Last summer I had the great privelege of attending a two day seminar with Building Science gurus Joe Lstiburek and John Straube. One topic that I really enjoyed was this 1915 four square house that Lstiburek and his wife Betsy Pettit retrofitted for major energy efficiency. Pettit's article describing the process is now available on their website, and I think it is a great example of how to extend the life of our older housing stock.
Older houses like this typically have undersized walls and roof rafters, making it extremely difficult to meet current insulation standards. Joe and Betsy found some creative ways to insulate from the exterior, leaving the interior mostly undisturbed while maintaining the character of the house outside.
Some highlights and observations:
- Exterior insulation was added at the roof and walls to stop air leakage and add thermal resistance.
- Cellulose insulation was added to the wall to the wall cavities, and spray-foam insulation was added inside the roof. Total insulation values of R-40 (walls) and R-60 (roofs) are nearly double the code standard in most new houses today.
- A ventilated space was added behind the siding, which prevents moisture from getting trapped in the walls. I like this nod to durability, a green strategy that is often overlooked.
- The finished house uses 54% less gas and electric energy than the original house, even though new living spaces were created in the attic and basement.
- Financed at today's interest rates, these upgrades are nearly cost neutral, even if utility rates do not increase.
In a milder climate like Portland, I suspect similar savings could be achieved with slightly less of an insulation investment. An upgrade like this would also provide a great opportunity to tackle seismic upgrades with little added cost.