Tag Archives: energy

Hunting for replacement ERVs

ventilation, ,

It was time to research replacement ERVs (Energy Recovery Ventilator) after two of our units broke down in 2020. A couple of key aspects re-emerged in that process.

  1. The heat recovery efficiency of our Recoupaerator 200 DX was unmatched based on HVI (Home Ventilation Institute) data, which was confirmed with my own testing.
  2. It looked like the Recoupaerator 200 DX was the only residential ERV on the U.S. market that used an enthalpy wheel for the heat and moisture transfer.

Other residential ERVs use a static core heat exchanger, or core in short. Unlike an enthalpy wheel, the core functions on the principle of cross flow.  The exhaust and fresh stream flow across each other in the core without mixing. In the process thermal energy is transferred through the core’s membranes. And if we want to get all technical, we are talking about sensible energy (heat) and latent energy (moisture).

The cores come in two shapes: square and hexagonal. And this apparently small difference has a big impact when it comes to energy recovery. A hexagonal core has more surface area and thus provides more opportunity for sensible and latent energy transfer.

A quick review of product specifications led me to conclude that an ERV with a square core would be out of the question for us, because of the rather poor energy recovery rates.

Looking at products with a hexagonal core, I was left with three available options:

  • Zehnder CAQ350 ERV
  • Panasonic FV-20VEC1, and
  • Broan ERV200 ECM (also sold under the Venmar brand name).

To help in the decision making process, I pulled the HVI performance data for each product so that I got a good comparison.

The three hexagonal core options appeared to be all in close range of each other. Zehnder seems to be a little bit of an outlier on the net air flow side for the test data, while the Panasonic and Broan are in close range.

Looking at the power consumed in watts, it was a close race, where Broan emerged with the least power consumption.

As for the energy recovery rate – or if you prefer the technical term, the Adjusted Sensible Recovery Efficiency (ASRE), we have another close race with Zehnder squeezing into first place, closely followed by Panasonic and Broan.

These were useful data to have, but I still was left without a clear preference between the three options. So I began to look at cost. And remember, these were pre-inflation prices. Zehnder came in just above $3,000, Broan landed just under $3,000, and Panasonic just under $2,000.

It looked like I was left with two favorites in this horse race: Panasonic and Broan.

Between the two, the Broan ERV seemed to be the most compatible. It has similar dimensions to the old Recoupaerator 200 DX and as such would fit nicely into the ventilation closet. It also had very similar controls and low voltage auxiliaries, just like the Recoupaerator 200 DX.

The Panasonic also had very similar dimensions to the old Recoupaerator 200 DX and as such would fit nicely into the existing ventilation closet. But its controls seemed rather primitive, and the auxiliary controls for some reasons all required line voltage. And it was unclear what advertised auxiliary controls would actually be available.

Based on my past experience, I was not in the mood to bet all my money on one horse. Diversifying my investment seemed to be a safer path to take. So I ended up ordering one Panasonic FV-20VEC1 and one Broan ERV200 ECM to replace the two failed Recoupaerator 200 DX.

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Failure of Recoupaerator 200 DX

ventilation,

The pandemic brought a kind of perfect storm for many of us. In our case, it was ventilation related. Two of our ERV’s broke down – right when we really needed to rely on good ventilation. Although, considering what other folks had to endure, ours wasn’t really a perfect storm but more of an inconvenient breeze.

We had three Recoupaerators 200 DX Energy Recovery Ventilators by UltimateAir in our building, one for each apartment. And as mentioned in the past, these ERV’s were one of my favorite green building gadgets.

Six months into the pandemic, the ERV for the garden unit broke down, followed by the one on the 1st floor. You may be asking: “What is the big deal? Just get replacement parts, or a new unit”.

I tried. I contacted UltimateAir, and got crickets chirping. I eventually found out that UltimateAir went out of business at the beginning of the pandemic.

I was now sitting on three ERVs with no tech support or good way of obtaining parts or even a replacement unit. That this was a disappointing experience is an understatement. I loved the setup, effectiveness and efficiency of these ERVs from UltimateAir.

But it looked like it was time to let go and research alternative products that I could use as replacements. And that had its own challenges because of the supply chain issues that reigned during that time.

We did the only thing that we could do: Ventilated the old fashioned way by opening windows, tried not to think too much about the associated energy penalty, and remained hopeful that the supply chain would eventually unclog.

