Solving a (self-created) Problem with Heat Distribution

First, some background…

Using a ductless mini-split to heat and cool a home (even a passive house) takes some thought.  One needs to think about where, exactly, the mini-split head, or cassette, will be placed, and how the warm (and cool, in the summer) air that it creates is likely to flow.  Take my home, for example.  We opted to place the “winter” mini-split head in the “living” area on the first floor (we also placed a second, separate, mini-split head at the top of the stairway to the second floor, which is essentially the second floor “hallway,” to cool the entire house in the summer).

That single mini-split head (on the first floor) heats the entire 2,000 square feet of living space (1,000 sqft on each floor) on all but the coldest days, and does the job amazingly well.  When the outdoor temperature is above 20 degrees, the 2nd floor stays within two degrees of the first floor (which, again, is at 70 degrees).  Frankly, that’s warmer than I prefer, since all we do is sleep on the 2nd floor).  But it makes my wife happy.  When it gets below 20 (and the sky is overcast during the day), the 2nd floor can drop to 66 degrees, and if the temperature drops to the single digits for prolonged periods it can eventually go a bit lower. In those instances, I’ll turn on the 2nd floor min-split, and it will periodically kick on, when necessary.

And now, the problem…

When the house plans were drawn, the architect anticipated that the entry to the first-floor office would be directly off of the living area.  He also anticipated that the first-floor mini-split would be mounted on the narrow wall between the living area and the kitchen area.  Both are shown in the drawing below:

(Ther drawing also shows an exterior door on the south wall that I decided against because it just wasn’t necessary.)

When I framed the interior of the house, I decided to move the office entry to the hallway because it unnecessarily ate up wall space in the living area, leaving no room for a T.V., for example.

I also had to find another place for the mini-split because the wall that the architect had intended to place it on was too narrow for the mini-split head; it wouldn’t fit.

Given those issues, I changed the first floor as follows:

Moving the office door to the hallway (and eliminating the unnecessary hall closet) freed up valuable wall space in the living area and widened the hall.

And as the drawing also shows, I moved the the mini-split to a wall that had suffficient room.

Here’s how it looks:

In this photo, you can see the location of the mini-split relative to the back hall:

And here is a similar view in which you can see the door to the office: 

So what’s the problem?  Somewhat ironically (at least in my view) the only problem that we’ve had is that, during the winter, the office, which is the room closest to the mini-split,  can be two to six degrees colder than the rest of the house, depending on the outdoor temperature. The only exception is during sunny days, when the office warms up perfectly.  But that leaves many winter mornings, days, and evenings when my wife isn’t happy (because the office is her place of work).  And it should be noted that she almost always works with the door fully open.

I pondered over this problem for two years.  Initially, I thought that the problem was the ERV.  More specifically, there is only one first-floor ERV supply, and it is in the office.  Why?  Because that’s where Zehnder said it should go.  And it’s consistent with the general rule; pull stale air from the kitchen/baths/laundry room and push fresh air into the bedrooms (the office could also be considered a bedroom).

But I eventually found out that the ERV wasn’t causing the problem, and had no detectable (at least by me) effect on the room temperature.  So while the ERV is constantly pushing cooler air into the room, the temperature (above 60 degrees) and flow ( about 24 cfm) of that air just isn’t enough to make a difference in the room temperature.  This should have been no surprise, as it is consistent with what the experts suggest.

So my current theory is a bit different.  First, after framing the office walls, I insulated them Roxul so my wife could work in relative peace if I chose to watch TV; admittedly a bad idea with regard to heating the room. But I also suspect that any warm air that makes it into the rear hall is probably more likely to rise up the stairs (which are to the right) than into the office (which is to the left).

The easy thing to do would have been to install some baseboard electric resistance heat in the office, which my wife (or a thermostat) could turn on as necessary.  But that clearly seemed like a wasteful overkill to me.  So what I decided to do instead was install a Tjernlund ASI AireShare Room-to-Room Ventilator fan. The idea came to me as I was painting the wall in the family area that separates the family area from the office.  Unsurprisingly, the air near the ceiling (which is almost 9′ high) was several degrees warmer than the general temperature of the house down among the living.  It therefore seemed reasonable to believe that, if I could push some of that air into the office, the problem might be solved and, since the fan only draws 25 watts at full speed and pushes the air at 75 cfm, I figured that its use would prove to be much more user-friendly and cost effective than baseboard heat.

