We are sometimes asked by our visitors for the scientific evidence for some of the claims made and advice offered on the site. But because woodheat.org is mainly intended for users, not scientists, we have resisted littering each article with scientific references. But we have made an exception for this section on the science of chimney venting, so below are some links to files and reports for people who want further reading.
This is the report of the first and most comprehensive study of the behavior of outdoor air supplies for natural draft woodburning fireplaces. It documented the first time outdoor air supplies were rigorously tested and showed that code rules mandating outdoor air supplies were based on opinions, not on facts.
This is just a summary of the report. This study had three objectives: to determine the frequency and severity of combustion spillage; to learn what design, installation and operation factors affected spillage; and to develop effective ways of preventing spillage in new and existing installations. From the report: "A significant finding of the study is that the actions of the user are the most important element in the proper operation of a wood heating system."
Investigation of Negative Pressure Test Protocols for Wood- and Pellet-Burning Appliances
The objective of this research was to design a laboratory test to determine how much negative pressure wood burning appliances could tolerate. Although the project did not yeild a practical test suitable for for certification purposes, it did produce many valuable insights into how woodburning systems respond in negative pressure environments. This study also revealed (again) that outdoor air supplies do not isolate the appliance from house depressurization or prevent combustion spillage.
Evaluation of Various Chimney Cap Designs
Five different chimney top terminations (caps) were tested in a wind tunnel to determine how well they resisted adverse wind presssures. The worst-performing option was a masonry chimney with no cap, and the best-performing termination was the baffled metal cap offered by factory-built metal chimney manufacturers. This file only contains a minimal summary of the findings, using the images and charts from the original report formatted in a condenced form.
This form was developed to record the findings of the house pressure test. The first page is the test report form and the second page is a check list to help organize the test proceedure. The form makes it much easier to carry out the test correctly.
JG