If you're sure that your vent line has no built-up lint or other obstructions for its entire length, then a dryer vent booster fan would almost certainly solve your problem. The booster fans from Fantech are completely automatic. they switch on when air pressure builds up in the vent line from the dryer fan running, and turn off when the air pressure subsides. They have both in-line models and models that would mount on the wall at the end of the vent run. More info available at the linked website below. Here is a link that might be useful: Fantech Dryer Booster Fans

gordonr, If there's nothing else I've learned during the course of my renovations, I've learned that everything ends up being more complicated than you expect. Once you open up the ceiling or the wall, there always seems to be something in the way of what you want to do. A floor joist where the tub drain needed to be, pipes where I wanted recessed lights to go, and now the recessed light over the tub is where it would make sense to run the duct. I can hardly wait to get to the kitchen renovation! I spoke with a rep in Miele's technical service group yesterday. Initially he was telling me he thought what I wanted to do entailed too long a stretch of duct - that it would reduce the performance of the dryer. I told him I expected that it would not be optimal performance, but what I was trying to determine was whether it would reduce it to the extent that a condenser dryer would have the same performance. He didn't seem to understand what I was getting at, so I gave an example: If the vented model has 15% better performance than the condenser model and the venting I'm doing reduces performance by 15%, then the condenser model would be generally equivalent, but if the vented dryer's performance is 50% greater, the same 15% reduction in performance would still mean the vented dryer was a better choice. I asked if he could give me any information about how much better the vented dryer's performance was than the condenser model and how much the venting I was considering would reduce the vented dryer's performance. At that point, he said he wanted to talk with one of the senior technical reps and put me on hold. When he came back, he told me that the dryer was rated for up to 60 feet (which I already knew) and that I should be fine with what I was planning on doing. He also told me that the sr. rep had indicated that having a condenser dryer in a closet could be problematic because it puts off a lot more heat than a vented dryer - you'd need a lot more air circulation into the closet with a condenser dryer. The closet I'll be putting the w/d into is 68" wide by 29" deep, so the extra heat and air circulation need may not have been as much of an issue for me as it might be for others with a more confined space. One learning that I took away from this: if you start to get the sense that the technical or customer service person you're talking to may not be as knowledgeable as you'd like, ask to talk with a senior rep. Like anywhere else, initial phone calls will be answered by more junior staff who will route the more complicated issues to more experienced staff. I've decided to go with a vented dryer, and now just need to decide between the Miele and the Asko. I'll let everyone know which one I end up with. Jan

If someone is trying to sell you a dryer, for long run applications, that is not a true statement. Beware of of that. All dryers are made to dry clothes at a cirtain speed, and to a spec sheet. If they were to change the speed of the motor, it would just use more energy, and get less drying as the speed and the finns on the impeller are disigned to move x amount of air at a speed that the heat will dry your close in a specific amount of time. For instance, it will move 135cf per minute, more than that your dryer is running long times and not drying properly. Now that I have said all that, what you need to do, is contact a venting service, that can come and look your system over, and you said you had only 2 90's and 50 feet, I have had them over 100' and 8 90's, and we installed on inline 4" fan/housing in the duck, and had a power line connected to the dryer, so when the dryer started up it also powered up the discharge fan/housing installed down line to help move the air, but also you have to install one that will not change the speed of the dryer motor discharge. Your local venting installer, some of the furnace firms have people that are fully experienced in this sort of addition, or long venting problems. Hope this helps you. Brent@CanBC

If you check the spec on your dryer I think you will find that you will be exceeding the ability of the dryer to move the air to dry effectively. Each load will take longer and therefore be more costly. I'd suggest that you look into a booster fan. Tjernlund makes about the best of them in my opinion. Watch their video on operation. You could take the 4" exhaust pipe (try to use smooth walled ridged pipe) and insulate and sleeve it with PVC on the portion under the deck. The vent should not terminate under the deck