In “Old House Newbies: Renovation Assessment and Preparedness,” I discuss a chat I had with Michelle Schmitter, a resource strategist and architectural historian who has spent the last 20 years working on old houses. Michelle won’t consider buying a historic house for restoration if it’s had insulation blown in to the walls. One reader, Jeremy, expressed concern:
Any ideas on how to improve the energy efficiency of an old house with plaster walls, if adding insulation (the obvious home improvement) is going to cause mold? This is unsettling, because lots of old home enthusiasts insulate their homes and install new windows, making the interior air-tight.
A lot of the information and guides available online–in particular from great sources like the Department of Energy–have helpful information on improving energy efficiency offer suggestions for home improvements that can actually damage your old or historic home. Here on OldHouseWeb.com, there are many resources for home insulation. You’ll note that even resources here have been culled from several sources, including a detailed insulation guide from the Department of Energy.
For information specific to older or historic homes, you need to consider the source and determine if any consideration has been made especially for old house. If you’re not sure what might damage a historic home, stick to publications and information from the National Preservation Society or from bona fide historic house experts. You’ll find both types of resources online (and both here at OHW) that echo what Michelle said about wall insulation in historic buildings:
Care should be taken not to reduce infiltration to the point where the building is completely sealed and moisture migration is prevented. Without some infiltration, condensation problems could occur throughout the building.
OHW contributor and inspector Bill Kibbel specializes in old and historic buildings. What’s he have to say about adding wall insulation?
If you’re considering blowing in insulation into finished wall cavities, then no, I don’t recommend it. Given the opportunity, I try to talk folks out of doing it. That doesn’t mean that I don’t recommend any improvements to increase efficiency. I just try to advise efforts that are cost effective and don’t significantly alter the historic character of old homes.
One recommendation that Bill makes (and gives details on) is how to insulate a finished attic. But the energy efficiency improvements you’ll need to make depends on your particular house. How can you find out what your house’s energy issues are and if you even need insulation? In a series of articles on insulating older and historic homes, National Trust for Historic Preservation (NTHP) recommends having an energy audit conducted by someone qualified who also has experience in historic construction. Don’t have the audit done in late spring or winter because there needs to be a significant temperature difference between outside and inside your home.
The NTHP also notes:
Regardless, when insulating, it is critically important to consider the uniqueness of your building, the characteristics of its materials, the climate in which it resides, and the specific building methods that were used in its construction. Always keep in mind that improperly adding insulation to a building has the potential to wreak havoc on its overall performance. You can (perhaps unknowingly) do irreparable damage to priceless historic features by adding insulation where it is not needed, inappropriate, or ineffective.
Energy efficiency is one of those topics that everyone is thinking and writing about for good reasons, including both fiscal and environmentally responsibility. If you’re ever unsure about a renovation recommendation you’ve heard about it’s best to ask! Post a comment or post a message to the forums.