HDC approves radon mitigation at 415 West William with paint condition

The Ann Arbor Historic District Commission on Jan. 9 approved a certificate of appropriateness for a radon mitigation system at 415 West William Street, allowing the unit to be installed at the building’s northeast corner on the condition that the fan and visible equipment be painted to match the home’s exterior.

The item was before the commission because staff and the review committee concluded the proposed location was highly visible from the street and therefore did not meet the Historic District design guidelines, but the applicant and staff told commissioners they had explored other locations and that the chosen placement was the only feasible option without extensive structural work. The commission approved the application after a motion by Commissioner Smith and a second from Commissioner Calderon.

Planning staff described the house and the proposal, saying long-term testing indicated a mitigation system was necessary on site and that the applicant proposed mounting the fan and piping on an exterior wall beside the front porch. Staff told commissioners the Ann Arbor Historic District design guidelines and the Secretary of the Interior recommendations favor locating mechanical equipment on rear elevations, roofs or alley-facing walls so that it is not visible from the right of way. Staff recommended a less-visible location if one existed, but said that if the commission determines the proposed site is the only feasible placement, the unit should be painted to blend with the exterior.

The review committee, which inspected the property on site, reported constrained crawl spaces, a narrow service pathway between the house and an adjacent owner-occupied unit, and a stair structure on the opposite elevation. Committee members said the contractor reported the crawl spaces on much of the rear and sides were too tight for the work required to route piping internally, and that relocating the unit would likely require substantial additional work such as rebuilding stair supports or removing deck boards and joists.

Applicant Brian Van Dynen of Geosyntech Consultants said the system design calls for the piping to run up the exterior of the house so any downstream leak vents outdoors rather than into living space. Van Dynen said the fan is somewhat larger than a standard radon fan (described in testimony as “about the size of two shoe boxes side by side”) and that a short picket fence already on the site could partially screen the unit. “We are willing to paint the equipment exterior of the house to match the exterior,” Van Dynen said.

Commissioners debated alternatives. Some favored a less-visible rear placement but acknowledged the narrow walkway and limited access could impede installation and access for maintenance; others emphasized the homeowner’s health and safety because testing showed volatile compounds in indoor air tied to contamination nearby. Staff and the applicant said the fan would require only routine replacement over the years, and that the chosen fan and a stack muffler were expected to keep noise below the city’s ordinance limits.

Commissioner Smith moved to issue a certificate of appropriateness for 415 West William Street, a contributing structure in the Old West Side Historic District, to install a radon mitigation system near the northeast corner of the building on the condition that the entire unit be painted to match the exterior color. Commissioner Calderon seconded. The motion carried and the commission approved the application. The chair reminded the applicant that all required city permits must be obtained and that the permitted work must match what the Historic District Commission approved.

Work on this property will proceed under the conditions set by the commission, and the applicant and staff said they will continue to coordinate on screening and paint color with the homeowner and contractor.