• What is PolyVent II?
  • What is PolyVent III?
  • How does it work?
  • How long can a JanAire PolyVent be?
  • What is the correct length for my application?
  • How big are the fans?
  • Can PolyVent be patched?
  • Is there a warranty?
  • How long with PolyVents last?
  • Installation time?
  • Time needed to replace poly?
  • Will JanAire PolyVents stand up to strong winds?
  • What happens in a power outage?
  • Rodents?

What is PolyVent II?

We call our curtain a PolyVent. A PolyVent II curtain resembles an inflatable air mattress propped up on its side and encased in a metal frame. A small, 1/40 th, 50 watt squirrel cage blower is connected by a flexible hose to the top tube of the “mattress”. As the blower fills the tubes with air, the”mattress” starts to rise, eventually filling the opening in the building behind the PolyVent II. PolyVent II is normally used on the bottom half of a stacked JanAire unit in dairy barns and is usually operated with an on/off switch.

What is PolyVent III?

PolyVent III is operated with two blowers. It has a special seal in either the second or third tube from the bottom of the poly. PolyVent III operates with two 1/40th, 50 watt squirrel cage blowers. One blower is connected to the top tube of the poly. The second blower is connected to the tube just below the solid seal on the poly curtain. Both blowers are connected with flex hoses. PolyVent III is used by itself on hog and poultry barns or in the top section of a stacked JanAire unit on a dairy barn.

How does it work?

Thermostats control the blowers which inflate the PolyVent curtain. When the temperature inside a building gets above the desired temperature for the building, the bottom blower will shut off, causing the bottom tubes in the JanAire PolyVent curtain to slowly deflate and collapse into the bottom gutter, out of the way. This action creates a small top opening that allows for fresh, outside, air to enter the building. When more ventilation is called for, the top blowers will automatically shut off. The remaining tubes will partially, or fully collapse until the desired temperature is reached. PolyVent is a very active system when weather takes wild swings during the spring and fall. A 5 foot by 100 foot JanAire PolyVent curtain takes less than two minutes to go from open to closed!

How long can a JanAire PolyVent curtain be?

JanAire PolyVent curtains can be as short as 8 feet, or up to 240 feet in length or any length in between. All JanAire PolyVent curtains are custom cut to the length you order.

What is the right length for my application?

That will depend on the type of animals you have and your location. Southern barns can use longer lengths than northern barns. Dairy barns typically use longer lengths than hog barns. Hog barns using 40CFM of minimum ventilation can use longer lengths than barns equipped with a 20CFM of minimum ventilation. We will help you find the right length for your application. Call us at 800-246-5387 for help.

How big are the fans?

The fan takes 50 watts of power, just like a 50 watt light bulb.

Can PolyVent curtains be patched?

Definitely! A roll of 4″ x 8′ Polypatch is supplied free with every new JanAire unit. When using Polypatch, the poly has to be clean and dry. In cold weather, an ordinary hair dryer can help warm the poly and Polypatch so they stick better. After the poly is cleaned, a 50/50 blend of Isopropyl alcohol and water, applied with a lint-free cloth, can be used to finish prepping the surface. A primer is available that will help the Polypatch stick better. Apply the primer and allow it to dry thoroughly (about five minutes) before applying the Polypatch.


JanAire PolyVent has a pro-rated warranty for up to three years from the shipping date that includes faulty workmanship or deterioration due to the action of ultraviolet rays. If needed, your poly will be replaced according to the following schedule:
From the date of shipping:

  1. Up to 12 months … 100% of cost of replacement poly
  2. From 13 months to 24 months … 50% of cost of replacement poly
  3. From 25 to 36 months … 20% cost of replacement poly

How long do PolyVent curtains last?

Our JanAire metal frame should last 20 years or more. The poly curtain will have a 4-9 year lifespan depending on conditions. The oldest poly that we know of was used for 16 years in the JanAire frame.

Installation time?

Starting with a framed opening, with barrier in place, competent installers tell us they can install a JanAire PolyVent in half the time that would be needed to install a conventional curtain. It is hard to be more specific due to all the variables involved. Example: Two people working at ground level have installed a 3′ x 168′ unit, from start to finish in three hours. The next day, those same two people working with stepladders, installed a 4′ x 120′ unit in four hours. Working conditions make a big difference!

Time needed to replace poly?

Two people can replace the poly curtain in a JanAire unit, under 100 feet in length, in as little as 20 minutes. Three people could replace a 150-foot length of poly in about 30 minutes (once they learn how).

Will JanAire PolyVent curtains stand up to the strong winds we have here?

You will not hear or see ANY annoying curtain flapping with a JanAire PolyVent curtain system! Because of its design, regardless of whether it is closed or partially open, the air pressure within the tubes keep it from moving back and forth in its frame. We have installations in some western states that have been hit with straight-line winds where the roofs were torn off the barns but the PolyVent was just fine!

What happens in a power outage?

If you lose power, the PolyVent curtain will fail in an open position, which is what you want so your livestock won’t suffocate! In cold weather, you can limit how much air enters the building by installing our Tether Kit to the PolyVent. Our experience shows there is a bigger risk with having a multi-stage control malfunction that does NOT OPEN a curtain when it fails, i.e. suffocating livestock. An easy fix for this potential problem would be to install a single-stage thermostat between the master control and the PolyVent blower. Then, set the temperature on the thermostat slightly higher than the setting for the master control.


JanAire curtains have been in use since 1987. If mice were as big a problem as some people fear, producers would have quit using our product years ago.

JanAire “Tips” for rodent control:

  1. Never place bait in a curtain. The bait is an attractant and will attract rodents to the curtain.
  2. Use bait stations around the outside of the barn.
  3. Use 20 inch lengths of 2″ PVC pipe on the inside sill with a couple packets of bait inside. The PVC pipe will give the rodents a place to eat and hide.
  4. Rotate the type of bait used with one bait manufacturer’s line up. Rodents can become resistant to a particular type of poison, so you need to switch baits accordingly. If you think it’s not working and you switch to another manufacturer you might wind up with the same type of poison and you’ll just be feeding the rodents instead of killing them.

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