If you have actually succeeded in building your home tight, the HRV is going to be a necessary addition.

I have only been running it for a few weeks, but what it does is remarkable.  I can enter the build in the morning and the place will be warm and oppressive.  The air feels stale and "dead".  Within a few seconds of turning the HRV on, you can actually sense the air begin to move and within even 10 minutes you can tell a marked difference in the "freshness" of the air.  That is interesting because it only moves about 200 cfm, but the volume of the place is upwards of 60,000 cubic feet.

I placed "intake" or stale air ducts in bathrooms, a large walk-in closet and the kitchen and the "exhaust" or fresh air ducts in the bedrooms and common areas.

I am glad I tried to place the intake ducts as high as possible in each location.  During finishing work, we were reminded how much warmer it is up in a high area.  Drawing off the warm air is a great strategy for both cooling the house and for making sure that the air returned to the home isn't too cool in the heating season.

Sounds like a winner. If I did the math correctly in my head, that works out to 0.2 ACH for the HRV. Have you done a blower door test to determine the additional infiltration? What is the efficiency of your HRV? And finally, what was used for the building heat loss analysis and how well did it compare to actuals?

The air feels stale and "dead".

It would be interesting to put numbers on exactly what you are sensing.

2012 IRC makes mechanical ventilation mandatory in residential homes due to the tight AI. Mechanical ventilation has been standard for commercial but residential usage has been slow. Except for the tight green energy builds, most builders just "build them leaky" as they want the "house to breathe" but we all know what that really means.


I am not a fan of standard bathroom exhaust fans for many reasons as they are a leaky energy hole in your building envelope. Not to mention poking holes in your roof for each bathroom fan is just another potential roof leak. Ideally one should install an ERV/HRV and run exhaust ducts from the bathrooms instead of putting in a $30 Home Depot fan and poking a hole in your roof for each bathroom fan. On a personal note, the other reason I hate them is out here in Arizona bathroom exhaust fans are an open door for scorpions & roaches to come in. I've literally watched them fall from the ceiling fan cover onto the floor or toilet. Nothing like waking up in the middle of the night and sitting on the toilet only to have a scorpion sting you and hopefully not in a sensitive spot, if you catch my drift.

With a proper HRV/ERV design, you can run 3 or more bathroom exhaust ducts, 1 kitchen (not near the grille), and 1 laundry room, combine the 5 exhaust ducts and simply poke just ONE 6" or 8 "hole in your wall instead of having 5 holes in your roof. Of course 1 intake/fresh air hole in your wall is needed. So 2 wall protrusions instead of 5+ roof protrusions.


I really like the American Aldes design but I think I will go with the Ultimate Air RecoupAerator 200DX as it allows one to run it in a NON recovery mode. In other words, you can just run the fan and bring in outside air WITHOUT conditioning it. This comes in handy in the swing seasons. In the spring or fall the outside temps can be 80F+ and the homes interior can get hot during the day but at night the outside temps can drop down to the 50s. So it makes no sense to "condition" the incoming outside air with the interior air as the interior air is hot and you want to cool it off ASAP with cool outside air. Running it in non-recovery mode allows one to do that. The American Aldes does not have that option, it's always on recovery mode.

Another plus to mechanical venting is filtering the incoming air.

Another plus to mechanical venting is filtering the incoming air.

Yeah. Getting a snoot full of pollen and sneezing your way to the door in the morning is more than enough reminder to start up the (filtered) ventilation unit when you get inside.

I am using the Recoupaerator 200DX. It is more noisy than anyone would have guessed, but we haven't yet had the time to open it up and see if something happened to it during the installation. It lives in an overhead storage area built above the Master Bathroom. When it runs at 100% output, you can just hear it in the living space below.

Since IRC specifies different ACH's for different rooms, how do you handle that with your HRV's?

I am not knowledgeable about the differences in available HRV's, but recall reading about some that are made for individual rooms with a occupancy detector of some sort.

Are the HRV's referenced above the whole house versions?

In an arid mountain climate, could I make my own? While I think I could, my gut says just buy one so it complies without question and deals with the issues related to humidity as well as heat recovery.

Since IRC specifies different ACH's for different rooms, how do you handle that with your HRV's?

You can put balancing dampers on the ducts or use adjustable vents or you can even build the restriction right into the system by utilizing different duct sizes.

There are also many different control methods utilizing timing strategies, user-demand switches, pressure sensing, humidistats, CO2 detectors, etc., etc.

My 200DX is a whole house unit.

