Energy Retrofit Series: How to Improve a Historic Home’s Energy Efficiency
"When it comes to improving the energy efficiency of historic homes, you will likely be changing the equilibrium of the home (how the house is at its most natural state)—as you change the drying rate of the home, you also need to evaluate the wetting rate of the home (the introduction of moisture from exterior sources)."
Considering an upgrade to your historic home? In this ongoing energy retrofit series, master craftsman Daniel Westbrook interviews industry expert Mark LaLiberte, founding partner and president of Construction Instruction. Mark has been educating the building industry on the science and physics of construction for more than 30 years, and in this series he’s sharing the benefits of constructing durable, energy-efficient, healthy homes.
Today, Daniel and Mark are chatting about important factors to consider when improving the energy efficiency of historic homes in the Pacific Northwest. When making changes of this nature, you must be mindful of what you are trying to fix because these “fixes” might actually be creating an even bigger problem than what you started with. Here are a couple of key takeaways:
Be mindful of the home’s equilibrium
As heat passes through the walls of a home, it helps preserve the materials the house is made of. The way air moves in and out of a home naturally reduces moisture levels, so the building materials are able to dry at a consistent rate. This helps prevent catastrophic damage if and when a leak does occur.
When it comes to improving the energy efficiency of historic homes, you will likely be changing the equilibrium of the home (how the house is at its most natural state)—as you change the drying rate of the home, you also need to evaluate the wetting rate of the home (the introduction of moisture from exterior sources). Your goal is to create a new equilibrium that accomplishes your goals and does not put the home or its occupants at risk.
Assess what’s working and decide whether work really needs to be done
Here's one example of an energy upgrade gone wrong: It’s common to see energy retrofits done on cold-climate houses in which a contractor has blown insulation into the wall cavities. Adding insulation seems like a no-brainer—but these older houses may have been leaking energy back and forth for years, which kept them in a neutral state. As moisture condenses on the now cold wall sheathing and drips to the bottom of the wall cavity, all of a sudden, new water exists that wouldn’t have been there before; over time, it can lead to studs rotting out at the bottom of the wall.
None of the potential pitfalls mean you shouldn't do the work—but they should remind you that historic buildings are still standing for a reason. If they’ve made it 80 or 90 years, step back and think about what’s allowed them to survive, and whether you're about to make a possible change that could have an adverse effect. Then, ask yourself the difficult question: Should nothing be done at all?
Watch previous installments of our energy retrofit series on Dunn Solutions, and stay tuned for more from Daniel and Mark as they continue to discuss energy retrofitting over the coming months.
