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Community and Q&A

Help for new Broan Smartsense fans as alternative to HRV

Monty Worthington | Posted in Mechanicals on

I have seen articles here talking about the new Broan Smartsense ventilation fan system and had a few questions about using it as an alternative to an HRV…

I am curious if anyone has used them, or designed a house for them – we are in our final design phase and our plan checking company requires make up air calculations.

2800 sq/ft 2 story house – stick built – California climate zone 3

The idea is to put in 5 Broan fans – then have the makeup air dampers attached to them.

My question is where do the intakes go? To the bedrooms (3), the upstairs (1), laundry (1)

Or do the fans auto reverse and use the same ducting for incoming air when needed – or do they exhaust a room while the electronics open a damper on an intake line to let in fresh air?

Sorry if this seems like a dumb post, but the system seems new and doesn’t have much online about it.

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Replies

  1. Aj Builder, Upstate NY Zone 6a | | #1

    7. What are the different ways that the Damper can be installed in my home?
    The most common way to install the Damper is to connect it to a home’s central duct
    system. In this application, outside fresh air enters the home through the Damper and is
    then routed and distributed through the home’s ducts. More information on this
    installation approach can be found in the Broan Automatic Make-Up Air Damper
    Application Guide. 14
    8. What if my home doesn’t have ducts?
    Homes without ducts can still utilize the Damper to help replace air which is exhausted
    from the home by the range hood or other exhaust fans. An installation illustration for
    this situation is included in the Damper’s Application Guide.

    http://www.broan.com/Catalogs/99044565A.pdf

  2. Monty Worthington | | #2

    Hi thank you for the follow up - I have already read the document you linked - and yes it does seem pretty simple, I guess I need a little more guidance - we will not have central ducting.

    From what I have read the incoming make up air should typically go to a bedroom right? With multiple bedrooms that would be a lot of intakes, though I suppose I could send it into the Master Bedroom which is southwest facing and has some solar gain. So how many incoming vents do I need? Based on 5 x 100cfm fans it looks like I would only need one incoming 6" air damper (500cfm exhaust potential) - could this be located anywhere in the home?

    If it can be located anywhere in the home I would guess that the best place would be to place it on a south wall high up (under a roof eve if possible) to allow for maximum solar gain and air mixing in the winter reducing the heat loss of incoming cool air. Is that assumption correct or am I reading that wrong?

    Also, it looks like it might be better to have a single 8" damper with intake to go over the minimum amount.

    Further, there will only be one exhaust fan on the second story - 4 on the ground floor, so is it still ok to have the intake on the second story where there is large open & clear stair case leading to the lower level?

  3. Danny Kelly | | #3

    Monty - you will find multiple opinions as to where to put your intake damper. Most will advise to put it in a laundry room or something in lieu of a bedroom - even though it is bringing in fresh air - this is untempered air so bringing directly into a living area could make your home uncomfortable during summer and winter extremes.

    Why do you have 5 exhaust fans? Seems like a lot for a 2800 SF house. I would follow ASHRAE 62.2 guidelines for calculating the proper CFM for your home's volume. You may be over-ventilating.

  4. GBA Editor
    Martin Holladay | | #4

    Monty,
    To clear up some of your confusion, let's clarify what you are doing:

    1. You have decided to install an exhaust-only ventilation system.

    2. You will be using Broan SmartSense bathroom exhaust fans. These fans can communicate with each other and will self-correct for underventilation by turning themselves on when necessary. These fans cannot self-correct for overventilation.

    3. The fans do not "have the makeup air dampers attached to them." The dampers you are referring to are separate units; these are motorized dampers designed to be installed in ductwork connected to outdoor air intake vents. You probably do not need 5 motorized dampers and 5 air intake ducts for your house -- I think one would be plenty.

    4. Once you have installed a motorized damper correctly, you will not have any fans bringing fresh air into your house -- only a hole in the wall that allows fresh air to be pulled into the house through a hole when your exhaust fan is operating.

