Last rock wool pick up

We had started to frame out the perimeter walls on the second floor, and at the same time insulate them with rock wool.

Well, the time had come to make one last trip to pick up the last batch of rock wool. If I measured and calculated correctly, this last batch should allow us to complete the 2nd floor insulation. I may need another bag for an odd job here or there. But the big task – the insulation of the building envelope – was about to be completed!


This felt like another milestone. The numbers are certainly impressive:

To insulate our building envelope I purchased 194 bundles (or bags) of rock wool.

That took care of the basement and 1st floor2nd floorand attic.






We unpacked, handled, fitted, and installed a total of 2,328 rock wool batts, each measuring 15 ¼ inches wide, 47 inches long and 3 ½ inches in depth (stud depth). At 4.975 square feet per batt, we installed a total of 11,581.80 square feet.

The total material cost added up to $6,348.37, including taxes. That translates into $0.55 per square foot of 3 ½ inch batts, or $0.16 per board foot (one board foot is one inch over one square foot).

That leaves us with a nice, comfortable, and quiet building interior. That’s right! The rock wool does not just provide thermal insulation, but also sound insulation.

Related posts:

2nd floor perimeter framing

2nd floor insulation strategy

Stuffing the attic – Part 2

Rock solid déjá vu

3rd layer – rock wool insulation

Sound Solutions


DWHR follow up

As I said in the last post, the primary benefit of running the DWHR performance test was the discovery that it wasn’t operating as intended. It gave me a chance to fix the problem and have the heat exchange and heat recovery process run at its full potential, which I measured at 46.7%.


That in turn should help me save some money, which is important to make this investment pay off. There is a lot of copper in the DWHR, and it doesn’t come cheap. We bought ours for $617.00 a few years back.


To sweeten the investment, Renewability provides an energy savings calculator on their website, to give the consumer an idea what level of savings could be expected.

Our DWHR (the R2-60 PowerPipe) serves the first floor and second floor bathroom showers. I assumed an average occupancy of 3 people per apartment, 0.75 showers per person per day and a shower time of five minutes. According to the energy savings calculator, we could expect annual savings of

  • 388,605 Btu (or 4.1 gigajoules),

which would translate into

  • $67.36 savings per year.

If I increase the shower time to 10 minutes, the expected annual savings increase to

  • 767,732 Btu (or 8.1 gigajoules),

which would translate into

  • $132.96 savings per year.

I guess the savings will lie somewhere in between the five and 10 minute shower time scenarios, and so will be the payback time for the DWHR, which would fall somewhere between four and a half to nine years.

That “M” word!

Using the calculator is not as straight forward as you may think – as I found out. First, it appeared to be down quite a lot, displaying an error message. This may just be a temporary issue, or so I hope.

Secondly, using the calculator, I was reminded that it is us (or should I say US) against the rest of the world. I think we must be the only culture left that doesn’t use the metric system. Canada does use the metric system (bless the Canadians!), and Renewability, the manufacturer of the DWHR, is a Canadian company.

The use of the metric system becomes relevant in the energy calculator if your fuel type is natural gas. The input field ‘Cost of Fuel’ uses the unit $/cubic meters natural gas – and not therms! A subtle detail that makes a difference in the calculator output.

How do you determine the cost of fuel?

And I am not talking about unit conversion – yet. Should I just use the cost per therm and ignore all the delivery charges and other add-ons?

I opted for what would I call the true cost. I added up the total volume of cubic feet of natural gas delivered over the past 12 months and converted it into cubic meters. I also added up the bill totals for the past 12 months and divided it by the total cubic meter volume. That gave me an average fuel cost of $0.55 per cubic meter of natural gas.

Closing comments

The $0.55 fuel cost is a snapshot. It is on a sliding scale depending on the occupancy of the building and natural gas prices.

I also have to take the calculator output at face value. I have not cross-checked the results through my own calculations. The fact that the advertised effectiveness of the DWHR was right on par with my own test results gives me some confidence into the energy savings calculator results.

Related posts:

DWHR performance test – good data

Troubleshooting test results

Test results to dream of

That heat is mine, and I plan to keep it!

DWHR installation

Drew Schmitt liked this post

DWHR performance test – good data

Although I would have liked a heat recovery rate of close to 90% for our drain water heat recovery (DWHR) unit, I knew that I couldn’t trust that number. Some good troubleshooting led us to the problem, thanks to some expert advice.

The pressure differential between the supply line to the domestic hot water tank and pre-heated water line from the DWHR prevented the setup from working properly, as did our less than perfect plumbing layout. Fortunately, we were able to resolve the issue with a quarter turn on a shut-off valve.


