Tag Archives: energy

2016 heating savings

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 1.464. Our deep energy retrofit improvements appear to have reduced our natural gas consumption by 1.264 therms/square foot/year. That equals a reduction in our heating needs from November 2015 through December 2016 by a whopping 86%!

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 461.83 kWh (or 1662.59 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 $1.47. 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 $3,400.

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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Buying a foreclosure – Part 8

Welcome waste (energy)

Start of the 2016 heating season


Welcome waste (energy)

Today, we are not pinching nickels, but degrees.

I mentioned in the last post that it took us until November 17 before we turned the heat on, whereas other Chicagoans fired up their furnaces in early October. Why were we still comfortable several weeks into the cold weather?

Waste heat!

Boiling the kettle, cooking dinner, baking banana bread … Then add in all the electrical appliances that produce waste heat: running the fridge, TV, laptop and desktop computers, having the lights on … all this and more produce some level of waste heat which is welcome during this season. Not so much during the dog days of summer, though.

But wait! There’s more. Let’s not ignore the four critters occupying the space. Two of them two legged, and the other two four legged. Believe me, they all have a healthy metabolism going, based on the heat they throw off! Seriously, body heat from building occupants is not to be ignored – not in the context of a deep energy retrofit.

Let’s think of these heat sources as miniature radiators. Individually, they don’t do much. But cumulatively they begin to matter, if – and this is a big IF – the building is well insulated  and as good as airtight. Because now this waste heat doesn’t escape. It lingers around and keeps the building interior at a comfortable temperature when others have long reached for their thermostats.

In this context, your furnishing and the actual interior of your building begins to act as a heat sink – it becomes thermal mass. Your oak dresser, your hardwood floors, your drywall, your bathroom tiles, you name it – they all store heat to some degree, which adds to the comfort.

Another gadget that helps us to delay the start of the heating season in the Energy Recovery Ventilator (ERV). It delivers fresh air into our airtight building envelope, but does so with the help of a heat exchanger. This allow us to recover most of the precious waste heat and yet still get fresh air.

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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.


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:


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.


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.


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.


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



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.


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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