Superinsulating My Old House
Aging office worker tackles challenging superinsulated retrofit and lives to tell about it.
January 03, 2009
A version of this article appears in the January/February 2009 issue of Home Energy Magazine.
The tall and narrow west wall was the only remaining uninsulated wall of my old home. The renovation plan was to insulate the wall and replace the original brick façade with an exterior insulation and finish system (EIFS). The old double-hung windows and the front door would also go. I’m superinsulating the remaining already-insulated walls of the house using methods other than those described here.
The decision to undertake this project resulted from several problems that guided me toward specific solutions.
The project was urgent—because:
- our natural gas costs were increasing;
- the façade looked shabby and the old windows no longer held paint;
- the wall’s low thermal resistance was both an energy and comfort problem;
- the wall’s sound transmittance let in noise from the street; and
- the brick veneer had no structural integrity (earthquakes happen here in Helena, Montana).
To solve these problems, I decided to
- insulate the walls to R-30 or beyond;
- air seal the façade;
- replace the old windows with triple-pane windows;
- create a façade that looked like the old historic façade; and
- reinforce the façade structurally.
The main house, and the addition, built at the turn of the century, originally had brick veneer on all four walls. However, the brick on the north, east, and south walls came crashing down during the Helena earthquake of 1935. The brick veneer on the front (west) wall survived because it was reinforced by the two-story bay window.
Old brick veneer is difficult to retrofit. You can’t insulate through brick or over it. My brick veneer was structurally weak, due to inadequate ties into the building and weak mortar from decades of moisture migration through the joints. The best option was to demolish the brick, which is what we did.
Driving flat bars into every second horizontal mortar joint, we pried the bricks apart, removing as many as we could in one piece. This big-chunk method is limited, of course, by how big a piece you can lift and throw into the dump truck. These bricks were crumbly and not worth salvaging. Steel-toed boots are a must for this type of work. Using a man lift and a dump truck, it took my work partner, Joel Repnak, and me only two days to remove all of the brick veneer from the west wall.
Next we removed the tarpaper and pried the full 1-inch plank sheathing off the studs. The original builders had installed the tarpaper, which was held loosely in place by the same ancient 16d nails that held the brick veneer precariously to the wall. The nails were driven about 1/2 inch into the planks, and the nail heads were buried in mortar joints on a spacing of about 2 feet in all directions. That tarpaper protected the wood sheathing from water leaking through the brick veneer, performing the same function as today’s house wrap.
After hauling the demolished brick veneer to the dump, we figured we were finished dealing with brick. However, when we removed the plank sheathing from the west wall, we found more bricks and mortar installed inside the stud cavities, from the floor joists all the way to the eaves. Don’t ask me what those wily old tradesmen were thinking when they laid this brick and mortar.
After we removed the confounded brick and mortar inside the wall cavities, we could see the giant air leaks from outdoors. The second-floor rim joist (or lack thereof) had holes you could reach your whole arm into. Since there had been spaces between the sheathing planks, and brick isn’t a good air barrier, this wall had been leaking a whole lot of air into our home.
We chose to use polyurethane insulation to fill all those voids and insulate the stud cavities. Even though low-density polyurethane isn’t a perfect air barrier, it does reduce air leakage, and it provides thermal resistance (R-3.8 per inch).
After the insulators filled the wall cavities with foam, and I installed a near-perfect air barrier—1/2-inch of CDX plywood glued and stapled to the studs. The CDX plywood also reinforced the flawed framing in the old frame wall. Years ago, I waited out an earthquake, standing in my bedroom doorway upstairs. The narrow house had a lot of sway from side to side. Hopefully this glued plywood will decrease that dangerous sway in the event of another earthquake.
Now that the wall was insulated and air sealed, the windows and front door were next on the list. Because of Helena's cold climate we ordered Duxton triple-pane, argon-filled windows with two low-e coatings (U-0.17). The frames of our new windows are insulated with polystyrene foam. There are only a few manufacturers of insulated window frames in North America. (Compare that to more than 40 in Germany and Austria.) Thermal bridging through structural materials around windows and doors causes major heat loss, and insulated window frames reduce thermal bridging. Exterior insulation covers the window’s structural framing and reduces thermal bridging still further. Because the windows face west, they heat the house during the summer, and we don’t have air conditioning. Therefore, we also chose spectrally selective low-e glass with a low solar heat gain coefficient (SHGC = 0.25).
