houston. Been doing a/c here for 12 years. It's Houston attics I was talking about.


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## Doc Holliday (Mar 12, 2011)

A Manual J is going to take into consideration the geographic location of your home (Houston), which way the windows face and for how long, if they're single or double pane, how many, insulation value, awnings and trees, etc. 

You may not like what you find meaning you may be needing to change out the entire system and duct work. 

You can purchase the software online and do it with a computer. There's also a few local companies that do it for a price. 

Cool Science is one of them. Can't tell you the price, though, but they are supposedly highly experienced at this, heat load analysis aka Manual J, as it's all they do.


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## Queequeg152 (Dec 2, 2011)

Doc Holliday said:


> A Manual J is going to take into consideration the geographic location of your home (Houston), which way the windows face and for how long, if they're single or double pane, how many, insulation value, awnings and trees, etc.
> 
> You may not like what you find meaning you may be needing to change out the entire system and duct work.
> 
> ...


i see, i wasnt sure if i was looking at a course textbook or something. am i right in assuming i can safetly go with the manual J-8 abridged version? my home is quite common , none of the out of the ordinary elements listed on the acca store. 

i did see a few sites that sold the software, but tbh im looking forward to the challenge of doing it by hand. i do alot of cad work at my job so i suppose ill copy this houses bluelines into vanilla cad so i can get the lengths of duct etc necessary when doing the manual D. hopefully i dont find anything i didnt want to lol...

i actually live in sugarland, around 59 and 90. lol if i end up falling through the ceiling or something i may just have to give you a call. :thumbup:


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## Doc Holliday (Mar 12, 2011)

Oh man, now you've gone and put me on the spot. I've never once performed a heat loss analysis so sorry, I can't help with the technical aspects. I only know what they consist of. 

A few of these other guys have though so hopefully they'll jump in.


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## beenthere (Oct 11, 2008)

Queequeg152 said:


> i see, i wasnt sure if i was looking at a course textbook or something. am i right in assuming i can safetly go with the manual J-8 abridged version? my home is quite common , none of the out of the ordinary elements listed on the acca store.
> 
> i did see a few sites that sold the software, but tbh im looking forward to the challenge of doing it by hand. i do alot of cad work at my job so i suppose ill copy this houses bluelines into vanilla cad so i can get the lengths of duct etc necessary when doing the manual D. hopefully i dont find anything i didnt want to lol...
> 
> i actually live in sugarland, around 59 and 90. lol if i end up falling through the ceiling or something i may just have to give you a call. :thumbup:


ACCA has a spread sheet for MJ8 you can download, and also one for Manual D.

Its involved, but well worth it.


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## Queequeg152 (Dec 2, 2011)

thanks beenthere, i wasnt aware of that spread sheet. 
so the actual manual J and D books are strictly guides for filling out these spreadsheets? or are they more of a learning discourse explaining why things are done this way and not this way? my manual J wont be here till tuesday, cant wait to dig in. 

i have another question somewhat unrelated to the OP. i was curious if there is someway i could quantify any improvement in air speed or even air leakage reduction? 

i have an regular vane anemometer i use for measuring airspeed. as well as a static differential presure gauge for 0-2 inches of water. im thinking i could run the ac blower without the cooling off, and the registers blocked with tape and cardboard or someting... and just measure the static pressure inside the ac plenum with the pressure gauge before and after. id just measure the airspeed comeing out of each of the ducts with the anemometer obiviously. 

i genuinely know nothing about hvac, is this idea hopelessly misguided? sounds too easy to be honest. ive seen how they use some soft of a fancy syncroness blower to pressurize entire houses to measure air leakage... but in this case id just be compairing before and after static pressures with the ducts blocked off. 

thanks.


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## beenthere (Oct 11, 2008)

A slightly better way is to use your static probes and manometer to measure the static in the return and the supply at the air handler. then use the install manual to tell you how much air it is moving. then measure how much is actually coming out of your supplies, and being taken back through your return. This will give you both total duct leakage, and tell you which is worse, return or supply.

I have seen systems that the return at the unit was getting 1600CFM, but only 1200 was being brought through the return grilles. While the supply at the air handler was putting out 1600CFM, only 1300CFM was coming out of the supply registers.


