Insulating and ventilating detached shop - no attic

[RedTravis88]

I'm in Pensacola, FL (hot humid summers, with about 14 days below freezing in the winter). I have a 20x24 detached workshop that I use for a mix of woodworking and mechanic work.

It's a 2x4 construction, trussed roof with ridge vent, 16" OC exposed wall studs, and a shingle roof (no ceiling). It has soffits, but no vents installed. My long term plans are to insulate and sheathe the walls, insulate the ceiling with fiberglass batts, and install a mini-split. However, before I can do that, I'll need to install a new roof due to some minor leaks.

Since I'll be conditioning the space, I assume I should decommission the roof vent and go with something like gable vents with exhaust fans? During the summer I may not run the A/C full time, so I would like to be able to vent the space. During the winter, I could close the gable vents and run the heat. Does this seem like the best practice if I'm not wanting to install a ceiling?

As for the roof underlayment, what kind would be best for Florida?

 

[racecougar]

Are you installing a ceiling or not? You mention that it doesn't have a ceiling now, but that long term you'll be insulating a ceiling. The answer to this question directs the path forward.

 

[RedTravis88]

Are you installing a ceiling or not? You mention that it doesn't have a ceiling now, but that long term you'll be insulating a ceiling. The answer to this question directs the path forward.

Sorry, I wasn't clear on that. I prefer to keep the rafters open, but I plan to insulate the underside of the roof.

 

[Built To Work]

In the same boat - will be watching this thread

 

[racecougar]

In that case, yes, you would eliminate the ridge vent. You could install gable vents and an exhaust fan to draw outside air through the building as desired. Note that you may want to produce insulated doors for the vents to seal them up when running the minisplit.

 

[dcg9381]

In that case, yes, you would eliminate the ridge vent. You could install gable vents and an exhaust fan to draw outside air through the building as desired. Note that you may want to produce insulated doors for the vents to seal them up when running the minisplit.

Agree, you treat this space like an envelope. No venting. Insulate the whole thing up. Foam board may work for you in some cases better than bat, but you've basically got one space to heat/cool as you don't have an attic.

If you want to move air, you need to consider where the air is coming from and how it will exit when not on HVAC. I like push/pull exhaust fans in the gable, but you could do just pull or push if there is a vent on the other side, but both create some leakage....

 

[Firebrick43]

If your not using spray foam or sheet foam directly against and sealed to the roof deck you need to have ventilation space and bottom to top ventilation behind other forms of insulation such as batts or moisture gets in there and cause mold and moisture damage to the roof deck.

 

[RedTravis88]

So here's where the confusion ensues...some say vent, some say no vent. There has to be an industry standard somewhere.

 

[racecougar]

So here's where the confusion ensues...some say vent, some say no vent. There has to be an industry standard somewhere.

Ridge and soffit venting with a ceiling and attic space would be the industry standard.

 

[Built To Work]

My Clerestory has soffit vents and some largish louvered vent on one side of the building. (upper right of the pic)
I am debating sealing it off - trying to educate myself on if it is needed. Maybe a bug screen and an industrial box fan in front of it?
It is too cold to work in there now.




Better pic:

 

[dcg9381]

So here's where the confusion ensues...some say vent, some say no vent. There has to be an industry standard somewhere.

First, it's kinda per insulation type. And then it's going to depend on what your climate is if you need some means to vent it even if you choose a non-vented insulation type (like spray foam).

The concern is that you cool that structure and there is a gap between the traditional insulation and the inside sheeting which allows condensation.. I think that's the debate here. You have at least one gable vent and plan on a push or pull fan, I'm pretty sure that I would not add a ridge vent or soffit vents, that'd be my call on this structure with traditional insulation. Someone can tell me that I'm wrong.


I assume that structure has some sort of sheeting / house wrap on the exterior between the panel and the siding?

 

[Built To Work]

I assume that structure has some sort of sheeting / house wrap on the exterior between the panel and the siding?

I am un-sure of the sheathing type, it's black and says Georgia Pacific. The siding looks like bead board.

I just had the roof and roof sheathing replaced. My plan was to do the exterior siding next then finish off the inside - hence the interest in ventilation.



Beadboard siding???



Still learning the terms - new to shed restoration.

 

[AdamMopar]

So here's where the confusion ensues...some say vent, some say no vent. There has to be an industry standard somewhere.

There is no confusion, there is a whole domain of building science that you can reference.

If you spray foam the whole outer envelope of you building no venting required. If you have unconditioned attic space it needs to be vented. Simple as that.

There is alot of misinformation out there by people who don't understand the science unfortunately.