Making a Closable Ridge Vent

[ToolsRCool]

Second post on similar topic, apology. Open invite to check my thinking on an idea I'd like to incorporate.

I'm building a new garage here in MI, it will have a 2nd story. Warm summers, cold winters. Walls and rafters will be fiberglass insulated with poly vapor barrier, roof peak will have a ridge vent. I plan to use rafter baffles and rafter insulation full length from soffits to the ridge, but for the last foot of them up at the ridge have a removable 1 foot long piece of insulation and matching removable 1 foot long baffle section in each rafter cavity.

In essence, this would allow the ridge vent to be selectively / seasonally blocked off from bleeding out 2nd floor heat in the winter, yet would still vent the underside of the roof sheathing from soffit to ridge at all times including the winter.

Summer: Last foot of rafter baffle and rafter insulation up at ridge peak removed, allowing 2nd floor hot air to escape the ridge vent, as well as venting of roof sheathing underside from soffit to ridge.

Winter: Rafter baffles and rafter insulation installed full length from soffits to ridge vent, allowing venting of sheathing underside, yet not allowing 2nd floor warm air to escape.

New garage heat will be high efficiency natural gas furnace breathing outdoor combustion air so no moisture adding to garage atmosphere. Unsure yet whether I'm going to run it at 40F continuous during the winter until needed, or just on/off on demand. No A/C, as I prefer to work in the summer with the sectional door open as it makes the garage feel larger.

In comparison to what I have now, which is a full ridge vent, zero insulation in the garage, and T1-11 paneling starting to pull away at the seams, when I run a heater now, I can see all the dust webs around the underside of the ridge vent flying strongly in the "wind" as the warm air is quickly going straight up and out the ridge vent. So my priority on the new build is to really get the ridge vent closed up from warm in-garage ambient air escaping during the winter, yet open to vent in the warm summer. Roof sheathing underside would be vented year round regardless.

Any "big" negatives of why this would not work?

 

[CraigStu]

So the 2nd floor has no ceiling? It is open to the roof structure?

 

[ToolsRCool]

Correct. 2nd floor ceiling is the bottom of the rafter boards. Call it an exposed cathedral ceiling. Typical attic structure, but 7' tall at the peak.

 

[Joe Reed]

Will the structure have gable ends? If so, I'd make the rafter baffles permanent and install gable vents.

My father made a small workshop area in the attic of his house. The attic had the usual triangular gable vents. To keep it warmer in winter he had matching triangular sheets of plywood to cover those vents. To exhaust more heat in the summer he installed a couple of those turbine vents near the ridge, and also put up plywood covers to block them in winter.

 

[dcg9381]

We finished up a structure in MI over the summer. Upstairs is living area. Foam and bat insulated. Exposed cathedral upstairs, only the center of the structure is finished on top, so "attics" are on the side.

We installed an ERV that vents on the gable end. The ERV can be programmed to specific humidity, temperature, and other conditions or may be activated manually.

I really can't speak to using it in the winter, but in the summer when not using AC, the building envelope tends to get a little humid. ERVs and HRVs can be used to control this, as well as recover heat.

 

[billconner]

I believe the negative pressure in the vented space above the removable pieces will **** warm moist air out of attic and into that space and condense. Just seems unlikely to get a near perfect seal year after year with that kind of area.

Leave it sealed year round and add gable vents or better an exhaust fan. Open a window and run fan to cool attic. Good insulated cover for fan on winter - like a rigid foam box.

 

[ToolsRCool]

Yes it will have traditional gable ends. May end up with the gable end vents as suggested, one on each end, one powered, one passive, draft across. Open windows may work as well, will have dormers on each side with openable windows.

 

[My Old Tools]

They make closeable ridge vents for metal buildings. Pull chain to close.

 

[E1271]

I believe the negative pressure in the vented space above the removable pieces will **** warm moist air out of attic and into that space and condense. Just seems unlikely to get a near perfect seal year after year with that kind of area.

Leave it sealed year round and add gable vents or better an exhaust fan. Open a window and run fan to cool attic. Good insulated cover for fan on winter - like a rigid foam box.

I agree, leave the inside sealed. Great idea but I don't see this being a long term one. I like the gable power and static vent idea, think about the average natural wind direction and install the power vent accordingly.

 

[Glemon]

Not a lot to add but interested in the discussion, I have an insulated garage with eave and gable vents. I cover them in the winter, but I am looking to get more airflow/circulation in the summer, as the insulation seems to do a good job of keeping the heat in the garage both in the summer and in the winter.

 

[hobie18]

Make it perfect for winter. Then open up the fans for summer. May still be too warm