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ventilation system approach in semi-tight radiant house

markt Member Posts: 26
I'm looking for design suggestions of ventilation for my house. I'm not a HVAC pro, but former contractor, more than capable of building/installing anything, but need some approach/design guidance. Here's the context:

I have a typical 1960's ranch house located in coastal SF Bay Area. In a recent remodel I installed radiant floors, new windows and doors, and spray foamed most of the envelope. We have no AC and no mechanical ventilation, except bath fans. I have not tested how tight it is, but it gets stuffy fairly quickly when closed up, which is admittedly rare -- temperate climate, kids and dogs coming and going, doors and windows often left open, etc. It's a totally open plan, basically one long room, and a wing with two bedrooms and baths which have doors, but no other interior walls in the house. Thermostat is fixed at 65 and it's generally perfectly comfortable.

There are three ventilation enhancements I'd like however, and I'm wondering if I can do it with one system. First, I'd like a little forced ventilation in the bedrooms -- they get stuffy when the doors (interior) and windows are closed, which isn't often, but still it would be nice. Second, I'd like make-up air for range hood. Third, I'd like whole house air during the occasional hot summer evenings. The pattern here is that when it's hot it can be 85-90 in the day, but by 9pm it's almost always dropped to 60 or less and blasting outside air in would cool effectively.

I've looked at off-the-shelf balanced ventilation systems, but there are not many plain systems (non ERV/HRV). I don't think I need the added complexity of heat recovery in my climate and lifestyle. And of course none of them qualify as make-up air for my 1000cfm range hood.

So I was thinking, can I do something like take a Fantech MUAS 1600 (14" EC inline fan, filter, motorized damper, controls) and duct it to a couple large'ish registers in the kitchen and the living room (which are just either end of one room about 16'x60'), and with a couple small branches to the bedrooms, and then run it at very low speed always on, targeting balanced flow with three always on 50cfm bath/laundry exhaust fans, and then crank it up for range make-up and hot evening cooling.

Is this plausible?



  • hvacfreak2
    hvacfreak2 Member Posts: 500
    The Mitsubishi Lossnay ventilation units are perfect for this. They are a passive ERV and include most of the controls you would need already included as well as remote enable points.


    Mechanical Enthusiast

    Burnham MST 396 , 60 oz gauge , Tigerloop , Firomatic Check Valve , Mcdonnell Miller 67 lwco , Danfoss RA2k TRV's

    Easyio FG20 Controller

  • BillW
    BillW Member Posts: 198
    In the area that you live, humidity control can be a problem. The two types of ventilators work as follows: A HEAT recovery ventilator tends to dry out the space it serves. An ENERGY recovery ventilator tends to balance the humidity in the area it serves. Either are about 80% efficient, and on cold days, can blow chilly air onto the occupants. Typically, the louvers for the units are located high on the wall so they do not blow directly onto the occupants. Either one is no big deal to operate, however, the HEAT recovery unit will require a drain for the water from the defrost cycle. They also must be mounted in a conditioned space. They typically run on low speed 24/7, and can be set to higher speeds when humidity changes, a party is going on or cooking . Thermostats and home controls offer many options including humidity sensors, timers and so forth. Ventilators can have their own ductwork, or be ducted into the HVAC system. Remember that they are NOT exhaust fans or range hoods, and be careful NOT to put the building under either a negative or positive pressure. Balance the system properly.