Our home shortly before the DEROur DER House

This is the pictorial story of our Deep Energy Retrofit, or DER for short. In simple terms, we added exterior insulation to our house to make it more energy efficient. In reality, we essentially rebuilt the outside of our house. The great news is that it works! The house is now uniformly comfortable, quiet and affordable to heat. And because our house is more complex than most, we are convinced that a DER can work for most any house.

I've created this site with lots of pictures and a narrative to share the process and many of the lessons learned. You will see that this was something of an experiment, trying different approaches that we had read about, plus a few new techniques of our own.

If you'd like to do something like this for your house, give me a call! I'm something of an energy nerd and work for Airtight Services, a company that insulates homes (something of a dream job, eh!). We would love to help make your home another model of comfort and efficiency.

So here is what we did in roughly sequential order:

The Plan
Starting with the Addition
The Air Source Heat Pump
Who needs a chimney?
Super Storm Doors
Did I mention the Porches?
Two Windows
Old Walls
LaBine Walls
More Fun with Windows
Saving the Front of the House for Last.
The Plan
We aren't the first to do this. Indeed, we borrowed ideas from some of the best Building Scientists out there. I blame Joe Lstiburek at Building Science Corp for getting me started. BSC has tons of technically excellent resources on their website. We used a variation on their Perfect Wall, incorporating features from the Alaskan REMOTE wall. The REMOTE wall adds a Membrane and then layers of insulation over a typically sheathed wall. All of this is securely attached with furring strips using Big long screws. The siding is then attached to the furring strips.

Not only do you end up with a tighter, better insulated wall, but you also get a much more durable wall. The structural part of the wall is protected from condensation related problems by the exterior insulation. The gap between the siding and the house, known as a drainage plane, allows any water that gets thru the siding to safely drain down and out of the wall (vs. seeping into the wooden structure of the wall). Paint should stay on the siding much longer too do to the gap (moisture travelling out a typical wall accounts for much of the paint peeling on most homes).

I'm also trained as a Passive House consultant (a whole different exciting story). While our house doesn't lend itself to PH wall construction, PH concepts of "thermal bridge free construction" were incorporated where possible, for example in window and door installations/openings and the removal of the old chimney.

Starting with the Addition
Ours is an old victorian house to which we added a single story addition (with full basement) back in 2000. Even though the addition was well insulated (with double wall construction and spray foam insulation between the studs), we started the DER here largely because it would be easier given that it was one story and had vinyl siding.
No surprise, the first step is ripping off the old siding. This is the easy part, especially with vinyl siding. If the siding is in good condition, most of it should be reusable. You will have to buy more - the house grows several inches in each direction - but reusing saves money and helps the environment.
As one starts ripping off siding, the reality starts to sink in that the house is more complex than the drawing of a wall cross-section. Every light, spigot, fan cap, door bell switch... has to be "extended". Oh yeah, the door and window openings also need to be modified. I'll include pictures and possibly stories about some of those variations.
Once the siding is off, prep work begins. First, a membrane is installed. We used a few different membranes, including house wrap (it was already there), poly and finally ice-and-water shield. We used an inverted drip edge to protect the bottom of the foam from bugs and water. We also used a combination of window screen and ridge vent material to keep bugs from nesting in the "gap".
The foam board starts going up next, in layers. We use layers rather than one really thick piece of foam because it is really hard to seal seams. By using large sheets and staggering the seams, we get a really good air/moisture seal at the joints that should last as long as the house.
We used 2" thick insulation boards. We also tried different types of insulation. After all, this was something of a laboratory experiment for me and the company.  Anyway, the first layer goes up with a couple of long cap nails - just enough to hold them while the second layer goes up. Ideally, the second layer goes up in a vertical orientation with the seams over the studs. In this way, the furring strips, which are screwed into the studs, cover the outer seems.
The Air Source Heat Pump

Air Source Heat Pumps (ASHP) have become popular in the Passive House world for several reasons and I wanted to give one a try. An expiring utility rebate on these heat pumps helped kickstart our DER.

I'm a big fan of ASHPs - they are nearly  as efficient and about 10x less expensive than ground source heat pumps (the sales folks call them geothermal - a bit misleading, but that's a different story). The logical building sequence was to mount the ASHP to a completed wall, so the outside wall that worked best for the ASHP became the starting point for the DER.
We picked the smallest and most efficient Mitsubishi "Mr. Slim". Mr. Slim is an example of a "mini-split" ASHP with inside and outside "fan/coil" units. The outside unit is similar to that of a whole house air conditioner. The inside unit mounts nicely on an inside wall . All of these heat pumps work basically the same way as your refrigerator which pumps heat out of the refrigerator and into your kitchen. In the winter, Mr. Slim pumps heat out of the outside air and into the house. By switching some valves, in summer Mr. Slim pumps heat out of the house. Pretty cool!

