Ventilation

[MetalBuildingFun]

I have a question about ventilation of our new metal garage. Once we completely insulate it, then add the plywood to the walls, and add the a/c where does the ventilation come from? I am curious about that. We will be storing the riding mower, a car, and other things like this in the garage.

So, when we are out there wood working the car will be moved out of the garage, and the riding mower will be in the back loft area with a wall between the front area and the back area. The mower is new and does not leak or have any odors coming off of it, but the car is an older 70's vette. Where is the ventilation when we are working in the air conditioning and also when the car is in there and the building is all closed up? This is hot humid south texas I need a/c and insulation, lol.

 

[glentre]

If your building is airtight, you will be recirculating the air already in the garage when the a/c is operating. If you are not producing any contamination like woodworking dust, welding fumes or painting, you will be perfectly comfortable and not need any ventilation (outside air). However, if you are airtight and are working on projects like dust-producing woodworking, welding fumes or painting, you will want some change of indoor air, the quantity depending on the amount of dust or fumes you are comfortable with. That air change normally comes from getting the contaminated air out of the garage through exhaust fans. But, if you are airtight and have exhaust fans running, you will not be exhausting the bad air because, other than infiltration through cracks at the doors and windows, there is no way for outside air to get in to replace the air you want to exhaust. At that point, you will need some way for the makeup air to enter the building. You can crack open the garage door, open the man-door or open a window. This is not a precise way to do this and will draw in dirt, leaves, bugs etc.

A better way is to calculate the volume of air in your garage in cubic feet and determine how many cubic feet of air you want to exhaust. Then, an exhaust fan would be selected to remove the required amount of air (cfm or cubic feet per minute). Also, to prevent unwanted outside air from entering when the exhaust fan is not operating, an automatic screened makeup air grille would be installed to provide a good cross ventilation from the outside entry air to the exhaust fan. The makeup air grille also could be wired to open when the exhaust fan is turned on.

This is a little more complicated than mentioned here and it would be recommended to talk to a HVAC engineer to properly size the exhaust fan and makeup air grille to match your particular circumstances.

Glen

 

[glentre]

As an addition to the above, I'm sure there are a number of articles on the internet regarding the design of ventilation air so, perhaps, you would be able to select the required equipment without having to go through a HVAC engineer.

Glen

 

[manwithtools]

Look at air to air heat exchangers to minimize energy use. Although I suspect your building will not be air tight enough to make this a consideration. It does not a take a lot of air to make up what is being used. No operation of vehicles with the doors closed regardless of building construction, ever. The out-gassing of anything in your metal building is far less than the leaks you will have.

 

[ambenz]

I would put IN a homemade exhaust extraction "POINT-OF-USE" duct along various points in the garage, over a welding bench, near the parts cleaning station, and over where you park the jalopy....as in the photo....

You could add electric dampers to each vent along with a switch on each port to enable the main fan....they make round "DUCTED" exhaust fans.....

If your running the car in a enclosed space, you will want a port out the side or car door as shown below....

Heck, you could even connect it to the exhaust ducts you built for the work areas, as shown below....

If your not savy in designing and connecting your own system, check out Nederman for a pre-engineered system!

 

[rpcraft]

If you just need general ventilation you can get it through your roof vents and just realize you are probably not going to get your interior 100 % sealed up. If you do have a low level of air circulation once construction is done and simply want it heated and cooled you can add a mini-split and have some direct fume extraction or exhaust system but obviously you want to limit it to just the area's you need it. If you are doing stuff that needs high volumes of fume extraction then build a system in using a fan that has some high CFM but be warned they are noisy and it might start pulling your conditioned air from the work area.

 

[MetalBuildingFun]

Thanks everyone, for the life of me I cannot figure out how to do the "multi quote" so I will just respond with this. You all have given me some great info and a lot of which I had read online before posting my question. The confusion is what brought me here to my post

We won't run the car while having the garage closed up, it is the fact it is an old car and when it runs, well you know that exhaust is awful on old cars so bringing it into the garage when it is time to close up for the night will leave fumes and I would like those to be exhausted out somehow.

