Insulation for Gable Roof Vents

[atourgates]

Insulation for Gable Roof & Ridge Vents

We're nearly done with a 44' x 60' insulated pole-barn (build photos coming soon), but I have a question about insulation and venting.

Our barn has ventilation in two places: gable-end vents on the front and back, and a continuous ridge vent.

We've insulated the barn by putting R21 fiberglass insulation between the studs in the walls and roof, and sheeting the entire thing with 1/2" plywood.

We're heating with radiant in the slab.

My question is: what should I do about the ridge and gable vents during the winter? My assumption is that I'll lose a decent amount of heat through both if I don't do something to block them?

I'm planning to just build a removable cover for the gable-vents, maybe just a square of XPS foam backed by a piece of plywood to cover the vents from the inside, that I'll put up in the fall, and remove in the spring.

But what about the ridge vent?

On the advice of both the insulator and contractor who's putting up the plywood, I left the cavity below the ridge vent uninsulated - marked with the arrow in this image.

Am I going to lose a ton of heat out there if I leave it open? Should I fill it with something? The plywood sheeting is all attached with screws, so it wouldn't be the end of the world to rent a scissor-lift for a weekend, remove the plywood along there, fill the gap with something, and re-fasten it. But I don't want to do something stupid that's going to do damage to my building.

Here's a profile of the front of the building showing the gable vent.

 

[The Cobbler]

venting should have been in unconditioned space . your contractors were aware you planned on heating the space?

 

[atourgates]

Yes - though we hadn't decided on how we'd insulate/heat when the pole-barn was built. Also, different contractors who erected the structure, and did the insulation/sheeting.

Clearly poor planning on my part, but what's my best option going forward now?

 

[burleyfarm]

Re: Insulation for Gable Roof & Ridge Vents

You don’t mention where you live.
Did you install your attic insulation along the bottom plate of the truss (ceiling) or along the roof line? It looks to me that your truss design intended for you to install insulation along the bottom plate of the truss, the ceiling and this would require the venting to remain as is year round.


Sent from my iPhone using Tapatalk

 

[atourgates]

North-central Idaho - USDA zone 6a (maybe closer to 5b due to our elevation). Summer cooling isn't really an issue, winter heating is.

The insulation was installed so that the building doesn't have an attic - directly against the underside of the roof, above the trusses.

 

[Toyomech]

Do you have ventilated soffits? Im not seeing your picture but the design sounds unusual. If there aren't soffits and you plywood against the roof rafters I don't see how the ridge vent is working. It sounds like a mix between conditioned attic space and unconditioned. Basically sounds like you "unconditioned" your building. The ridge vent is supposed to work in conjunction with ventilated soffits. Gable end vents are like having open windows in your building without an attic.

 

[atourgates]

I don't believe we have ventilated soffits.

Here's a few photos of the soffits on the building.

There's maybe some ventilation happening just from the ribbing of the roof material, but I don't think there's any other ventilation installed in the soffits.

 

[yeldogt]

If the insulation is in the roof deck there is no venting ?

Venting is really not understood very well ... ideally it should be eliminated. Why build and then punch holes in the structure.

What are you venting ?

 

[kj_mustang]

Hope your trusses were rated for adding plywood to the top chord.

 

[atourgates]

Why build and then punch holes in the structure.

What are you venting ?

Ha! Those are exactly the questions I'm asking. Intuitively it seems like I should eliminate/fill the roof vent. But I fully admit that I don't understand the principles of building ventilation and moisture control.

 

[yeldogt]

There are two items -- people have this idea that you vent an attic to remove moisture. Where is the moisture coming from? People assume it's from the house ...and it can be. But studies show it's often coming in the vents. The key is to seal the upper layer of the building --- use a good vapor barrier with fiberglass. Sealing up a building stops warm air from being able to bring moisture through a wall -- it's powered by the stack effect.

The second item is the ideal of a cold roof and ice dams --- again the problem is really heat leaking into a buildings attic.

Studies show that it's only in very extreme climates are there roof temp differences.

What's the VB protecting the fiberglass insulation?

Any tight building may need some ventilation. You can't expect any heated building to be able to take a lot of snow covered vehicles in the winter without have some way to get that added humidity out of the air?

If you take care of the conditioned space --- they rest is taken care of.

 

[atourgates]

What's the VB protecting the fiberglass insulation?

Any tight building may need some ventilation. You can't expect any heated building to be able to take a lot of snow covered vehicles in the winter without have some way to get that added humidity out of the air?

The roof is constructed from the outside in: 29ga Ribbed Steel -> 30# Felt -> 15/32 OSB -> Fiberglass Insulation -> 15/32 Plywood Sheeting

There will be at least one vehicle regularly parked in there during the winter, that'll doubtless drip some snow and bring moisture with it.