Tag Archives: research

Cool ideas?

Sometimes I get these seemingly insane ideas, only to find out later that they were somewhat rational. The subject matter of those ideas is typically not my strong suit. That’s why I tend to be infuriatingly quick to dismiss them.

Air conditioning is on my list of subjects that are not my strong suit. I grew up in Germany, where air conditioning is virtually non-existent. I ran into active cooling for the first time while visiting the Caribbean, and again years later when I moved to Chicago.

I regard summer air conditioning in the Midwest as a necessary evil and have a pronounced dislike for the temperature extremes we have to tolerate between the outdoors and conditioned indoors. I dread stepping into a grocery store or office building that feels like an ice box.

Since we started our deep energy retrofit, I’ve had to wrestle with the question on how we will keep cool during the dog days of summer without creating an ice box. I quickly learned that “cool” is somewhat secondary. The primary problem to tackle is how to keep the relative humidity at a comfortable level, i.e. under 60% (preferably at 50%).

We already have an Energy Recovery Ventilator (ERV) that supplies fresh air into the house, yet keeps the outside heat and mugginess at bay. My seemingly insane idea was to install an air-to-water heat exchanger in the fresh air supply duct to remove humidity through condensation, and deliver pleasantly dry air into the house through the ERV duct system.

Simply put, I wanted to run the muggy outside air across a cold air conditioning coil to dry it out. But I was told that there was no such air conditioning device that could be combined with an ERV. Yet, I clearly wasn’t alone with this idea.

Just in the past couple of years I started reading about ‘Magic Boxes’ that basically combine the function of an ERV, or HRV (Heat Recovery Ventilator), with that of a small air-to-air heat pump, i.e. a small air conditioner.

 

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Unlike our ERV, which uses and enthalpy wheel as a heat exchanger, a Magic Box uses an integrated air-source heat pump to transfer thermal energy between air streams. But they also can provide some additional limited conditioning – additional cooling (and drying) as well as heating.

One company (Build Equinox), located two and a half hours south of us, brought the CERV (Conditioning Energy Recovery Ventilator) to market just a few years ago. The CERV has an advertised heating capacity of 3,850 Btu/h, and cooling capacity of 2,400 Btu/h. These numbers vary depending on outdoor temperatures. One article listed a price of $4,500 for the CERV.

A competing product is the Boreal 12000 by Minotair out of Quebec, Canada. This Magic Box is more compact than the CERV and, in heat pump mode, has a listed heating and cooling capacity of 9,400 Btu/h and 8,700 Btu/h respectively. I read one article that pointed to a price of around $3,200 for the Boreal 12000.

Either the CERV or Boreal 12000 could be used instead of an ERV or HRV.

Going back to my original idea, combining an air-to-water heat exchanger with our existing ERV, I came across what looked like a promising option. An article on GreenBuilidngAdvisor.com described a variety of air-to-water heat pumps that could provide chilled water to the air-to-water heat exchanger.

In this function, the air-to-water heat pump would basically function as a chiller. But it could also reverse its cycle and produce hot water for domestic hot water consumption or a hydronic heating system.

The challenge would be to find a right sized unit that I could combine with our ERV, and that would be affordable. If you thought the CERV or Boreal 12000 were expensive, prepare yourself for a sticker shock while shopping for air-to-water heat pumps.

Nevertheless, I feel vindicated that my idea wasn’t that insane after all. But it has only brought me somewhat closer to a solution that would provide cooling and a comfortably low relative humidity during the dog days of summer in our deep energy retrofit.

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How did I miss this?

On a deep energy retrofit like ours, the clock is always ticking. Not only was it ticking, recently the alarm went off too: I have known for a number of years that I had till this year (2016) to install renewable energy components and claim the juicy 30% Residential Renewable Energy Tax Credit.

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We are interested in a photovoltaic and solar hot water system. Knowing that the time to claim the tax credit was running out, I took the first steps of organizing the project and was surprised – pleasantly surprised:

The tax credit has been extended. With limitations, but still, it has been extended.

The government actually got something done! Wouldn’t you think that’s BIG news? I can’t believe that I missed this.

“Note: The Consolidated Appropriations Act, signed in December 2015, extended the expiration date for PV and solar thermal technologies, and introduced a gradual step down in the credit value for these technologies. The credit for all other technologies will expire at the end of 2016.”

Source: Energy.gov

The good news: The Residential Renewable Energy Tax Credit for photo voltaic and solar hot water system was extended until 01-01-2022.

The bad news: The Residential Renewable Energy Tax Credit for fuel cells, wind turbines and geothermal heat pumps is still running out at the end of this year (2016).

