Garage Ventilation

Today was the first sunny day with all of the windows installed and the eaves buttoned up in the new garage. I was working on the stairs and noticed that the upstairs windows were fogging up. A hop skip and jump up the stairs revealed that the top five feet of air in the building were 200 degrees and full humidity. I opened the windows, which helped, but I think I need to learn about garage ventilation.
One hitch, I want clean air. Any place I suck air into the building I want it to go through a filter.
Any thoughts?

http://www.bigassfans.com/

It's cooler near the ground. Put a few openings with regular whole house filters (like a forced hot air system uses) in opposite walls just above ground level with swing louvers on the inside (like the openings at the back of a restaurant kitchen installed backwards).

Put a huge whole house fan in the center of the roof blowing out. It will draw cooler air from ground level as well as allow escape for the already hot air right in it's vicinity.

Variable speed fan would be cool - but just using a thermostat at 100F should suffice.

It would cost more, but I'd consider using a motorized damper on the air intake louver to help keep out bad weather (I see you're in Houston, so a big storms and wind are a concern.) The damper gets interlocked with the exhaust fan thermostat, so it opens and closes when the fan operates. If you can put the air intake on the north side or in a shaded area that would be best.

edited to add: in your climate a split system air conditioner would be a lot better, if you have the cash.

If you put an air intake down low be sure to put a metal grate over it. I put a decorative wooden cover over mine and it quickly became a Bed, Bath, and Beyond for critters.

I did mine more as a "clean" air intake for painting but the idea is basically the same.

The upstairs room will have AC and the garage part probably will to some extent, but I don't want to pay to keep the whole building cool all summer. There will be a lean-to off one side, so it would make sense to put the intake there, yes?
I assume I want to get the fan as close to the peak as I can?

In reply to mazdeuce: Another thing that will help a great deal is to add a de-humidifer. I have one with the drain going out through the wall. It pretty much runs 24-7 here on the Gulf Coast of Alabama where the humidity is really high. I would think the conditions are very much the same as Houston. Even though the garage temp remains high it often feels much cooler. The added benifit is it keeps tools, projects, etc. from rusting.

I also added a 12,000 BTU window type A/C unit mounted in the wall. It has a hard time cooling down the shop/garage unless I let it run at 80 + degrees and then turn it down when I know I will be working out there. With the dehumidifer running 24-7 it also helps reduce the humidity that the A/C unit would have to do. If I had to do it all over I would use the mini split A/C someone else mentioned.

A dehumidifier is a good idea, but only if the garage is closed. If you have ventilation, the dehumidifier won't be able to keep up.

"passive" wind driven fans work well too. They are the ball shaped roof mounted fans that spin when the wind hits them. As they turn, they draw hot air up and out. Very cheap to run and almost maintenance free

In reply to mad_machine:

The idea of cutting a hole in my new roof is a bit unsettling.

The roof doesn't have a ridge vent? Gable vents? I know you have this desire to seal up the building as much as possible, but the roof should be vented in some way.

Likewise, if you plan to put a ceiling on the rafters of the second floor, you should to vent the air space between the rafters.

Some of this stuff is Code and while you like saying "we don't have codes here" there is often a very good reason for these requirements - they make sure the building lasts.

Lastly, if you want to filter the outside air, plan on buying filters in bulk and probably replacing them monthly. The filters you'll find at Lowes Depot for residential systems are designed for recirculating system and not a lot of dirty outside air. Additionally, a typical residential exhaust fan is not designed to pull outside air through a filter, so you may need a second fan to pull in air.

A Big Ass Fan would be the first thing I'd do in the high-roof area.

with no vents.. you are going to continue to have issues with heat and humidity build up. As you do not want to cut into your roof (do not blame you) I would suggest some gable vents

It was always the intention to have active air movement at the gable ends. Like everything in this process, I'm attacking the problem as I get to it. It would be easy to add a ridge vent but I'd rather not if I can help it. They let in enough dust to be a pain long term.
I was just surprised the other day to find that air movement was already a problem even with a 180 square foot hole in one end of the building.

You may be forced to add a ridge vent whereever the rafters may be covered with ceiling, as well as vents in the exterior soffits.

The garage door opening is too low to have much affect on getting air out of the roof pocket.

If you don't have ventilation you're going to have mold before you know it.

DaveEstey wrote: If you don't have ventilation you're going to have mold before you know it.

This is especially true if you have A/C in the upstairs section, the unseen side of any wall coverings (drywall, panelling etc) will tend to get condensation where there is a temperature differential (cool one side, hot & humid other side).

Top gable end vents would be my recommended solution, especially seeing as the shingles are all nicely in place. Pity none of us thought to suggest vents earlier.

Venting has always been planned. My house has ridge vents, vented eaves, passive gable vents in one attic and a thermostatically activated gable fan in the other attic. I really do vent the stuff I build. I left off the ridge vent on purpose so that I could bring in air when and where I want it and I could filter it. I'm not trying to build a NASA clean room, but after years and years of things getting dirty just because dust blows in the building, I want things clean. If they hadn't moved the band field trips from Tues/Wed to today and tomorrow I'd be putting in a fan today. Mostly I was just wondering if I was missing any options.