Summer is heating up, and if you live in a Condo with no AC you are probably getting anxious.

Related: If you are unable to open your windows all the way, fix that here.

Installing proper Air Conditioning in condos is typically difficult or impossible because the building management generally does not allow any modifications to the external structure. (ie.. holes in the wall, window modificaitons, etc.)

Usually the most feasible option is to get a portable AC and attempt to get the exhaust heat out a window or door. This usually doesn’t work too well because it’s hard to get a good seal for most windows/doors, leaving you with problems:

  • Warm air from outside leaks back inside
  • You can’t properly close the window/door which lets in noise and is not secure.
  • If it rains you will probably get a bunch of water inside.

There is another option that works very well if you have the following:

  • In-suite laundry with dryer
  • Booster fan for the dryer exhaust

If this applies to you, congratulations! You can use the existing system that blows hot air from the dryer outside and use it to blow hot air from the AC outside. The fan is jsut sitting there anytime you are not using your dryer, so let’s use it a bit more to do exactly what it was designed for! 🙂

There are two key parts to this hack:

  • Ducting: Connecting the exhaust from your AC into the dryer duct
  • Electrical: Triggering the fan to run when you turn on the AC


You will need to get some flexible ducting to connect your AC exhaust into the booster fan – readily available at Home Depot.

Wye-style Joint
Wye” Y-style Joint
Tee-style Joint
Tee” T-style Joint

You’ll also need a duct splitter – either a T (tee) or Y (wye) style connection – Y is probably better, but choose the one that will fit the best. Also at Home Depot, for around $12.

Measure the diameter of the existing ducting (most likely 5″ or 6″) and make sure your ducting and connector is the same size.

Here is my duct connection, which is on the ceiling of the laundry room directly above the dryer. The AC unit is in another room which is why it’s coming through the wall. I cut a section out of the original duct from the dryer to the booster fan and inserted a “Tee” style joint to connect the duct coming from the AC.

Duct Connection
The first time I used duct tape for an actual duct… doesn’t look great but it’s airtight.

NOTE: It is critical that you make the connection before the booster fan (in between the dryer and the booster fan) – if you connect after the booster fan it will blow the hot air back into your AC and probably overheat it.


Disclaimer: Do not proceed unless you have experience with home electrical wiring. Turn off breaker panel before doing anything. This site provides information only – what you do with it is up to you and your responsibility.

The dryer booster fan typically uses a current trigger delay switch to turn on the fan, which works as follows:

  • The switch can sense the electric current that is drawn by the dryer when the dryer is running.
  • It will immediately turn on the booster fan and keep it on as long as the dryer is running.
  • Once the dryer is done, it keeps the booster fan running for a few minutes to clear all the heat and moisture out of the dryer vent.

We want to have the exact same behavior for the AC unit – the good news is that the current switch can detect current draw from more than one device. You just need to pass more than one wire through the sensing loop. When we are done, we will have one wire for the dryer and one wire for the AC going through the switch sensing loop. so turning on either the dryer or the AC will turn on the booster fan – perfect!

AC Current Switch
AC Current Switch with red wire (Dryer) and white wire (AC) going through the sensing loop.

Remember that electric current needs 2 wires to complete the circuit, and the current flow in one wire is always the exact opposite of the other wire. This means that if you run both wires through the sensing loop, they will cancel each other out and the sensor will detect zero current – and won’t turn on the fan. Make sure you only run one of the wires through the sensing loop.

Easy Setup Method

The simplest way to get AC is to use a portable AC unit and connect the hose that is intended for the window directly into the dryer duct. This is the fastest to set up and most wont require any holes in walls or anything. The downside is that your AC will need to be relatively close to the laundry and might require a duct extension hose.

Slightly More Involved Option…

In my case, I really wanted the AC in the bedroom, which was nowhere near the laundry. I decided to use a window AC unit (which are actually a lot more powerful in terms of cooling power for your money) and install it in the wall between the bedroom and the closet. This resulted in the heat being exhausted in the closet (heating it up), so I added a vent near the top of the closet and connected that to the dryer duct. Thus, when the booster fan kicks in, it sucks the hot air from the top of the closet and keeps it cool.

Your Setup

Your setup will vary based on the layout of your condo and how much effort you want to put in. ( and how comfortable you are making holes in your walls, of course… ). It may take a little design and planning, but I’m sure you’ll come up with something that works! The two main ideas you will need are connecting the exhaust to your dryer vent, and triggering the booster fan via the current sensing switch. Please post a comment if you find this useful and get something set up! Excited to hear if anyone else can make this work.