Vent a standalone garage?

[Morris Minor]

I now have a standalone garage. It has a plasterboard ceiling under non-loadbearing grade beams with a  pitched roof over the attic space. No insulation.
I don't see that there's any kind of ventilation. Heat has nowhere to go other than up through the plasterboard to the sun-heated attic space. The garage doors are tight. The only relief is when the doors are opened and you're lucky enough to get a breeze. I'm thinking this would also not be great in cold weather with hot wet cars pumping moisture in there.
With the disclaimer that I'm no building expert, shouldn't there be some kind of way for the air to get in below, go up through the ceiling, then out through the roof? Some kind of convection driven air movement?

[giant_mtb]

Looks like you've got a window there...

Most garages I've been in don't have dedicated ventilation...occasionally a gable vent or soffit venting...my parents' garage is soffit vented, but they're stuffed with insulation anyways because fuck the cold. You could climb up in the attic and install a gable end vent, but I don't think there's any real reason to. 

[giant_mtb]

If there's a drain in the floor, I wouldn't worry much about snowy wetness dripping off the cars...that's what the drain is for.  Maybe install a ceiling fan in there if you want some movement?

[MX793]

If there's a drain in the floor, I wouldn't worry much about snowy wetness dripping off the cars...that's what the drain is for.  Maybe install a ceiling fan in there if you want some movement?

I think it's actually against code to put a drain in the floor of a newer garage.

[FoMoJo]

Stick a half a dozen vents on the roof.  It could get really hot in the attic.  I would've thought most building codes would've called for roof vents.

[Morris Minor]

I said plasterboard, which is British for Sheetrock. I need to climb up inside and take a closer look.

I have so many little projects here. The house is really nice but there are lots of little things wrong: not important individually but collectively add up to a level of shittiness I can't live with. Today I swapped the buttons for the garage door opener buttons. Now the left one opens the left door and the right one opens the right. Stuff like that.

[giant_mtb]

I think it's actually against code to put a drain in the floor of a newer garage.

This confuses me.  And probably varies greatly depending on zoning and code.

[FoMoJo]

I said plasterboard, which is British for Sheetrock. I need to climb up inside and take a closer look.

I have so many little projects here. The house is really nice but there are lots of little things wrong: not important individually but collectively add up to a level of shittiness I can't live with. Today I swapped the buttons for the garage door opener buttons. Now the left one opens the left door and the right one opens the right. Stuff like that.

Drywall?

[shp4man]

Cheap, powered by the wind.

[Morris Minor]

Drywall?

That's it.

[Morris Minor]

This confuses me.  And probably varies greatly depending on zoning and code.

Gasoline vapor has a high density. So you don't want it collecting in low points like drains. I vaguely remember horror stories from childhood involving car owners in their garage inspection pits lighting cigarettes.

[FoMoJo]

Don't want people draining various petroleum products and other toxic liquids into the storm drain system, i suspect.

[MX793]

This confuses me.  And probably varies greatly depending on zoning and code.

Don't want people draining various petroleum products and other toxic liquids into the storm drain system, i suspect.

This.  Your vehicle has a fluid leak, or you spill while performing an oil/coolant change, and that flows right into the storm drain system, which in turn can pollute the greater water supply.

[Morris Minor]

Took another look. There are soffit vents but no vents in the roof. So the heat has nowhere to go.
I'm thinking gable-end vents at each end, vents in the ceiling, and vents in the garage walls would help a lot.

[MX793]

Took another look. There are soffit vents but no vents in the roof. So the heat has nowhere to go.
I'm thinking gable-end vents at each end, vents in the ceiling, and vents in the garage walls would help a lot.

You know what doesn't have these kinds of ventilation issues?  A carport.

[CaminoRacer]

This.  Your vehicle has a fluid leak, or you spill while performing an oil/coolant change, and that flows right into the storm drain system, which in turn can pollute the greater water supply.

But that's exactly why I want a drain. Easy cleanup

[giant_mtb]

But that's exactly why I want a drain. Easy cleanup

Yuuuuup.  Isn't the drain meant for doing oil changes??

[Rupert]

You know what doesn't have these kinds of ventilation issues?  A carport.

This is really a thread about the superiority of carports.

[AutobahnSHO]

This is really a thread about the superiority of carports.

Carports keep air on your cars so they can breathe.

[Morris Minor]

Well my cars are definitely not breathing - they basically sit in a near-airtight big box.
I've been warned not to leave the doors open, bears wander in.