“A taxpayer may claim a credit of 30% of qualified expenditures for a system that serves a dwelling unit located in the United States that is owned and used as a residence by the taxpayer. Expenditures with respect to the equipment are treated as made when the installation is completed. If the installation is at a new home, the “placed in service” date is the date of occupancy by the homeowner. Expenditures include labor costs for on-site preparation, assembly or original system installation, and for piping or wiring to interconnect a system to the home. If the federal tax credit exceeds tax liability, the excess amount may be carried forward to the succeeding taxable year. The maximum allowable credit, equipment requirements and other details vary by technology, as outlined below.”

Source: Energy.gov

But – the clock is still ticking. Here is more fine print: If you would like to claim 30% of the Residential Renewable Energy Tax Credit on photovoltaic and solar hot water, you have until the end of 2019. From 12-31-2019 till 01-01-2021 the tax credit for systems placed in service is reduced to 26%. And for systems placed in service between 12-31-2020 and 01-01-2022, the credit is further reduced to 22%. Once you’ve missed this last deadline, you are left hoping for another extension.

You can access details about the Residential Renewable Energy Tax Credit here:
http://energy.gov/savings/residential-renewable-energy-tax-credit

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Disturbing study

Out of all systems we touched during our deep energy retrofit, the domestic hot water plumbing revealed the most unexpected surprises and opportunities – and as it now turns out, potential risk.

An article published in Environmental Science: Water Research & Technology by William J. Rhoads, Amy Prudena and Marc A. Edwardsa states:

“This study raises concerns with respect to current green water system practices and the importance of considering potential public health impacts in the design of sustainable water systems.”

(Environ. Sci.: Water Res. Technol., 2016,2, 164-173)

The researchers point to increased residence time of water in plumbing systems that have been built with water conservation (i.e. low flow fixtures) and efficiency in mind to get their green building credits. To quote hot water guru Gary Klein:

“…the rules for sizing the piping do not have a way to account for these lower flow rates and fill volumes. On top of that, standard engineering practice is to add a safety factor on top of the calculated design. The result of this tension between the plumbing code, engineering practice and water use efficiency has the effect of dramatically increasing retention time in the piping.”

That increased retention – or – residence time comes with risks:

“Concentration of 16S rRNA and opportunistic pathogen genus level genetic markers were 1–4 orders of magnitude higher in green versus conventional buildings.”

(Environ. Sci.: Water Res. Technol., 2016,2, 164-173)

A write up of the study was published in Chemistry World.

pipe-sizes

Let’s unpack this by taking a step back:

Thanks to Gary Klein, we have an efficiently structured plumbing system that maximizes energy, water and material conservation.

Well – maximizes with a lowercase “m” because the Chicago Plumbing Code got in the way. ½” is the smallest fixture branch (or twigs) size that is allowed (Chapter 18-29-604.5 Size of fixture supply). Yet the combination of our structured plumbing system and low flow fixtures validates 3/8″ fixture branches (twigs) and fixture supply lines, which would help keep excessive residence time at bay. This is a matter of right sizing the piping for fixture branches (twigs) and fixture supply lines to match the flow rate of the fixture they serve. Gary Klein puts it this way:

“lower flow = smaller water volume to deliver = smaller pipe sizing”

The 3/8″ fixture branches (twigs) may be unimaginable in Chicago, but other places have caught on to the smaller pipe sizing principle, as I found out when visiting my friend Oliver in Sweden.

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I have come across a lot of bitching and moaning about the Chicago Building Code and inspections. Yet I learned to appreciate the code and the inspection through the process of our deep energy retrofit. Even if some things seem cumbersome and over the top, it is with our safety and welfare in mind. And the plumbing code is unambiguous about it:

“18-29-101.3 Intent: The purpose of this chapter is to provide minimum standards to safeguard life or limb, health, property and public welfare by regulating and controlling the design, construction, installation, quality of materials, location, operation, and maintenance or use of plumbing equipment and systems.”

Chicago, I am glad you watch my back! Except that sometimes you don’t. Sometimes the world is moving faster than you are. And everything having to do with green building is picking up speed every year. That includes encouraging developments in water conservation and low flow fixtures. I am sure ½” fixture supply pipes once were a rock solid safety standard – before the emergence of low flow fixtures. But these days… As Gary Klein points out:

“Reducing flow rates without reducing pipe volume is a recipe for disaster, as the study points out.”

Will I swap out all of our low flow fixtures with regular ones? Nope, not yet. And Gary gave me a little peace of mind:

“You actually were able to reduce the volume [and residence time] by the way you did the [structured] plumbing.”

Dear Chicago: I would appreciate it if you would live up to your health and safety intent. Take note of the study “Survey of green building water systems reveals elevated water age and water quality concerns” and adjust the plumbing code to allow smaller pipe sizes. Stay abreast of the green building developments, and in the process keep us safe – keep watching our backs!

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3/8 inch and flowing

“I told you so!” – was coming to my mind while looking at the plumbing in a Swedish single family home built sometime in the 1970’s.