Another test

It’s time to run the performance test once more to see if I could get some credible readings. I attached the temperature probes again to the three data points on the DWHR:

  • Cold potable water in (Tci)
  • Pre-heated potable water out (Tco)
  • Hot drain water in (Thi)


As before, I took readings every 20 seconds while Cathy was taking a shower upstairs. Once I punched the readings into the spreadsheet, I saw some good data emerging.

The data


The heat recovery rate for our PowerPipe R2-60 maxes out at 46.7%, which is a smidgen above the published performance rating of 46.1% by the manufacturer Renewability. Still, this took me by surprise.

I am somewhat suspicious of the performance ratings you find in product literature. Maybe the performance is inflated to help in selling the product. Maybe the laboratory test set up is so removed from the real world that test results don’t translate.

Yet, the DWHR results were right on the mark, as were the results for the ERV testing. Maybe I need to adjust my attitude?

The real value of the DWHR performance test was the discovery that the setup didn’t work as intended. I would have had pre-heated water sitting in the DWHR, doing a whole lot of nothing, whereas it should have fed into the domestic hot water storage tank. That could have gotten expensive, because next to no heat recovery translates into next to no savings!

Related posts:

Troubleshooting test results

Test results to dream of

That heat is mine, and I plan to keep it!

DWHR installation

Larry Jackson liked this post

Troubleshooting test results

I ran a first performance test on our drain water heat recovery (DWHR) system, and got readings that were too good to be true.

Because I was at a loss about what could have caused the wonky readings, I picked up the phone and called the manufacturer of our DWHR. Joel, the technical manager, volunteered to look at my test data and look over the plumbing diagram. That led to some very helpful troubleshooting.

Reversed hot water flow?


My close to 90% heat recovery readings could be caused by hot water flowing from the domestic hot water storage tank towards the DWHR, and not the other way around. This is a very unlikely scenario, but still worth testing.

I attached the temperature probes along the pre-heated return line to the domestic hot water storage tank and started running the shower. I could trace the hot water flowing from the DWHR toward the domestic hot water tank through the readings on the temperature probes.

Good! It was flowing into the right direction. But – it was flowing very, very, very slowly!

The pressure issue

Joel from Renewability reminded me that there is a certain pressure loss associated with the DWHR. The copper spiral around the outside of the DWHR creates a flow resistance that causes some amount of pressure loss. To be precise, the rated pressure loss for our R2-60 DHWR module is 1.4 psi at a flow rate of 2.5 gallons per minute (gpm).

To manage the pressure loss and maximize the heat recovery of the DWHR, Renewability recommends a certain plumbing set up, called the equal flow configuration. A diagram of that setup is provided with the installation instructions.

And because our DWHR installation was half an afterthought, our plumbing set up doesn’t comply with the equal flow configuration. Bingo!


It’s all in the plumbing, baby!

Our domestic hot water storage tank has a cold water supply that feeds into the bottom of the tank. The pre-heated water line from the DWHR is connected into that cold water supply line.

The pressure in the cold water supply line is greater than the pressure in the pre-heated water line (remember the pressure loss issue?). That pressure differential slows the flow in the pre-heated water line almost to a halt. I basically have water sitting in the pre-heated water line and DWHR spiral, rather than flowing. And that is the reason why that water was picking up all that heat from the inner tube of the DWHR.


To balance the flow, Joel recommended to shut off the existing cold water supply into the tank, and instead force all the supply water to the domestic hot water storage tank through the DWHR. And I have just the right valve in the right spot to do that.

Let’s see if that will yield more realistic test results. Can you wait ‘til the next post?

Related posts:

Test results to dream of

That heat is mine, and I plan to keep it!

DWHR installation


Test results to dream of

Winter appears to be out of sight. But before it gets out of mind, let’s look at the performance of one of our heat recovery gadgets – the drain water heat recovery unit (DWHR).


We installed this beauty in the basement, at the bottom of the sewer stack that drains the 1st and 2nd floor showers.

While I want to let the shower water go, I would love to keep the heat that is in that water. The DWHR allows me to recover and reuse a large chunk of that thermal energy.

Water running down a drain stack tends to cling to the pipe walls. While the hot drain water is running down the inner copper tube of the DWHR, it transfers its thermal energy to the cold potable water that is flowing up in the outer copper spirals, effectively pre-heating it.


That is the theory. But what I really want to know is if the heat exchanger works as promised and what percentage of the thermal energy I actually recover. The technical term of what I measure is “effectiveness” or “empirical heat transfer rate.”

Testing the effectiveness of the DWHR is remarkably similar to that of the ERV. I look at three data points:

  1. Cold potable water in (Tci)
  2. Pre-heated potable water out (Tco)
  3. Hot drain water in (Thi)


I attached my temperature probes to each data point at the DHWR unit and took readings every 20 seconds for 10 minutes while Cathy was taking a shower upstairs.

