Duct insulation in conditioned air space
Duct insulation in conditioned air space
(OP)
I know that codes do not require duct insulation when SA or RA ductwork is installed within a conditioned air space. Is there any thermal benefit to installing insulation in/on this duct? I need documentation to prove the point. Thanks.





RE: Duct insulation in conditioned air space
Uninsulated supply duct with temperature bellow space temperature may develop condensation. If air heating is used via supply air, heat distribution will not be achieved according to design hwn having considerable losses over duct surface even if it takes place in heated space.
This is not something code articles should convince you about. You need to learn trade first.
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space
knowledge is power
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space
knowledge is power
RE: Duct insulation in conditioned air space
as per any kind of codes, of course i'm not familiar with florida codes, but in generals it is fire codes that prescribe insulation in some cases, and energy efficiency coded in others, both are prescriptive if applicable.
we also did not learn if supply ducts serve for ventilation only or for cooling as well. i can hardly imaging that condensation is not an issue if duct serve for cooling - how high air flow rate you need to cool with relatively high air temperatures?!
un-elaborated request to apply more insulation resembles mentality of some contractors - they fear of condensation, are not familiar with calculations, but do not want to seek for professional advice.
RE: Duct insulation in conditioned air space
Drazen, I think you missed the point. I was looking for back-up that insulation on duct, that's purpose is to cool, installed in a cooled space, is a waste. (unless for acoustics) Thanks for trying, though.
RE: Duct insulation in conditioned air space
@ Iservem, Please refer to the post Drazen,first paragraph.My experience why a supply duct should be insulated is based solely on geographic location circumstances. In one of my project,US territory in the pacific.the USAF-OICC decided to have the duct insulated after the ductworks and diffusers are having a lot of condensation. they have this condition 9mos in a year.Other buildings have corroded ducts and diffusers due to condensation.
So, it looks like all you need is graphics and calculations to show what is appropriate the situation. HTH
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space
did you discuss with the person who gave this opinion?
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space
http://www.jm.com/content/dam/jm/global/en/hvac-in...
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space
It lays out the calculations you should do to determine the necessity of duct insulation.
Armed with ASHRAE and calculations supporting your position you should be good to go.
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space
if you are the owner tell this architect to support his opinion in written approved from a registered HVAC engineer.
if you are an employee, then make sure you don't bear the responsibility on your shoulder.
as your project has more than one management, you need a lawyer support not an engineer support.
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space
Regarding insulation: assuming this is cooling and the duct is above the conditioned space, there is no energy waste since all the "cold" would drop down.
As for humidity, it depends on your inside conditions. If you supply 55°F air, the outside of the duct will be a touch above 55°F.
But the approach to insulate in such situations can backfire as well if your insulation ins't vapor-tight. If this isn't an area with high infiltration 9i.e. lobby) this may not be a problem. not sure if in florida lobbies are usually treated differently.
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space
knowledge is power
RE: Duct insulation in conditioned air space
LEED has nothing to do with sustainability. Here some entertainment on LEED
Some interior designers and landscape architects came up with a scheme to make money and give you credits for a building barely meeting code without any verification (no, verification by the design team that profit from additional LEED fees doesn't count).
Take the $30K you pay to USGBC and the $100K you pay the AE for the paperwork, and the $100K the GC needs for the paperwork and use that same money to get a sophisticated HVAC control system and build airtight... that would be truly sustainable. but it doesn't give you a plaque.
RE: Duct insulation in conditioned air space
I gave you a star for that link, I watched that lecture to the end, at times I laughed my ass off, But I also learned a few things.
B.E.
You are judged not by what you know, but by what you can do.
RE: Duct insulation in conditioned air space
a lot to learn from his website. i had spent nights just reading and reading..
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space
It doesn't matter where you are, south Florida, California, Michigan, Canada; if you put uninsulated ductwork in a conditioned space you are going to have condensation problems. The only possible exception to this would be in a dry arid environment and your space RH is close to or below 40%. The fact is the temperature of the air in the metal duct is going to control the physical temperature of the ductwork as HerrKaLeun mentioned above. It should be noted (and has been observed by me personally) that even insulated ductwork can get condensate if the air temp inside is sufficiently low.
Another benefit of insulation on ductwork is that it keeps the temperature of the air 'in' the duct more constant. This is so the temperature of the air coming out of the most remote diffuser is as close to design as possible. This is beneficial as it helps to maintain constant temperature throughout your space. Without it you will get hot and cold zones.
Based on your statements above, I surmise your argument for not insulating exposed ductwork is from observation of existing installations of exposed spiral metal ductwork. What you may not realize with these installations is that even though the spiral metal duct is not externally insulated, it is in fact internally lined with insulation. The internal lining and metal exterior of these ducts is much more visually appealing than duct with external insulation.
Regarding insulation of the return duct, totally unnecessary as the temperature of the air in the RA duct is about the same as the conditioned space so little to no heat transfer will happen. I would consider lining RA duct near the AHU or a fan for acoustic purposes though.
RE: Duct insulation in conditioned air space
I appreciate your input, as it is on topic and I have learned a great deal throughout this thread.
Here's my point (or gripe): The SA & RA ductwork are in conditioned air space and are to receive R-4.2, 1" duct liner. I do not believe any more insulation is of ANY benefit, but because the project specifications seem to be a "cut & paste" compilation of contradictions that were never sorted through until now ... the architect wants to put 1.5" ductboard on the outside of the duct, in addition to the 1" liner. Resulting in R-10+ for no benefit, but a significant waste of material (and labor). which of course will result in a change order request and battle for nothing!
RE: Duct insulation in conditioned air space
knowledge is power
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space
As for code, check in your copy of the Florida Mechanical Code. In International mechanical code (to which I happen to have easy access), section 603.12 states "Provisions shall be made to prevent the formation of condensation on the exterior of any duct." Having worked with FMC in the past I know that it closely mimics IMC (early versions were identical and last I checked there were few differences) and would be very surprised if this verbiage is not in it somewhere. Don't expect any code to say "provide insulation on ductwork" because not all ductwork is sheet metal or requires separate insulation.
HerrkaLeun posted earlier about supply air being 55°F, this is a very common temperature for supply air. It also happens to be the dew point for air at 75°F and 50% RH. However, since no-one can guarantee that your space will never stay at this temperature and RH (you will have people in the space right?), the dew point is going to go up and down as well. So any surface that has a temperature close to 55°F is going to be subject to condensation, this includes uninsulated metal duct. Therefore to meet building codes, something needs to be done to raise the temperature of the surface of the duct. The easiest, cheapest, best method is insulation.
I don't know if I missed it earlier or not, but for the architect to want BOTH ductboard and liner is overkill. Go with one or the other.
RE: Duct insulation in conditioned air space
RE: Duct insulation in conditioned air space