Some plumbing lines were partially exposed to keep them in the interior conditioned space. What caught my eye right away was a 3/8 inch branch (or twig) coming off of a 3/4 inch trunk line.

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The use of 3/8 inch plumbing lines (or twigs) fits right with the material and energy conservation goals of an efficient domestic hot water delivery system, as was explained to me by the hot water guru Gary Klein. The problem for us in Chicago is that the smallest allowed pipe diameter per plumbing code is 1/2 inch. The rationale behind this limitation is, so I assume, concerns about pressure drop and insufficient flow capacity. But it also puts a limit on the efficiency of our hot water delivery system.

Seeing that a built 3/8 inch twig line didn’t cause the world to implode was rather exciting. Not only that, but the 3/8 inch cold water line services three fixtures: 1) the toilet, 2) a sink, and 3) a shower, while the ? inch hot water line only serviced the sink and the shower.

plumbing-041 plumbing-042

 

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The structured plumbing system that I have described in a previous post, recommends the use of 3/8 inch twigs. But each twig should just service a single plumbing fixture, not multiple fixtures.

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Serving three fixtures with cold water and two fixtures with hot water using a 3/8 inch twig lines would take us – so one could argue – into deep water. That begs the question: Why would several fixtures on one twig be acceptable?

The bathroom in the Swedish single family home is meant to be used by a single person at a time. In other words, you shouldn’t need to worry about somebody flushing the toilet or using the sink while you take a shower.

And I used that shower. There was no problem with the water flow rate or the water pressure, despite the nine feet long 3/8 inch twig. And being the nerd I am, I let the shower run while flushing the toilet or turning on the sink faucet. There was a very brief but minor pulse in the shower’s water flow, but other than that, no detectable flow reduction or pressure loss.

For full disclosure, I should mention that the bathroom in question was on the 1st floor and only a few feet away from the water heater and water main. The second floor bathroom has a different set up. Here a 1/2 inch twigs (or branches) services the various plumbing fixtures, probably to mitigate pressure loss that may come with the elevation and friction that comes with the longer pipe run.

Now – is that 3/8 inch twig I observed an exception? Apparently not. I noticed almost the exact same setup in a restaurant men’s room — a 3/8 inch twig servicing all fixtures.

As unscientific and nerdy as this is, I am delighted to see proof that 3/8 inch twigs can work and can be safe. But to whom can I take my “I told you so?”

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Fan(fare)

Has the cabin fever set in by now? If so, let me lead a quick expedition into the hot and muggy summer months. Even though we may yearn for summer heat at this time of the year, once it is upon us, we are rapidly looking for ways to keep cool. How do you keep cool?

I dislike the typical excessive air conditioning we exercise, but I am a big fan of ceiling fans.

You could argue that any ceiling fan would do a good job as it is most likely to operate more efficiently than a conventional air conditioning system. This comparison is somewhat unfair as the product of air conditioning is different from that of a ceiling fan. But then again, humanity is famous for buying products that are non-essential.

We needed to make a decision about what ceiling fans we should acquire for our deep energy retrofit. I started by looking at the extremes. On one end there is the $25 product, cheap but flimsy, “delightfully” humming along while it moves air (for all those lovers of white noise), and dumping the one thing from the motor and light that we want the least – heat.

On the opposite spectrum is … well, other than expensive, I don’t really know. This is a good time to consult the EnergyStar product list for ceiling fans.

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EnergyStar rates the efficiency of ceiling fans by how much air they move (cubic feet per minute or cfm) with one watt of energy. If you download the list of certified ceiling fans in Excel format, you can easily sort for the most efficient EnergyStar certified models. Here is a summary of the top three contenders as of February 2014:

ceiling-fan-03

There are plenty of other efficient ceiling fans on the EnergyStar list. But after my big time-waste tracking down an EnergyStar efficient range hood, I acquired an attitude. If I can’t find a product listed on the EnergyStar list in a simple online search, I move on.

Back to the top three contenders that were all easy to track down. The Haiku and MidwayECO are built with the efficient and very quiet electronically commutated motors (ECM’s). I assume that the Aeratron is also powered by an ECM, but couldn’t find corroborating information in the specifications.

The Aeratron is a ceiling fan unit only, while the Haiku can be fitted with a 1,500 lumen LED light module. The Midway ECO comes with a light module that takes four LED or CFL bulbs with the GU24 pin base. Tthe typical light output would be around 3,600 lumens. The Haiku can be dimmed as can the Midway ECO, as long as dimmable LED or CFL’s are used.

Prices for the models vary widely as of February 2014:

  • Haiku from $825 to $920
  • Midway ECO from $476 to $529
  • Aeratron from $224 to $349

Because we need dual functionality from our ceiling fans (air movement and light), the Midway ECO emerged as the best contender, even though it is still a very pricey piece of equipment.

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