If the intent is to move warm air, ideally, these ventilator fans would be installed with the intake high on one side of a wall and the diffuser low on the opposite side. In doing that, the bay in which the fan and diffuser are installed acts as the vent; air enters from the top and is pushed out through the bottom. However, I decided not to do that because, as I stated earlier, I had insulated the office walls with Roxul, and I didn’t want to completely remove the insulation from the bay in which the fan was to be installed.  Of course, this meant that the warm air would be brought into the room closer to the ceiling than the floor, which is less than ideal.  But the room isn’t that big (it’s about 120 square feet), so I was hoping that it wouldn’t matter.

With minimal effort, I was able to cut the hole on the intake side of the wall about a foot from the ceiling, clear out the insulation in a space of about 18 inches, and seal off the bottom of that space with a piece of 1/2″ foam board and caulk.  Prior to sealing off the bottom of the space, I fished Romex up from the basement and installed a variable speed wall switch. The intake vent and fan are located at the top of the space, and the diffuser is located at the bottom.

You can see the intake for the fan in the upper left-hand corner of this photo…


…and the exhaust above the chalk/cork boards in this photo (it’s a bit difficult to see because it is a narrow diffuser rather than a traditional vent)…

Here’s a better photo of the diffuser (my apologies for the temporary “flow-detector”) and the variable speed switch…

The fan has now been in service for about a month, and I am happy to say that it has performed better than I had anticipated.  So far, it has resolved the issue completely.  For example, last night the low was 23 degrees, and the entire house, including the office, maintained 70 degrees +/- one degree. While not annoying, the fan is detectable at full speed.  However, we run it at what I would estimate to be one-third to one-half speed, and it is essentially silent.

Thinking about using Home Depot (Cree) LED light bulbs? You might want to think again.

About a year ago, just before we moved in, I purchased about 100 Cree LED light bulbs from Home Depot.  I was surprised that the house used so many.  But regardless, ten of those bulbs are in our kitchen area, and those are the bulbs that get the most use.  Not a lot of use.  Just more use than any other bulbs in the house.  Anyway, since installing them, five of the ten have failed.  That’s also quite surprising, particularly when Cree claimed that the bulbs would last over 20 years.  Here’s what one of the burned out bulbs looks like:


Note the burned-out element.  First they start to flicker, and eventually they go dead.

Of course, I could send the bulbs back to Cree for “replacement or refund” (Cree’s option) (shipping is on us). Oh, and Cree may require a receipt, which of course I didn’t save.  Call me crazy, but I’ve started replacing the burned out bulbs with Cree’s new updated, slightly less energy efficient, 60 watt equivalent (10 watt actual), 27+ year LED bulb:


Home Depot still sells the old style bulb (not that I would buy any).  But for some unknown reason, they’re more than twice the $4 I paid for them last year.  This updated bulb currently runs just under $3.  I am also saving all of my receipts.  I will be paying a visit to the Manager of the local Home Depot store if they continue to fail. Maybe we do get what we pay for.

ERV Maintenance – Keeping the Bugs Out

While learning about radon and ERV balancing, I also learned a bit about ERV maintenance that no one had previously mentioned.  Specifically, on my house the ERV is in the basement and the exterior intake and exhaust vents run through the rim joist just below the first floor, which places them less than two feet above ground level.  On some of the houses I’ve read about, the ERV is placed about the living space and therefore vents in a location that is much less accessable, but may be advantageous when it comes to bugs that commune near the ground.

The exterior vents on my house look like this with the covers on:


Once the cover is removed, you’ll see that Zehnder provides a screen to keep critters out; it has about a 1/2″ mesh.   That clearly wasn’t sufficient in my case because there are a large number of bugs both large and small, that can fit through it.  On the exhaust side, this isn’t a problem because the air is constantly pushing things out (at least while the ERV is on).  But on the intake side, these bugs are attracted to the opening and end up inside the ERV.  I spoke with Zehnder, and they said that they don’t make any external pre-filter. Evidently, bugs are a lesser problem in Europe (I’ve seen that many places in Europe don’t even use window screens).  Also, this might be an issue that is more problematic to those of us who live in more rural areas and/or those of us who have the supply vent near the ground.