It wouldn't be feasible to make your own HRV, but there are other ventilation methods that can meet code, including simple exhaust fans. Obviously, they aren't heat exchangers.

Posted By ICFHybrid on 21 Jun 2013 12:18 AM

I am using the Recoupaerator 200DX. It is more noisy than anyone would have guessed, but we haven't yet had the time to open it up and see if something happened to it during the installation. It lives in an overhead storage area built above the Master Bathroom. When it runs at 100% output, you can just hear it in the living space below.

Strange that it runs so loud. Let me know what the manufacturer says and whether it is a defect or normal for them to run that loud. Something to consider if mounting them above or next to a bedroom.

Can you program them to run at certain times and in non-recovery modes or must it be done manually each time?

Renew Air runs very quiet

Posted By cmkavala on 21 Jun 2013 08:19 PM
Renew Air runs very quiet

Do you know if it has a non-recovery vent mode?

Could this be your issue?

Recoupaerator Noise

Could this be your issue?

Ha ha, yes, there is a definite thumping or knocking component to the noise........ I think your discovery just moved it up on my list of things to do....

If you hear the unit startup you can tell it is running, but if you don't hear the startup, you probably won't hear it. That is the level of noise in the living space.

The two questions most asked about the 200DXs have to do with two modes.

1. "EconoCool" mode in which there is NO heat (or moisture) exchange. Obviously, the exchange wheel is disabled and bypassed completely. In this mode, the unit acts as a dual fan, exhausting air from the exhaust vents and putting fresh outdoor air in through the inlets. This mode can be set "ON" and then operates automatically when the temperature is above a certain level, or it can be accessed by a dedicated switch and turned on and off by the user.

2. "Boost" mode which is simply a switched input that turns the unit to full speed until the signal disappears. Typically this is the one in which you place a time switch in each bathroom and if there is big bad smell or lots of humidity, the user can set the timer to run the unit on 'HIGH' for a certain amount of time before automatically turning off and going back to normal operation.

Of course, you can use any kind of controls to run these modes. A humidistat put on the Boost Mode would run the unit on high whenever the humidity was above a certain level.
There is a pressure-sensing option that runs the unit to balance the pressure in the house at any level between lower inside and lower outside.

The standard control appears to be a rheostat that runs the unit 24/7 in a variable range between 'LOW' and 'HIGH'.

I selected this unit because, at the time, it was the highest efficiency unit available with high end capacity and it had an accessible control board.

Cool...and there is nothing I love more than an accessible control board

If a single HRV is used with ductwork that varies in size to control the airflow volume by room, how does one disinfect the interior surfaces of the ductwork on a periodic basis?

Won't condensation occur in the duct work? And if condensation happens, won't mold and/or bacteria grow?

I would not expect mold to be a problem because mold needs both moisture and an organic food source. I have not heard of any issues associated with bacteria, but if the air filter or maintenance was inadequate, that could perhaps be a concern. I would like hear and learn more about this.

Why would condensation happen?

Incoming moist air is conditioned as it passes thru the core,
condensation only occurs in the exhaust side of the system and is blown out in vapor form, same as your bath exhaust fans

If I recall correctly, a good HRV has a way to prevent such problems. I don't know if that means routine filter and other maintenance.

Bathrooms and kitchens have the largest airflow requirements. They produce the most moisture. That air contains the most energy as well as a lot of air contaminants. If the air from those rooms must travel through ductwork, that path seems like a risk for such pathogens.

Since I worked with an insurance company to help correct sick building syndromes, I have seen the health risk and remediation problems inside of ductwork. CO is a dry climate, and the problems still occur.

That is why I am more focused on single room HRV's.

Considering summer with A/C, if you take warm, humid exterior air and run it through an HRV, you will sometimes end up with condensation and saturated ventilation air in the ducts. A properly balanced ERV or dehumidification will help.

Mold tends not to grow where it dries out once a day. So I wouldn't worry about short term high humidity (in ducts or elsewhere).

Posted By jonr on 24 Jun 2013 09:42 AM
Considering summer with A/C, if you take warm, humid exterior air and run it through an HRV, you will sometimes end up with condensation and saturated ventilation air in the ducts. A properly balanced ERV or dehumidification will help.

Mold tends not to grow where it dries out once a day. So I wouldn't worry about short term high humidity (in ducts or elsewhere).

jonr,
having built and used ERV's in Florida and Louisiana, some of the most hot and humid climates, I have never seen sweating on the interior supply side , even when run 24/7, maybe it the manufacurer? I have used mitsubishi and aprilaire , both with a lossnay core