Lined Metal Ductowrk versus Wrapped External
Still trying to sort through all my options as it seems I have yet to get the perfect quote ( not speaking of pricing mind you ). But, today's quote threw a curve to me as the installers seemed to do everything by the book, checking for leaks in my home, carefully building a heat load calc ( Manual J and D ) , etc etc and suggested many things no one else had done, including measuring the leakage around my existing vents and returns.
Their philosophy was ot get the ductwork done as perfect as one can and then worry about the equipment next as most other installers had gone fairly quickly to the equipment, even the other 2 who had done some level of heat load calcs. They also seemed less inclined to get into the higher end equipment unless the calculated cost payback demonstrates it is a worthwhile purchase.
Not all my quotes are back in but the last installer wants to use lined metal ductwork for the main trunk part of the system. I'm assuming their calculations via software is taking inot account the friction losses due to the lining as well as increaisng the duct sizing due to the lining thickness ( will verify this ). They said the liner they use has a mold preventative, etc added to it.
I have a few questions to ask them but was curious if a lined duct system ( for the trunk ) can be effective and if it can stand the test of time ( say 15 years ). I'm fairly ignorant of this type of insulation and aside from the obvious concern of fiberglass being able to blow throughout the system, I was curious as to how effective it can be, if done right. Also, how much insulation does one get if using 1 inch thick lined insulation.
Thx in advance. I'm close to making a decision and everyone's help here has helped me better evaluate each installer.
i want metal on the inside!
hard enuf to push a fluid, without intenionally adding any restrictions!
darn sure do not want fiberglass linner!
why not put ducts into conditioned space?
Last edited by cem-bsee; 03-18-2008 at 05:36 AM.
harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!
Thx Cem Bsee.. it's in the attic so not much I can do about where the ductwork is going to be. I'm going to discuss this with the installer as soon as I receive their quote to see where they are in other respects. I very much liked everything about their approach, their testing, etc. They spent about 3 hours at my home, and were the company who most consistently said what I read here in terms of how they load tested the house, performed all the required calculations and also how they verify the system once installed. Only caveat for me was the lined ductwork, and of course will have to wait to see what the final pricing is. Thx I'll need to ask more questions today about the lining itself.
Originally Posted by cem-bsee
Hard to size the ductwork without knowing the equipment specs.
Lined sheetmetal has about the same FR as ductboard.
Standard 1" is an R4.2 value same as 1" ductboard.
Thx Beenthere. I actually have confidence this company will properly account for the friction losses of the lined ductwork. I'd say if anything at all I do beleive they know what theya re doing form a duct design perspective and sizing things to match properly. Course I could be wrong but of the 6 or so quotes i've worked on, this one was the most thorough in terms of the emasurements taken and the detail of what they would be doing. It may, of course, be the other 2 companies that performed heat load calcs were doing similar things but not verbalizing it as well though no one else took the time to measure how much leakage I currently have. SInce every installer had quoted pricing usng the existing vents/boots, it was nice to see how much leakage is associated with them. And the current leakage is high enough to warrant having them better sealed.
Originally Posted by beenthere
All that said, I'm still struggling a bit to accept the idea of a lined duct as my gut instincts make me lean toward wanting metal with wrapped insulation. They did mention some of the pitfall sof wrapped, one being damage cause by homeowners stepped on, sitting on, etc. and the potential for it to become damaged and or torn. It seems to me the biggest disadvantage is simpply the time ( labor and cost ) of doing it right. It also seems somewhat odd that we would run R8 flex duct coming off the lined trunk which at best would still be R4 ish.
Am thankful for you guys to put this in proper perspective. Perhaps in the big scheme of things I'm simply over thinking it. Late last night I had to share some insight with my higher power at home ( spousal unit ) that I find it odd we went out and spent XXXX.XX dollars on a refrigerator and yet seem to be balking at what the hVAC system is going to cost. I think we are getting over the price now and getting more into the let's do it right ( though that doesn't mean we need a 23 SEER AC and all the bells and whistles.. just a good system done right is enough ).
Everything else about this installer seems in place though they are the only ones who are making an effort to keep the equipment down in price versus going to more elaborate systems. I know they have installed the higher end equipment and are willing to do so but they try hard to show the homeowner how long it will take to payback the investment.