My initial attempt to deal with the situation involved adding a piece of window screen over the opening:


That’s about a week’s worth of accumulation.  Typically, I found beetles and moths on the screen trying to find a way in.  The screen did a good job of catching them.  But when I checked the internal filters, there continued to be a significant number of small living flying bugs (and quite a number of dead ones) buzzing around or on the internal supply filter.  At the intake, I could see these bugs were small enough to work their way through the screen to get in.

In addition to the bugs that got into the system despite the window screen that I added, the supply filter continued to gets dirty very quickly.  Zehnder says that the filters should generally last about six months with periodic vacuuming.  While the exhaust filter appears to easily last that long, the supply filter turns pretty black within weeks.  And as I indicated earlier, we live “in the country.”  It’s almost shocking.  And unfortunately, periodic vacuuming doesn’t do much more than remove the dead bugs.

Two things annoyed me about this situation. First, I don’t like to see bugs flying out of the ERV when I pull the intake filter.  And second, although I can afford it, the filters can only be purchased from Zehnder and cost about $22 each.  So changing them often (say once per month) is both costly and wasteful.

In my second attempt to remedy the situation, I purchased a roll of “pollen proof” window screening from Home Depot for about $10.  It’s basically the same as regular window screen, but the mesh is much finer; fine enough to keep even the small bugs out of the system.  It worked well, actually too well.

Although we generally keep the windows open (and the ERV off) during the summer, we do occasionally close things up and turn on the ERV and a/c when the weather gets too humid.  We recently went through a period like that.  Following that period, the humidity dropped, but my wife and I were both out of town for a week, so we turned the air conditioning off and left the ERV on.

When we returned, I noticed that the radon level in the basement had risen.  This was surprising, and the fiirst thought that entered my mind was that maybe the whole “pressurized house” theory of keeping radon out wasn’t true after all.  So I pulled out the manometer and took a reading. To my surprise, the gauge showed that, instead of being positively pressurized to about two pascals as it had been when I last checked it, the house was negatively pressurized to about eight pascals.  At first, I thought that something was wrong with the gauge.  But then I thought to check the pre-filtering pollen screen that I had placed over the ERV intake.  Sure enough, it was completely clogged with bugs and “dirt.”


I removed the screen and took another reading with the manometer.  As I anticipated, the house had returned to a state of positive pressurization.  Over the next few days, the radon level sank back down to just above 1.

Obviously, I needed to find a different way of pre-filtering the incoming air.  Currently I’m using this product, which I also purchased at Home Depot:

IMG_1039 IMG_1038

It seems to stop most of the bugs and dirt, although not as much as the pollen screen. The mesh is more open than the screen, but it is a “maze” that is about an inch thick.  So while some of the smaller bugs still appear to get through, I suspect it will be much less prone to clogging to the point where it will affect the pressure balance inside the house.

But I now have an idea for a removable, cleanable, pre-filter with a larger surface area.  Once I build and install it, I’ll report on how well it works.

As I mentioned earlier, maybe in those situations where the supply vent is located high on the exterior of the house the bugs and dirt aren’t an issue.  But if they are, remedying the situation becomes a whole lot more difficult.

LG Condensing Clothes Dryer – About 20 Cents per Load

Throughout the construction process, I was undecided with regard to how I wanted to dry clothes in the finished house.  I knew that a conventional dryer wouldn’t do, because I didn’t want to deal with the issues presented by a vent to the outside.  So I was debating between a drying closet and a condensing dryer.

Asko makes a drying closet that would have served the purpose.  But I didn’t think that my wife would buy off on it in the long run; it would be so slow at drying clothes that it would be impractical and frustrating.  So I turned to condensing dryers.

My choices were fairly simple. There were only two to choose from; Bosch and LG.  I ended up going with LG simply because it was less expensive.  I was able to purchase an LG model DLEC855W from a Sears Outlet.  It was a floor model, in perfect condition, and ran about $800.  I also picked up the companion LG washer for about the same price, also from the Sears Outlet.  By the way, you can shop the Sears Outlets across the country via the Internet.

Both the washer and dryer have relatively small profiles (23.5 inches wide by 33.5 inches tall); much smaller than the Kenmore front-loaders that we had at our prior house.  But we’ve found no problem with their capacity.  Both machines do an excellent job and have easily handled everything we’ve put through them.  And they both fit nicely under the laundry room countertop (they’re also stackable).


