Deep Energy Retrofit of a 19th Century Maine House
This project is personal: the renovation of our family’s house in Maine. It is a work in progress. The goal has been to take care of a century of deferred maintenance and to make the house as energy-efficient as possible for year-round living. The great challenge has been to make all this work invisible, so that in the end it still looks like an old Maine house, not a renovation in the suburbs.
The givens in that challenge were:
- we would save the original exterior siding and trim;
- we would save the original windows;
- we would keep the kitchen as true as possible to the original;
- we would keep or match all original interior doors and trim;
- we would not change anything about the room configuration, except in the attic.
We discovered some unpleasant surprises along the way:
- rotted sills on the about two thirds of the perimeter of the house;
- rotted siding and framing in the attic;
- original 2×8 floor joists that spanned over thirty feet with no support;
- a chimney that needed complete rebuilding; and
- we had to replace the entire roof.
UPGRADING THE BUILDING ENVELOPE TO 21st CENTURY STANDARDS
One of the long term goals for the house is to make it island-able – that is, able to function independent of the power grid when necessary. The first line of attack in achieving this goal was to insulate and air-seal the house, which until this year was in its original un-insulated state.
In an ideal world we would have pulled off the siding and done the work from the exterior, installing insulation between the studs, rigid insulation and liquid applied air/water barrier outboard of the studs and sheathing, and a vented rainscreen behind new clapboard siding. The aesthetic/sentimental requirement to preserve the original exterior required us to explore ways we could safely insulate from the interior. The great concern here was not to recreate the kind of condensation problems that had ruined the attic (see below under Surprises). The first step was to remove the interior plaster, which after 120 years had served its useful life.
We opened up the walls to find beautiful fir studs, essentially unchanged from the condition they were in 100 years ago.
We filled the stud cavities with closed cell (vapor impermeable) foam sprayed tight to the exterior sheathing. While foams are not our first choice in most situations, in this case it was the only thing we knew that would guarantee no warm interior air would get through to the face of the sheathing. More on that below.
We then placed 1” of rigid extruded polystyrene (XPS) insulation over the interior face of the studs to block thermal bridging where foam insulation was interrupted by stud framing.
Finally we covered the XPS with lath and drywall.
This brought the interior wall surface about an inch further into the room than it had been before – a sacrifice we were willing to make given the extra thermal protection it gives us.
There is risk in the approach we have taken. Water in heavy, windy rains typically gets behind wood siding. Our concern is that now that there will be no air moving through the walls, this water could get into the sheathing boards and sit there, causing them to deteriorate. Over the next few years we will monitor the moisture levels in the walls most exposed to the weather and see if this is a problem. If it is, we may have to do what we have tried to avoid and take down the existing siding and install a proper rainscreen, as described above. Our thinking is that it would not be that much more difficult to do this later compared to doing it now, and hopefully we may not have to. An architect can take this kind of risk when he is the client!
The original roof framing was in good condition, but was built with 2×6 joists at 24” on center.
Already way too light for the span, the added weight of insulation would have made it even more structurally unsound. We also had to consider the fact that the surface of an insulated roof would stay cold and thus would carry far more unmelted snow than the old un-insulated roof. And from an insulation standpoint, 6” was hardly deep enough to provide a decent insulation cavity. So we decided to sister all the rafters with 2×10’s to give us the strength and depth required by codes today.
Original joists with new sistered joists starting to go in.
As we got into it, we found that the fitting the sisters to the deflecting existing framing was far more time-consuming than simply re-framing the roof. Since the old wood decking and shingles were coming off anyway, re-framing made sense.
New 2×10’s and new chimney
We filled the new roof framing cavities with a combination of 4” of closed cell spray foam and an additional 5-1/2” of fiberglass.
New rafters with 4” of closed cell spray foam.
Then we attached 1” expanded polystyrene (XPS) to the bottom face of the rafters to achieve a total insulation value of around R-54. Not Passive House level, but pretty good.
Fiberglass and XPS cover 4” of foam
Another tricky challenge has been the basement. The original open water well for the house is located there, and obviously a source of moisture. The original stone foundation walls also leak badly in heavy rains . There is an interior perimeter drain that collects that water and carries it to a drain and to daylight in the lower front yard.
We paid good money to building envelope consultant to help us with this and he pretty much threw up his hands and told us what we already knew: that there is no great solution short of filling in the well, rebuilding the walls and putting in a new floor. Not in the budget. We considered the approach of completely encapsulating the floor and perimeter stone walls with heavy polyethylene and insulation, basically making the basement space a part of the house. But with all that poly the basement would be essentially unusable, not to mention the difficulty of making the polyethylene barrier completely vapor-tight around all the existing structure, wiring and piping. Nor did my wife want to lose the look of the original stone wall.