My biggest concern is my lungs and the fact that they are unable to handle any kind of fumes, even perfumes. We have a dust collector and all tools will be hooked up to it when used so there will be little dust, but not all can be collected as any woodworker knows. I use a mask to protect my lungs and eye protection as well. When painting or staining my husband does that task and it will be with the big door open and the side walk door open as well for good ventilation meaning all a/c will be gone from the building at that time.

Here is where it gets sketchy for us. We go into our new building and there is no light coming in anywhere except at the top roofline on both 16' ends. I think they did not put the rigid closures into those sections. We have sealed the base rail with NP1 to keep water out so there is no air flow or light coming from there at all. The insulation we used is called Prodex 10M Plus and the way it is installed is by using a heat gun to weld the pieces together to allow an airtight seal for no air leaks. Then it is taped along the seam as well. There is zero light coming in from the insulation first layer that went on between the frame and the R-Panels. The second layer goes on from inside and when we do that there will be total enclosure of the building. With just this one layer on the building we can tell there will be a significant benefit to having chosen this insulation.

https://www.insulation4less.com/insulation4lessproduct-62-prodex-total-10m.aspx

The big doors are windstormed to 150 MPH and they are a very tight fit against the frames with no light showing at all. The seals seem to be doing their jobs very well. The walk door also has no light showing, and the window has not been installed yet. It will also be wind stormed so I doubt there will be air leaks coming in from that either.

So, this is why I question our need for air flow and getting some oxygen in there when we are woodworking in there with the a/c going and it all closed up. The back 8 feet will have a wood storage loft with a wall and a walk door. This will be the lawn/garden area where the riding mower is located. There will be two fans in the wall for this area, one bringing cooler air into the area and one circulating it back into the front 22 feet of the garage. So, I don't want to mix any possible fumes, and if we have them I need them vented out.

I will attach a drawing for some idea of what we are doing. But, I was looking at the church building behind us earlier today and that is what got me to thinking about our air when I saw their vent above the huge door out back. It is the kind with fins on it and this is what I ran across earlier. I do know I need to do some more investigating on the proper size for our building but I think this is what we need.

https://www.northerntool.com/shop/tools/product_200673805_200673805?cm_mmc=Google-pla&utm_source=Google_PLA&utm_medium=Fans%20%3E%20Exhaust%20Fans&utm_campaign=Strongway&utm_content=52853&&lid=92700046533044610&ds_s_kwgid=58700003118431779&ds_e_product_group_id=643062724982&ds_e_product_store_id=&ds_e_ad_type=pla&ds_s_inventory_feed_id=97700000001662305&gclid=EAIaIQobChMIn-r-t9LQ6QIVDdvACh0gYApFEAQYASABEgLuRfD_BwE

Finally, we plan to use a DIY MR. Cool 18K because it not only has the a/c aspect but we can also use the dehumidifier on it's own, and during the winter when it is still so humid out here and the a/c doesn't want to come on because of the cooler temps outside. Ask me how I know that says the a/c in the dining room window just for dehumidification in winter, lol. I'll be looking into an integrated dehumidfication only option for the a/c in the house when it needs replacing.

See doc attached of our garage drawing.

 

[CraigStu]

I am not sure exactly what type of heat/AC you will have but I know our house heat pump has an outside air inlet. Just a simple maybe 3 inch PVC pipe to the outside. Here it's a code thing as is a vacuum test of the overall house to get an occupancy permit. The house is so sealed up that they require an outside air inlet. Look at the instructions that come w/ your unit to see if it has an inlet.

