Tag Archives: ERV

2nd floor ventilation system

I had a plan for the 2nd floor duct installation, and I had my six and eight inch round ducts. But they are not your everyday ducts. They are special for a couple of reasons.

Quality material

First off, they are called GreenSeam or GreenSeam Plus and they have built-in neoprene gaskets in the longitudinal seams. Once you snap and lock the pipe together along the longitudinal seam, the gasket should render it airtight.


The GreenSeam Plus, which is easily identified by the green band around the pipe end, has a gasket that is supposed to seal the travers joint, in addition to the longitudinal gasket. Furthermore, the GreenSeam ducts come in 26 gauge, compared to the thinner 30 gauge ducts you typically find in the big box home improvement stores.

In summary, I have sturdy 26 gauge ducts with gaskets for air sealing at the traverse and longitudinal joints. And the last time I checked, they were only incrementally more expensive than the big box products.

Air tightness

The ventilation system duct work should be airtight for a number of reasons. You want to control where the fresh air is delivered and where stale air is removed from the building. Leaky duct work would deliver or remove air where it is not needed, or where it could even be damaging.

The GreenSeam duct products with their gaskets make it a whole lot easier to air seal your ventilation system. To nip any remaining leaks in the bud, I sealed all seams on the outside with duct mastic. This is particularly important on elbows and tees, which have moving parts and joints without gaskets. And, of course, I sealed around all sheet metal screws I used to hold the duct work together.


The duct mastic also helped with air sealing the transition from a rigid to a flexible duct. The flexible duct was pushed over the rigid duct after it received a good coating of mastic on the duct end. Everything was then tightened up with a big zip tie.


Now that we had the technical aspects and quality control issues addressed, it was time to throw some ducts around!

The installation started at the ERV end for the supply and return lines. From here I could run the ducts to the various supply and return points (see also 2nd floor ventilation layout in preceding post).

We ran all the ducts in the attic above the 2nd floor ceiling joists. We had to lower a couple of ceilings toward the back end of the building (the bathroom and second bedroom) to have sufficient space for the ducts. The attic toward the front was tall enough to fit everything in.

A big thank you to our friends Vincent and Rubani for assisting me with the installation!

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Lessons learned: 1st floor ventilation

We have a special friend. His name is Erv, and he brings us fresh air into the house year round. Other people have the same friend, but they call him ERV, or sometimes by his full name: Energy Recovery Ventilator.

The ERV is a well appreciated equipment. Because our house is almost completely airtight, we need mechanical ventilation to remove the stale air and bring in fresh air. The ERV does just that, assures good indoor air quality, and in the process keeps us comfortable with the enthalpy wheel. It acts as a heat exchanger and removes excess moisture.

I like to put it this way: Using the ERV is like keeping windows open during the winter to get fresh air in, with the exception that it doesn’t get cold. It works so efficiently that it helps us to delay our heating season by up to four weeks.

The fresh air is distributed across our 1st floor apartment through a system of ducts, supplies and returns. I was about to embark on the ductwork installation project for the 2nd floor. But before doing so, I wanted to review our 1st floor ventilation system: What worked, and more importantly, what could we have done better?

Stale rooms (with a lowercase s)

The 1st floor ventilation system has fresh air supplies in key rooms to assure fresh air distribution across the apartment. A series of undercut doors, ‘indoor pressure balancers’ and ‘between room vents’ help move air from room to room and to eventually to the returns in the two bathrooms.

We can easily flush stale air out of the apartment by cranking up the ERV. However, if we run the ERV on the low setting (low airflow), the library and living room remain somewhat stale for longer than any other rooms in the unit.

In other words, the fresh supply air is not mixing sufficiently with the room air. The velocity from the fresh air supply in the foyer is good, but too slow when moving on to the library and living room.

To avoid something similar on the 2nd floor, I plan on adding a fresh air supply to the library and living room.

Noise transmission

The first time we fired up our first floor ventilation system, it sounded like a roaring jet engine. That problem was quickly solved with two three-foot pieces of insulated flex duct connecting the ERV to the rigid ducts. I made sure we had a 90 degree bend in each flex duct, and our ventilation system fell completely silent – almost.

While the noise transmission from the ERV is under control, we still had some transmission from room to room. For example, the fresh air supply of the office and foyer are connected by a six foot duct. The noise transmission through this short duct is as such that two people – one in the office and the other in the foyer – could have a conversation with each other. The longer the duct between supplies, the more faint the noise transmission.

To minimize the room-to-room transmission on the 2nd floor, I plan on using a three foot piece of insulated flex duct with a 90 degree bend right after every supply to act as a sound muffler. This will also increase friction and reduce velocity, but I will try to make up for it through more generous duct sizing.

2nd floor ventilation layout

The plan below shows the 2nd floor ventilation layout with the improvements mentioned above:

  • Using flex duct at each supply as a sound muffler to reduce room-to-room sound transmission
  • Adding fresh air supplies to the library and living room to improve mixing with the room air and a more efficient flushing of the stale air, even at lower airflow rates.