Our experience with the dryer has been extremely positive.  I haven’t yet hooked it up to a drain.  But it has a small drawer that collects the water and is very easy to empty; usually every load or two.  It takes about an hour to dry a typical load of clothes.  I had expected twice that amount of time.  And it turns out to be pretty frugal with regard to energy usage.  Last weekend, three loads consumed 4 kWh of electricity.  At a rate of 15 cents per kWh, that translates to about 20 cents per load; certainly lower than I expected.

Some were worried that the dryer would add significantly to the indoor humidity.  But that hasn’t turned out to be the case.  In fact, while the laundry room feels a bit more humid while the dryer is running, there is no measurable difference in the indoor humidity after the dryer has completed it’s cycle; the indoor relative humidity been consistently in the 40-45% range since last fall.

The heat factor seems to be similar.  The temperature in the laundry room goes up a couple of degrees while a load is drying.  But that quickly dissipates once the load is finished.  The extra heat is an advantage in the winter.  But even last October, when the temperatures were fairly warm, the added heat wasn’t an issue.  Part of that may be due to the fact that the laundry room is on the north side of the building and has a window that we opened on the warmer days.  But even so, the heat buildup in the laundry room seemed no different that it was in our prior home with the vented dryer.  So I don’t anticipate that it will be a problem this summer.


Short-Cycling Mini-Splits

On December 7th, I installed an egauge energy monitor on twelve circuits; the two lines supplying power to the house (2), the two heat pumps (4), the water heater (2), the ERV (1), the well pump (1), the family room circuits (1), and the dryer (1).

At about the same time, I set the first floor mini-split at 70 degrees and the second floor unit at 66 degrees.

One of the first things that I noticed when reviewing the egauge data, was that the heat pumps were both “short-cycling;” that is, they were turning on and off at intervals as short as three to five minutes.  When “on,” the unit would draw about 1kW.  When “off,” the unit would draw about 20 watts; just enough to power the internal fan on the wall unit (which runs continuously).  Here are a couple of examples:

Screen Shot 2014-12-08 at 1.12.28 PM


Screen Shot 2014-12-09 at 1.57.59 PM

This didn’t always happen.  Occasionally, one heat pump or the other would “flat line” at 300-400 watts.  This could go on for hours, and in a couple of instances, days.  But then the unit would revert back to the short-cycling.

Screen Shot 2014-12-13 at 3.51.27 PM

The short cycling didn’t seem to have a strong correlation to outdoor temperature.  For instance, sometimes the first floor unit would short-cycle while the outdoor temperature was in the 30s and flatline when it was in the 40s.  At other times, just the opposite would occur.

Having said that, the first floor unit stopped short-cycling when the temperatures dropped below 20 degrees or so.  But the 2nd floor unit continued to short-cycle even at those low temperatures.

I contacted both the local HVAC company that installed the units and Mitsubishi’s National Sales Support Manager John Bart, and presented both with a summary of the data.  I had learned about John when we were beginning construction of the house.  He had participated in a Passive House webinar where he discussed the Mitsubishi mini-splits. Shortly after that webinar, I contacted him with questions about the type of mini-split system that might be best for my house, and he was very responsive.  In fact, it was his responsiveness that caused me to go with Mitsubishi over the less expensive Fujitsu units.

It appeared to me that the local HVAC guys (who installed the system) didn’t know quite what to make of the data.  However, John, who was clearly more familiar with the Passive House concept, asked for additional information; a floor plan, photos of the wall units, and the Passive House heat load computation, which was (is) about 8,000 btu/hr.  Given that information, he surmised that the units were oversized, and sent the information over to his Northeast Tech office.

To back up, both mini-splits are 12,000 btu units, and can power down to somewhere around 3,500 btus.  John suggested that, at the more moderate temperatures, even 3,500 btus was probably too much for the house.  However, he acknowledged that it was perplexing that the short-cycling stopped for sometimes lengthy periods of time, even at those more moderate temperatures.  He added that even the smallest (9,000 btu) mini-splits would probably have had the same issue because their low end was very close to the low end on the 12,000 btu units.  He suggested that a Mitsubishi regional tech visit my house to assess the situation and to install remote thermostats for both units.

Mini-splits (at least Mitsubishi mini-splits) come with a remote control.  However, contrary to what some may believe (in fact, even the local HVAC contractor believed it), the remote does not have a built-in thermostat.  In fact, the thermostat is located in the “cassette” that hangs on the wall and dispenses the heat.  As I understand it, the sensor measures the incoming air, and in doing so, provides the data that helps the unit decide when to power up or down.  But apparently it isn’t like the old days, when a single thermostat turned the furnace on or off.  Rather, as I understand it, with these units there are five sensors; three on the outdoor condenser and two on the indoor wall unit, that collectively tell the unit what to do.  In other words, things are much more complex than they used to be.

