Category Archives: research

On the hot chair

We are on the hot chair indeed. Winter is closing in on us and we need the heating equipment installed. To get there we found ourselves exploring some hot and some not so hot options. Here is the story in installments.

Let’s start with the design workshop a little over a year ago. Even though we did not have the mechanical engineering expertise at the table we went home with many ideas on the shape and kind of heating system we need for the building.

We continued our research into the most appropriate systems during the following months and eventually were able to solicit the guidance and expertise of a mechanical engineer.

The starting point

Cathy and I are not fans of forced air systems. They sure are pretty cheap but the dry heat in winter and associated air flow feels very uncomfortable and we both get the creeps thinking about all the indoor air pollutants that get agitated, re-circulated and blown around.

See also:

Impacts of Forced Air Distribution Systems on Homes and Potential for Improvements
Control of asthma triggers in indoor air with air cleaners: a modeling analysis

I grew up with hot water radiators and I am a big fan because of their comfort and effectiveness. It did not take us long to add cast iron baseboard radiators powered by a solar hot water system to our wish list.

We would also like that same solar hot water system to cover the majority of our domestic hot water needs. For the cold and cloudy days, we dream of a biomass furnace as a backup to the solar hot water.

Reality check

We quickly learned that the existing cast iron radiators are too powerful in terms of heat output for our efficient building envelope. I don’t have exact numbers, but based on a back of the envelope calculation one or two of our old radiators per floor would satisfy our heating needs once we are done insulating.


Our green team educated us about the 150 to 180 degree Fahrenheit needed to power cast iron baseboard radiators, on which we had our eyes set.

A solar hot water system operates at about 120 degree Fahrenheit, which would leave us with a delta of 30 to 60 degrees. To bridge that gap we would need a furnace. That would conflict with our zero-energy goal because of the frequency at which we would use the furnace.

Hydronic radiant floor heating would be a perfect match for a solar hot water system and the 100 to 120 degree water it could produce. Our problem is that there are existing beautiful hardwood floors throughout the building, which we would like to restore. Those stand in the way of radiant floor heating.

What about the systems that are installed underneath a floor, attaching to the subfloor between the floor joists? Well, we would have to push the heat through a subfloor, a small air gap and then the hardwood floor. Very old and very dry wood is not a good heat conductor, so we need a better idea.

No matter what we do, we will need a backup heat source to the solar hot water system. My dream of using a biomass furnace as a backup system quickly dissipated as the residential sized efficient models appear only available in Europe.

What about geothermal?

Geothermal would be a costly proposition. Plus, we would rather invest our money in an efficient building envelope, which would allow us to downsize the heating system and our energy consumption.

Similar to the cast iron radiators, the geothermal system would leave us with a temperature delta, in this case of up to 100 degrees Fahrenheit. We would end up paying a big electrical bill for the condensing pumps that would bridge that temperature gap.

Couldn’t we get the power from a photovoltaic array system? Yes, if it is big enough. But we would then be on the path of making everything bigger and more expensive, rather than smaller and more efficient.

Another option would be to dedicate a furnace/boiler to make up the temperature difference. But either option conflicts with our energy efficiency and carbon footprint reduction goals.

Service desert

Do you have plans for some sustainable renovation or remodeling? If yes, it is very likely that you have given some thought to the project schedule. It is equally likely that you’ll need to commission the help of some experts, such as a mechanical engineer and an installer for the mechanical systems.

This is where it can get tricky, as we found out. Why? Because we sit in the metropolis Chicago, which is proud of its “green” accomplishments and incentives, and I expected it would teem with engineers and mechanical contractors eager to design and install cutting-edge, high efficiency building systems.

But Chicago turns out to be a service desert when it comes to affordable, knowledgeable and skilled green building expertise, particularly on the mechanical side of things and even more so for residential rehabs.

Let’s start at the beginning. We organized a design workshop late last summer and were on the move to finish the design for the green building rehab. Except that the process came to a screeching halt for about three months. I was unable to find a mechanical engineer – and I already had been looking for about two months prior to the workshop!

A mechanical engineer was absolutely critical to the process to assure that the insulation of the building envelope goes hand in hand with the type and size of the heating and ventilation system. My nightmare scenario was to end up with an oversized (and costly) heating system or an undersized insulation assembly.