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## Queequeg152 (Dec 2, 2011)

i think i see what you are saying, by probe i assume u mean a pitot tube? the pressure gauge i have is a dwyer 2002 magnahelic, but i dont have a pitot tube for it. i see tho how you could use a pitot to measure the static pressure at a specific part of the duct, then just calculate the flow. something tells me however we are not talking about a simple Bernoulli equation to calculate the flow rate. id have to read up some on that, been a few years since pe201,202 lol...
http://www.dwyer-inst.com/Products/Product.cfm?Group_ID=26&sPageName=Ordering

do you think i could build a pitot tube? im thinking steel brakeline tubing or something along those lines...


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## beenthere (Oct 11, 2008)

If you have the manual for the unit. All you nee to do is check the static pressure. you wouldn't have to use a pitot tube. A pitot tube could be used, but isn't necessary. Dywer A303 static probe is all you need, and you can make it up yourself.

Using a pitot tube to measure velocity pressure, and then determine CFM. The formula would be 4005 times the sq rt of the velocity pressure divided into the sq ft of your duct work you took the vp of.

EG: a 2 sq ft duct. vp = .05, the sq rt of .5=.2236. .2236 time 4005=895.5, 895.5 times 2 sq ft equals 1791 CFM.


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## Queequeg152 (Dec 2, 2011)

beenthere said:


> If you have the manual for the unit. All you nee to do is check the static pressure. you wouldn't have to use a pitot tube. A pitot tube could be used, but isn't necessary. Dywer A303 static probe is all you need, and you can make it up yourself.
> 
> Using a pitot tube to measure velocity pressure, and then determine CFM. The formula would be 4005 times the sq rt of the velocity pressure divided into the sq ft of your duct work you took the vp of.
> 
> EG: a 2 sq ft duct. vp = .05, the sq rt of .5=.2236. .2236 time 4005=895.5, 895.5 times 2 sq ft equals 1791 CFM.


excellent, thanks alot im ordering one of those right now.


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## Queequeg152 (Dec 2, 2011)

i went ahead and sealed all the duct work i could find that was leaky over the weekend. i cut two small holes in the dryway and had a look around the small area that houses the plenum.

its actually not as small as i thought. i cant stand or crouch even, but i think i could crawl around, i have some leftover osb from a siding project, im thinking i could lay it over the rafters and crawl about somewhat easily. 

anyway when i was putting the ductwork back together i noticed the inner part of the duct is actually like a plastic meshwork? that cant be good can it? any hole in the outer covering would mean a leak... what do you guys think about this stuff? 

heres a picture.


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## beenthere (Oct 11, 2008)

Replace that duct, its garbage.


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## Doc Holliday (Mar 12, 2011)

New code requires R-8 insulated ducts. Not certain but you may be able to purchase it yourself from Quiet Flex on Britmoore, north of Clay I believe.


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## Doc Holliday (Mar 12, 2011)

beenthere said:


> Replace that duct, its garbage.


 
I've never seen that mesh liner duct before.


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## Queequeg152 (Dec 2, 2011)

house was built in the 70's so, im guessing builders were more caviler back then. 

ill look into that store doc, thank you. 
im going to wait till i get my books in tho. id like to get a good handle on what im doing first.


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## kilosos2 (Oct 14, 2010)

I wonder how many more of your ducts are like that ? Actually what the hell? How the hell is that a duct ...with all those holes?


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## beenthere (Oct 11, 2008)

Doc Holliday said:


> I've never seen that mesh liner duct before.


Only seen it a couple times. old mesh garbage.


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## Queequeg152 (Dec 2, 2011)

kilosos2 said:


> I wonder how many more of your ducts are like that ? Actually what the hell? How the hell is that a duct ...with all those holes?


pretty sure they are all like this.


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## kilosos2 (Oct 14, 2010)

Time to replace them!

http://www.homedepot.com/h_d1/N-5yc...0053&langId=-1&keyword=r-8+duct&storeId=10051

http://www.homedepot.com/Building-M...splay?catalogId=10053&langId=-1&storeId=10051

Have you gotten any quotes yet for replacement to see whats the cost between getting a contractor and DIY?