At any rate, last Friday the Mitsubishi tech showed up and installed the two remote thermostats.  These thermostats (product MHK1) are manufactured by Honeywell specifically for the Mitsubishi mini-splits, and it appears that they resolved the issue.  In my opinion, Mitsubishi provided outstanding customer service in dealing with this issue; something that I find sorely lacking with many companies these days.

Since last Friday, the 2nd floor unit has been idling; meaning that the compressor has not turned on.  In other words, even during the evening lows, which have gone down to the low 20s, the first-floor unit has handled the entire job of heating the house, and the second floor has not gone below 68 degrees.  So the picture, from the egauge perspective now looks like this for both heat pumps:

Screen Shot 2015-01-20 at 4.10.23 PM

A couple of notes…The second floor heat pump is the horizontal red line at the bottom of the graph.  It’s showing about 30 watts.  As I said earlier, this heat pump has been in idle mode since the remote thermostat was installed.  The more prominent red line is the first floor heat pump.  The outdoor temperature early this morning was in the high 20’s, so my guess is that the three vertical jagged lines are defrost modes.  However, they’re the only three such lines that occurred during that night.  So I could be wrong.  They may instead be cycling blips.  But at one hour intervals, they’re a far cry from the three to five minute intervals that were occurring.

First Full Month Heating and Energy Usage

We’ve now been in the house for about two months. But our electric bill runs (roughly) from the 21st to the 21st.  So last week we received our first “full month” electric bill.  Given that it’s the first full month, the information gleaned from the bill is, of course, very preliminary.  But I thought I’d share it anyway.  The important numbers were as follows:

Average Outdoor Temperature During the Period: 53 degrees

Total Electric Usage: 551 KWH

Total Cost for Electricity $90.94

Cost per KWH: 17 cents (all fees and charges included)

The last week of this billing cycle, it got fairly cold.  Nightly lows were as low as 19 degrees.  Daily highs were in the high 20s to mid 30s.  But again, the average temp for the month was a relatively mild 53 degrees

The house is two floors plus a basement.  Square footage is 1,000 per floor.

All lights are LED; 40 and 60 watt equivilants.  Most are 60s.  Only a few are 40s.

The house is completely electric.  Oven is convection.  Cook-top is induction.  Water heater is heat-pump.

We have two Mitsubishi mini-split heat pumps.  Both are 12,000 BTUs.  Each has one cassette.  One cassette is on the first floor.  The other is on the second floor at the top of the stairs.

For all but the last two days of the month, we used only the first floor heat pump.  Some days I didn’t use it at all.  Other days I left it on.  Mostly I was trying to get a feel for how it operated.  I was surprised to find out that the fan on the indoor cassette unit always runs (albeit at a very low rate), even when it is putting out no heat.

The single heat pump, kept the house “comfortable” down to the 19 degree low.  However, when the outside temp got below freezing, it appeared to put out heat all the time.  This kept the first floor at a pretty consistent 67 or 68 degrees at night and 68 to 70 degrees during the day.  The second floor temperature (which is where the bedrooms are) varied; at night it got down as low at 64 degrees, and during the day, with a little help from the sun, it rose to 68 or 69 degrees.

That’s why I put the word comfortable in quotes.  I found this to be quite comfortable.  After all, for us, almost all of the time spent on the second floor is spent under covers.  But my wife was not quite as content.  So for the last couple of days, I turned on the second floor heat pump.  This quickly brought the second floor up to 68 and significantly reduced the working time for the first floor heat pump.  Both heat pumps were set to 65 degrees. I’m not sure why a 65 degree set point on the heat pumps results in a 68 degree environment.  But it does.

A couple of things seem clear to me.  First, at 68 degrees the house is exceptionally comfortable.  Not a hint of a draft, even when the wind is howling. And second, a clear, sunny day makes a measurable difference in the form of a reduced heat load.

Next week, I will install an eGuage energy monitor on the main feed and 12 circuits.  So beginning then, I will have a much better read on the energy consumption for the heat pumps, water heater, and ERV.  I will also install Hobo temperature/humidity data loggers on all three floors and outside. This will give me the ability to monitor and report on the performance of the house over the long term.

