Of roof combs and vented ridges. [Or, why old buildings teach us old tricks].

Roof section axon, comb vent.

Roof section axon, underside of roof lath detail.

Yesterday I worked on a detail for the ecoMOD team, who's working here in the Field School on the 6th iteration of UVA's ecoMOD project, in partnership with Falmouth Heritage Renewal.The detail, for a modified comb vent at the ridge of a hip roof, is based on both vernacular detailing and on basic thermal properties [heat rises!] The team had already run some tests using fluid dynamic modeling, and I was tasked with taking those findings and translating it to a simple, field-buildable detail that could be easily replicable on other houses in Falmouth or around Jamaica. 


By just adding some additional furring, and some strategically placed blocks, the ridge section can be lifted above the main body of the roof, allowing heat to escape. The blocks are placed to provide enough support for the ridge cap, as well as to get secure fastening surfaces and eliminate punctures through the corrugated roof sheathing. The ridge section is lapped over the sheathing to protect the sheathing fasteners and keep out driving rain. Insect screen can be installed under the ridge furring blocks as well.

Additionally, the students found that by placing lath on the underside of the rafters, the naturally occurring convection loop [heat rises!] is accelerated and aided, as long as complementary floor level vents are also installed. With temperatures reaching about 140 degrees Fahrenheit at the ridge, pulling 75-80 degree air from under the house becomes critical to keeping cool. 


This detail will be used here on ecoREMOD2, and will hopefully become part of the library of details that can be used on historic homes here in Falmouth that FHR works on - and represents, for me, the kind of technologies I'm interested in finding, highlighting, and understanding on this research trip. The other aspect of the students' work that's of interest to me is the quantitative analysis. While I'm not an engineer or a scientist, partnering the qualitative with the quantitative, especially on details and strategies that haven't been analyzed like this, is the way that this kind of research reaches beyond the anecdotal, the observational, and the merely descriptive to the provable and applicable, for both historians and architects. Or, also, those crazy enough to try being both.