Sealing fresh air intake of ERV
OwnerBuilderMN
| Posted in Mechanicals on
I am building a house in climate zone 5 and built it as tight as possible and insulating the walls to R-34. I spent a fair amount of time air sealing but I am installing an ERV and I am concerned about the fresh air intake of the ERV.
I am using a FanTech SER 150 which does have a motorized damper on the fresh air intake. However, the fresh air intake pipe will be about 20 ft long (6″ diameter) and being that one end is open to the outside it would be a very long cold pipe in the winter.
My plan was to use a motorized damper on the end closes to the outside. However, I am surprised there is nothing on the market (that I can find) where the entire housing is insulated. Not to mention the damper itself is just a thin piece of metal. I suppose I can put duct insulation around it but that usually only insulates a pipe to R-8 or so (right?)
So what is the best way to:
1) Keep the cold air outside as much as possible when this isn’t running (I will have ERV connected to bathrooms to run on a timer and when users call for it).
2) What is the best way to insulate the pipe to something comparable to the rest of my insulation?
3) Are there exterior dampers that work in reverse of the typical clothes dryer vent? One that is normally closed but when air is sucked through it the flap opens?
I am also concerned that the standard duct dampers will not stand up to the occasional -30 degree weather when it is basically exposed to those temps at the end of the pipe.
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Replies
A damper near the outside end of the pipe will keep air from circulating in the pipe, and that will greatly reduce the amount of heat you’ll lose through the wall of the pipe itself. Do use insulation on that pipe, I like the “sock” type that is a long tube, I don’t like the spiral wraps since they’re harder to work with.
The damper should be ok in the cold as long as it isn’t exposed to moisture that could cause ice and a freeze up. The actuator itself might not like extreme cold (lubricants tend to thicken in the cold which can sometimes be a concern), but you’d normally put the damper immediately inside the structure where it should be protected.
Bill
That Fantech unit is pretty mediocre on specs. There are much higher efficiency units out there for similar price range. Getting a higher efficiency unit is worth it in Zone5, it saves you money on heating cost plus the fresh air supplied is also much warmer. For a budget high efficiency unit look at the Panasonic Intellibalance.
For the ERV inlet, you always insulate the pipe. Those insulation sock work the best. I like to use semi rigid aluminum ducting as it is much less restrictive than flex but way easier to route than rigid and pull the sock over it. You want to make sure you tape the membrane on the sock on both ends, you don't want inside air getting in there and causing condensation issues.