Based on this very preliminary information, I have a few initial thoughts.  First, I was a bit disappointed in the first month’s electric bill.  Both the KWH used and the overall cost were higher than I anticipated.  But I’m thinking that this is due more to unrealistic expectations (and an unexpected 17 cent/KWH overall rate) than house performance.

One way to try to put this data in context is to compare this first full-month electric bill to my energy cost from one year ago, when we lived in our prior 2,800 square foot house, built in 1987, which used propane heat. The average temperature last year was 51 degrees; a couple of degrees cooler.  At that house, I followed our energy usage pretty closely.  Electric usage was easy (just read the bill).  But I had to gauge propane usage by my readings at the end of each billing period.  Each night, we set the thermostat back to 60 degrees and at least three days per week we left it at 60 degrees during the day because we were both at work.  We never raised the thermostat past 69 degrees.  But frankly even I thought that was uncomfortable.  It pretty much always felt colder than either of us would like.  At any rate, my total energy cost for that house during the same period last year was $428.43, and my electric usage was 881 KWH.  But remember, we were heating an additional 800 square feet.

It will be interesting to see how things play out in the long run.  Taking a SWAG based on this admittedly limited data, I’m thinking that when all is said and done, we have a good shot at being under 6,000 KWH total energy usage for the entire year.  That would result in a total energy bill of about $1,000.  And if it looks like that prediction is proving to be fairly accurate, I may start looking for a PV system next spring.

Energy updates will follow, once I get the monitoring systems installed.

Final Blower Door Test – .3 ACH @ 50 Pascals

Drew McDowell, the Passive House Rater, came in on Saturday and performed the fourth and final blower door test.  The prior tests were all done manually (I believe they’re called “single source” tests); meaning that the Rater watches fluctuating readings on the meter and uses his judgment and observation to determine an average flow rate. In this fourth test, Drew used that method as a starting point, and came up with a value of about .28 or .29 ACH.  However he then followed up with a computerized test where the PC took dozens of readings in ten-degree increments (i.e. at dozens at 10 Pascals, dozens at 20 Pascals, dozens at 30 Pascals, and so on up to 70 Pascals) and then averaged and charted the results, and used the collective information to refine the computer’s 50 Pascal readings.   Also, unlike the manual test, this computerized test was performed in both directions; first while blowing air out of the house (i.e. depressurization), and then while pulling air into the house (pressurization).

The result came in at .3 ACH @ 50 Pascals.  Copies of the reports are visible below:

Download (PDF, 477KB)

Download (PDF, 259KB)

This was up a bit from the prior test (.24 ACH), which was performed before the installation of insulation.  I’m not sure how that happened, being that it seems to me the insulation and drywall should have made the house tighter, if anything.  But regardless, I’m very happy with the result.

Two observations worth noting.

First, as discussed in a (much) earlier post, we used a trio of products by Prosoco to seal the gap between the windows and sills.  The final product in the trio, R-Guard Air Dam, is essentially a very robust caulk that is used to seal the gap after the installation of a foam backer rod.

The windows were installed about a year ago.  We’ve been in the house now for almost two months, and I’ve been chipping away at the interior work as time allows.  Recently, when I began working on interior trim, I noticed a small gap in the R-Guard around one window.  That prompted me to inspect all of the windows, which led to the discovery on similar gaps at three others.   I suspect that the gaps were due to human error at the time of installation; the thickness of the application in those areas appears to have been very thin and the product appears to have simply shrunk.  Fortunately, the gaps were easy to find and seal because I hadn’t yet trimmed out any of the windows.  But the discovery caused me to think that my slow pace paid off.  Had the interior been finished by a hired trim carpenter, or had it been finished immediately after the drywall was finished (which was last spring), those gaps would have never been discovered.  To be clear, none of the gaps were deal breakers.  But collectively, get enough small gaps and I imagine it’s possible to break the .6 ACH limit.

The second point worth noting is that, during the final blower door test Drew and I went around the house with the thermal camera and smoke pen looking for leaks.  The only weak points we found were the exterior doors (all ThermaTru), which I’ve talked about extensively in a prior post.  Again, obviously the leaks weren’t deal breakers.  But frankly I expected much better given the amount of money those doors cost.  If I had the chance to do it over, I’d be looking at Intus for the doors as well as the windows.