Must admit, buying a refigerator is a LOT simpler than this! Just so many different opinions out there and of course each installer is, in the end, still a salesperson. Is never totally easy trusting the person who wants to sell a product with thei rown given limitations! If i can get past the idea of lined duct, it may work out!
Wrap can always be repaired, or removed and replaced.
Liner, if it comes loose, is a much harder repair.
So I personally don't see wrap having a pitfall.
Stay with wrapped ducting. I've seen the problems that can occur with lined duct work and it's always very time consuming and expensive to repair. If your contractor is concerned with damage that can happen to wrapped duct, imagine what the damage would be if a lined duct was crushed or deformed in some way. The only advantage of lined duct is that it's usually quieter than un-lined.
No lining on the inside of the duct. It is the worst place you can put it for indoor air quality. Holds the dust, breeding ground for mold. If it gets wet you are SOL.
Keep the insulation on the outside. Seal the duct seams with mastic.
I would agree, Wrap the outside and keep the inside clean.
Originally Posted by beenthere
To all above, much thanks. It seems overwhelming that most prefer insulation on the outside, if properly done . My gut feel is I tend to agree. I did speak with the installer about how they line the inside and felt better about it after doing so. I really don't have the memory to recall the details but it sounded like it was a well done effort so at least that part doesn't bother me as much. Plus is warranted for 10 years, so again, is a lil something. It was confirmed to be R8 worth of insulation as well and based upon how they were using their heat load software ( Manual D and J ) and the amount of time they took to measure the house, windows, vent locations, direction of home, even measured home in leakage, I feel certain the friction losses were properly factored into the sizing equation. They also measure and verify duct flows after the install is complete, as well as complete pressure testing.
Originally Posted by second opinion
Of the 6 contractors I've spoken with, they are the only ones to do this. While we have over 350 HVAC contractors in the county I live in, it seems more simply means more to sift through. While the internally lined duct is one issue I am a lil hesitant about, everything else about this contractor is superb, even down to their Angie's list ratings.
I've been amazed after reading here how many contractors are blowing smoke out their rear ends. Is a shame because I know there are many many good ones out there and many of you here have been incredible in helping me understand this stuff. Based upon what I've learned here, I feel very comfortable with these guys. They seem to take the time to do things right, do their own work ( no technicians, no subs ), and don't work fast.
I spoke with the sales guy form the other company I am dealing with today and he disappointed me ( and yes I realize he is a sales guy but he is also the one who did all the measurements for using with Wrightsoft. I think this company does most things well but after looking at his duct design I found some obvious flaws, especially as compared to 2 other companies that had performed heat load calcs. It wouold have resulted in a couple returns being undersized and the supply to my bonus room being undersized. They also stated they did not leak test the system after the job was complete, something the first installer does do, nor did this one verify any pressures inside the system once done.
Just seems to be difficult to find a company who does it all right! I may speak with the owner tomorrow on the mis sizing issues but probably will end up with the other company, even with the internally lined duct. It isn't that I’m ignoring anyone's advice here but at this point it simply seems the lesser of the evils since they do so many things so well and that is a cut way above the rest. If i live to regret it I'll be the first to eat some crow and say I was warned. We'll see how it plays out after I work with the owner of the latter company. Both companies remain in the game but there is a gap that is widening between them )
If your only issue with the contractor you like is the lined ducting, ask for a price difference for un-lined and wrapped. A ten year warranty sounds good and maybe there's a lining product out there that some of us here are not aware of that performs better than our expierience has shown. Maybe the contractor can give you the name of the liner maker and you can post it here. I have to admit I'm curious why this contractor uses lined ducting besides the fact that it may save some labor hours.
I rarely complain ( too much ) about getting older with exception of the shoulder pain I'm currently experiencing.. but seems my 40+ memory sometimes really kills me ( I prefer to think it's the 40+ being BUSY but fear it is the former ). I'll see what I can do for getting the detail. I know it is made locally so it may well be a custom project though certainly the type of insulation no doubt is a standard product of sorts. I do know after asking several time he feels very storngly about how well the product works and based on his user ratings ( 2 diff places including Angie's List, not to mention BBB lack of complaints ) it would appear he is having good success with it.
Originally Posted by big johnson