Include provision for future ventilation?
The second story of my old farmhouse is gutted. I am in the middle of running electrical, etc and getting ready to close up the walls. It doesn’t need it now, but as I keep working, the house may eventually need a ventilation system. Should I include provisions now while the walls are open for a ducted ventilation system later? Is separate ventilation ducting overkill? What type/size of ducting is typically used for the application? Is it best to locate grilles in the floor or walls?
I have done a lot of reading on the topic but I would like some input others.
I plan to heat/cool upstairs with a minisplit in the hallway. There are two bedrooms and small 1/2 bath that total 450 sqft. Another minisplit will go downstairs later. An old oil furnace takes care of heating now. The first floor is ducted. I don’t plan on running a heating duct up the second floor because warm air should make it’s way up there on its own. All the partition walls are 2×4.
Thanks
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Replies
a typical HRV uses a 4" vent, so if the walls are 3-1/2", you have to pad them out with strapping. And you can vent bathrooms through an HRV in addition to using it to provide fresh air. Ventilation ducting is not overkill; it is a necessity in a tight house, and it only makes sense to install them when the walls are open. You have one chance to do it right. Install the outlets high on interior walls, and not right above beds, tables or seating areas. We often install BR outlets in closets so the air is well tempered when it gets to the people.
Brian,
Bob's advice is good. For more information on this topic, you might want to read these three articles:
Designing a Good Ventilation System
Ducting HRVs and ERVs
Installing a Heat-Recovery Ventilator
Part of my question was motivated by the difficulty involved. I would have to punch through load bearing top plates to run any ductwork. Both first floor partition walls support second floor joists. Either that or build out a couple of chases in an already small home.
I looked at using the zhender corrugated tubes instead of galvanized duct, but it seems like a lot of expensive stuff is required like the manifold and box, tube fittings, registers, etc. Not to mention the tubes are only 2.5" ID making head loss significantly higher than a 4" round duct.
Any suggestions?
The concept of the Zehnder tubes is:
1) They are smooth and resist sharp bends, so that helps the head loss, and
2) Their designs use lots of them with very low flow rates in each. That reduces heat loss, and also means you need to buy more of their expensive special hardware.
Another option is the Lunos system, which doesn't require ducts. http://foursevenfive.com/product-category/ventilation/ With the e2 and eGo options, you can do a lot of what you can do with a conventional system, and though they are expensive, by the time you add up all the bits and labor you need for a conventional system, Lunos can be substantially cheaper, especially if your ventilation needs are modest. Even cheaper is the knock-off version available at Home Depot:
http://www.homedepot.com/p/VENTS-TwinFresh-Comfo-32-CFM-Power-5-in-Single-Room-Energy-Recovery-Ventilator-Twinfresh-Comfo-RAI-50-2/204785337
There are two ~200 sqft bedrooms (incl closet) and a 21 sqft w/ a panasonic exhaust fan upstairs. What are the downsides to doing the following:
- A supply in one bedroom and exhaust in the other
- A supply in both bedrooms and no exhaust upstairs
These two options require only 2 ducts instead of 3 (supply in each BR and exhaust in the hall) and I don't have to cut up my new framing as much. Also if I install registers in the floor in one of the bedrooms I don't have to cut through my bottom plates to run ducts up the wall. This is not a platform framed house, without getting into detail, the bottom plates have more structural function than they normally would. I know installing ventilation registers in the floor isn't ideal, but what are the implications?
Brian,
Most HRV or ERV installations supply fresh air to bedrooms and the living room, and exhaust from the bathroom, laundry room, and sometimes the kitchen ceiling (but not the range hood).
Your idea to install supply ducts to the bedrooms makes sense. There is no need to have an exhaust duct in your bedroom.
Are there any issues associated with having two supply ducts upstairs and no exhaust? I'm thinking along the lines of slight positive pressure upstairs. There is a door at the bottom of the stairs that will probably be shut most of the time and will impede airflow between upstairs and down. I suppose we are only talking 20 cfm or so though so maybe its a non-issue.
What about having registers in the floor? (see above)
Thanks