The results were excellent! Just by touching the outer coil, I could feel how the cold inlet water water got increasingly hot toward the top outlet (Tco). Once I had punched the numbers into my spreadsheet, I came close to 90% effectiveness (or a 90% heat recovery rate).

But therein lies the problem: If it sounds too good to be true…

A quick web search will tell you that the effectiveness of DWHR units typically ranges from 40% for smaller units to 70% for the largest units. Plus, the in-house test data by Renewability for my DWHR (called the R2-60) is listed at 46.1%.

Something is amiss and I would like to find out what it is.

Related posts:

That heat is mine, and I plan to keep it!

DWHR installation

ERV performance test


Biting the borer before it bites back

I am talking about the emerald ash borer. But before we go there, let’s start with page one, chapter one.

So far, I already have cut down two trees – the mulberry tree that was in front of the house, and the tree of heaven in our neighbors yard that was right next to our house. I am now about to add a third tree to the list: The ash tree in the vacant lot.


Before you think that I am an arbophobe (if there is such a thing), let me make my case.

There has been an emerald ash borer infestation in Illinois and in our community. It is an almost certain death sentence for our ash tree that hosts this little, shiny, bright green beetle.

Our friend Anne participated in a tree evaluation in Douglas Park about two years ago. The verdict was that most ash trees in the park were infected. The following winter, tree crews moved in, taking down ash trees – a lot of them.

The crews were back last fall and early winter, taking down every single remaining ash tree in the park. We lost a lot of trees! While few still looked normal, most showed at least the first signs of the ash borer infection, while others had been standing dead for a year already.

We are only half a block west of Douglas Park, and we have that ash tree in the yard. The last thing I want to add to the look of our yard was a dead tree among the piles of building materials I am hoarding.

And the borer has made our tree his home. Woodpeckers like to go after the emerald ash borer larvae. Extensive woodpecker damage on an ash tree is a typical sign of an ash borer infestation. And that woodpecker damage was hard to miss.


Rather than being sorry later in the year, I decided to be proactive now and bust out the saws.

ash-tree-02 ash-tree-03

With the ash tree gone, its neighbor – the smaller elm tree – may appreciate the extra room to grow and prosper. That’s the silver lining of this story that I’m holding on to.

Related posts:

Mulberry tree not to be

Rooting for removal

Drew Schmitt, Anne Alt liked this post

Seeding sedges

These two pending items have kept me out of the yard and away from therapy (gardening = therapy): (1) The teardown and rebuilding of our back porch and (2) the basement wall insulation.

Cathy and I were getting very restless and decided that we need a fix. On the search for a sliver of landscape that could handle our bursting green thumbs, I honed in on the parkway in front of the house and vacant lot.

We don’t think highly of turf grass, unless it has sound raison d’être.

The turf grass in the parkway is a one dimensional space filler – a patch to prevent a mudflat between the sidewalk and curb. Not a sound raison d’être in our book.

That parkway is screaming “stormwater infiltration and rain garden!” But to get that growing idea into the ground, I need a whole lot of native sedges … one sedge per square foot.

I collected plenty of seeds this past summer from the sedges in the front yard. I also have saved trays and pots over the years so that we can grow our own plants. I busted out the tape measure and added up the square footage of the parkway to calculate that I need 580 plants. Then I started seeding sedges.


32 pots per tray = 32 square feet worth of sedges. That is, if every pot produces a sedge.

To assure a good germination rate, I filled the pots with potting soil and topped them off with a coarse sand layer. I sprinkled 10 to 20 sedge seeds into each pot and covered them with a mulch layer of stone ships.


This is half science and half anecdotal evidence. The sedge seeds like to have close contact to the growing medium to draw moisture (without drowning), yet maintain good access to oxygen. The layer of sand does just that.

The stone chip mulch layer is a capillary break that prevents the sand and potting soil from drying out too quickly. It also creates a microclimate with a high relative humidity that protects the germinating seedling from desiccation.

The trays will sit outside all winter long. That provides ample time for the seeds to slowly imbibe the needed moisture. Plus, the frigid winter temperatures take care of the cold stratification that should break the seed’s dormancy.

Will it work? It should, based on past experience. But late spring will tell us for sure.

Related posts:

Garden reflection and scheduling realities

The back porch project

Following the control layers

From wish list to reality

Front yard clean up


Garden reflection and scheduling realities

Our work has almost exclusively focused on the house for the past six years – and for a good reason. We wanted to move in, have the garden apartment and 2nd floor unit ready to rent, etc.