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## Doc Holliday (Mar 12, 2011)

kilosos2 said:


> Time to replace them!
> 
> http://www.homedepot.com/h_d1/N-5yc...0053&langId=-1&keyword=r-8+duct&storeId=10051
> 
> ...


 
I'm in pretty much the same city as Q. I can tell you it's $200-$250 per individual duct run, installed.


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## Queequeg152 (Dec 2, 2011)

i haven't actually, the people i had over last time didnt seem interested in replacing just the ductwork.


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## Queequeg152 (Dec 2, 2011)

Doc Holliday said:


> I'm in pretty much the same city as Q. I can tell you it's $200-$250 per individual duct run, installed.


so with 13 registers, thats 2,600 - 3,250? thats not terrible i guess. ill have to see what materals cost, this would take me several weekends if i did do it im guessing.


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## Doc Holliday (Mar 12, 2011)

Queequeg152 said:


> so with 13 registers, thats 2,600 - 3,250? thats not terrible i guess. ill have to see what materals cost, this would take me several weekends if i did do it im guessing.


 
Yup. I'm betting you have a few Y's which means that from the plenum itself there is fewer than 13 duct take off's. One big one split into two smaller duct runs and then to the registers.


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## kilosos2 (Oct 14, 2010)

Here's some info on ductboards. You might be interested in some of their information. The 3rd link is a guide to make ductboards and install flex ducts correctly.

http://www.naima.org/insulation-kno...ation/fiber-glass-duct-board-fabrication.html

http://www.naima.org/insulation-resources/installation-application.html

http://www.naima.org/publications/AH116.PDF


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## Doc Holliday (Mar 12, 2011)

Oops, I forgot you had a long trunk line so there might actually be 13 take offs from that.


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## Queequeg152 (Dec 2, 2011)

excellent kilosos thanks alot. looking at this pdf about duct board worried me,i dont have anything that could cut grooves like that, i wonder if i couldnt have one fabricated by a professional? 
does one typically replace all the plenums when they redo duct work? im guessing it depends on the condition they are in... 

btw what are these tools called? maby i could score some on craigslist or something since i just need it for this one project

edit: ah wait i found them, there not too expensive are they... u think i could get away with just one? im thinking a v groove tool? i could make triangle bits as well as squares with one i imagine...


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## Doc Holliday (Mar 12, 2011)

I just did a quick search and found an Amcraft on E-bay for $59.99. Malco has complete kits for well over $300. 

Shiplap duct cutting tool.

http://www.amcraftinc.com/amcraft/page1.html

http://www.toolbarn.com/malco-fgvk.html?ref=base


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## kilosos2 (Oct 14, 2010)

I have gotten away by only using the Red tool and the Blue tool. Cut with the red tool the first 3 cuts and then the last one is blue. Fold , staple and tape. And your done! I don't know if your going to use reducing extended plenum or just one size. But that you would figure out after you do all your manual d calculations.

http://www.amcraftinc.com/amcraft/page3.html

http://www.ebay.com/itm/Amcraft-108...210?pt=LH_DefaultDomain_0&hash=item35bb23055a

http://www.ebay.com/itm/Amcraft-110...560?pt=LH_DefaultDomain_0&hash=item519ebabe78

Thats what they look like but you have to buy the right size to cut which ever size ductboard you plan to use.


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## rdc (Sep 6, 2010)

I am in Houston, replacing my 30 year old flex duct, which is the same mesh kind as shown above. I also needed some ductboard y's. Found a good source for both on Westpark just east of Gessner. R8 flex from Johns Manville. All new fittings as well.


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## bobinphx (Nov 25, 2011)

some folks like ductboard, some like flex duct, some like sheet metal. When I re-did my ducts, I went with sheet metal. The cost was not bad and install was easy with a pair of tin snips, self tapping screws, mastic and tape. I can tell you that the electrical bills have been down 25 percent, since the change. Please read up on flex duct installation and read up on ductboard. There are some specific things you have to do for ductboard sealing when you expose the raw fiberglass when cutting. as far as which is best, I will say that there are no issues with steel ducts.. no air contamination (ie fiberglass and mold breeding ground, they are cleanable and the last longer. Just my thoughts and what I have been told.
I also forgot to add that a central line duct, is normally much better, in terms of air flow then a plenum box. I also feel that WYE's, pants WYE's and even Tri-WYE's are better then a plenum box with takeoffs.... again, just my two cents work... remember to watch that static pressure also!!!!!


