Energy at the Whitney Boarding House: What We Learned

             How can historic buildings be modified to improve their energy performance? The Connecticut Trust decided to use its own headquarters as a test case. In 1989 the Trust restored the building, originally constructed in 1827, with the aim of demonstrating good preservation practice. Energy efficiency was not a primary goal, although reasonable care was taken to provide thorough weather stripping on the windows and insulate the heating ducts.

As a result, the Boarding House, like many old Connecticut buildings, has no storm windows and not much insulation. Most noticeable is the cold air that comes up from the cellar through the gaps in the floor.

            Facing rising energy costs and concerns about wasting resources, the Trust commissioned an energy audit of the building last winter. Bill Hoffner of Hoffner Conservation, an energy consultation firm based in Norwich, performed the audit in March. In May, he described the results at a House Talk. Joining him, New Haven architect Jay Warren Bright discussed energy saving from a preservation angle.

 
            For his test, Hoffner first investigated the building by eye, pointing out obvious places where we waste energy (such as those floor boards). Then he set up a big exhaust fan in a door. With an infrared viewer Hoffner could see where cold air was working its way indoors. He stressed the importance of sealing gaps, explaining that it’s moving air that makes us feel cold, and that insulation doesn’t stop drafts.

Hoffner gave the Trust a written report that outlined recommendations and estimated energy savings. Among the recommendations:

• block the gaps in the floor and add insulation to the cellar ceiling to keep heat in the first floor (Hoffner suggested spray-in foam, but foam can’t be removed easily, making it less desirable for historic buildings)
• seal gaps around pipes and wiring, which draw warm air out of the building
• add additional blown-in cellulose insulation to the attic, with fiberglass batting as a dam to hold it in place
• consider adding storm windows
• caulk around door and window trim, baseboards, and anywhere else there is a gap that can let air in
• insulate the doors leading to the cellar and attic
• add weather stripping to doors and where the window sash meet
• swap incandescent light bulbs for more efficient compact fluorescent ones
• investigate more efficient HVAC systems and water heaters now; when the current ones fail there probably won’t be time to study the alternatives

            Bright also pointed out that any building is a coordinated system of components—structure, cladding, finishes, windows and doors, HVAC, plumbing, roof, foundation—any one of which interacts with and affects the performance of the others. For instance, if you add insulation to a stuccoed wall, the wall will no longer be warmed by heat escaping from the house, and it will be more vulnerable to cracking as it reacts to outdoor temperature changes. Sometimes, features that seem wasteful can in fact serve a useful purpose. Bright cited a house of the 1840s that has siding of overlapping square boards rather than tapered clapboards. Gaps between the boards cause lots of air leakage, but they also allow moisture in the wall cavity to evaporate. Sealing the gaps could trap moisture in and cause rot.

            Bright also warned against using new products that have not been tested to see how they perform over time. New replacement windows, for instance, generally carry a guarantee of twenty years for the glass and only ten years for the parts. With periodic maintenance, traditional wooden windows can last 100 years or more. With the addition of well-designed storms, which is greener?

Windows were a major topic. Both Bright and Hoffner recommended V-seal plastic weather stripping and removable rope caulk can be used to block drafts in the winter and can be removed in the summer to open the windows. Exterior storm windows not only provide insulation, they also protect the primary sash from weathering, which means less frequent reputtying and repainting.

A less expensive alternative to storms is plastic sheeting installed with double-sided tape and tightened by heating with a hair dryer. Bright said that a narrow air space, not more than ¾ inch, actually provides better insulation than a wide space. He recommended installing the plastic on the individual sash and then using rope caulk to block drafts around the edges and at the meeting rails.

            Fireplaces and chimneys can pull heated or cooled air out of a house. The first thing is to close the damper. If there is none, or if it doesn’t work, a plastic trash bag filled with fiberglass insulation can be stuffed up the chimney (hang something down the chimney to remind you to remove the bag before starting a fire!). In addition, caulk where the wood trim meets the often uneven masonry of the fireplace. Special caulk for high-temperature areas is available.

            The final area of major concern was the attic. If it is not used as a living space, it’s best to insulate the floor. A consistent layer of loose insulation six inches thick is generally enough. Also seal any gaps around chimneys or vent pipes, which can draw heated air up from below.

            Hoffner and Bright suggested that some common strategies are actually less helpful. Insulating the Boarding House’s walls would be difficult: either the exterior clapboards or the interior plaster—both historic—would have to be removed to install batting, while blown-in insulation tends to settle. In any case, the greatest energy loss is through the attic and roof, so it would make more sense to concentrate there. Storm doors also don’t add much protection relative to their cost; better to be sure that the exterior doors have good weather stripping to block drafts.

            The Trust is working now to put some of these results into practice. For the summer, we’ve set the thermostats higher than in past years and we’re keeping blinds and shades closed on sunny days. The Building Committee is starting to look into bigger projects such as the floors and caulking. We’ll continue to report on what we accomplish.