To insulate... or not to insulate...

[Andrew Wayland]

You can insulate with cellulose. It has borax in it for pests. It's also not plastic, and will rot away when it's removed from the building. Plastic that insulates for 30 years, then sits in a landfill for hundreds, doesn't make sense.

Wiring in conduit will allow you to add to the system easily. An machine requiring a larger wire size isn't a problem, just snake new wire, as long as it meets code in the size conduit you are using.

Cellulose is very interesting to me: it’s only blown in after the fact, right?

If that were the case: I wouldn’t need to think about insulating now, and could just do it down the road when time allows.

Better yet: I suppose I could prepare for cellulose by adding a vapor barrier before I put up the walls (although I’d have to confirm this wouldn’t cause condensation pockets)

[Dave Seng]

Dense pack cellulose is blown into open stud bays. Blowing in cellulose after the walls are closed up will typically be more expensive than if you simply insulate before you close things up. Insulating with standard fibreglass will be the fastest/easiest/cheapest solution. It's not often that you get the opportunity to get something good, fast and cheap. Usually it's a pick 2 out of 3 situation.

[Jim Dwight]

I insulated the walls of my shop garage despite the fact that it is not conditioned. I can how run a little resistance heater when it's really cold and it makes a significant difference. It also has insulation in the ceiling but none under the slab. I might yet put in a mini-split or something to make it conditioned. I don't enjoy time in it during really cold weather or really hot weather. I just used fiberglass. I have mice I'm trying to get rid of right now in my crawl space but I have no signs they've visited the walls. When I bought the house they had a path from the crawl space to the pantry. They liked that a lot and I didn't know about it until a year or so ago. I fixed it but waited to put out poison until they ruined my double oven. Mice can be a pain but they look for nesting places and food. They decided my oven was a good nesting place. Walls stuffed with insulation are not good nesting places and fiberglass insulation is not food for then (but they will use it for nesting material if they can tear it out. Long way of saying I don't think you should worry about mice in walls other than to eliminate their access points.

[vince dale]

I stand corrected. My thermostat is in Fahrenheit not Celsius.

Definitely insulate now. Insulation works to keep the heat in but also helps to keep heat out. I've seen my shop can be as much as 6* C difference inside to outside in the summer.

[William Hodge]

Cellulose is very interesting to me: it’s only blown in after the fact, right?

If that were the case: I wouldn’t need to think about insulating now, and could just do it down the road when time allows.

Better yet: I suppose I could prepare for cellulose by adding a vapor barrier before I put up the walls (although I’d have to confirm this wouldn’t cause condensation pockets)

Some current thinking calls for a vapor barrier at the innermost layer, in order to keep warm air away from cold surfaces. The idea is to air seal the building envelope at or behind the paint layer.

It might be easier to dense pack ahead of sheetrocking. I don't remember, I work on old buildings.

Whatever you do, don't use foam. Some foam causes so much environmental damage in the off gassing of the expander chemicals that it will take longer than the life of the insulation reducing heat loss to pay back the environmental harm in its application. Plus, what do you do with it when it's in the way when remodeling? carves and scrape it out, and throw it in a landfill. end of rant.

[Andrew Wayland]

Some current thinking calls for a vapor barrier at the innermost layer, in order to keep warm air away from cold surfaces. The idea is to air seal the building envelope at or behind the paint layer.

It might be easier to dense pack ahead of sheetrocking. I don't remember, I work on old buildings.

Whatever you do, don't use foam. Some foam causes so much environmental damage in the off gassing of the expander chemicals that it will take longer than the life of the insulation reducing heat loss to pay back the environmental harm in its application. Plus, what do you do with it when it's in the way when remodeling? carves and scrape it out, and throw it in a landfill. end of rant.

I was literally reading up on Vapor Barriers when you replied.

Spray foam is likely out of the question anyways. We installed it in our basement, and like you mentioned: had to rework some wires... It was a nightmare.

I am still considering XPS foam sheets, just to the stud bay and can-foamed around... but only on the workshop side of the garage (this would give me more space to fish new power leads around if needed, as the XPS would only eat up 1/2 the stud bay...

My cellulose idea has to do with the fact that I’m leaning towards Plywood or Slatwall for the interior. I could install vapor barrier or insulation netting behind my finish walls. Then down the road when I decide to insulate, I could unscrew the finish walls (again: there isn’t any plaster or anything... just screwed to studs) and try and dense-pack the bays. It wouldn’t require an entire gut of the garage... seems to be the best pest-deterrent... and also seems to be the most cost-effective

[roger wiegand]

. Plastic that insulates for 30 years, then sits in a landfill for hundreds, doesn't make sense.

