Passive ERV for make-up air

ellessebeeMarch 30, 2013

I know that make-up air for kitchen vents has been discussed at great length on this site but I have a slightly different problem. We are renovating a house and the plans called for an ERV for bringing fresh air into the house without opening windows to dust and pollen. The HVAC guy has proposed a 90cfm unit ducted into the return of the AC air handler. I don't intend to run the ERV full-time and don't want to run the air handler unless the AC is on. We will have hydronic radiant (floor) heat. I really want the quite and no breezes! But we will also have pretty strong bathroom vents, kitchen vent, dryer and central vac that will suck air out. I want to control where the make-up air comes from. The 90cfm ERV will not be adequate for make-up air for any of these things singly let alone when more than one is running. I would like to find a passive system that would filter and temper incoming air when one of the other appliances is turned on and exhausting air. I want to prevent random air infiltration if possible, especially from the flue, attic or basement. Does anyone know of any way to do this? It doesn't need its own exhaust mechanism since the others would serve that purpose. My HVAC guy is clueless - also as to whether we whould duct the ERV into the air handler or just let it run through the wall somewhere. Thanks so much for any opinions.

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barometric damper like this product: skuttle 216

in tight houses in La. we put a 12x12" filter grill (& filter) to soffit. 6" duct from filter grill to return with barometric
damper @ return plenum.
adjust the wieght on the lever on the damper to
cfm required by ashrae 62.2
air is cleaned, measured & dehumdified before
entering house.
no motorized parts, no high expense of erv.
this has worked well for me for 15 years.

hvac companies really need to learn about
ashrae 62.2 instead of relying upon others
to educate them. their field is heating VENTILATION
and air conditioning.

with ERV, you are in hot climate?
how do you know that your house is tight
enough to require fresh air?
anyone tested with a blower door to measure
air infiltration?

    Bookmark   March 30, 2013 at 11:42AM
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energy_rater_la: Do you have a diagram of your setup with the barometric damper? (We had a home energy audit done with a blower door test. They said our house is tight and before it can be further modified (seal crawl space, foam attic, etc.), we have to provide makeup air via an ERV. I talked to one of the contractors who said they could install one, yes, but another idea is just a duct from outside through a filter into the existing HVAC return. It would provide makeup air, but since we are in GA (high humidity in summer), I don't want all that moisture in the house. Your answer said the air is clean, measured, and dehumidified. How??)

I appreciate your experience and info.


    Bookmark   September 6, 2013 at 6:36PM
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cleaned by filtering air through filter in filter back return air grill

measured by barometric damper. lever has adjustable weight to adjust cfm of air entering duct.

dehumidified by cleaned, measured air entering
return of hvac system and passing over coils to
dehumidify before exiting supply grills.
keeping ambinet Rh from entering living space
without being conditioned.

the difference between the one contractor's recommendation is the barometric damper in the duct..

no diagram. each install has been designed to configuration of house, and location of return air plenum.

what are your plans for dehumidification?
what method of heating/cooling? sized by manal j?
how much make up air is required?
what is cost of erv, including fresh air intake & install of both?
how would this cost compare to install of whole house dehumidifier?

pretty high RH here in La also.
different methods of controlling Rh.
I have heat pump with vs air handler unit
controls Rh very well..
I also have an april air dehumidifier...just no
need to run it often as the vs ahu
of the correctly sized hvac system keeps
Rh @ 52% most of the time.

given the choice between ERV & wholehouse
dehumidifier...I'd pick the latter every time.
whd can be set up to have fresh air intake also.
I can give you the phone number of the company who sold me my april aire dehumidifier for you to have a conversation with them if you email me.

best of luck.

    Bookmark   September 8, 2013 at 10:49AM
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