Most capable and green-minded mechanical engineers I know through my professional network do not work at the residential scale. The few I knew or found that take on residential projects were booked to the gills and unable to help.

I finally stepped outside the Chicago market and contacted IBC Engineering near Milwaukee, Wisconsin. I had worked with IBC before and respected their expertise.  I was fortunate enough that they agreed to work with us.

This allowed us to restart the design process in November, three months after the workshop.

This was the first significant delay and only the first problem solved. The next one was already knocking at the door, namely finding a local, green, technology-savvy mechanical contractor. We knew that we need the innovative and out-of-the-box thinking kind.

Don’t get me wrong – they are out there – in rural Wisconsin, Michigan, Indiana or the far exurbs of Chicago, but not in Chicago proper as far as I can tell and I have done a lot of searching and asking around. And I am not the only one looking. I know of a couple of green-minded general contractors that are on the search for mechanical expertise in the Chicago dry lands.

How can it be that a population center such as Chicago is critically underserved, considering that the city has pushed green building technologies for quite a while? I expected a well developed if not saturated market but was mistaken.

If you are a future remodeler and interested in green building systems, be prepared to go on a search for the right expertise, because you won’t find it waiting on the street corner.
Here are some resources I tapped into during my search:

Do you know of any other good resources? Let us know and we will post them!

Following the control layers

I had a quiet moment to step back and sieve through some of the information we had researched and accumulated over the past months.

Amongst them, a podcast posted on the page with an excerpt from a seminar called “Building Science Fundamentals” taught by Joe Lstiburek and John Straube.

This kind of resource is priceless and gives me the chance to check once more on the technical details of our design and may be stumble across opportunities for further improvement.

The podcast outlines of the four principal control functions of a wall, listed below in order of importance:

  1. Rain control layer
  2. Air control layer
  3. Vapor control layer
  4. Thermal control layer

The water is a little muddied by the fact that some control functions can be combined in one layer. Take our project for example. Our masonry building shell (mass storage wall) is the rain control layer.

The spray polyurethane foam (SPF) is our air control layer, essentially providing us with an airtight building shell. The SPF also performs as a vapor control layer, which, in our case, allows the wall assembly to dry out to the exterior and interior, depending on the season. Last but not least, it is also our thermal control layer.


I appreciate products that can do more than just one simple thing, meaning that I get something for my money.

The podcast explains that if one flips the wall section by 45 degrees, one ends up with a floor section. Flip the floor section by 180 degrees and you get a roof section.


The control layers of the floor must connect to the corresponding control layers in the wall, which must in turn connect to the corresponding control layers in the roof.

What really stuck with me was a design review recommendation that suggests taking a pen and tracing each control layer on the plans, from the floor through to the walls and roof. Whenever my pen has to leave the paper, while tracing a control layer, I have come across a design flaw. And it didn’t take me long to find one.

The thermal, vapor and air control layers are switched from the interior of the building to the exterior at the top of the foundation wall.


That switching of the insulation from the inside to the outside would represent a design flaw, or does it?

After thinking about it for a while, I noticed that the root cause for this design flaw lies a few feet farther down and unfortunately is something that I cannot address. I am talking about the damp proof between the footing and foundation wall … or lack thereof.


Because my old limestone footings and foundation wall has no damp proof layer, I have to find ways to let the foundation wall dry out.

That can only occur effectively to the inside of the building, because the outside of the foundation wall is covered by soil.  We will leave the foundation exposed in the basement and install a mechanical ventilation system with an Energy Recovery Ventilator (ERV). That system would supply sufficient air movement and exchange to assist in the drying process.

I find myself in the position where I need to balance the need of adequate moisture management against an apparent design flaw. The moisture management aspect overwrote the principle of contiguous control layers in the wall.

My common sense tells me that this is a good weighing of the priorities and I hope we won’t regret it.

Deciding on exterior doors

Maybe I should take a short break from the windows. How about doors instead? We still have to resolve the exterior door issue for the basement front and back.

Having secure doors that make a break-in difficult is important to us. My research earlier this year led me to a couple of commercial steel door products that would do the job and somewhat met our energy requirements. The problem was the price tag. Around $1,500 for a steel skin door with foam filled core and thermally broken steel door frame. Ouch!