We installed the windows from the inside for practical reasons. Triple-pane windows are heavy, and my house is tall. We installed the new windows in the old double-hung window frame. The interior trim is attractive, and I didn’t want to make a mess indoors, so we left the interior finish intact. The usual problem with installing a new window in the old double-hung window frame is insulating the weight pockets—the vertical cavities next to the windows that hold the sash weights. The weight pockets weren’t a problem for us, since we stripped the exterior sheathing off and sprayed foam insulation into the cavities.
I knew the existing frames were out of square, but I underestimated how far out of square they were. Nor did I know how narrow the face of the new window frame was, and that created additional fitting problems. I added a little more than 1/2 inch to the absolute width and height of the window when measuring. This was the minimum clearance space between the old window frame and new window, given the out-of-square openings.
Installing the windows was difficult and time consuming. We installed the window from inside against 3/4 inch x 3/4 inch fir stops. We had to rip the stops into long wedges to accommodate the square window in the out-of-square window frame.
My hockey buddy Ken Robbins developed a unique EIFS system he calls R-Tech, which is similar to other proprietary EIFS systems, including Dryvit. EIFS has suffered some notable failures when moisture has gotten trapped behind the foam, mostly in rainy climates. However, our climate is arid, and R-Tech’s workers are moisture control evangelists. R-Tech’s flashing details and perfect caulking, along with our careful window detailing, won’t allow any moisture to penetrate the foam, or the Tyvek weather barrier underneath.
EIFS is usually installed over an inch or two of polystyrene foam board. Ken balked when I told him I wanted 4 inches; he told me that this wouldn’t be cost-effective. After Joel and I demolished the brick, I discovered that the ledge left by the brick veneer would accommodate 6 inches of foam. Ken rolled his eyes when I requested 6 inches, repeated his cost-effectiveness argument, and prepared a new higher estimate.
The EIFS installation, including the exacting 6-inch polystyrene foam application and the 3/16-inch two-color latex-stucco finish, cost me a total of almost $11,000. Considering that there is less than 500 square feet of wall space on that façade, that’s more than $22 per square foot!
I chose EIFS because I needed a beautiful façade to face a major street in a historic neighborhood. The face-lift, comfort benefits, noise reduction, and energy savings together made the expensive EIFS worth it to my family and me.
Planning and Intangible Benefits
We’ve found the exterior retrofit to be the most effective strategy for achieving superinsulation and superior airtightness in a retrofit. Also, retrofitting from the exterior minimizes the indoor mess—preventing the domestic tranquility index from plummeting into the red zone.
This project involved a million details. I haven’t even mentioned the double-decker porch we built to replace the decrepit old one.
Planning is the key to our success so far. The city building department wanted drawings and cost estimates before issuing the building permit.
I’ve made dozens of drawings, materials lists, and work plans.
Retrofitting work is physically challenging for a late-fifties office worker like me. Luckily, I exercise a lot. In the ten weeks Joel and I worked on this project, I’ve acquired a farmer’s tan, lost 15 lb, and reconnected with my inner carpenter. I should do this every summer!
Phase 2 on the north wall is well under way. We’re removing steel siding, applying 4 inches of foam, and reinstalling the same siding. I’ll tell you about that challenging project another time. Our energy bills give 13 months of historical consumption, so monitoring the success of the project will be easy.
John Krigger is the coauthor of The Homeowner’s Handbook to Energy Efficiency and a teacher at the Web-based training institute Saturn Online.
For more information:
For questions about his retrofit project, contact the author at firstname.lastname@example.org.
Visit www.homeownershandbook.biz to learn more about and purchase The Homeowner’s Handbook to Energy Efficiency. The book is also available for purchase from the Products section of Home Energy’s Web site, http://www.homeenergy.org/homeownerhandbk.php.
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