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Looking for advice on a simple, economical and balanced ventilation product

MJDesigns | Posted in Mechanicals on

Broan is marketing automatic make-up air dampers (models SMD6 or SMD8) that are synchronized to introduce fresh air into the HVAC’s return ductwork whenever a bathroom or kitchen range hood exhaust fan is operating. Premise is to balance or equalize the air pressure within the house. I’m assuming that’s better than using an “exhaust only” or “fresh air intake only” strategy to ventilate a tightly constructed house. Has anyone had any experience with these products. Only downside I can see is that one must use Broan ventilation products exclusively so that they can communicate with one another. Are there similar functioning systems available with more product flexibility (ex. Panasonic fans?). We live in climate is zone 5 in central OH … 5708 HDD’s and 797 CDD’s. I had read some articles on ventilation strategies on this site as was considering UltimateAir’s RecoupAerator H/ERV for our home that’s in the design stages, but I’m thinking there’s a considerable price difference between that product and Broan’s balanced solution. Any advice you can offer would be appreciated by this new member. Awesome site!

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  1. GBA Editor
    Martin Holladay | | #1

    Ventilation air flows are low -- generally in the range of 40 to 60 cfm. An energy efficient house is likely to have sealed-combustion appliances, so backdrafting is usually not a concern -- especially with the low air flows required for ventilation. (Big range hood fans are a whole other story.)

    Either an exhaust-only or a supply-only ventilation system can work well, if you don't want to spring for an HRV.

  2. kevin_in_denver | | #2

    Panasonic makes a great inexpensive little ERV:

    One or two is usually enough to satisfy ASHRAE 62.2 .

    It's hard to say if the fresh air would be distributed effectively to the bedrooms, but if each door had a transfer grille: , then Fick's Law and natural convection would automatically spread the fresh air around. If your heating system is forced air, it will distribute the fresh air throughout the house even more quickly, but only if there is a heating or cooling demand.

    The best (but not the perfect*) available way to control an ERV is to use a carbon dioxide sensor, but that control isn't yet an inexpensive off the shelf item. Good HVAC companies can install a ventilation system that is CO2 controlled, and it's common in commercial buildings. At least one company has done it residentially:

    All the above is more complicated than a continuous exhaust-only ECM fan, and may or may not pay for itself, depending on the climate and other variables.


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