    5. Here's what you do: you drill a hole in your rim joist and install an outdoor air intake. You connect that outdoor air intake to a duct. You install the motorized damper in the duct. The duct leads to a grille mounted on the wall of a room where you want fresh air. It can be anywhere in your house: your basement, your laundry room, a bedroom, a bedroom closet, or your living room. In cold weather, the fresh air duct may cause comfort complaints if it is poorly located.

  5. 5C8rvfuWev | | #5

    Hey Martin, that was so dang clear .... you really should think about becoming a writer, y'know? Thanks.

  6. Monty Worthington | | #6

    Thank you very much for the answers - it certainly cleared things up in my head...

    Now onto deciding where to put the fresh air intake.

    With regards to why we are using 5 exhaust fans, we will have 3 1/2 baths, and a laundry room - so the fans needed are 5. Fortunately it looks like we only need one air intake.

    One idea is to put the air intake in our large pantry/wine storage off the kitchen as we would love to keep that are cooler than the rest of the house - might be a good location for it most of the year. We have very very few hot days here.

    Our upstairs is our living area and we will have 13ft ceilings in much of the area with an open concept - so really one large space - I was thinking that putting the fresh air intake up high in that area to minimize the effect of incoming cold air might the best idea - I might put it into the laundry room as that is little used, but it is also right off of the bedrooms...hmmm decisions, decisions...

  7. GBA Editor
    Martin Holladay | | #7

    AJ,
    I disagree. Monty is describing a home ventilated with an exhaust-only ventilation system, not an HRV.

  8. Aj Builder, Upstate NY Zone 6a | | #8

    Monty, the home you are somewhat describing is designed by a pro and vented by an HRV. And the details are handled by the pros not the homeowner.

    What I am saying is to me if a home is large enough to need 5 Broans, has 31/2 baths.... at some point a whole house HRV instead of 5 Broans.

    I could be wrong, How many sqft is this house? Custom high end or.....2800sqft...Where exactly in California, California has coastal to mountaintop. My California sister lives where you would just leave the windows open, my LA friend deals with air that is not quite as nice to be polite.

  9. Monty Worthington | | #9

    "Monty is describing a home ventilated with an exhaust-only ventilation system"

    Mr. Holladay is correct - the design intention was to not use an HRV as we are in a very temperate coastal zone, and exhaust was the main goal, with the correct amount of MUA in the design.

    The information/corrections provided helped in confirming the correct use of the Broan Smartsense system with MUA.

    Now an argument could be made that this is not the best system to use for ventilation of a new home, but I haven't seen anything that convinces me it isn't a good solution...

  10. Bill Ogrodowicz | | #10

    I have a 32 year old 1400 s/f home - one story, all electric, built on a concrete slab with central a/c & heat. I am about to insulate the attic space with spray foam between the rafters. This will give me an air-tight, unvented attic. The walls however are insulated with fiberglass batting and the windows are single pane (definitely not an air-tight envelope).
    I am going to replace the ceiling lights in both bathrooms (located at one end of the house) with Broan recessed fan/light kits vented to the outside to remove humidity. At the other end of the house is the kitchen with a vent hood over the stove (rarely used) vented to the outside. The kitchen is open to the living room where there is a wood burning fireplace which is never used, damper closed and glass doors on front that remain closed. The range hood, with its damper closed, and the fireplace are not allowing much air if any to escape through those routes.
    Would I benefit from a vent fan located in the living room / kitchen area, exhausting to the outside to remove stuffiness; and if so, wouldn't that be removing some of my conditioned air before it could be drawn into the return air ductwork?
    Since the range hood is hardly ever used it is not giving any benefit of removal of humidity. Is there an alternative that would exhaust humid air from that end of the house? Perhaps a separate vent hood tied into the ceiling lights?
    Could it be assumed that the walls/windows/doors would be leaky enough to allow sufficient fresh air to be drawn in to replace the air that is going to be pulled out through the exhaust vents? If not, would a fresh air vent ducted directly into the return air plenum be viable?

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