Workshop envelope

← Back to workshop series indexPublished: 2016 July 31Last updated: 2016 November 29

For effective dust collection (more on this in a later post), I need to ventilate all cutting/sanding tools with 1000 CFM of airflow, which is sufficient to change the entire shop air roughly every nine minutes (30’ x 30’ x 10’ = 9000 ft³). So is there any reason to bother tightening up and insulating the workshop envelope?

The benefits of airtightness/insulation are:

• comfort while not cutting/sanding (assembly, glue-ups, computer modeling for CNC, etc.)
• easier to convert the workshop into a living space
• possible noise reduction (unlikely to matter, given distance between workshop and residence)
• reduce condensation-related tool rust due to daily temperature swings

The primary downside is cost. A metal barn or roof-on-poles (similar to a park picnic area) would be significantly cheaper to build than a full structure. There may also be property tax benefit for a 800 sqft open porch + 200 sqft building vs. 1000 sqft building.

I’m not too concerned with comfort: Aside from being a workshop (where you keep warm by working), the Pacific Northwest’s marine climate is fairly mild. The following chart from WeatherSpark shows that only about three months have lows near freezing (reducing temps by 3–5 °F to compensate for 1000’ elevation compared to Kelso airport):

My biggest concern with an open space is that condensation may hurt my tools. There are several solutions to that problem:

• Add lubricant or wax to tool surfaces to prevent rust.
• Keep rustable tools slightly above ambient temperature via, e.g,. a small low-wattage light bulb. (At $0.07/kWh, a 25 W light bulb would cost about $15/year to run.)
• Keep an airtight but uninsulated envelope and run a dehumidifier to keep the air dry. A 70 pint dehumidifier sufficient for the space would cost $250 to purchase and about $100/year to run. (745 W power draw at 100% relative humidity, assuming 4 hours of operation per day. I made up the 4 hours number, though.)

I raised a GreenBuildingAdvisor.com thread on this topic, and at least one woodworker in my climate zone has a “cutting tools in unconditioned space” setup that’s working out for him.

However, I’ll be doing more than just table saw and hand tool woodworking — I have a small CNC mill and wouldn’t be surprised if I end up buying/building a laser cutter in the next 5 years. Those tools have sensitive electronics that definitely need to be kept inside.

So that leads me to a relatively airtight structure rather than an open one.

I’ll leave it unconditioned for now, but with a proper building envelope it’ll be easier to adapt the structure down the road if I decide to actively heat or cool it.

See the thermal modeling article for more details.