The approach we decided upon is to insulate the first floor joists with open cell foam (removable if we need to get at a pipe or a conduit someday, unlike closed cell foams). We will re-cover the well with a more airtight cover. This will isolate the basement thermally and deal with most of the moisture migration. But it means we will have to handle keeping the basement above freezing and dry by mechanical means. We are not doing this work at this stage, however, preferring to evaluate the house’s performance after a year.
Probably the toughest challenging to achieving an air-tight, well-insulated house was our desire to keep the original windows, whose wavy glass throws so much beauty on the walls when the sun is low in the sky and gives the house so much of its character. Had this not been a priority we would simply have removed the old units and used triple glazed European sash that we use on our Passive House projects.
Instead, working with Sergei and Matt we came up with a several-pronged approach:
- First we had all the existing sash re-glazed using the original glass. Where the old glass had already been replaced we did not try to match it with fake old glass. We fixed the upper sash in place and foamed the cavity they are in. We kept the lower sash operable, replaced the sash cords where necessary, and then sealed those cavities with caulking.
- Since we needed to modify the interior trim anyway due to the now-thickened walls, we built in a little shoulder around the interior trim opening for removable lightweight gasketed glass panels made up in a local shop.
- We are also making up removable glass panels that can be installed on the exterior, just as the original screens were. We will deal with moisture and condensation between the sashes with little trays of salt, as Sergei did at his “Pushkin house”. Voila: triple-glazed windows!
We also replaced the badly deteriorated windows in the attic and added new windows to make a brighter stairwell. These are American-made Alpen high efficiency outswinging casement units (R-7) which have a profile closer to the original sash than the bulkier European triple glazed units.
Finally, we added two operable Velux roof windows in the attic to give additional ventilation and light.
With the house as tight as we are making it with the new insulation and upgraded windows, keeping good indoor air quality when the house is buttoned up in the winter becomes important. To deal with this we installed a Zehnder energy recovery ventilator. Basically this uses a very efficient small fan to exchange fresh outdoor air for stale indoor air. The two air streams slowly pass by each other in a matrix of small vapor-permeable tubes wherein around 90% of the heat and 50% of the humidity in the outgoing air is transferred to the incoming air. It removes the stale air from the bath and kitchen areas and distributes the fresh air in all the bedroom and living spaces at an imperceptible velocity (15/cfm).
ERV unit and ducts under the east gable.
With energy demand cut as much as possible, the next phase of the project is energy supply. Hopefully the new high efficiency Morso wood stove will provide most of the heat we need. We plan to continue using the existing oil-fired boiler and radiators as a supplement and replace the boiler when it dies with one that is wood-fired.
We are working with Revision Energy on a plan for an 8kw pv array on the roof. While we initially assumed the roof was not suitable due to its predominantly east and west facing slopes, we have learned from them that the loss in efficiency is between 20-25% — an acceptable trade-off when the only other option is a ground mounted system which would require clearing a significant amount of woods.
We will be using EnSync’s Home Energy System inverter with a 1okWh lithion ion battery. This is a hybrid ac-dc energy system that will connect rooftop panels directly to battery storage without having to be converted from dc to ac and back to dc. It will allow living completely disconnected from the grid during power outages. Our larger goal is to make the house as future-proof as possible as the world moves toward a direct current transactive energy economy. For more on this subject, see our earlier blog And read below under Future-proofing.
Even though we found no evidence from an initial inspection the exterior, we discovered once we got into construction that many of the original chestnut sills were badly deteriorated. After scratching our heads on how could we affordably jack the house and replace the old sills, we learned that Will, our electrician, has an interest in old structures and had invented a metal rig to make this job far easier than anything we were considering. He generously loaned this to us for the project and the replacement work was not nearly so involved as we had feared.
Deteriorated sill above. New sill going in below. Note Will’s jacking device.
#2 Attic gable walls
In 1996, right after we bought the house, we insulated and refinished the attic into two bedrooms for overflow space for the children. Following best practices of the time, we stuffed the joist cavities with fiberglass batt insulation and called it a day. It was an expensive lesson in building science. When we opened up the walls we found that the studs and the sheathing were completely rotted and that the paint on the exterior and the drywall on the interior were basically all that held the walls in place.
Here is what happened: in wintertime the warmest, most humid air found its way to the attic. As it escaped through the walls through gaps in the insulation the moisture in the air condensed on the cold interior face of the exterior sheathing, just like water forming on a can of beer. The insulation then acted as a sponge and held the water, causing the rot. In the rest of the house, where walls were completely uninsulated, condensation had occurred as well, but immediately dried as air moved through the wall. This is the reason that in this climate it is essential to prevent any vapor from contacting a cold surface—something foam insulations are very good at.