But the house is only half the adventure. The other half is the landscape around the house, which has been buried somewhere at the bottom of the task list. And it starts to get to me. I am a landscape architect and I feel that I am keeping myself out of my own playground.

Some readers may know about the Elmhurst pilot project, that was not only about a sustainable landscape, but also a functional and beautiful landscape. Cathy and I have similar plans for this project.

One major accomplishment, thanks to Cathy’s hard work, was the acquisition of the adjacent vacant lot to the east. That got us talking and thinking about the garden again, except that the long to-do list of house projects is keeping us from the yard tasks.

For our sanity’s sake we took on small ad hoc projects such as carpet weed treatment, planting some sedges in the front yard, and building a raised vegetable planter. But our yard resembles a building material storage depot, not a garden.


The glass half full

Recently my parents visited. They have a garden to die for! I knew their interest was as much in the yard as in the house. I dreaded the thought of their eyes catching a glimpse of the mayhem that is our yard.

Fresh from the airport, they stepped out of the truck and instead of heading for the front door, they headed right into the yard. I felt like hiding under a rock – which isn’t that difficult in our yard.

To my surprise, the only thing they saw was the glass half full. They loved the amount of space we have and didn’t stop talking about and imaging all the options and possibilities. In short, they didn’t see mayhem, they saw potential. You have to love my parents!

The exterior tasks

Besides the focus on getting the garden apartment and second floor rented, another good reason for stalling on the yard projects is lurking in the corner.

Building a landscape (or a garden) follows a certain process. The different tasks are sequenced so as to avoid doing things twice. Site clearing, earthwork and hardscape installation comes first followed by soil improvements and planting.

And in our case, finishing the construction outside of the building is the task topping of the list. There is the looming demolition and rebuilding of our back porch, plus the foundation wall insulation from the outside.

It looks like the porch will be torn down and rebuilt before too long. I hope to tag on the foundation wall excavation right after that, weather permitting. Are we really getting a step closer to building a garden?

Relates posts:

From wish list to reality

What to do with the carpet

Front yard clean up

A timid start

The back porch project

Following the control layers


Inspecting windows

I had a couple of visitors this morning: The president of Newtec windows and a technical expert from the manufacturer that supplies Newtec with the vinyl moldings.

I again got my smoke pen out so that we could take another look at the air leakage of the 1st floor casement windows. I didn’t need the smoke pen. I actually barely got to the window. My visitors took the window seat and carefully inspected the corners, with the windows closed and open.

We quickly agreed that the corners are the problem. We identified an increasing gap between frame and casement in the corner when the window is shut and locked.

The frame has a set of inner and outer gaskets. When the window is shut and locked, the casement is supposed to press into the gaskets, which would provide the specified air seal.

window-34 window-35

However, with the increasing gap in the corners, the gaskets and casement are not in full contact, thus the air leakage.

Very good. We have identified and agreed on what the problem is and that it needs to be fixed. My visitors took that information with them, and promised to get back to me in due course with a solution. I guess there are a couple of ways to go about it and I am really interested to hear how they plan to plug the gap. Stay tuned!

Related posts:

Adjustment attempts

Checking on casement corners

Breeze hunting

1st floor replacement windows

The world of windows

Blower door test – after insulation


Adjustment attempts

Buying local pays off: If there is a problem with the purchase, it is easy to get face to face with your vendor!


Our 1st floor replacement windows were manufactured by Newtec around 2 ½ miles down the road from us. Once I had tied the air leakage problem to our casement windows I jumped in the truck and paid Newtec a visit. I was hoping for some kind of technical fix. May be a replacement gasket that would stop the air leaks in the corners of the operable casements?

It turned out that the gaskets are molded into the window profile and cannot be changed. But the window locks can be adjusted to pull the casement closer into the frame.


I gave that a try and I believe this reduced the air leakage on the lock side, at least a little – but not enough. Adjusting the locks had, however, no effect on the opposite hinge side. Those corners remained drafty cold air highways.

I reported back to Newtec, who arranged for a service technician to visit and take a look in order to fix the casement windows.

He also tried to adjust the the locks, but was no more successful than I was.

On the hinge side, he installed a set of latches that should pull the casement closer into the frame upon closing.


That didn’t lead to any improvements, either. He consulted with his headquarters and I was told that the problem appears to be with the hinges. They are sticking out just a notch too much and prevent the casement gaskets from sealing up against the frame.

Newtec couldn’t offer an immediate solution to the problem, but wanted to get the technical experts together and have them take a look at the windows. They will be knocking at my door in a couple of days and I am curious to see what they have to offer.

Related posts:

Checking on casement corners

Breeze hunting

1st floor replacement windows

The world of windows

Blower door test – after insulation