writ­ten 6/27/25, updat­ed 6/27/25

Back to DIY Projects Page

---

---

---

Materials and Cost

Option­al: Remove­able Win­dow Seal­ing Tape (~$10–12)

Note: as of this writ­ing, a dual hose win­dow kit on Ama­zon will cost you about $33.99; from Home Depot is $37.18. How­ev­er, you can also buy foam inserts that fit into them for $35.99 because, appar­ent­ly, the kits don’t keep out heat as well as you’d think.

Owned Sup­plies

---

Process

Measurements

Ori­ent the AC unit and fig­ure out how hoses should be placed to fig­ure out how much of the open­ing you’ll need to fill will the vent mount. Take your mea­sure­ments which will tell you how much mate­r­i­al is need­ed.

My win­dow is 31″ x 58″ (W x H), with each open­ing about 28″. I’m work­ing with an Ecoflow Wave 3 for which the hoses have 2 slight­ly dif­fer­ent open­ing sizes. After ori­ent­ing the machine and hoses for the space avail­able, I knew that I need­ed the win­dow to be open about as much as it can be.

NOTE: For a dual hose unit, try to place the exhaust hose high­er than the intake hose since heat ris­es, and air under the hot­ter expelling air should be cool­er. For a sin­gle hose unit, you won’t need to open the win­dow as much

---

Materials

Gath­er any owned equip­ment, then pro­cure nec­es­sary tools and mate­ri­als (I ran out to Home Depot)

Note: My win­dow has a screen, so I left it down and placed the vent hoses on the oth­er side. If yours does not have a screen, it would prob­a­bly be a good idea to fac­tor in a mesh screen to pre­vent bugs enter­ing the hoses when not in use. Prod­ucts like Fiber­glass Mesh Rolls, or Vent Mesh Rodent/Bird Screens are options.

---

Fitting

With sup­plies in hand, test the Rigid Foam Board on the win­dow. Mine was best sit­ting inside the lip of the win­dow jamb. If more mate­r­i­al is need­ed, mea­sure and mark with the Sharpie. Secure the foam board in place (either low­er the win­dow onto it, or use mask­ing tape), then place each vent hose in its desired spot and trace with the Sharpie

---

Cutting

Time to make cuts! Depend­ing on cut­ting loca­tion, make sure to put down a drop cloth, news­pa­per, or oth­er cov­er­ing for easy cleanup. The foam pieces will get every­where

First off, I put togeth­er the main win­dow pan­el by cut­ting the piece to make it whole using mea­sure­ments (in my case about 8in). I used a Square and a Util­i­ty Knife to score both sides, then all that’s need­ed is a lit­tle bit of force to snap the piece off (I just used the edge of a chair for lever­age)

Next are the holes! My Ecoflow hap­pened to come with a Vent Hole Tem­plate, so I used Mask­ing Tape to adhere that to each traced hole

I’m sure a jig­saw would be the eas­i­est and clean­est way to accom­plish this, but I was­n’t about to shell out anoth­er $200 for that (maybe at some point in the future).

So, I used a Util­i­ty Knife to cut the cir­cu­lar shape. Because the foam board was too thick for just the util­i­ty knife, I poked holes with a ran­dom tool (can be a screw­driv­er) and con­nect­ed the lines with a Sharpie.

Then with the util­i­ty knife, I cut the round pat­tern and a cross pat­tern on either side to facil­i­tate removal

At this point you can use any vari­ety of meth­ods to chip away at the foam (e.g. mal­let, screw­driv­er, knife). I end­ed up using a Craft Knife to deep­en the util­i­ty knife cuts all the way around, and it was excel­lent for smooth­ing out the holes

Mal­let

Craft Knife

---

Assembly

Back upstairs! First up: make sure the main pan­el pieces fit into the win­dow. Next, dry fit the hoses. Used the craft knife to make some adjust­ments.

Anoth­er dry fit of all pieces. Looks good!

Now to con­nect the two pieces of the main pan­el with the HVAC Alu­minum Foil Tape. I’ve nev­er used that kind of tape before. It’s like putting on a vinyl where you have to peel away the back­ing. When attached, the hold feels extra strong, so be care­ful not to rush and mess it up.

After anoth­er dry fit

Mov­ing on: now to adhere the Dou­ble Reflec­tive Insu­la­tion. This real­ly is an option­al thing, but I want­ed to do this because man­u­fac­tur­er word­ing on the rigid foam boards notes that its only rat­ed to 75F. Giv­en the beat­ing sun and 100F heat, I want­ed some­thing else to both block heat and afford a lit­tle more weath­er resis­tance to the pan­el.

Fun Note: The mate­r­i­al is just like sun­shades for a car. One of the favorite things I’ve ever bought are cus­tom dri­ver and pas­sen­ger win­dow shades for my car, and it lit­er­al­ly uses the exact same mate­r­i­al except with an edge lin­er to look pret­ty

To attach the insu­la­tor, use Mask­ing or Painters’ Tape (painter’s is eas­i­er to remove) to adhere the mate­r­i­al to the foam board, then cut to size. Then, use the HVAC Tape to secure it to the foam board.

Make sure you’re apply­ing it to the prop­er side!

NOTE: This will add some width to the foam board, which isn’t nec­es­sar­i­ly a bad thing, but if it’s too tight, you may have to trim some off the foam. I left mine the way it was and just jammed it in there. It was a tight fit, but that works for seal­ing out weath­er and bugs. It is foam after all and will com­press a lit­tle.

Cut the vent holes out with scis­sors. I left a lit­tle bit of excess mate­r­i­al around the open­ing for a lit­tle more bug/weather bar­ri­er.

Lat­er, I end­ed up secur­ing each hole with 4 pieces of HVAC Tape because I real­ized that air move­ment might bal­loon out the space between the insu­la­tion and the foam board.

Finishing Up

We’re pret­ty much done at this point! Go ahead and place it all into the win­dow, place all the hoses, and check out your hand­i­work!

The only thing left to do is to seal the cracks around the foam board and the vent hoses.

I used Mask­ing Tape for easy removal, but if you want some­thing bet­ter, buy some Remov­able Win­dow Seal­ing Tape (XFas­ten brand on Ama­zon is $11.99, appears to be based in Flori­da).

DONE!

---

Notes

• The whole sys­tem works well, and removal is as easy as remov­ing tape
• Sound is a prob­lem, though. I can hear every­thing out­side. Like birds in the morn­ing. When you’re get­ting your best sleep. I con­sid­ered some sound­proof pan­el­ing to put in front of it but then real­ized that I don’t use the unit too much unless there’s a heat wave. Not only that, but the pan­els are pret­ty expen­sive.
• It also makes my room smell like an attic with all the out­door smells. Per­haps it would be dif­fer­ent if I’d used the Win­dow Seal­ing Tape?

---

Back to DIY Projects Page