MILS Ventilation Project https://milsvent.pages.dev/ This journal describes the design and implementation of a ventilation system at the Manitou Island Light Station. quarto-1.10.18 Wed, 19 Aug 2026 04:00:00 GMT More data, more sensors Alex Hirzel https://milsvent.pages.dev/posts/20260819_another_sensor_more_data/ I was able to visit the light station today to grab the latest sensor data and begin an experiment. First, the data:

Figure 1: Data as of today.
]]> analysis field https://milsvent.pages.dev/posts/20260819_another_sensor_more_data/ Wed, 19 Aug 2026 04:00:00 GMT First look at some logger data Alex Hirzel https://milsvent.pages.dev/posts/202608_initial_analysis/ Recently, I was able to pull off the first few days of data from primitive data loggers I installed in the keeper’s dwelling on August 12. As a reminder, these are very primitive devices (Govee H5074) that only retain 2 weeks of data, and rely on connecting with a smartphone app via Bluetooth to download the data. The data retrieved so far, in raw form, looks like this:

Figure 1: Draw data as read from Govee H5074 sensors.

A start-up transient is clearly visible because I turned the devices on at my house, took them to the island, and finally deployed them into the basement and outside. This whole process was done by around 3pm local time.

(a) Sensor located in the basement of the keeper’s dwelling.
(b) Sensor located outside of the keeper’s dwelling.
Figure 2: Sensors that log temperature and humidity are installed indoors and outdoors at the Manitou Island Light Station.

One interesting pattern in this data is that outdoor temperature and outdoor relative humidity correlate inversely; this makes sense, because relative humidity is relative to temperature, and the temperature increases diurnally, shrinking the relative humidity. It is more clear to consider a measurement of absolute humidity, which is independent of temperature and quantifies the moisture present in the air.

Sensors that directly measure absolute humidity are not as accessible or as easy to deploy, but the existing sensor values can be used to estimate absolute humidity with some accuracy.

Figure 3: Absolute humidity as a function of temperature for selected relative humidity values.
Figure 4: Absolute humidity as a function of temperature, relative humidity, and dew point.

An easy option down this line is to think in terms of the dew point: the temperature at which relative humidity becomes 100%. This is a bulk property of some given air, and it can be used to compare different air masses in the sense of absolute humidity, while also indicating how close that air is to condensing on a surface of a given temperature. Shown below are the indoor and outdoor dew points calculated from data so far—as well as the basement air temperature—to allow us to think a little more clearly:

Figure 5: Basement temperature compared to dew points of indoor and outdoor air.

This now clearly shows the problem: the dew point of the air is very near to the temperature of the air. In order to reduce condensation, we need to reduce the dew point.

]]> analysis field https://milsvent.pages.dev/posts/202608_initial_analysis/ Mon, 17 Aug 2026 04:00:00 GMT Our initial problem statement Alex Hirzel https://milsvent.pages.dev/posts/001_problem_statement/ We are here to address a moisture issue in a remote structure on Lake Superior: our goal is to reduce average moisture in the basement of the keeper’s dwelling at the Manitou Island Light Station, pictured below:

A photo of the keeper’s dwelling and light tower at the Manitou Island Light Station.

A photo of the keeper’s dwelling and light tower at the Manitou Island Light Station.

This light station has a rich history that begins in the 1850s, when the island’s easternmost section was reserved by the federal government for lighthouse purposes. This is noted on Douglass Houghton’s survey of the island, which was completed several years prior in 1845.

Excerpt from the 1845 GLO survey of Manitou Island.

Excerpt from the 1845 GLO survey of Manitou Island.

Having visited this light station several times, I feel motivated to help in any way that I reasonably can. Most of the time, when I visit, I find that the basement humidity is very high, with several surfaces feeling wet to the touch because of condensation. Some of these surfaces are metal ducting, but some are wood including the first floor’s joists. I have begun doing some research into possible solutions for this, and will detail these in future posts.

Apart from this, the building is urgently in need of a new roof and better grading/drainage, and the site in need of vegetation removal; these are not areas where I am as skilled. Because of this, I will start with trying to ventilate the basement.

]]> story https://milsvent.pages.dev/posts/001_problem_statement/ Thu, 23 Jul 2026 04:00:00 GMT