Thread: Closed cell spray foam insulation in a large steel shed?

You're bang on the money with your concerns.

Its easily solved though by adding ventilation in your work space, how much ultimately depends on the size of your workspace and whether you're trying to hit a humidity target.

Also depending on how much dust extraction you have in your space you might be fighting a losing battle with "over insulating" the space. From my experience foil backed insulation does plenty good job of insulating, but obviously doesn't do much for noise.

Your concern is humidity within your shed with all walls and ceiling sealed against leakage. How sealed are your doors/roller doors etc? Do you have air locks on doors? Because humidity lives IN the air, so whenever you open a door from inside to outside, you’ll introduce humidity into the shed. Unless you pressurise the shed with more air, thereby pushing shed air out whenever a door is opened.

This is a hard task without ventilation fans etc, and when we talk of ventilation it’s usually with outside air which is humid!

A dehumidifier or air conditioner will work for either scenario but to get positive pressure you’ll need to bring in outside air into the room, which makes your humidifier and or air conditioner larger, or work harder. It’s doable but can get exxy.

I should explain that I am only researching to get an idea of what budget I would need for my dream workshop.
We are in South East Queensland so it is hot and humid for much of the year. I suppose there are two issues. One is the comfort of working in the space. The other is the humidity and humidity differential and how that might affect timber. Either stored timber or work pieces.
I am also interested in reducing noise because I prefer to work in the evening.


I forgot that the dust extraction would be moving the air through anyway. I guess the problem would be when the workshop is not in use. What is going to happen to the timber in the shed then?
No, I don't imagine the roller doors would be sealed.

Originally Posted by DaveVman

I should explain that I am only researching to get an idea of what budget I would need for my dream workshop.
We are in South East Queensland so it is hot and humid for much of the year. I suppose there are two issues. One is the comfort of working in the space. The other is the humidity and humidity differential and how that might affect timber. Either stored timber or work pieces.
I am also interested in reducing noise because I prefer to work in the evening.


I forgot that the dust extraction would be moving the air through anyway. I guess the problem would be when the workshop is not in use. What is going to happen to the timber in the shed then?
No, I don't imagine the roller doors would be sealed.

I’m in SEQLD also, and all my comments apply. I don’t have issues with humidity in autumn or winter, late spring and extended summer yes, so if you are serious with your concerns then AC or dehumidifier is required

Although I'm in Perth I'm in a similar situation to you, where woodworking is a hobby so i spend my nights/weekends in the shed.

Humidity isn't much of an issue here in Perth except in the winter periods, like Runningman says a reverse cycle AC is the best all round solution.

In terms of working at night, i've gotten around this by setting aside tasks that don't make loads of noise late at night, ie hand sanding, finishing, using drill press, hand plane/sawing etc. My neighbours main bedroom and study are about 2 meters from shed wall and have never had a complaint.

You need to factor in the air quality in a well sealed shop. Our house was blower door tested with the results just over 1 air exchange per hour. Pretty tight. When that tight you need to bring in fresh air to remove the moisture from breathing and other household activities. Our fresh air is run past the stale air going out through an air to air heat exchanger to warm it up some, thus saving heating costs. The air to air exchangers work in the opposite way when cooling a home. With a shop you want to keep in mind the off gassing from glues, finishes, et cetera needs to be removed in the same way or you could affect your health. Good dust collection, as already mentioned, is on top of the general air quality.

The other thing to think about is that if you keep your shop very dry all the wood you get and store will eventually dry out until it reaches equilibrium. The furniture you make from that wood will gain moisture and move if it isn't in the same dry environment in a home. It makes the most sense to have the shop humidity set the same as in your home if you condition the air in it.

Keep thinking and dreaming about that ultimate shop/shed. It'll happen.

Pete

I am just west of brisbane. My place gets hotter than brissy in summer as I'm on the west side of the mountain. A little colder in winter also.

I put up a thread late last year in the reno section about house insulation. All that applies to your place along with a few other considerations.

1. Openings. If your shed door leaks or you work with it open or it's open a lot you have that problem.

2. Dust as mentioned above. Possibly other things I can't think of at the moment.

Anyway the short answer is build you shed in the most reflective colour you can. Zincalume, surf mist, whitehaven. Line it with fiberglass batts. My place is up to 7 degrees cooler. Optionally sarking or insulating foil. Foil backed glass batts are good but they are more per sqm for the same R rating. I put the thickest I could fit in my roof, R3.5 and foil sarking. Cost about $5 sqm.

Humidity does not build on it's own. You are either providing a moisture source inside the shed or it's coming in from outside.

There is really only 2 kinds of insulation. Those that reflect heat back out (or in) and those that (usually trap air and) slow heat flow through the surface. Expanding foam is hideously expensive toxic and won't do a better job than equivalent glass wool. I favour glass as it's fireproof inedible and lasts essentially forever. The other trendy materials like paper have come and gone because despite the BS marketing people eventually find out they are rubbish.

Finally you can get 8x4 cover sheets on gumtree, chipboard/mdf. They will aid insulation and also give you a lining you can crew things to like shadowboards. Cheaper than plasterboard. Obviously susceptible to moisture.