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2nd floor on demand pump

plumbing,

My current modus operatus is wrapping up loose ends. This includes the installation of the on demand hot water pump on the 2nd floor. But this time I did it with confidence, because I had the installation experience from the 1st floor under my belt, including a correction.  And I had the helpful hands of our friend Rubani assisting me.

What is this on demand hot water pump all about? Here is the super short version:

The on demand pump is activated through the push of a button. It pulls water from the hot water line and pushes it into the cold water line. Once the pump senses a rise in the water temperature, it shuts off. This primes all fixtures on the hot water branch the pump is connected to, effectively cutting the delivery time of hot water to seconds.

The on demand hot water pump is just one piece in the puzzle of an efficient domestic hot water delivery system. If you haven’t caught my earlier posts on this system, let me provide you a brief summary with links:

When you are in your bathroom or kitchen and turn on the hot water, do you have to wait for a minute or two (or longer) for the hot water to arrive? Is so, you do not have an efficient hot water delivery system. An efficient delivery system cuts the wait time for hot water to arrive to a few seconds, as mentioned above.

And it does more: It reduces water waste and as such helps with water conservation. It also results in material conservation, as the ground rule for an efficient domestic hot water delivery system is a compact layout and smaller pipe sizes (made possible through the water conservation efforts).

See also:

You find that in an efficient domestic hot water delivery system all pipes are insulated and that it effectively manages structural and behavioral waste of hot water, which again feeds into the water conservation mentioned above.

See also:

An efficient hot water delivery system relies on structured plumbing rather than the traditional trunk-and-branch layout. With a structured plumbing system, the on demand pump is placed at the end of the one hot water branch that services all fixtures.

See also:

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Fanning over efficiency

ventilation,

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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2016 heating savings

heating, ,

It is friggin cold outside, and I can’t shake the urge to keep talking about heating related matters, so here we go again:

One goal of our deep energy retrofit was to save energy, and along with it, some Benjamin Franklins. The money we invested in tightening and insulating the building was meant to save us dollars on our heating bill, for instance.

But how would we measure how much we save? Our problem was that we had no starting point. We bought our building as a foreclosure in 2009 and thus had no data – no access to utility bills – that would tell us what it took to keep the building heated and comfortable.

That said, there are plenty of buildings in our neighborhood that could serve as a comparable (comp). Not only are they the same construction type, but also in the same energy deficient shape as our building was before we started with our deep energy retrofit.

I found a building that was a good match, and the owner that was happy to share their utility data with us.

To compare apples to apples – or in this case, therms to therms – I calculated the amount of therms used per square foot per month for both buildings. Our building’s natural gas consumption is reflected in the blue bars, while the comp, or pre-retrofit state, is reflected in the red bars.

Data reflections

Why is there natural gas used during the summer months (off heating season)? Because in both cases natural gas is used to produce domestic hot water, i.e. washing the dishes, running the washing machine on warm or hot cycle, taking a shower, etc.

You may have seen me bragging about turning our heat on as late as mid November. If you look at the consumption for November 2016, you see that we mostly used domestic hot water while our neighbor in the comp building had the boiler already buzzing away.

Looking at the big picture, our building consumed 0.200 therms/square foot over the course of one year, while the comp usage was at 0.976. Our deep energy retrofit improvements appear to have reduced our natural gas consumption by 0.776 therms/square foot/year. That equals a reduction in our heating needs from November 2015 through December 2016 by a whopping 80%!

For our metric friends (i.e. the world with the exception of the U.S.): Our natural gas consumption equated 63.04 kWh (or 226.95 MJ) per square meter, while the comp came in at 307.89 kWh (or 1108.39 MJ) per square meter.

I typically don’t like to measure the improvements in cost savings, as supply cost and taxes may vary between jurisdictions or energy companies. In addition, the fixed costs on the gas bill, although often small, prevent accurate scaling to a square foot basis.

Yet getting an approximation of the monetary savings would give us a sense of the potential return on investment. We paid $0.27 for natural gas per square foot over the course of a year. The cost of the comp were $0.98. The estimated total cost savings for the 2,900 square foot of conditioned space in our building from November 2015 through December 2016 would be in the range of $2,000.

Yes – I am beaming right now! Yet, this somehow seems too good to be true. I think the flaw with my analysis is that I have based it on one comp only. I plan to find another couple of buildings that I could include in the analysis. That should give me a number that would be easier to defend.

Stay tuned, because I will keep you posted!

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