 

[glentre]

Looking at the sketch of your building, we get a better idea what your are trying to do. Your larger area is 3520 cu ft. Using a 2800 cfm exhaust fan to recirculate air from the larger area to the smaller area and back again using a second fan the same size will theoretically give you an air change in the larger room every 1.3 minutes which is moving too much air. The drawing seems to show the return air fan located low in the dividing wall near the walk door where it will blow dust and dirt all over from your shop floor and into the air.

Having an internal dust collection system for all of your woodworking machines is a real plus in your situation as it doesn't need any outside makeup air to function properly. Recirculating air from the larger area to the smaller and back again will not resolve the problem of removing the remaining dust and paint/stain fumes from the building as you will just be moving it around. Actually, you will likely find dumping the excess dust into the smaller room will end up covering everything in that room with a layer of dust and the fumes will likely dissipate to an acceptable level but not be removed from the building.

Instead of just moving bad air around, you will need to get rid of the dust by either improving your existing collection system which could include a good dust filter in the fan moving air from the larger to the smaller room, use better work techniques to keep dust production at an acceptable minimum or exhausting it to the outside. In that case, you will need outside makeup air whether it be in the form of an outside air intake option in your HVAC unit or a separate automatically operated intake louver unit in the wall. It is understandable you don't want to exhaust air you have already paid to cool but, shy of a really good dust collection system and a self contained fume hood with proper fume removing filters, your only option is to exhaust some air.

Improving your existing dust/fume collection systems would appear to be the cheapest long term solution.

Glen

 

[K'ledgeBldr]

Garage doors are no-where close to being air tight. Plenty of replacement air there.

 

[glentre]

Garage doors are no-where close to being air tight. Plenty of replacement air there.

I missed this at first too but the OP says the garage doors are 150 mph rated and they are a very tight fit against the frames with no light showing at all and that there is doubt there would be any air leaks. Of course, the garage doors could be cracked open a bit but then they would be sucking **** from the outside apron or ground. If the window is screened, it could be cracked open when the exhaust fan is on and bring in much cleaner air. This is assuming the OP goes the route of exhausting air to resolve the dust/fume problem in which case makeup air would be required to come from somewhere.

Glen

 

[MetalBuildingFun]

Looking at the sketch of your building, we get a better idea what your are trying to do. Your larger area is 3520 cu ft. Using a 2800 cfm exhaust fan to recirculate air from the larger area to the smaller area and back again using a second fan the same size will theoretically give you an air change in the larger room every 1.3 minutes which is moving too much air. The drawing seems to show the return air fan located low in the dividing wall near the walk door where it will blow dust and dirt all over from your shop floor and into the air.

Having an internal dust collection system for all of your woodworking machines is a real plus in your situation as it doesn't need any outside makeup air to function properly. Recirculating air from the larger area to the smaller and back again will not resolve the problem of removing the remaining dust and paint/stain fumes from the building as you will just be moving it around. Actually, you will likely find dumping the excess dust into the smaller room will end up covering everything in that room with a layer of dust and the fumes will likely dissipate to an acceptable level but not be removed from the building.

Instead of just moving bad air around, you will need to get rid of the dust by either improving your existing collection system which could include a good dust filter in the fan moving air from the larger to the smaller room, use better work techniques to keep dust production at an acceptable minimum or exhausting it to the outside. In that case, you will need outside makeup air whether it be in the form of an outside air intake option in your HVAC unit or a separate automatically operated intake louver unit in the wall. It is understandable you don't want to exhaust air you have already paid to cool but, shy of a really good dust collection system and a self contained fume hood with proper fume removing filters, your only option is to exhaust some air.

Improving your existing dust/fume collection systems would appear to be the cheapest long term solution.

Glen

Thanks for the response. The drawing is meant to show a small fan in each the top side and lower side to recirculate the a/c air into each room so that the back area can have some of the humidity removed from it. If this approach does not work we are prepared to go another route which might be a separate mini split for that area. The reason we don't right now is the smallest we can find is 9K which is overkill for that room size.

