The flex duct is a type of duct with flexible metal or plastic. Flexible ducts can be used to transfer air from one place to another. They are usually used in residential houses, commercial buildings, and industrial facilities.
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Which is better, R6 or R8 flex duct?
The R-value of the flex duct is the measure of how well the material resists heat flow. R-6 has a higher insulation level than R8, which means it will better resist heat flow.
R8 can create a better pathway for those that use it. If you must follow the industry standard, there is no reason to hesitate the first time you use it.
The insulation is at the roofline. The attic is part of your conditioned space. No insulation divides it from the rest of your home, reducing your heating costs by 10-30%.
We’re talking about unfinished attics with metal trunk lines and no insulation. Most heating units are positioned in the attic, often very hot.
Finishing an attic in your home and heating/cooling could save you 10-30% on your energy costs. The initial investment may not be practical. Well, it could be worth considering if you plan on living in the house for a long time.
We’ve always used a thermal barrier at the roofline and not the ceiling line. If your inspection department says you need a sealed attic, look for cathedral ceilings.
A sealed attic does not need to be vented; therefore, the insulation rules do not apply. Uninsulated ducts in a conditioned space are okay if nothing goes wrong.
Consider a sealed attic over a 1000 square foot home, 50 CFM of supply air Attic will be possibly 80F in the summer.
Sealing the attic with R8 & R7
Construction contractors in Georgia are required to install flex duct (R8) and duct wrap (3″) on any new permit, dating back to 1-1-2008.
The cathedral ceiling is no longer an attic as it means “above the church’s cross-beam.” Sealing up the space will not change where your heating load hits.
Carnak has a sealed attic roof insulated with a total of about R7. Heat transfer then is what 81F can drive through a sheetrock ceiling.
My wife is storing some heirlooms in the attic. I added about 40 CFM of supply air to guarantee low humidity. So now the air in the attic above the ceiling is the same as below.
Because of what happened here in a hurricane, wind-driven moisture entering through soffit vents saturating and ruining ceilings before a roof even failed, she wanted no vents.
Fan coils and insulated ductwork in the attic are not radiated by high-temperature heat.
Attaching R6 flexible ducts
Is it acceptable to use heavy-duty zip ties to secure your flexible duct?
Yes, this is fine. It should be two zip ties for every connection—one for the inner sleeve and another for the outer one.
According to some estimates, 25% of total house energy loss can be leaked. Missing ducts can prevent heating and cooling from doing their jobs properly.
The right way is zip ties and mastic. Using tape runs the risk of temperature changes, causing the glue on the tape to unstick.
For example, code only requires a single smoke detector per level. But you can use the cheapest (not anywhere near legal to use in commercial) smoke detector.
The contractor said he would install the system just like he would at his own home. You can check out the wall of pride and shame to see some of the differences.
RES Check and duct insulation
I got the RES Check report and noticed no mention of insulation specs anywhere in the document. Our inspector told me that supply ducts should be insulated with R8 and R6.
RES check no longer requires additional insulation like the 2014 IECC Residential 403.2.1 (Prescriptive) requires because of recent changes in statutory energy efficiency standards.
Ducts in attics shall be insulated with a minimum standard of R-8. All other ducts shall be insulated with a minimum standard of R-6.
RES Check gives you the minimum requirement for both supply and return ducts. If RESCheck says R8 for supply, that is the minimum ducting you need to install on the ducts outside the conditioned envelope. Similarly, if RESCheck says R6 for other vents, it should be installed on any other vents located outside.
RES Check, Rem Rate, HERS, etc., are Simulated Performance Alternatives. If you are designing with one of these programs, R405 is applicable.
But if you are not using a program, R402 and R403 are applicable. And if you are using ResCheck, and the design calls for R-8/R-6 duct insulation, that’s what shall you try.
Type of duct tape for insulation
My local inspector requires a labeling tape like the product known as mylar. The product’s tag number is 181.
Most of that drywall inside of your attic is soundproofing. We don’t put any on because we want our customers to be unaffected. The duct liner is primarily for making the house quieter and less noisy.
Based on my experience, you should always wrap the insulation around ducts as much as possible. You can tell if it is lined or not by lightly rapping it with your knuckles.
The lining is the same as fiberglass in terms of insulation value. Add perforated or solid liner for additional protection.
Ceramic paint is a mixture of latex paint and ceramic. You can use a corner for sealing water from leaking through building fibers.
The color is almond, and it’s pretty soft and velvety. We apply it at a thickness of about 1/16 inch. The cost is higher than fiberglass, but the look is worth it.
The highest R-value flex duct
Flex duct can be expensive, so I would try to wrap it or get it covered. Wrapping might also help with condensation building up in between the complex ducts.
IMO flex (when properly sealed, sized & installed) is a good thing. I know that hard duct has its benefits, but you are wasting money if it isn’t sealed.
On the other hand, Flex leaks at plenum/duct collar and supply box. Just the pros & cons based on my testing, sealing, and experience.
A corrugated aluminum duct (insulated or not) is typically used in air distribution. Foil flex, which is plastic but has a silvery, reflective outer covering, is more common.
The PVC plastic in your dryer’s ductwork will become brittle if exposed to high heat or direct sunlight for too long. It can cause the duct to gain ground, becoming easier to break. Those ties also get brittle if exposed for too long, regardless of their material.
When comparing estimates, be sure to compare features, warranties, capacities, and efficiency.
Compare the features and details of the “extras” like the thermostat, filter, humidifier, fresh air provisions. Compare the guarantee/warranty of the installation.
