Duct gauge and types of duct insulations

This is the 9th part of the full HVAC course. In this part, we will continue with the ducting series. In this article we will learn about duct gauge and types of duct insulations.

G.I sheet Gauging System (As per SMACNA) : (Height and width considered no length)

The ducts are the path that air travels through your grow room. They can usually be found behind the fan, heating element, lights, vents, etc. You want to make sure they aren't too small or too large. Smaller ones may not circulate enough air while larger ones may create too much turbulence. This could lead to mold, mildew, leaf curl, or other conditions.

A duct system is a way to transport air from one location to another. Most houses have some sort of ductwork that transports fresh air into rooms through registers and out through vents. These vents are designed to provide good airflow. If your home has poor ventilation, then you may notice that you feel stuffy and hot in certain areas. This could mean that you need new ducts installed.

Before you decide to install new ductwork, make sure you measure your current duct size. This can be done by measuring the distance between the studs at both ends of the ceiling opening where the duct passes through. This information will help you determine what size ductwork you need. You should think about installing larger duct sizes if you live in a smaller space. Or vice versa, if your house is large, you can install smaller sized ducts.

24 Gauge - A 24-gauge duct allows for greater airflow than a 20-gauge duct, but still provides adequate circulation to maintain good air flow throughout the grow space.

20 Gauge - A 20-gauge allows for less air flow than a 24-gauge but has better air movement.

Above image is a rectangular duct. Pick the greater dimension from from height and width of duct, and as this duct is of GI sheet, usually 20 gauge thickness is oftenly taken for GI sheet. But some times 22 an 24 gauge thickness of GI sheet are also used in the industry.

* Elements of a duct :

Above image shows the various elements of ducts. Acoustic lining should be maximum up to 3 meter. This reduces sound.

Types of Duct Insulations :

* Thermal Insulation :

Duct carrying cold, chilled, hot air is covered with thermal insulation to reduce the cooling or heating losses, and also to get readoff heat or thermal exchanges in addition to thermal insulation is covered with vapor barrier ( i.e; of aluminum foil or treated paper ) to prevent condensation of water on cold ducts.

Material of Thermal Insulation :

* Glass fiber / fiber glass.

* Glass wool or blanket foam (25 mm thickness and density 24 to 32 kg / m³ )

* Rigid Board ( Same as Glass wool )

Here rigid board cost is considerably more and is used when only duct is exposed and appearance is important. i.e; rigid board is used for appearance purpose of duct and glass wool is used when duct is above false ceiling. As per standards, complete supply and return duct should be insulated after acoustic lining.

In some cases thermal insulation is applied at the end of the ducts up to 10' due to cost considerations. Because, the velocity will be high in motion inside the ducts since starting position itself. But at the last portion / end position of duct, velocity gets decreased and air gathers at the last portion, thereby chances of condensation occurring is more.

* Glass wool / Blanket Foam

It has thickness of almost 25 mm and used internally above false ceiling. It has a density by weight of 24 to 32 kg/m³.

cloth : it is used to protect fiber glass.

* Aluminum foil : It is used as a vapor barrier.

* Bird net : It is used to protect thermal insulation.

* Aluminium tape : Nitrile rubber and glue. Nitrile rubber comes in varying thicknesses of 3 mm, 6 mm, 9 mm , 13 mm. Glue is an adhesive like fevicol.

* Acoustic Lining :

Ducts are frequently lined internally with acoustic insulation to absorb sound or noise, and to overcome vibration. In this case, acoustic lining also serves as thermal insulation. However, care must be taken that fiber glass do not get flaked off (to become less rigid ) in air stream or to become less tensile and get delivered in occupied space. And this is a very serious concern, inhaling glass fiber may cause serious lung diseases / chest diseases.

* Materials used :

* Fiber glass with rigid board : Thickness 25 mm and density 32 kg/m³ for duct acoustics. 50 mm Thickness and density 48 kg/m³ for wall acoustics.

* Aluminium perforated sheet with 26 or 28 gauge thickness and also nuts, bolts with rubber washers.

* Nitrile rubber with glue or adhesive : Normally round and oval ducts are preferred in this.

Note :

* Acoustic lining should be done internally in machine connection up to 3 m.

* Acoustic lining is done only at the starting piece of machine connection up to 3 m (10') and supply plenum.

* Thermal insulation is done on duct after installation of duct on site.

* Acoustic lining / inside insulation is done before installation of duct on site.

Well here completes the 9th part of the full hvac course. Hope you guys got something to learn about duct gauges and duct insulation in this part.. Till then, keep learning.. keep growing..

Access Previous parts of this course, if you have missed it, by clicking Below..

Part 1 -- Click Here!!

Part 2 -- Click Here!!

Part 3 -- Click Here!!

Part 4 -- Click Here!!

Part 5 -- Click Here!!

Part 6 -- Click Here!!

Part 7 -- Click Here!!

Part 8 -- Click Here!!