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## rdc (Sep 6, 2010)

Bob, I'd love to have all sheet metal but its a lot of work to piece it together and then insulate it. I am using SM elbows for my corners, flex for the straight runs, pulled tight and supported. This new flex is smooth when its pulled tight. Seems like a good compromise. I thank Fred at askweldin for that tip.

Originally I was just going to replace my old flex duct and Ys with new. Then I got a look inside the plenum. My flex duct is filthy and the duct liner in the plenum is too. Now I'm wondering if I can just remove that duct liner and wrap this plenum from the outside, or whether I have to get a new one to do that. Has anyone ever refurbished an old filthy plenum like this one?


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## Queequeg152 (Dec 2, 2011)

rdc said:


> I am in Houston, replacing my 30 year old flex duct, which is the same mesh kind as shown above. I also needed some ductboard y's. Found a good source for both on Westpark just east of Gessner. R8 flex from Johns Manville. All new fittings as well.


id you dont mind me asking what kind of results did you get? id be super happy with 25% reduction is power usage. it would pay for itself in like 2 years at that rate. 
thanks for the tips, ill check those places out when i get that far. ive been stuck on some other issues, so my weekends have been monopolized so far. 

bobinphx, RE spiderduct vs trunk and branch setups. 
i have been able to read a bit into this manual j book a well as some other pdf's. and from what i can tell my existing duct is definatly a spider type setup. there are atleast 3 triangle plenums that split 9" duct into 2 6's. it dosent seem excessively convoluted as it is setup currently, but do you think it would be worth it to look into building a big trunk duct out of duct board? how do you get that into the attic? id rather not fabricate it inside the attic, yet dragging up like 10 pieces and assembling them in the attic sounds incredibly daunting. 

unrelated... but. 
im also looking into having more cellulose blown into the attic, as it is currently less than 6 inches in most places. .
this place is hopeless i swear. 
how should i go about building a new duct system taking into consideration that id like to blow in another 6" of cellulose? im thinking i would just hang the duct and plenums like 7" off the raters and have it blown in after? i dont see how i could get around in the crawl space with another 6" of cellulose in there. 

ALSO, someone left a bunch of foil in the attic... apparently its a "radiant barrier". i for the life of me dont understand how this does anything inside an attic. if anything it should be on the roof actually reflecting sunlight away from the attic. but no, its sitting on top of the insulation? what exactly is it doing? we all know that matter not at absolute zero will emit electromagnetic radiation in what ever wavelength it wants too, but will materials like hot wood really emit enough radiation to necessitate a reflective surface to keep it away from the conditioned space? i seriously doubt it personally... and what little radiated heat it reflects goes where? reflected back into the roof sheathing? what do you guys think i should do with this stuff? take it out? put it back on top of the new duct/cellulose? 

honestly my gut tells me, someone was sold a load of BS when this stuff was installed, but i really dont know.


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## rdc (Sep 6, 2010)

I got a huge reduction from opening up the blower side of the condenser and cleaning that - there was about a 1/2 millimeter layer of matted stuff covering a large part of the condenser grill. So make sure you check that. Who knows who may have run your AC without a filter? That saved me $100/mo in electricity.

I don't have any other results yet as I'm in the middle of revising my design, now that I've seen the plenum. But I'm targeting 20% reduction of cooling bills in the summer. I will also benefit from everything being clean. 

Regarding trunk duct: I read bobinphx's message as being against trunk and in favor of Ys like you already have. Pick a duct traveling from your air handler going to a Y or a register and remove it and have a look inside the plenum. If its clean then you can just replace the duct. Your earlier pic of the duct looks clean, a good sign. My mesh is clogged with dust. BTW, triangle is not a plenum, its a distribution box. You can buy those prefab cheaply at the AC place I mentioned. Ask for ductboard triangle box.