#3 Strange framing practices
As we took down the crumbling interior plaster we discovered that one of the reasons for cracks upstairs was that some of the original 2×6 second floor fir joists spanned 26’—double what code would allow today. We inserted a heavy wood beam in the kitchen to cut that span in half. If you look, you can see that the kitchen ceiling is now furred down by about 3″ to hide the new LVL beam, which is upset in the joists.
#4 Deteriorated chimney
Shortly after buying the house we had the original brick flue checked and found it leaky. We had it lined with a lightweight concrete system that is designed for retrofitting chimneys that have no flue liners. We did not realize that there is a life-expectancy for these retrofits. We learned this this winter that ours was definitely past. We had to take down the original chimney and rebuild it from the basement up. We used an old photograph of the house to match the original height and cap profile, which had been lost over the years.
We loved the old plaster walls and hated the idea of replacing them with modern sheetrock. Sergei told us about the American Clay wall finsh system, which he had used on another project recently. We saw some samples and decided that would be a reasonable compromise from re-plastering the whole house. We did the first floor living and dining rooms and the bedrooms upstairs with the American Clay product. American Clay also claims valuable health benefits: the clay releases negative ions into the air which combat the EMF effects of computers and eliminate static electricity. This apparently significantly improves the indoor air quality for people with allergies to pollen and pet dander. With our pets Wally and Mimi as residents, we will see if that proves true.
In removing deteriorated interior plaster we had to completely take apart the original beaded board kitchen cabinets. We put them back as close to the original configuration as possible, and were able to save most of them, at the same time incorporating a new sink and appliances. We did agree to replace the formica countertop with local slate. The floors were badly deteriorated linoleum over plywood. We took all that up and put down new fir floors.
The old kitchen.
The one area that wasn’t considered sacrosanct was the attic. Here we exposed the new brick chimney and opened it up into one big flexible skylit space with a built-in bunk and cabinets tucked in the low spaces.
The area of the house that was not touched was the lean-to on the back containing the bathroom, which we re-did in 1996. We chose to save this for a later project.
Getting ready for direct current microgrids
If predictions of current trends in energy are correct, ten years from now we will be living with a distributed energy grid, where neighborhoods and communities generate their energy locally and buy and sell energy to the power grid. Because power is generated and stored as direct (not alternating) current, and because most loads in our homes are natively direct current (think all high performance mechanical equipment, pumps, electronics, and lighting), the US will be moving more and more toward a direct current energy platform. This is already happening in the Third World, which is not burdened by an outdated energy grid infrastructure. Cost will drive this, because every time you convert energy from ac to dc or back, you lose energy (and money) in the form of heat. It’s why the wall wart for you IPhone gets hot.
Part of the reason for installing EnSync’s Home Energy System is to make the house ready for that new energy reality. Our new wiring has individual circuits to appliances, motors, lights, outlets, etc. So when, for example, direct current refrigerators come on the market, we can switch over the refrigerator circuit from the AC to the DC side of the inverter and it will be supplied direct current through the same wiring. Energy savings can be between 7% and 15% for each time energy is converted. When you think that photovoltaic energy that gets stored in a battery in your house and then used by a modern refrigerator is inverted four times, the numbers start to matter. Some say savings in dc net zero homes could be as much as 30% over ac homes.
The other electrical change we have made is more about health than future-proofing. More and more is coming out about electromagnetic fields’ (EMF’s) association with cancer and other health issues. Sleeping next to a floor outlet or light fixture exposes you to significant EMF radiation even when nothing is turned on. As a safeguard, we have placed a master switch in each bedroom that controls all floor outlets and lights so that when we are sleeping we will be in an EMF free environment. Interestingly, there are no EMF issues with direct current wiring.
General Contractor: Sergei Breus, Inc.
Lead Carpenter: Matt Jordan
Lead Millwork Carpenter: Joe Hermans
Carpenters: Andrew Monk and John Warfel
Excavator: Jim Gross
Mason: Dennis King, Dennis King Masonry
Insulators: Pete Anselmo,Builders’ Installed Products
Drywall: Keith Fitzgerald, Drywall Connections
American Clay: Mike and Kollin Krinkert
Kitchen Cabinetry: Jeff Schaller
Plumbing: Jason Perkins
Electrical: Will Lounsberry, Will Power
Structural Engineer: (Another) Jim Gross
Help with colors: Jean Kee, The Painted Room
It is misleading to call Sergei’s team carpenters. They do demo, they jack houses; they paint; they install ERV’s (Sergei is a licensed ERV commissioner); they do whatever it takes!
 A thermal bridge is a short-circuit in the insulation envelope of a building, where heat can escape. Every wood framing member in the building envelope is a break in the insulation blanket and a potential thermal bridge, unless it is covered with insulation.