We do plan to use a system of filters to make sure we aren't transferring dust from one space to the other, we just wanted to make sure we could change some of the a/c air into the smaller section of the garage, and remove some of that humidity from the back area.

The big fan is a sample of what I found online, and as I noted I know I need to find something that would be appropriate in size but it would probably be mounted above the walk door in the larger front area of the garage to allow exhausting of the fumes I am concerned with regarding the car, and any remaining fumes in the building after my husband paints, or stains anything and then closes up shop for the night. I am also concerned about just getting some plain ole' good oxygen in the building when we are in there even if that means I lose all of my a/c for a few minutes. You are right too, I am near the coast, sand would be blowing into this building pretty quickly if I were to be cracking those doors, or the window.

But that doesn't mean in the winter I won't take advantage every chance I get to open everything up and turn off the a/c unit.

 

[MetalBuildingFun]

I missed this at first too but the OP says the garage doors are 150 mph rated and they are a very tight fit against the frames with no light showing at all and that there is doubt there would be any air leaks. Of course, the garage doors could be cracked open a bit but then they would be sucking **** from the outside apron or ground. If the window is screened, it could be cracked open when the exhaust fan is on and bring in much cleaner air. This is assuming the OP goes the route of exhausting air to resolve the dust/fume problem in which case makeup air would be required to come from somewhere.

Glen

These doors are also well insulated too, so air flow is probably not available between the sheets either. They are the Amarr 2412, rated 150 MPH, fully insulated. The front door is 12'W x 9'H and the back one is 6'W x 7'H

https://www.google.com/url?sa=t&rct...402_2502.pdf&usg=AOvVaw1eGdnV-FsQhjFrBE1yo35X

I was also thinking we could build a filter setup for the window when we need fresh air to come into the building.

 

[glentre]

You are wise to start out with simple and relatively inexpensive solutions and to move to something a little more sophisticated if that doesn't work. Your mini split units should have optional fresh air intakes which should satisfy your need for a little oxygen.

On another but related subject, you apparently do get some freezing weather in the winter in your area but with high humidity at the same time. If your garage is unheated at any time and the inside temperature gets cold, you will need to be careful about opening the doors if the next day is warm and humid. The warm and moist air will enter the garage and immediately condense on everything including tools, machinery, cars and even floors. Don't ask me how I know.

Good luck with your project.

Glen

 

[MetalBuildingFun]

You are wise to start out with simple and relatively inexpensive solutions and to move to something a little more sophisticated if that doesn't work. Your mini split units should have optional fresh air intakes which should satisfy your need for a little oxygen.

On another but related subject, you apparently do get some freezing weather in the winter in your area but with high humidity at the same time. If your garage is unheated at any time and the inside temperature gets cold, you will need to be careful about opening the doors if the next day is warm and humid. The warm and moist air will enter the garage and immediately condense on everything including tools, machinery, cars and even floors. Don't ask me how I know.

Good luck with your project.

Glen

LOL, right about that condensation in the garage, it happens in our regular garage every winter because we have no a/c or heat in there. We do plan to cool and heat the new garage at all times though. We want comfort while working so hopefully we won't come across that issue. Regarding the a/c bringing in fresh air I could not find anything online about that with the Mr. Cool DIY units so I just left a message with MR. COOL and await their return call regarding that question. I appreciate all your help. If this is the case, maybe we can forego adding another hole in our building to put in a vent after all, I would rather not do that if I don't have to, and just opening the window to vent would probably work also.

 

[Whiskey30]

I tried sending you a PM, but I am too new to the forum. I am getting a shop built and am trying to figure out what insulation I am going to install. You mentioned you used Prodex insulation. Did you put it directly onto the panels? Does it work well for a condensation barrier? Did you add more insulation between it and finished walls, like rolled insulation? I have read over the Prodex website, but am looking for input from someone who has installed it. I have been reading a ton of threads on insulation and its similar to asking what is the best oil for your car...

Thanks

 

[tbev]

How's the Prodex work / holding up?