We had the time to step back from the whole issue, rethink and wait for the lucky coincidence that may spark a new idea.

The new idea was triggered when we were looking at storm doors. We ran into a category called security storm doors.

Rather than spending $1,500 on a heavy duty commercial door that has no NFRC rating, we could spend up to $600 on a light duty residential steel door with a security storm door to the outside.

We have no illusion that the residential steel door, typically a gauge 22 or 24, would not offer the security of a commercial door, typically with a gauge 16 or 18. But that security deficit is bridged by the storm door, typically manufactured out of heavier duty steel.

We found an affordable product with a large laminated security glass pane and a three point lock system. I am sure someone could still break in, but only after having gotten the neighbors’ attention.

The security issue appears resolved, the price tag of $600 seems much more reasonable, but what about the energy side?

We had no problem finding an affordable, pre-hung, 22 gauge residential steel door with a foam core, a thermally broken aluminum threshold and U-value of 0.14 (R-value of about 7). The door has the ever-important NFRC rating and as such would qualify for the tax credit and comply with the Chicago Green Homes Program.


Now that we shifted the security performance onto the storm door, I also feel comfortable with the wooden door frame of the pre-hung steel door. That eliminates the worries about a thermally broken steel frame, satisfies our energy expectations and carries a much more reasonable price tag.

Furthermore, if we install the security door relatively airtight and with good weather stripping, we may be able to add another R-1+ to the whole assembly, which gives my energy-ego a big boost.

Highly-Insulating (R-5) Windows and Low-e Storm Windows Volume Purchase Program

Here is another incentive that may help us with the replacement window decision. This time it’s not a tax credit but a program by the Department of Energy (DOE) called the “Highly-Insulating (R-5) Windows and Low-e Storm Windows Volume Purchase Program”. I stumbled across it in a GreenBuildingAdvisor blog post.

“The aim of this volume purchase initiative is to work with industry and potential buyers to make highly insulated windows more affordable.”

… states the DOE web site. Hey, great! This is right up my alley. Anything that could make this big investment less hurtful on our pocketbook is welcome!

So, how does this program work? There are 30-plus vendors that qualified for the DOE volume purchasing program – vendors that sell “high performance windows” with U-value of 0.22 or less.

The windows volume purchase web page allows the user to browse through different window types for new construction, retrofit windows, patio doors and low-E storm windows. I can select my window size range (listed in unit inches [UI]) and get access to a list of participating vendors.

This program can be a real big time saver. Rather than going from vendor to vendor to find out if they have high performance windows, I have a preselected list right at my fingertips. The program is also an excellent resource to quickly find local vendors of high performance windows.

I began to call around to see how much savings I could expect from the program. This is where it got interesting. It was officially launched on May 27, 2010 and some participants are organized, others are not.

With some vendors, I communicated with a sales person who was designated to just deal with the DOE program sales, while others had no clue what I was talking about. I literally had to point them to the web site so they could see their name in the participating vendor list. Some had to get in touch with their corporate headquarters to investigate what this was all about.

This made it rather difficult to get my hands on the pricing information. I had to be very explicit and persistent that I was only interested in the DOE volume purchase initiative pricing structure, the same structure that had been submitted to and approved by the DOE.

Despite all the confusion I caused with my inquiries, I eventually got some pricing that appeared to be in line with the DOE program.

Because we are about to replace the basement windows, I used their size range (up to 70 UI) for my inquiry and got a price spread of $138.00 to $328.00.


I am not sure, but my gut tells me that some of the prices are not that different from the regular sales prices, which puts into question the objective of “making highly insulated windows more affordable”.

But so what? I still can get a 70 UI high performance window for under $200, right?

Well – you have to look out for the air leakage (AL) rate. Like I contemplated earlier, the insulation value of a window can be negated by a high AL rate. If we would like to keep the AL below 0.05 cfm/sf, we are looking at more than $200.00 per window.

As helpful as the DOE program is, it is important to remember that there are windows that are even more efficient than those included in the program. That is why I kept the Uniframe double hung by Great Lakes Windows in my list.

The question now is if the price delta to the next runner up (the Serious Windows product) can be justified by additional energy savings.