Category Archives: ventilation

Chiberia 2019 – ERV hibernation

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Two aspects of our mechanical system fell victim to the Siberian express that ran over us during the last week of January. One of them was the Energy Recovery Ventilator (ERV).

The ERV typically operates down to 10 degrees Fahrenheit (-12 degrees Celsius). Below that, the enthalpy wheel freezes up, and a temperature sensor in the ERV shuts the unit off. That meant that we were without mechanical ventilation for three days.

That’s not too much of a problem, as we could crack open a window or two to get fresh air into the building. The down side was the big energy penalty when opening the windows.

I can report that it didn’t get stuffy despite the presence of two human beings and two dogs, and that humidity levels stayed under control as was evident by the minimal condensation at the bottom of the windows during the early morning hours.

Our ERV is an earlier model of the RecoupAerator 200DX. With the current model, temperatures below 10 degrees Fahrenheit (-12 degrees Celsius) should not be an issue as the unit comes with a pre-heating element.

The element is built into the fresh air intake and is tied to a temperature sensor which pulses it on and off as needed to maintain the incoming air at 12 degrees Fahrenheit (-11 degrees Celsius) to prevent the enthalpy wheel from freeze up. This allows the unit to operate at outdoor temperatures below 10 degrees Fahrenheit (-12 degrees Celsius). And if combined with a solar PV array, it can even operate at a low carbon footprint.

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Fanning over efficiency

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There are several useful tools in the cyberworld that can assist with making energy efficient decisions. One of those tools is the Energy Star website with its Product Finder section.

But there is also a cautionary tale here – hidden in the fine print, if you will. I recently ran into this head on, while looking into ceiling fans.

One of the big home improvement stores had a sale on ceiling fans that I wanted to take advantage of, because it included a number of Energy Star certified products. I went to the Energy Star Product Finder to look up the performance specifications of the fans that were currently on sale.

Well, the dichotomy between ceiling fans that meet the minimum efficacy levels and ceiling fans that seem light years ahead of those levels is quite remarkable!

The minimum efficacy levels set forth in the product criteria are as follows:

  • At low speed, fans must have a minimum airflow of 1,250 CFM and an efficiency of 155 cfm/W
  • At medium speed, fans must have a minimum airflow of 3,000 CFM and an efficiency of 100 cfm/W
  • At high speed, fans must have a minimum airflow of 5,000 CFM and an efficiency of 75 cfm/W

A ceiling fan sized 43” to 60” meeting the above criteria, in addition to the luminair requirements, will carry the Energy Star label. And most of those fans may exceed those standards by a factor of about 1.3.

Yet there are ceiling fans on the market that leave those requirements in the dust. Take the Emerson Midway Eco (CF955) that I researched and purchased for our 1st floor:

  • At 561 cfm/W at low speed, it is 3.6 times more efficient than the minimum requirement
  • At 475 cfm/W at medium speed, it is 4.75 times more efficient than the minimum requirement
  • At 336 cfm/.W at high speed, it is 4.5 times more efficient that the minimum requirement

On the extreme end, the Home Decorators Collection – 60in Aero Breeze at 1447 cfm/W at low speed, exceeds the minimum requirements by a factor of 9.3.

Bottom line: Look for the Energy star label on products, but don’t buy just yet! Do your research first, because there may be a product that blows those Energy Star requirements out of the water – and saves you money down the road.

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Wet duct insulation!

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Let’s stick with the ventilation subject for a moment, dear readers, because I need help with a hack. I hope that some of you can point me in the right direction. Here is the problem that needs solving:

The duct insulation in the flex ducts that connect to my ERV is getting wet every winter.

Why do I have the flex duct in the first place?

The purpose of the flex duct is to stop vibration transmission from the ERV to the rigid ducts.

Why does the duct get wet?

During the winter month the fresh air intake carries cold air and the exhaust duct from the ERV to the building exterior does the same. This cold air often cools down the duct below the dewpoint. That causes any moisture that is lingering in the flex duct or that gets past the duct sleeve to condense on the flex duct core. It is subsequently absorbed by the fiberglass insulation around the flex duct. Theoretically, this should not happen. The outer duct sleeve should prevent any air, and with it moisture, from getting to the flex duct core.

The weak points in this system are where the flex duct connects to the rigid duct, and even more so, were it connects to the ERV.

I use sturdy duct zip ties and even have the tool to zip them as tight as possible. But even with utmost diligence, it appears impossible to make these connections airtight.

An added complication is that the ERV needs occasional maintenance, which in some cases requires me to disconnect the flex ducts from the ERV. The zip tie system makes disconnecting and reconnecting fairly easy, but apparently fails to get it 100% airtight. I am also concerned that handling the duct during the maintenance operations may lead to breaches in the duct sleeve.

Solutions?

Is there a product out there that would be better than flex duct but still provide the vibration isolation? Or is there a better system for connecting and sealing the flex duct to the ERV?

Whatever a better and air tight solution may be, it must allow for easy disconnection and reconnection of the duct to the ERV.

Any suggestions? Who’s going first?

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Ventilation closet framing

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My recent activity has been driven by my intent to get to the electrical installation. The last framing item that was standing in the way was the ventilation closet, because of its access doors and the issue of sound management.

To understand the decision making process, let’s look back at the 1st floor ventilation closet, which is directly underneath the 2nd floor closet and about the same size. But the access doors to the closet are on the bedroom side.

Our rationale was that in addition to accommodating the ERV, the ventilation closet would have additional shelf space for clothing and linens. The one drawback was the noise issue when the ERV was running. And it should run during the night hours when you are sleeping, at least during the heating season.

Don’t get me wrong, the ERV doesn’t make a lot of noise. It actually runs very quietly. And most folks would probably think of it as white noise. Nevertheless, the noise could be eliminated – or more accurately – shifted from bedroom to the living room. Because no one would be sleeping in the living room, the little noise the ERV would make wouldn’t bother anyone.

With that lesson learned, I was posed to place the access door to the 2nd floor ventilation closet on the living room side. And once I had scored two very nice salvaged oak doors from the ReUse Depot, I was finally ready to finish up the framing.

I will write more about additional sound management efforts for the ventilation closet in upcoming posts. Stay tuned!

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2nd floor ventilation system

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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.

Installation

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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