Exterior Foam Insulation

Just to backtrack a bit…For the exterior insulation, we used two two-inch sheets of Polyiso held to the sheathing with 5/4 by 4″ poplar furring strips and six-and-a-half-inch Fastenmaster Headlok screws.  The one-by-fours cost us about 25 cents per linear foot.   That seems like a decent price, particularly since they’re a full 1″ thick (actually the thickness varied a bit, but was generally about 1 1/8″, so we planed them down to 1″).


We’re using Polyiso because it has a higher R-value than EPS (which is what the ICFs are made of) or XPS (which is what we added to the outside of the ICF foundation).  Polyiso has an R-value of just over 13 for 2″.  Tuff-R and Super Tuff-R are Dow’s Polyiso panels.  Super Tuff-R has a more durable facing than does Tuff-R.  R-Max Thermasheath 3 is another brand of Polyiso that Home Depot stocks, and appears to be less expensive than the Dow products.  The R-value is the same for all three products (i.e. R-Max reports 13.1 and Tuff-R reports 13).

Home Depot in our area stocks R-Max.  It is $30.25/sheet off the shelf and on the Interweb.  I went to the local store and told them I needed 150 sheets.  They put it through their “bid room” and came back with a quote of $26.73/sheet, which is an 11.6% discount.  So the total cost ended up at just over $4,000.

Choices in Window Installation

The window installation has been one of the more difficult issues to deal with.  The first part of that issue was deciding which product/method to use to flash the windows and achieve the necessary level of air-tightness.

We tested three products/methods on the basement windows.  The first was Tremco’s ExoAir Duo Membrane.  This is basically a flashing tape that is applied to both the inside and outside of the window jamb gap.  Half adheres to the window, and half adheres to the jamb, thereby completing the seal.  Spray foam is applied in between the two (before the second side is applied.  This product seemed to be the least favorable.  First, it was difficult to get the tape to seal to both surfaces without undesirable waves.  But the bigger issue was that it seemed almost impossible to get the spray foam to fill the gap without pushing the tape outward.  It was obvious that this would make it difficult to properly trim out the window box; at least not without significant difficulty.  We estimated that it would have cost approximately $750 for enough of this product to do all 19 windows in the house.  Here’s the best and worst of what it looked like:

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The second product that we considered is also made by Tremco.  It’s called the Exo Air Trio, and seemed to be a much more effective product.  It basically consisted of a a compressed foam band with adhesive on one side.  It is applied to either the window or the jamb.  Once unrolled, it begins to expand, so you have to plan out the installation a bit.  But the expansion rate is rather slow, so it’s not a mad rush.  Once fully expanded, the foam completely seals all of the gaps between the window and the jamb.  It looked pretty effective, if not a bit amazing.  The biggest downside was the estimated $1800 price tag to do all of the windows.  Here’s what the installed product looked like:


The third option (the option that we went with) uses a three-part solution by Prosoco.  Unlike the other two products, the Prosoco solution seals the gap and flashes the window.  The first part of the process involves the application of Prosoco R-Guard Joint and Seam Filler, which is described as  “a fiber reinforced fill coat and seam treatment.”  It basically appears to be a pink, fibrous, rubber caulk.  It’s applied to all of the seams in the rough opening.  After that, the R-Guard Fast Flash was applied to the entire opening (and the exterior of the opening).  Like the Joint and Seam Filler, it’s applied with a caulk gun.  But then it’s smoothed out with a spatula to create a consistent rubber-like covering over the entire area.  Once dry, it really leaves one with the impression that the opening will be impervious to water and moisture:


Then the window is installed, and an appropriately sized backer rod is installed in the gap surrounding the window on the interior surface.  The final step is the application of the R-Guard Air Dam product to the face of the backer rod:

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All in all, it appears to be a pretty bullet proof system that interplays well with the Zip System sheathing, and should serve us well.  On top of it all, we estimate that it will cost us somewhere around $500 to cover the installation of all of the windows.


Compromise on the Roof

The roof is complete.  I initially intended on using Certainteed Landmark Solaris shingles.  It’s a “solar reflective” asphalt shingle that claims to reduce roof temperatures by up to 20%, according to the company.  But at approximately $190/square, it was pretty pricy.   So we ended up using Certainteed’s Landmark Pro, which appears to be essentially the same, but without the reflective coating.  The cost was about $96/square.

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