As a heater, it has a rating of 10kBtu - about 4 times smaller than the smallest available gas furnaces. Efficiency varies with outside temperatures, but most of the winter it is between 300 and 400% efficient. On the coldest days it drops to about 200% efficient. Much better than the well advertised 100% efficient electrical resistance heaters! An unlike older designs, it works well below 0oF.

As an air conditioner, Mr. slim is smaller than any available central air system and about twice as efficient (SEER = 26). Mr. Slim also works incredibly well as a dehumidifier.

One of the really cool things about a well designed Passive House or otherwise superinsulated house is that a small "point source" heater will heat the entire house with no ductwork required!

Although our modeling showed that Mr. Slim would be too small to heat our house, we wanted to test to see how well he could do. So we turned the thermostat down on the furnace and except for one day, Mr. Slim did the heating for the entire 2011-2012 heating season! We used 2,570 kWh for the season at a total cost of $318. But we are getting ahead of ourselves. Back to the retrofit....

Who needs a chimney?

For some years our chimney had served no real purpose. The fireplace had been long abandoned. The furnace and hot water heater had been upgraded to "sealed combustion" units. We had looked into various pellet stoves and Russian fireplaces, but the old, unlined chimney was unfit to use for any of those things. So we had capped the chimney to reduce air leakage a couple years before the DER, but my Passive House training made me painfully aware that the chimney was a large Thermal Bridge - leaking heat out of the house.

So what do you do? Remove the chimney brick by brick until it is below the attic floor level, then recap and insulate! Be careful throwing the bricks down as they are heavy and will dent the driveway...

Of course you have to fix the holes...in both roofs. No one said this was going to be easy. At least we got some great antique bricks for use in the gardens!

And some day, if we find the time, we will remove another story of chimney and gain a linen closet for the bathroom. Looking for volunteers!

Super Storm Doors

As we round the back corner we come upon a pretty nice Anderson sliding glass door. One of two actually. Double pane, low=e, plus a nice wood finish. But it is now sitting in an R=40 something wall. We've already decided to upgrade the windows to R-5 triple pane performance. But that would cost a huge amount of money for these doors - assuming we could even find such a thing.

After scratching our heads a while, we decided to add a new sliding glass door "Storm Door" style exterior to the existing door "in" the new wall of insulation. The Anderson door that "fit" was designed to go into a 2x6 wall. So the back wall got 3 layers of 2" foam! That's a pretty well insulated wall.

Note to self: it gets tricky hanging 3 layers of foam board. You might want to try 2 layers of 3" insulation if you think you need this much insulation.

So we built a wooden box (buck) and attached it to the wall. After appropriate weather sealing we then installed the new sliding glass door. Works like a charm! And we found an even less expensive slider that "fit" for the next door that was made for a 2x4 wall, so we didn't have to do another 3 layer of foam wall.

Other notes for these pictures: We used 6-mil poly as the membrane on the rest of the addition. The addition windows were already triple pane, fiberglass windows tuned for the south side (solar heat gain coefficient of 0.49). The rear, east facing window was already doubled to 6 pane, or about R-10 (u=0.10). So all of these picture windows were left in place with additional trim added to meet the new wall. The downspouts had to be moved a few inches toward the back, so the sunken drains had to be moved...which meant the retaining wall had to be rebuilt...no wonder my back hurts!

Did I mention the Porches?

You may not have noticed, but we have a few porches and/or decks around the house. We love these, but if you are going to go to the bother if reinsulating the house, you really need to consider what to do with these. Fortunately the back deck was not

attached to the house and was (relatively) easily pulled away for the retrofit and returned afterward, much like the rainwater collection system that resides next to it (yes, another project!). The south deck and the front porch (and it's roof) were a different story. For the back deck, we decided to disconnect it, modify the supporting pillars and slide it out and over 5" in each direction, then reconnect. After adding insulation, of course. Here are my boss, Matt, and our chief crew leader, Greg, working on this bold endeavor. Again, it is Much easier to add insulation while you are building the house! When we finally got to the front porch, we decided to leave them, but trimmed away about 5" of roof and floor so that insulation could be fitted over/through the connecting structure. . .  . .
Two Windows

The Super Storm Door technique worked so well, we decided to copy the basic concept for most of the other windows in the house. Most of the original windows were double hungs with window weights. And most of them had been upgraded somehow over the years, from inside storms to replacement sash kits to replacing the entire window. Keeping these windows felt good (the preservationist in me) and saved the work of re-trimming the window openings. And the R-2 or 3 of the window is added to the R-5 of the new windows - so we ended up with about R-7 windows. Not only are they energy efficient and comfortable, winter condensation and its good friend mold are things of the past!