30 years? I can't find any source that suggests that the commonly used foam insulation doesn't last much, much longer than this if protected from water and UV. I certainly put it in places like under our basement floor where I expect it to last 100's of years. What is the source of this information? Yes, the R-value drops 10-20% over the first two decades, but it then looks pretty stable for a long time after that, and it's a consistent enough effect that you can plan for the derated value by upping your initial levels so that you achieve the desired long-term target.

Even organic insulators like wool or horse hair are still in place insulating pretty much as well as they ever did after 2-300 years, why would we expect these relatively inert polymers to require replacement more quickly? We hear a lot about the very long lifetime of plastics in the exposed environment, why should they not last even longer on the protected environment inside a wall?

If this is true I'm going to be sorely disappointed! A reference to the source studies on this would be greatly appreciated.

[William Hodge]

30 years? I can't find any source that suggests that the commonly used foam insulation doesn't last much, much longer than this if protected from water and UV. I certainly put it in places like under our basement floor where I expect it to last 100's of years. What is the source of this information? Yes, the R-value drops 10-20% over the first two decades, but it then looks pretty stable for a long time after that, and it's a consistent enough effect that you can plan for the derated value by upping your initial levels so that you achieve the desired long-term target.

Even organic insulators like wool or horse hair are still in place insulating pretty much as well as they ever did after 2-300 years, why would we expect these relatively inert polymers to require replacement more quickly? We hear a lot about the very long lifetime of plastics in the exposed environment, why should they not last even longer on the protected environment inside a wall?

If this is true I'm going to be sorely disappointed! A reference to the source studies on this would be greatly appreciated.

I was talking about the time between renovations more than the amount of time the plastic lasts in the walls. I don't know how long it lasts undisturbed. At some point, it is coming out, and going in a landfill, where it will last for quite some time.

Meanwhile, the plastic bits spread into the environment from the manufacturing and installation processes do spread all over the place. Granted cellulose will spread around, too. I would rather deal with wood than plastic.

Nothing is perfect. I use plastic, too. On the other hand, lessening the amount of plastic we use will lessen the amount of plastic we put into the environment.

[Bill St Amant]

best practices [at least for a house] is to have vapor-permeable air barrier, not a vapor barrier. A vapor barrier will stop the transmission of water vapor from the interior to the exterior. Southeastern MA you are still a mixed climate so sometimes the hot side is going to be the interior and sometimes the hot side is going to be the exterior. If there is a vapor barrier, then water vapor from the hot side can meet the dew point inside the wall and condense, leading to wood decay. You don't have this problem with a vapor permeable air barrier because the wall assembly can dry to either the inside or to the outside. Joe Listerbuk of Building Science Corporation has a website that you can read, [and read and read about this stuff.] If you do want to do a vapor-permeable air barrier without stripping the siding, then you could brush or spray the inside face of the sheathing and stud walls and then insulate. i am more a fan of mineral wool insulation than cellulose. I like than mineral wool is fire-proof and can never rot. This discussion may be over-kill for an accessory building. Practically, the reason to install an air barrier in a workshop is that sound travels through air pretty well. if you stop more air, then you cut down on the noise. If you do put in an air barrier, then you might consider putting either a solar-powered constant fan or electric powered ventilation system on demand to help with the interior air exchange -- how much you'd need would totally depend on the dust collection and the type of solvents you are using.

[Andrew Wayland]

best practices [at least for a house] is to have vapor-permeable air barrier, not a vapor barrier. A vapor barrier will stop the transmission of water vapor from the interior to the exterior. Southeastern MA you are still a mixed climate so sometimes the hot side is going to be the interior and sometimes the hot side is going to be the exterior. If there is a vapor barrier, then water vapor from the hot side can meet the dew point inside the wall and condense, leading to wood decay. You don't have this problem with a vapor permeable air barrier because the wall assembly can dry to either the inside or to the outside. Joe Listerbuk of Building Science Corporation has a website that you can read, [and read and read about this stuff.] If you do want to do a vapor-permeable air barrier without stripping the siding, then you could brush or spray the inside face of the sheathing and stud walls and then insulate. i am more a fan of mineral wool insulation than cellulose. I like than mineral wool is fire-proof and can never rot. This discussion may be over-kill for an accessory building. Practically, the reason to install an air barrier in a workshop is that sound travels through air pretty well. if you stop more air, then you cut down on the noise. If you do put in an air barrier, then you might consider putting either a solar-powered constant fan or electric powered ventilation system on demand to help with the interior air exchange -- how much you'd need would totally depend on the dust collection and the type of solvents you are using.

I caved: ended up buying mineral wool for the walls. I’m using MemBrain from certainteed for the vapor barrier: is that what you’re referring to when it comes to permeable membranes?