[giant_mtb]

I've never had an issue with an airtight garage, but I see your point.  And yeah...critters will get all up in there, especially if you leave doors open overnight and have anything like bird seed or similar in there.  Which is never a good idea, because also, thieves.

[r0tor]

Doesn't seem much different then my attached to the house garage - shrug-

[93JC]

I now have a standalone garage. It has a plasterboard ceiling under non-loadbearing grade beams with a  pitched roof over the attic space. No insulation.

That's your problem right there: no insulation. I'll elaborate below.

I don't see that there's any kind of ventilation. Heat has nowhere to go other than up through the plasterboard to the sun-heated attic space.

Heat wants to achieve an equilibirum; it moves from hotter things to colder things. The heat in the occupiable part of the garage (below the ceiling) won't go up through the ceiling to the attic space: the attic is hotter than the garage. In the summer your garage roof is being bombarded by solar radiation, in addition to the conductive gain through the roof deck itself. Without insulation the heat from the attic is transferring down through the ceiling into the occupiable part of the garage below. Being seemingly otherwise well sealed it's turning your garage into a hotbox.

With the disclaimer that I'm no building expert, shouldn't there be some kind of way for the air to get in below, go up through the ceiling, then out through the roof? Some kind of convection driven air movement?

You do not want to have air movement between the attic and the occupied space below, vents from the ceiling into the attic will exacerbate the problem rather than help. You're trying to think of ways to relieve the heat that's already in the occupiable part of the garage by punching holes in it, but the best solution is to prevent the heat from getting in in the first place (i.e. no holes!).

First of all add gable vents to increase the ventilation through the attic. This will help to transfer heat out of the attic and back into the ambient air. Less heat in the attic = less heat to be transferred from the attic into the garage. To really solve the problem you need to insulate. Insulate immediately above the ceiling, as much as you can. Insulate your walls if you can; looks like they're already finished and painted in the photos, unfortunately.

[93JC]

I think it's actually against code to put a drain in the floor of a newer garage.

This confuses me.  And probably varies greatly depending on zoning and code.

Don't want people draining various petroleum products and other toxic liquids into the storm drain system, i suspect.

For everyone's info a floor drain would typically be connected to the sanitary sewer, not the storm sewer, but either way it's bad. The sanitary sewer ends up at a wastewater treatment plant that won't be able to treat the oil and other crap that might leak from a car, and it'll end up polluting the environment. Or it'll congeal and clog the pipes before it gets to the wastewater treatment plant. If you're on a septic system it'll clog up the septic tank. Dumping oil or any other automotive lubricant or chemical down the drain is a colossally ignorant and stupid thing to do.

Commercial garages have their drains connected to oil interceptors, which skim the oil off into a storage tank and lets gravel and other grit settle to the bottom before the wastewater leaves the property. Residual oil has to be periodically removed from the storage tank, and sediment has to be cleaned out of the bottom of the interceptor. (Commercial carwashes have these too.)

[Rupert]

I've never had an issue with an airtight garage, but I see your point.  And yeah...critters will get all up in there, especially if you leave doors open overnight and have anything like bird seed or similar in there.  Which is never a good idea, because also, thieves.

Does bird seed attract thieves?

[giant_mtb]

Does bird seed attract thieves?

Errybody gotta eat mang.

[Morris Minor]

That's your problem right there: no insulation. I'll elaborate below.

Heat wants to achieve an equilibirum; it moves from hotter things to colder things. The heat in the occupiable part of the garage (below the ceiling) won't go up through the ceiling to the attic space: the attic is hotter than the garage. In the summer your garage roof is being bombarded by solar radiation, in addition to the conductive gain through the roof deck itself. Without insulation the heat from the attic is transferring down through the ceiling into the occupiable part of the garage below. Being seemingly otherwise well sealed it's turning your garage into a hotbox.

You do not want to have air movement between the attic and the occupied space below, vents from the ceiling into the attic will exacerbate the problem rather than help. You're trying to think of ways to relieve the heat that's already in the occupiable part of the garage by punching holes in it, but the best solution is to prevent the heat from getting in in the first place (i.e. no holes!).

First of all add gable vents to increase the ventilation through the attic. This will help to transfer heat out of the attic and back into the ambient air. Less heat in the attic = less heat to be transferred from the attic into the garage. To really solve the problem you need to insulate. Insulate immediately above the ceiling, as much as you can. Insulate your walls if you can; looks like they're already finished and painted in the photos, unfortunately.

Hey thanks. One of the items on the inspection for the home was that it needs more insulation blown in to bring it up to standard - this may be a good add-on to the project. I'll also get the gable-end vents put in.

[giant_mtb]

Good advice and knowledge.