I will also blow cellulose into my attic. I have already sealed it and built dams around the bottom of my rafters. But have to redo duct first. I will be lifting it up in the air also. I am adding a bit of floor joists on top of the attic rafters to build a raised floor in a few spaces so I can still get around after the insulation is added. Make sure you use wide strap to hang the duct, and support enough so it doesn't sag. Strap available at AC supply. I will hang the strap with wire and eyehooks screwed into the rafters.

Radiant barrier - I'm installing some because its cheap enough DIY and easy enough to install and it looks good when you sell the house. I dont expect dramatic results from it, but it does have some effect. The idea is that your roof absorbs sun's heat and radiates that into your attic, heating up insulation which then spreads into interior. Barrier will reflect the radiated heat back to the roof. For installation options see attic foil dot com. I'm using their stuff and it works well.


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## Doc Holliday (Mar 12, 2011)

Filter on a condenser? Inside is the evaporator coil. On this side of the system, the inside of your home in which enveloped air is being (re) circulated and conditioned, is where a return filter would be associated with the system, not on the outside condenser. 

You can also take a hose to your (outside) condenser, rinse off the coils as best you can. Best to turn it off first. 

Now you'll be becoming close to having proper cfm across the coils which means close to a properly running system. Close, not perfect, but close(r).


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## Doc Holliday (Mar 12, 2011)

Btw RDC, I'd scrap that plenum and get a brand new one. It's actually less headache and much less time consuming and possibley even cheaper. Granted you'd have to install it yourself but it's not a big deal to do so. If you need some tools to do it with, I'm in Houston as well. 

I can't charge you as that is against the site rules, to offer my services for monetary gain, but if you do enough of your own work than when I have the time I wouldn't mind assisting. 

Btw, that would mean my tools never leave my line of site, you do the work in front of me type deal. :thumbsup:

..if you need it.


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## rdc (Sep 6, 2010)

Sorry if I mixed up the terminology - the evaporator coil up in the attic, not the condenser outside (although a lot of water condenses on that evaporator, probably the source of my confusion). 
Doc, thanks for your offer, I will PM you.


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## Queequeg152 (Dec 2, 2011)

rdc said:


> I got a huge reduction from opening up the blower side of the condenser and cleaning that - there was about a 1/2 millimeter layer of matted stuff covering a large part of the condenser grill. So make sure you check that. Who knows who may have run your AC without a filter? That saved me $100/mo in electricity.
> 
> I don't have any other results yet as I'm in the middle of revising my design, now that I've seen the plenum. But I'm targeting 20% reduction of cooling bills in the summer. I will also benefit from everything being clean.
> 
> ...


Hey thanks for the tips, do you mind elaborating on how your are going to build a raised floor? id like to build something like that in my crawl space if i can. otherwise you would have to crawl through the new cellulose i imagine. also what are these rafter dams you are talking about? are you talking about these? 










i dont know about your system but my air handler is currently sitting on the top of the raters, im not terribly comfortable lifting it up, so i thought id build some sort of dam around it? ever seen something like that? 

re: radiant barrier,
i understand the concept of reflecting radiated heat, but i guess im not convinded hot wood emits enough heat to necessitate a reflective surface. i could be way off though, as is frequently the case. ill have to take a look at that website when i get a chance. 

i would think that creating a ventilated envelope of air between he roof sheathing and the attic would be better? it seems like ive seen something like that done with polystyrene foam boards that took air up the soffit vents and out the attic vent. 
regardless i think ill just roll it all back up, and reinstall it later, no sense in not using it i guess. 

thanks.


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## Doc Holliday (Mar 12, 2011)

This is the right way.


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## rdc (Sep 6, 2010)

Queequeg152, that picture is correct for what I did for ventilation, stapling those foam channels up there, and I also put cardboard beneath them to block the insulation from falling into the soffit.

Re lifting the air handler, no, I'm not going to do that. I will build a short wall around it with plywood. My floor will be 2x8s spaced 12-16 inches apart, held in place by 2x4s nailed to the rafters and cross-braced. I will put plywood on top after I blow the insulation. I will also build a short wall around the attic opening. My water heater is up there too so I have to be able to get around. 

The radiant barrier I'm using is nailed to the bottom of the rafters, so it works as you described, creating an air channel where soffit air can flow up to the ridge vent. You can also just lay that sheet on top of your insulation. I'm not familair with the Lo/Mit that Doc Holliday is recommending.


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