PRESERVING A HISTORIC HOME with BUILDING SCIENCE
Historic Preservation is mostly about preserving and protecting buildings, objects, landscapes or other artifacts of historical significance. The Historic Molette House, ca. 1825 has a lot of significance in the Molette Family, as well with the people near the Molette’s Bend area near Selma, Alabama. When the home was moved nearly 3-mile to it’s new location (check it out on YouTube), the move and its renovation made front page news: 19th century home moved, renovations planned.
In the first post about this house, we talked about our approach to preserve both the original house, and its new addition and make it energy efficient with a high performance building enclosure. The goal is to moisture, air and thermal control layers on the outside of the structure to help prevent any unwanted and potentially damaging outdoor conditions from reaching the original or new wood framing, finishes and equipment, and to maintain its historical integrity*. Generally, the more of these that can be contained within a conditioned and controlled environment, the more “preserved”, or durable, it will be. Having the home last another 200 years is very feasible.
Coming up with an appropriate design for a home and its building enclosure, we integrate home performance (energy) modeling and the design of the heating, ventilation, air conditioning (HVAC) and water heating systems. The design currently specifies ducted mini-split heat pump systems for the heating and air, an ERV (enthalpy/energy recovery ventilator) for fresh air venitlation and a tank-less gas water heater. Since the home will be occupied only about half of the year, we chose the tank-less to help minimize tank losses while the homeowners are away. More on the systems in a later post. We’re focusing on the enclosure for this post.
Below are a few section details of the Molette House which is currently still under construction, and the photos under the details show our progress. A few things to note as you look through:
- We’ve created an uninterupted barrier around the entire building enclosure by providing a CONTINUOUS moisture, air and thermal barrier (a.k.a. the protective shell) on the outside. We’ve essentially created what Southface Energy Institute refers to as a “beer cooler”, which is a tight, well insulated container. In this case we’re keeping the home’s structure AND the beer inside.
- Air Sealing: At all openings and top and bottom plates of the exterior wall, we’re applying a continuous bead of sealant between the insulated structural sheathing and the framing, because much of the air leakage that typically occurs in exterior walls is at these locations.
- Ventilated Rain Screen: The 1/4″ gap behind the siding is ventilated at the top and bottom of the wall around the entire home to promote proper moisture control, thermal performance and durability of the cladding. We used Benjamin Obdyke’s Homeslicker
- Roof Ventilation: Ventilation for the roof assembly is provided with the vented nail-base insulation that is installed on top of the roof deck.
- Window Flashing: Because these were custom shop-built (or re-built) wood windows, as opposed to manufactured flanged windows, the window flashing has been extended up the jambs to the header. We used a liquid applied flashing by ZIP System, called Liquid Flash
- Encapsulated Crawlspace and Attic: Because we have the entire structure, including attic and crawlspaces, all of the equipment will remain in conditioned or semi-conditioned space, which helps the equipment last longer and work less to maintain comfortable conditions throughout the home.
- “The Perfect Wall“: This wall assembly is ideal for climate zone (3) this house is in because it promotes drying to the inside and out. Some climates are more suited for one way travel, either inward or outward only.
- Historic Eave Profile: The original cornice detail will be maintained, with the exception of a continuous 1/2″ gap being added to provide proper ventilation at the top of the wall assembly
The original house with a glimpse of the new addition at left. As you can see the original interior wood paneling is still in place. The homeowners have decided to leave it in tact, so we will be insulating from the outside by using netting to hold the blown insulation in place before installing the insulated structural sheathing.
The insulated structural sheathing (ZIP System R Sheathing) is starting to go up on the new addition.
A good view of the new addition
Rear view looking at the new addition.
View looking toward the back porch.
Thanks for stopping by! We look forward to sharing more as we finish up this wonderful project!
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