Clothes Dryer Makeup Air - A Better Way?

[alternety]

Good plan. I have a similar arrangement. Keep in mind that with no wind, the warm moist air is going to tend to go up to the soffit. I have not really seen this to be a problem in my case.

There are devices that can control the damper by sensing power in the appliance cord. I do not know if there are ones for 240V. Search around on home control sites. They will also have the motorized dampers.

[alb]

so what type of duct pipe did you guys use to draw outside air into your clothes dryer?. I am doing something similar and looked into the home depot aluminum flexible duct (usually used for the exhaust part) but i noticed that if i pass my hand through it in the inside i can see little pieces of aluminun on my finger and I dont want that on my clothes... Anyway, any recommendation will be appreciated. I am also looking into flexible plastic ducts but they are quite expensive. Let me know. thanks

[alternety]

I just regular old galvanized duct of the same or larger size as the exhaust. You may have to explain to the inspector what it is for and why it is not insulated. It enters the laundry room and opens just above the dryer. On the outside I use standard opening grill with screening (no wasps). Make that as big as you can. There is a significant pressure drop. Try to avoid the exhaust area.

[Hube]

Why not just install a pipe from the outside and bring it down to the floor, terminating with 2 -90 degree elbows to form the letter "U"
This is known as the "anti-spill method" This "U" shape provides a trap which will only allow air to come in only as it is required by the Dryer. no damper is needed.
Also make sure you install a insect screen at the point of entry.
If your dryer has a 4" diameter exhaust then a 5" diameter pipe will suffice while allowing for any insect screen restriction.

[alternety]

That would appear better than a straight pipe but there are issues. If you house is not very tight there will be drafts through this pipe. You have now provided a low resistance link to the outside. It will increase overall infiltration.

Why you run any exhaust fans air will be drawn in through the pipe.

If you have a non-sealed combustion system for heating it probably won't matter, since you already have a chimney. Although the route of drafts will probably change. I prefer positive sealing and isolation of my external air paths.

[Hube]

[QUOTE=alternety;241783]That would appear better than a straight pipe but there are issues. If you house is not very tight there will be drafts through this pipe. You have now provided a low resistance link to the outside. It will increase overall infiltration.

Why you run any exhaust fans air will be drawn in through the pipe.
End of quotes.
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Alternety;
if the house is not very tight then no combustion air is ever required as it is already there because the house is not very tight.

In a tight house there will be NO drafts as this anti -spill type will allow air only to come in as it is required by any of the exhausting appliances.

Note that the poster (sixlashes) said his house was VERY TIGHT.

[alternety]

This is an older post and I did not go back and read the whole thing. If the house is tight, the only source of draft is if there are any exhaust/exchange systems that are not balanced with their own makeup air.

In my own environment I have only three controlled points of interaction with outside air. A heat recovery air exchange system, the range hood with its' own powered make-up air system, and the dryer. And a couple of doors that really don't seal as well as they should. I also have an issue with certain drain systems within the house that were built, in contradiction with plans and instructions, without traps. Plumber either thought I was crazy (not an isolated view among the builders) or just did not want to work that hard. I am working on these entry points, but retrofit is tricky.

It is hard to balance, and keep balanced, external air exchange systems. In all likelihood there will be some interaction with this laundry vent if it is not actively managed (i.e., closed when not in use).

I am a real fan of tight houses. I have about 6,000 sq ft and I use about 800 gallons of propane for heat, hot water, and cooking in a year in the PNW. And that is with stupid walls. I designed for SIPs. Engineer had no idea what they were. Wound up doing studs with spray foam. Each stud is a heat leak so I will not equal a SIP for heat loss, but I am airtight. I did not put on an external sheet of foam board because of fire issues and depth of wall vs already ordered windows and doors. I live in a forest. Since this is my last house, this annoys me very very very much.