The basic process was to remove the exterior trim, cut off the sheathing that covered the window weight wells, remove the weights, then built the extended window bucks out from the wells. This took more figuring than I was used to, but it worked out in the end. The toughest part was actually figuring out what sized window to buy so that the glass was about the same size. When we put the new windows in the holes, we made spacers to fill the approximately 1" gap between the two windows which gives us plenty of room to get in to do things like latch and unlatch the exterior windows.
Old Walls

The bulk of the main house had cedar siding over random width, tongue and groove 1' siding boards. The siding was carefully removed, as it was old and fragile. The old house paper was removed, that is what didn't just fall off. To allow the ice and water shield (membrane) to stick (rather than just remove 100+ years of accumulated dust) the house boards were first

primed. Window bucks were built. Then the membrane was installed followed by polyisocyanurate (Celotex or Tuff-R) insulation boards. This insulation is a bit more expensive than the other types, but it has a higher R-value per inch, has a nice surface for taping, cuts nicely and is said to be better for the environment. We primed the back side of the cedar before reinstalling on the furring strips. A bit of caulk and a new coat of paint, and the house started looking pretty nice again.

LaBine Walls

One area that needed serious attention was the exposed stone foundation. In some parts, this wall had 3 feet of vertical exposure. Looking at the house with an infrared camera illustrated how much heat was escaping from the foundation. Remember, these basements were dug over 100 years ago. I'm not sure what level of mechanization was available, but apparently it was easier to build stone walls up than to dig down.

So I designed a system to extend the insulated wall down over the foundation by hanging a support system from the wall above. We ended up dropping the insulation to within about 6" of the ground level, covering 2/3 or more of the exposed foundation. We used Hardie Board siding on this lower level to improve water resiliency.

Along with extending the membrane down over the foundation to help air seal the joint, I'm very happy with the whole project. Pat, my main helper on  this phase of the project dubbed the system "The LaBine Wall". I'm good with that!

More Fun with Windows
Several windows got their own special treatment. The most noteworthy is probably the window swap in one of the kid's rooms. The one we inherited was a horizontally configured double slider with a "fixed" window in the middle, probably installed in the 1950s or 60's, I'm guessing over a kitchen counter? The openings were less than 2' square, hard to open and high off the ground: hardly egress ready. Did I mention that it was a leaky single pane with a rotted out storm?  And my daughter wanted to keep it because it made beautiful ice patterns most winter mornings...
The brand name arch-top casement that I found at the Habitat ReStore was a big hit, and a big improvement. While I didn't know the glass specs, casements are usually pretty air tight and any double pane window would be better than what we had. And God forbid, if we ever have a fire, a person would be able to get out of this window.

Of course, the whole wall had to be ripped apart to make the switch. The wall was thickened by adding horizontal 2x4s (a good technique for reducing thermal bridging), fire stops were added at the floor level (the house was balloon framed), new outlets were added and new cellulose insulation was installed to fill the many gaps.

While its not a perfect match, it fits pretty well in the wall above the kitchen's arch-top windows. 

Don't forget the New Roof
The middle high roof over the upstairs bath and bedroom closets was poorly insulated. And because the ceilings in the closets are "vaulted" style, there are few options to upgrade the insulation. Add to that, I had just made a big hole in the roof by taking out the chimney. So we did a double layer of 3" polyiso insulation and added a metal roof (reflects summer heat and improves collected rainwater quality). We also did the south side with it's solar hot water panels. Not a project for those afraid of heights.
Saving the Front of the House for Last
We saved the front of the house for last, not only because we wanted to practice before we got to the most public part of the house, but because it would be the most technically challenging part to retrofit.

Again, the porch had to be trimmed about 5" away from the house to allow for a continuous layer of insulation (see pictures below).

Areas of rotted wood had to be rebuilt. A kick out flashing has been installed to eliminate this problem.

The fancy shingled covering the high gables are old and delicate and will be a challenge to reinstall without splitting. We are planning to get a large lift in the spring to finish this part of the project. 

Composite photo of the front of the house as it had been "staged" for the National Solar Tour. Going from left to right shows most of the progression thru the DER process.
End Note
As realtors are fond of saying, a house is never complete until you are ready to sell. While this may be true, the performance upgrades of our DER are substantially complete. Our heating bill last year was $318 using a very small Air Source Heat Pump. Our projected heating bill for the 2012-2013 heating season using the natural gas furnace is less than $225.

A herniated disk has slowed me down on the final residing of the front of the house, but slow and steady progress continues.

Additional projects involved in the DER include:

  • The ERV was upgraded to a new Recouperator in late 2011.
  • A dividing wall was built in the basement in an attempt to keep my office warmer
  • The root cellar walls were super insulated
  • Two basement windows were upgraded with interior double pane windows
  • A good sealing dryer vent was installed
  • A solar hot air panel was installed to help heat the attic
  • The interior of the front foyer wall was rebuilt
  • I'm sure I'm forgetting something...

We've also recently added a new charging station for our all electric Nissan LEAF.

The projects continue!

I must also add a note of thanks to all who have helped and inspired me in this grand project, including my boss who thinks this is an awesome project and my wife who puts up with constant disruptions. Thank you all!