12X24 Shed/Workshop - What's the best way to insulate?

[Charlie Velasquez]

If the studs are open it is cheaper to cut foam board to fit with 1/4" gaps all around then foam the gaps to seal it in place. Fire code will require drywall over insulation unless it is rockwool. Install rough wiring or empty conduit before insulating.
Bill D.

Before you decide to go with uncovered foam board insulation, look up the Station nightclub fire in Rhode Island. There is a reason codes require it to be covered with drywall or equivalent one hour rated material.

I know code requires foam insulation to be covered if the space is a livng space because of the off gassing when it is heated, but I was under the impression stand-alone sheds did not have to be.

[Bill Jobe]

Charlie, I can certainly relate to your disclaimer, but mine would read 'kids and grandkids'.

[Tom Bender]

Hi Bob
In a former career I made a lot of heating load calculations for various buildings. The loads from biggest to smallest are usually;

1. Air (makeup, leakage etc)
2. Window transmission (well it was a long time ago and there were a lot of single paned windows)
3. Roof transmission
4. Wall transmission
5. Other (in your case the doors could be pretty bad)

So wall insulation is not so important. I think you will be surprised at the effectiveness of your plastic cocoon.

But you will want to insulate. It just doesn't have to be ultra insulation in the walls. Your roof vent item implies a need for air flow from the eaves to the ridge above the insulation. This may need more thought.

Spray foam insulation is really effective and quick, but really ugly. Look before you leap.

[Damon McLaughlin]

Hi Damon,
This is helpful. Could you possibly provide a link to Home Depot or Lowes of the exact product that you used? Is your foam board, between the studs, exposed? I was thinking I would just leave them exposed instead of investing in material to cover them. My shed is like a gambrel-type so I would have to also go all the way up the inside of the roof with the foam board as well. Just not sure how to handle the area around the ridge vent. I'll have to do some you tube-ing to see how that is handled. I'd love to see some pics and you could send directly to my email address - bbessette55@gmail.com. Thanks for your advice!

Bob,

I'm sorry I didn't see your message until just now. For the walls I used 1" foam board insulation. I had to cut it down to fit between the studs. I have the foil side facing towards the inside of the building. I did not cover up the walls. Here in eastern Washington our coldest temperatures will be as low as minus ten but our normal winter days will be in the teens. Though this board does not provide a large R value I find it very adequate.

For the ceiling I used this Rockwood insulation. I chose this because its easy to work with and doesn't itch. You'll want to wear a dust mask as its quite dusty to work with. Once in place its fine. I may one day cover up the ceiling with hardiboard.

With just the two above I kept my thermostat set at 68 (plus or minus) and it was fine. But the floor was always cold.

So this fall I insulated the floor with 1" insulation boards, the 1" version of this board. Lowe's doesn't stock the 1" but they ordered it and had it the next day. It has good R value and a high compression rating. I then used this tongue and groove subfloor right over the foam boards. I used vinyl flooring on top of that.

Whatever I set my thermostat to, say 68 degrees, the walls, floor and ceiling are all 68 degrees. My electric bill floats between $35 and $50 a month when leaving the heater on 24/7. The one thing I probably could do is use a bit of foam insulation around the two window frames.

[Bob Bessette]

Before you decide to go with uncovered foam board insulation, look up the Station nightclub fire in Rhode Island. There is a reason codes require it to be covered with drywall or equivalent one hour rated material.

Yeah, I remember that horrible fire. Thanks.

[Bob Bessette]

Thank you Tom. I appreciate it.