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ERV croaked – Part 4a

I am having fun with my sequential blog post titles … maybe to compensate for the inconvenience of having a sequential problem with our Energy Recovery Ventilator (ERV).

Both of our ERVs (both RecoupAerator by UltimateAir) have been running flawlessly for the past two years. But earlier this month, our 1st floor ERV showed symptoms that were reminiscent of the problems we had during the winter of 2013/14 with our basement unit.

When we ran the ERV, the building cooled down rather quickly. That indicated that something was amiss with the heat exchanging process. Based on our past experience, I knew that there were two probable causes:

  1. The enthalpy wheel stopped running.
  2. One of the blower motors and/or control boards croaked.

Well, it took no time at all to determine that it was the motor and/or control board. I made a quick call to UltimateAir and a few days later we received the replacement parts. It was time to start tinkering again:

I have a suspicion that the problem may lay with the heat sink on the control board. Two years ago, when I went through the same process in the basement, I noticed that the replacement board had a significantly bigger heat sink than the original board. I also recall vaguely that Matt at UltimateAir pointed out that the board on our 1st ERV may give us the same problem.


Or was it the fibers from the enthalpy wheel that started clogging the impeller that did the motor in? I am curious to know that the experts at UltimateAir think.

On a side note – this blog begins to pay off! Because everything is documented, it’s easy to look up a problem of the past to remind myself on how to fix things – like the ERV.

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Onset of nerdiness

Strange things happen once one embarks onto the deep energy retrofit road. For instance, a level of nerdiness sets in.

You don’t just turn on the thermostat in fall. You make a note about when exactly you turned it on. This year, it was the evening of November 1st.

Not nerdy enough? How about this:

Back in the day, when I was more than young – when I was a kid – a hybrid of joy and eager anticipation clocked in once a week, triggered by the release of the next episode of a science comic book.

Some may argue that things haven’t really changed that much, except that the comic book was replaced by the monthly arrival of our utility bills. I devour them almost immediately, and they almost always make for some interesting reading.

Such as our natural gas bill for last month, which claims that we used more gas in October 2013 than October 2014!


Therms 10/2013: 32.51
Therms 10/2014: 22.52

Average daily therms used 10/2013: 1.02
Average daily therms used 10/2014: 0.75

That seemed strange, particularly because this October seemed so unseasonably cold.

Well, let’s separate fact from fiction. October 2013 was cooler, at an average daily temperature of 50 degree Fahrenheit, compared to 51 degree Fahrenheit for October 2014.

That still doesn’t explain away the difference in natural gas consumption. Nor do the extra two days on the October 2013 bill, although they could account for as much as 2.04 therms. To get to the bottom of this, I have to turn to the Energy Recovery Ventilator (ERV).

With an almost airtight house like ours, mechanical ventilation is less a choice than a necessity. It maintains good indoor air quality (IAQ) by removing pollutants and excess moisture, and as such protects us from what is known as the sick building syndrome.

The ERV doesn’t just ventilate the building, but it also has a built-in heat exchanger, the enthalpy wheel. This makes it an extremely useful piece of equipment, particularly during the heating season, as we get a supply of fresh air without the typical heat loss.

We had our fair share of ERV problems last year, starting in October. The air in the building got stale rather quickly, with no functioning mechanical ventilation. To maintain good indoor air quality, we fell back on the age old method of non-mechanical ventilation – opening the windows.

The problem for us was that there is no heat exchanger when you open the windows. We got plenty of fresh air – but is was cool October air. With that we had a lot of heat loss, which led us to turn the heat on about a month earlier than usual.

And that, ladies and gentlemen, probably explains the difference of 10 therms in the gas bill between this and last year.

If you find this remotely interesting, you have officially joined the club of nerds!

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Blower door test – after insulation

Picking an ERV

Design workshop

ERV – keeping the heat!

ERV performance test

ERV croaked – Part 1


A patriotic piece of equipment

I am talking about our energy recovery ventilator (ERV).


Patriotic because it has been engineered and is largely manufactured Ohio? That too – but I really had something else on my mind:

So far this summer the nights have been nice and cool, allowing us to open the windows and let the apartment cool down over night. That wasn’t an option last night, the night of July 4th. The fireworks kept going well past midnight, keeping us up … and even more so, the dog.

Fortunately, we have new triple glazed windows. Once they were shut, the thunderous fireworks turned into nothing more than white noise.

But how would we use the cool night time temperature to cool the place down? That is where the ERV has its great entrance with its EconoCool option.


EconoCool gets activated by flipping a small lever switch. A sensor in the ERV’s fresh air supply stream gauges the temperature, and if it measures between 55 to 70 degree Fahrenheit, the enthalpy wheel (heat exchange wheel) turns off. That stops the heat exchange process and brings the fresh, cool night time air into the apartment, even with all the windows closed.

We managed to drop our indoor temperature by four degrees Fahrenheit, from 73 at midnight to 69 this morning. That makes for a happy 5th of July!

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