By Allan Bullis
This is a story on one of the most unusual weatherization projects in the State of Vermont. Starting two years ago, State Architect Tricia Harper contacted me at Common Sense Energy (CSE) to develop a plan to weatherize the statehouse as they had done in the past for other historic State buildings.
The Statehouse was built in 1838 and rebuilt after a devastating fire in 1857. The core building is the house chamber with wings to east and west. The statehouse got additions in 1888, 1900 and 1987. It was decided to approach the upgrades in a phased approach with the first phase focused on the east and west wings of the main building. This was completed in December, and the second phase is to be done this summer.
There are three discrete attics, all of which were poorly insulated. Making matters worse, there was mechanical equipment and ductwork located in the attic; this is very undesirable because it is outside of the thermal envelope. Only the attic flat areas had insulation, and they only had two inches of blown fiberglass, for an insulating value of R-6. The numerous vertical transition areas where ceiling heights change had no insulation.
Other complications included the presence of asbestos in part of the attic space. Insulation had to be removed in both wings using an industrial vacuum by contractors certified to work with asbestos remediation. Other work that needed to be performed before insulation work was completed included installing catwalks for maintenance work, upgrading the fire detection system, repairing and sealing ductwork, adding insulation on ducts, and general maintenance.
Getting this all accomplished so the weatherization work could be completed before the current legislative session took a tremendous effort by Peter Hicks and Tricia Harper on the Buildings and General Services staff, CSE, and the contractors.
I also found that the foundation and walls were not insulated. There is no moisture barrier on the exterior, and if it were insulated, this might potentially create conditions where the masonry walls are susceptible to damage from cycling through freezes and thaws. Further testing would be needed to determine if the walls could be safely insulated.
The attic area was clearly in need of attention, and insulating and air sealing would not only reduce energy loss but help reduce ice dam formations and reduce the migration of moisture. Both of these steps help preserve buildings. The initial thought was to apply spray foam insulation to the bottom of the roof as there were air handlers and duct work in the attic space. After discussions with historic preservation experts, this was ruled out because it would be difficult to remove, if that were needed. The next option looked at was to install an air barrier under the roof and blow in cellulose. This was ruled out due to the high cost. The final option was to isolate the attic space by air sealing and adding cellulose, and this was clearly the most benign and cost-effective approach.
The attic had many pathways for air to escape from heated areas, some of them unusual. They included gaps around each of the ceiling supply and return ducts, pocket doors, mechanical chases, and attic accesses. The most challenging item was sealing the numerous ceiling lights. They have a three-inch hole in the ceiling and are lowered by aircraft cable to change the bulb. A solution was to use a rubber roof boot to attach to the light with weather-stripping to seal to the ceiling. Montpelier Construction performed the air sealing work and installed house wrap a minimum of six inches away from transition wall areas to prepare for dense-pack cellulose. Energy Efficient Construction was hired for installing cellulose in the walls and the attic “flat.” Normally attics are insulated to a minimum of R-49 but out of safety concerns to maintenance workers, the top of the ceiling joists were left exposed, resulting in an average of R-35.
The building was tested with multiple blower doors with help of Efficiency Vermont. At the start of the project the test came in at 33,000 CFM@50 Pa. The post-construction test showed a 10% reduction. Heat savings will be $2100 per year with a payback of about 10 years not counting savings in air conditioning. An added benefit of the project is the reduction of intrusions by moist outside air during the summer, reducing the dehumidifying requirements.
Allan Bullis is CEM, LEED AP, and Auditing Engineer at Common Sense Energy.