As an experienced builder, I’ve had the pleasure of working on countless projects in the Southend area, each one presenting its unique challenges and opportunities. Today, I’d like to share with you a particularly fascinating aspect of my craft – the role of plastering in improving a home’s thermal performance and energy efficiency.
The Hidden Treasure of Horsehair Plaster
When I first laid eyes on the 1920s bungalow you mentioned, I couldn’t help but feel a sense of excitement. The original horsehair plaster walls were a true treasure, and I knew that with the right approach, we could unlock their full potential.
Horsehair plaster has been used for centuries, and for good reason. This time-honored technique not only creates a beautiful, smooth finish but also offers some remarkable thermal properties. Unlike modern drywall, horsehair plaster acts as a natural insulator, helping to regulate the temperature within the home.
As I delved deeper into the history of your home, I discovered that the walls had been insulated with materials salvaged from an old barn. This added an extra layer of intrigue and made me even more determined to preserve the integrity of the existing plaster.
Navigating the Vapor Barrier Conundrum
One of the primary concerns I often encounter when working with older homes like yours is the issue of moisture management. The internet can be a minefield of conflicting information, and I’m glad you reached out for my expertise.
The confusion around Tyvek, Typar, and other housewraps is understandable. Many homeowners mistakenly believe that these products act as a vapor barrier, which can lead to moisture problems when paired with the breathable nature of horsehair plaster.
Let me clear the air on this matter. Tyvek, Typar, and similar water-resistive barriers (WRBs) are not vapor barriers. In fact, they are quite permeable to water vapor, allowing the wall assembly to dry to the exterior. This is a crucial detail that sets them apart from traditional 15-pound asphalt felt, which is more vapor-retardant.
So, in your case, you can confidently use either a housewrap or asphalt felt as your WRB without worrying about trapping moisture within the walls. The key is to ensure proper installation and detailing to maintain the integrity of the air barrier.
Enhancing Thermal Performance
Now that we’ve addressed the vapor barrier concerns, let’s dive into the exciting realm of improving your home’s thermal performance. As you mentioned, the lack of insulation in the exterior-facing wall presents a significant opportunity for enhancement.
I’m a big proponent of blown-in insulation, particularly cellulose or fiberglass, for a project like this. These insulation materials can be effectively dense-packed into the wall cavities, significantly improving the overall R-value and reducing heat transfer.
However, before we dive headfirst into the insulation installation, it’s essential to assess the condition of your lath and plaster. If the lath is in good shape and the nails are holding up well, we can likely proceed with a dense-pack approach without any major concerns.
In the event that the lath or nails are in poor condition, we may need to consider a lower-density insulation approach to avoid the risk of cracks or even a blowout. In that case, low-density cellulose would be the preferred choice, as it is more air-retardant than low-density fiberglass.
Balancing Vapor Drive and Thermal Bridging
As we delve deeper into improving the thermal performance of your home, we must also consider the delicate balance between vapor drive and thermal bridging.
Given your location in Grafton County, New Hampshire, you’re situated in Climate Zone 6, which brings its own unique set of challenges. The presence of the original plank sheathing and oil-based wall paints from the 1920s can actually work in our favor, as they tend to be more vapor-open than modern materials like OSB or plywood.
However, if we decide to incorporate insulating sheathing beneath the new cedar shingles, we need to be mindful of the potential for moisture buildup. To maintain a reasonable level of drying capacity toward the exterior, the R-value of the insulating sheathing should be at least R-5 for 2×4 framing in your Climate Zone 5 (or R-7.5 in Zone 6).
One clever solution I’ve employed in similar situations is the use of perforated fan-fold XPS insulation. This product offers a slightly lower nominal R-value, but the perforations allow for some drying to the exterior, mitigating the risks associated with a fully vapor-closed assembly.
Preserving the Charm of Antique Windows
As we discuss the thermal performance of your home, it’s important not to overlook the role of the original windows. Those wavy glass panes are a true testament to the craftsmanship of the era, and I’m glad to hear that you want to preserve them.
In my experience, retrofitting these antique windows with modern weatherstripping can make a significant difference in their air tightness. And if they’re in reasonably good condition, installing an air-tight, low-E storm window over them can bring their thermal performance up to nearly code-minimum standards.
Harvey Tru-Channels and Larson’s Premium Series low-E storm windows are two excellent options that I’ve had great success with in the past. They not only enhance energy efficiency but also maintain the charm and character of your home’s original fenestration.
Embracing the Challenges, Celebrating the Rewards
As I reflect on the various projects I’ve undertaken with Southend Builders, I can’t help but feel a deep sense of pride and satisfaction. Restoring and enhancing the thermal performance of older homes like yours is a true labor of love, and it’s a privilege to be entrusted with the care of these historic structures.
The challenges we’ve discussed, from navigating the vapor barrier conundrum to balancing thermal performance and drying capacity, are all part of the rewarding process of breathe new life into a home. By leveraging the inherent qualities of horsehair plaster, carefully managing moisture, and intelligently incorporating insulation and storm windows, we can transform these beloved dwellings into energy-efficient havens that honor their rich history.
I can’t wait to get started on your project and see the transformation unfold. Together, we’ll unlock the thermal potential of your 1920s bungalow, ensuring that it continues to provide comfort, efficiency, and a sense of timeless charm for years to come. After all, that’s what Southend Builders is all about – delivering exceptional construction services that enhance the lives of our valued clients.
So, what do you say? Are you ready to embark on this exciting journey with me? I’m eager to roll up my sleeves and get to work, and I promise you’ll be thrilled with the results.
