I have an air-exchanger, and the hoses are little loose. That is I can feel the air flowing out between the motor and the hose.
Here is a picture of the overall thing:
Here is closer picture that shows where the air escapes from exactly:
How do I make it more air tight?
I see that there is some sort of sticky aluminium foil or something that they used before:
Maybe that's what I need to use again? If yes, what's it called?
I agree with Michael, and add that you could also use large HVAC zip ties. If the lines seem to come loose easily, then you would be better off using a tape. Now, "Duct" tape and "Duck" tape are not the same. "Duck" tape is what most people see as the old fashion silver/gray colored roll of tape that now comes in wild designs and colors and can be bought at every store that sells tape. "Duct" tape is designed for duct lines, HVAC, and is usually an aluminum foil type tape, and a common brand is 3M.
The metalic tape is simply called "Aluminum Tape". I have had excellent results with the 3M brand as the ones I used had awesome glue.
Be prepared to spend some more than "duct tape" but it will last longer without degrading as much.
There is another tape that is more flexible than the metal tape. Called GORILLA tape it looks sort of like duct tape but with a much more durable backing and also incredible glue. Again be prepared to spend a hefty price for a premuim product. GORILLA tape sticks well to glass, plastic and metal but not quite so good for wood.
I normally place 2 or 3 screws through the flexible duct and not the insulation. i then hook it on the metal wire that runs through the interior flexible duct and tighten them until snug against the collar. This is however extremely challenging if you haven't worked with the flexible duct before. Then Foil tape the inner pipe (not the insulation and exterior plastic) to the collar of the duct work that you screwed your flexible duct to. Pull the insulation back over pipe and it should be sealed as long as your taping skills are adequate. For mounting the ducts higher you can use standard metal strapping. Make sure not to kink any ducts or strap it to tight and crush the insulation or the duct. If you crush the insulation to much, you will decrease its R-value. Screw the strapping into studs, or if screwing only into the drywall, use some heavy duty drywall plugs.
The way we usually seal flex ducting is with zip ties. Slide back the outter covering and insulation, use a zip tie on the inner layer, some duct tape will make it seal even better. Now slide the putter cover and insulation back over and use a zip tie to keep the insulation in place. Duct tape only on the inner flex duct fails because of the flexing when air is pushed. zip tie only on the inner will hold but may not seal 100% so I usually use both a tie and tape on the inner with great success.
